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My UH12R : Thrust System

My UH12R : Lift System

My UH12R : Control Surfaces

My UH12R : Thrust Duct

My UH12R : The Hull

My UH12R : Lift Duct

My-UH12R : Frame

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My UH-12R

The Model's Construction

The Construction

2015-12-31T23:59:00.000-08:00

Welcome to the new home of The Hovercraft Homepage. I had originally developed this site back in 1996 under the web site URL iti2.net/aolshove/hover.html to provide basic hovercraft-related info to the web as there was very little information available at the time. In 2000, I bought the domain www.HovercraftHomepage.com which I used until 2008 at which time I allowed it to expire and used only www.Olshove.com/HoverHome which brings us to 2010 at which point I retired the original web design in favor of a blog type maintenance. I have omitted several pages keeping only those for which I've seen the most activity. If you are missing a particular page, email me at the email in the "Contact Info" below, and I'll work to recreate the page here.

My interest in hovercraft began back in 1985 when I stumbled across a volume of "Jane's Surface Skimmers" in my high school library. In 1997, I constructed my first hovercraft (the one in the image on the left below) which was a Universal Hovercraft UH-12R designed by Bob Windt. There's a link on the left that cronicles the construction of that craft. In 2000, I sold that UH-12R and purchased the original Sevtec Vanguard prototype from its second owner, originally designed and constructed by Barry Palmer of Sevtec SEVs. I restored and sold that hovercraft after an unfortunate incident where it flew off the trailer onto the highway on the way to the NW Hover-In. I inherited my last and final hovercraft which was a 14' Sevtec Vanguard (pictured on the right below) from a gentleman from Seattle in 2001. After years of use, the wood top deteriorated and I restored it in 2005 with a fabric top and pressed it into service again until 2008 at which time I sold it to gold prospectors in Alaska and am not currently in possession of a hovercraft. My current hobby is restoring a 1968 Ford Mustang Convertible.

In February of 1996, I began the process to create a hovercraft newsgroup on Usenet called alt.rec.hovercraft which has been in use ever since. You can still participate via Google Groups.

More recently, however, people are fond of internet forum sites such as HoverLovers on Yahoo Groups.

2010-02-22T15:54:00.000-08:00

UH12R In Action!

						I had just finished the final touches of construction in October of 1998 and had taken the 12R down to my father's house to get his assistance in tuning the Hirth 2-stroke thrust engine. After fitting the air intake with a splash guard and and tuning it with the best jets, I was raring to get out on the water but the only water for hundreds of miles was the low, narrow, Dolores River. Feeling my oats, I decided to give it a go. This picture shows me skimming by the area where we launched the craft.
						The run was farely short. I ran down from the launch site a little ways and turned around where I am when this picture was taken.
		And then I'd run up past the launch site under a bridge a little ways past where these pictures were taken, turn around and head back down.
						Looks like I'm having fun huh? Well, after a couple of runs, I came up over a little section of rapids and around the corner towards the bridge where I kinda lost control and hit the bridge pillar (the one on the left in the pictures above). Sorry, suffered too much mental trauma to record that part. The 12R got a crunched starboard bow corner and the lift engine sheared off and would have sunk in the river if not for the duct guard and battery cables. About 20 hours of reconstruction later, the craft was stronger and better than new and ready for another adventure.
						So, in June of 1999 after the reconstruction, I went out on a little lake near (30 miles away, actually) my house called Highline Reservoir. The lake wasn't terribly crowded that day but there was a fair amount of wind. Because the ramp area was pretty small and with me being a novice, I had a little trouble lining up with the dock to go up the ramp. In this picture, I'm putting around in displacement mode (no lift air) so that I wasn't affected so much by the breeze while attempting to approach the dock.
						Here I am buzzing around out on the lake.
						This is a zoomed-in view of me from the picture above. All in all, it was a good trip except for a few inconveniences such as a very fine dust that was around the ramp parking area that made hovering between the trailer and the ramp a very dirty affair. Bystanders didn't seem to like it either when the wind blew the cloud in their direction. I have since outfitted my trailer with a winch that allows me to load and unload the craft quickly by myself so that I can theoretically back the trailer to the water and launch and load the craft like a boat thus avoiding dusty parking areas.

2010-02-22T15:17:00.000-08:00

Miscellaneous construction details

						This is the hot-wire cutting bow that I used to cut out the rudder and trim wing shapes. It consists of a piece of highly resistive wire such as nicrome (as is in the case here) or steel such as guitar or piano strings strung between two rods of spring steel like the kind used for model airplane landing gear.
						This is a close-up of one end of the bow. Notice the alligator clip that brings the power from the cutter box. The clip can be moved back and forth on the wire to allow the cutting wire to get hotter or cooler.
						This is an internal view of the cutter box. It contains an AC transformer, a fuse, a wall plug, a switch, and a reostadt (sp?) which is a standard household dimmer switch. This particular cutter was build by an electronics tech/electrician friend of mine who really likes to wire things up complicated. The transformer used here has several secondary windings that supply varying levels of power but a transformer with a single secondary winding works fine and simplifies the construction considerably.
						Here is a (very) rough drawing of how the hot-wire system is put together. The dimmer switch (reostadt) functions as the cutter power switch and heat adjustment. Turn it up to set the wire hotter and turn it down to set the wire cooler. The lines going to the plug are the primary (input) leads and the lines going to the cutter are the secondary (output) leads. If anyone wants to contribute information on the construction of a better cutting system, feel free to contact me and I'll replace this. NOTE I am not responsible for injury resulting from the use or construction of this cutter. This cutter uses AC voltages that are sufficient to cause serious injuries or death. Do not cut styrofoam in an enclosed area or without a respirator.
						A (very generous) friend of mine gave me his old garden tractor knowing full well what I intend to do with it (play 'Taps' here). Fact is, this is the last time that this tractor is going to know what it feels like to have a Briggs & Stratton 11HP electric start engine vibrating in its belly.
						This is what the engine looks like. UPDATE!: After rebuilding the carburator and fixing an oil leak, I mowed my lawn with it about 6 times. After showing my father the mower and telling him what I planned for the engine, he just couldn't let a perfectly good rider go to scrap so he offered to buy me a brand new engine in trade for the mower. "Okay, if you insist", I said and ordered myself a new Tecumseh 10 HP lift engine with recoil and electric start and a 3 amp alternator. :-)
						And this is the new lift engine still in the box. Ain't she a beut!?! BTW, This model of Tecumseh is also EPA approved.
						After I had installed the lift system, the craft was too heavy to hang from the ceiling in my garage so it came time to put my baby outdoors under a tarp. That very week for a couple of weeks in a row, we had temperatures exceeding 100 degrees. When I looked under the tarp to check on the craft, I had found that the very top of the thrust duct had expanded and split. Evidentally, I had allowed an air bubble to remain between two styrofoam layers that form the duct and the bubble had expanded in the heat and had essentially 'popped' splitting the top of the duct open. These pictures are of repairs I had to make to the damage. I basically hacked out the foam and filled it with expanding spray foam and sanded it level with the rest of the duct. I had also discovered another bubble that ran down from the top along one side which I drilled several holes in and pumped spray foam into the void to prevent this from happening again. I then coated the (really pourous) spray foam with epoxy filler and sanded it smooth and then laid a layer of glass over the area. You can see evidence of the damage in pictures in the thrust system section as I hadn't painted over it yet.
						A week later (after repairing the thrust duct) I came out to check on it again as we were still suffering from 100+ degree weather. You can imagine my joy (massive sarcasm) at seeing that the nose of the craft had wrinkled up and shrunken like a prune. Technically, it would have worked fine but I just couldn't feel good about the craft with that kind of a blemish after working on it for a year and a half. So, partially in a fit of rage and partially for repair reasons, I hacked the white bead foam, that had formed the nose, out. I laid down layers of pink foam until I felt that there was enough to form the lip and I cut and sanded and filled with spray foam until the shape I wanted appeared and then I coated the whole area with epoxy filler, sanded some more, filled some more, and then glassed over the area and painted it. You really can't tell that the damage had even occured.
						This is a close-up of the trim wing actuator. It's operated via a marine shifter/throttle cable. I've since beefed up the arm.
						This is a close-up of the rear steering pulley. It pivots against spring tension to keep the cable tight.

2010-02-22T15:04:00.000-08:00

Construction of the Thrust System

						One of the primary components of the thrust system is, of course, the engine. I was going to use a Polaris 440 racing engine but thought better of it since it was a free-air style of engine and was guaranteed to over-heat on me and be a consistent source of aggrevation. So, off I went to my father's snowmobile boneyard and picked out an older Hirth 634cc 2-cycle fan cooled engine. Heavier but more reliable according to pops. So, I yanked the beast and hauled it home. One of my concerns about the 12R design is that it doesn't really consider nor offer solutions regarding engine vibration isolation so off I went in search of the perfect vibration isolator. I wasn't happy with what I found out there due to high price ($15/mount!). The engine mount consists of a heavy engine mount plate, 4 isolators, and a lighter base plate. This photo is of the engine plate mounted to the engine.
						This is an exploded view of one of the vibration isolators. The big rubber piece on the right is placed directly on the base plate with the lip pointing up. The engine mount plate is then fitted on top of the large piece with its top being run into a large hole on the engine mount plate (see above picture). The smaller rubber piece is placed with its lip down into the top of the engine mount plate. The metal sleeve in the center of the photo is pushed down through both rubber pieces to hold them together and prevent shearing. The sleeve also provides a place for the compression of the rubber to stop when the bolt is tightened. The bolt is placed up through the base plate through the entire assembly and through the large washer at the top and a nyloc nut is tightened on. Not shown here are rings that I placed around the lower rubber pieces to hold them together in the event that they start to split or break apart.
						You can see in this photo how the engine mount is assembled. In this photo you will also notice the engine pulley (sheave) that drives the prop via belt. Got it from and it fits a standard (snowmobile) 30mm tapered shaft. It has 5 grooves but I was only able to use 4 of them since the back cylinder of the engine gets in the way. No biggie, it was the same price as a 4 groove pulley.
						I then started work on the propeller. It was purchased from UH and was as rough as the lift fan (see lift system) and needed the same attention. Sanding, balance, and glass. The balance was completed the same way as the lift fan using a spindle and rails. The prop was balanced, the light side weighted, and balanced again until the prop stopped spinning on its own. For weight, I drilled out a 3/8" hole, and melted some lead with a torch and poured it into the hole. As you can see here, I had to do this 5 times. The holes were covered with glass and sealed with epoxy when I glassed the prop. I don't know if this was the best idea but it seemed the least likely to affect the aerodynamics of the prop at the time.
						The hub was fitted to the prop and the upper pulley was mounted on the shaft with the bearings. I placed extra locking collars to the front of the bearings in case the locking bearing collars start to give way. The lock screws seemed pretty small to me.
						Finally, I mounted the thrust engine and drilled out the 6 3/8" engine mounting holes. I ran into a bit of a problem when I found that I'd measured the belt length wrong and the 56" belt required me to raise the engine 3/4". I treated 3/4" x 2" x 13" wood strips and placed them on top of the craft's wooden mounts. Why didn't I just order a longer belt you ask? Because it took a week to order the first one in! :-)
						Judgement day! I nervously filled my gas tank with 40:1 fuel, pumped the fuel bulb, choked the engine, and pulled the recoil starter cable. The darn thing wouldn't start so I fiddled with the carb settings until it finally fired up... reluctantly. After some more adjustment, I got the engine to spool up. Slowly at first to ensure that the prop didn't contact the duct and then faster and faster until I blew all the leaves from my yard into the neighbor's prize winning roses. Just kidding, but she did blow up a hurricane... and made alot of noise. I discovered that the previous owner of the engine used a blow torch to cut a hole through the baffles in the muffler so that it was a straight shot. I've since replaced the muffler.
						That test was good enough for me! I hovered her around to the back yard, cranked her up and flew for the first time! Around the trees, between the bushes, through the flowers (oops!). It was very maneuverable. I stopped by cutting lift, cranked the rudders hard to one side, kicked up lift, and hit the thrust, and she would come about. I could move around the yard in short bursts like this and eventually only had to cut lift to stop on a couple of occasions. Otherwise I would just use the thrust and rudders to turn. Woo Hoo!
About a week was spent installing guards on the lift and thrust ducts to keep objects out of the prop and fan, and keep my fingers on my hands. :-)

2010-02-22T14:39:00.000-08:00

Construction of the Lift System

						First off, I'd like y'all to know that I dropped the ball in documenting the construction of the skirt and for that, I'm sorry. I thought I had taken more pictures but got caught up in the construction process and simply forgot and so this section won't be as complete as I'd like it. This is the only picture I took of the actual construction process. The skirt was constructed from about 8 running yards of 18 oz/sq yd vinyl coated nylon 60" wide. The material was cut into two 30" wide strips. One 30" wide strip made up the right side and rear skirts and the other made up the left side and front skirts. The plans provided a template for the shape of the seam on the front corners and the rear corners. I copied each template onto a piece of card stock and used it to draw the seam location on the skirt material with a yellow marker which can't be seen in this picture. This picture was taken after the rear corner of the right side skirt had been marked and cut. The white template is in the position of a yellow line that shows where the actual seam will be. The excess 1.5" to the left is where the seam will be glued with the back skirt. The material on the far left is scrap that was removed. When two seams are mated (like the side skirt seam and rear skirt seam) and then turned inside-out (outside-in actually), the result is a curved corner. Since there are 4 corners on the craft, 8 of these seams had to be cut and joined with their counterparts. Each of the 4 skirt panels have seams on each end. The side panels have a rear seam on one end (the rear) and a front seam on the other (the front). The rear panel has a rear seam on each end (mating with the rear of seams of the side skirts) and the front panel has a front seam on each end (mating with the front seams of the side skirts). The rest of the construction process involved adding lengths of material to the top or bottom of the skirt panels to allow the skirt to reach areas of the hull not normally in direct contact with the skirt. Examples would be a 3" extension of the bottom of the front skirt to reach the air splitter in the lift duct and a 3" extension of the bottom of the rear skirt to accommodate the step. One other extension that wasn't documented in the plans but is a good idea is an 8" extension to the top of the front skirt to accommodate the rise in the hull at the nose.
						After constructing the skirt, I laid it out beneath the craft (which you can't really see in this shot but it's hanging above.
						I then used thumbtacks to temporarily attach the skirt in its position on the skirt attach strips first on the outside...
						...and then on the inside. You can see in this shot where the extra 3" of material are made useful to accomodate the step in the bottom-rear.
						After I felt comfortable with the position of the skirt on the attach strips, I wrapped 1" of skirt material around a 3/8" diameter nylon cord and drove a 5/8" #6 screw (and washer) through the material and cord and into the attach strip every 4" starting at the outside rear...
						...along the outside sides...
						...and then around the front Notice in this shot that the skirt has been extended several inches at the top to accommodate the rise of the nose. I did this to ensure that the contact line of the skirt to the ground was even and level all around.
						I then did the same thing on the bottom (inside) attach strips starting from the rear and working forward. Since the hull curves in toward the center of the craft at the front, there was too much material on the inside which had to be overlapped upon itself to take up the slack.
						After I screwed the skirt to the rear and sides, I attached it to the front and air splitter as shown in this picture. Notice again how an extra 3" of skirt material comes in handy to reach the air splitter.
						This is what the 12R looks like with the skirt attached and hanging from the ceiling over my car. Reminds me a little of a nesting hen or something.
						To better assist me in removing wrinkles from the skirt, I placed a small blower fan in front of the lift fan splitter, sealed around the edges of it, and inflated the skirt. These 4 photos show how the skirt looked before adjusting for wrinkles.
						After the skirt was fitted, it came time to finish the lift fan which came from UH rather rough. Finishing involved sanding the fan smoothe, glassing it, and balancing it which is what each of the photos represents. Balancing was accomplished by leveling 2 rails and inserting a spindle through the fan and placing it on the rails. The spindle consisted of 2 1/2" ID/1" OD locking collars locked to a 1/2 bolt. The fan is considered balanced when it can be placed at rotation on the spindle and not start spinning on its own. In the case of this fan, balancing required a heavy 2" washer to be bolted and epoxied to the hub at the root of one of the blades (not shown).
						After the fan was complete, it was time to install the lift engine. This was accomplished by reinserting one of the plywood disks that was originally used to form the duct. The fan hub with bushing were bolted to the center of the disk. The 1/8" steel mounting brackets were then positioned temporarily against the wood mount approximately where the engine bolt holes would line up. The engine in this photo is suspended from the pulley system I used to hoist the craft to the ceiling.
						The lift engine was then lowered down and the shaft was mated with the hub (temporarily) to find the center position of the engine. The engine to 1/8" steel mount holes were marked as were the 1/8 steel to wood mount holes (8 holes total). The whole works was removed and the mounts were drilled.
						The 1/8" steel mounts were then bolted to the hull and the engine was bolted to the mounts. Finally, the fan was fitted to the shaft of the engine and locked on. If this were a perfect world, that would have been the end of it, but Murphy's Law required the alignment to be off slightly and so I had to auger out the holes on the steel mounts to allow fine adjustment of the engine. Also, as long as I'm complaining, the fan bolts were practically inaccessible. The photo to the right shows the angle at which the lift engine is mounted. Pretty steep.
						Finally I got to test the lift system! It started up easily enough and I made sure that the fan didn't contact the edge of the duct. I slowly brought the throttle up and the skirt started making the most gawd-awful flapping noise you've ever heard and was vibrating wildly. I expected 'skirt flutter' to happen but wasn't expecting it to be quite so violent. I shut the engine down to idle and was able to push it around the garage with very little effort. After I was happy with everything and ensured the spectators that the flapping was normal for hard surfaces, I loaded the ma-in-law up and pushed her around the driveway and spun her around in circles... well, SHE had fun. :-) Next it was the pa-in-law's turn and then my turn with the pa-in-law while my wife, Kelly pushed us (thanks hon!). Now that's a payload!
Ahead lies the task of adjusting the skirt when on cushion to ensure the most efficient fit when traveling at speed on water. No skirt drag is the goal... as little drag as possible will be the reality.

2010-02-22T14:09:00.000-08:00

Building the control surfaces

						The plans required me to make 3 rudder pivots made from 3/4" x 1" x 40" strips of pine and 1 trim wing pivot made from 3/4" x 1" x 46" strip of pine. The problem is that 3" on each end had to be rounded to 5/8". I don't have a lathe, so I had to do it the hard way. First, I marked where the 5/8" peg was to be located and marked the edges of the peg.
						Next I cut down the previously marked lines which made a square 5/8" x 5/8" square peg.
						Finally, I held a peice of 50 grit at each end like a shoe-shine rag and sanded the corners off making the final rounded shape until my calipers told me that I was around 5/8". Not precision, but it'll do.
						Each of the 3 rudders were constructed from 2 pieces of 1" thick styrofoam cut to 34" x 3" and 34" x 12" joined together by the rudder pivot discussed above. The trim wing was constructed in the exact same manner except the foam pieces were 40" long. The template sitting on the rudder was to be used as a template to cut the rudder shape with a hot-wire and is a cross-section of how the rudder will be shaped.
						Since the above template was made of light cardboard, it was too flimsy to cut the pointed end of the rudder and so it was replaced by 1/8" plywood templates which gave a much better result. This is an end view of how the rudder looks after being cut. The curved lines you see indicate that the hot wire was too loose and drags behind in the middle during the cut. This was remedied for the other 2 rudders and the trim wing. The lines sanded off and didn't result in problems.
						This is a view of the rudders and the trim wing after being cut and coated with the first coat of glass cloth and epoxy resin. The trim wing is the longer one on the left.
						After glassing the rudders, I made a mark 3" from the top on the trailing edge and made a cut from the top of the pivot to the mark. This resulted in an angle that would allow the trim wing to clear the rudders. Finally, I rounded the top of each rudder to allow moisture to run off and glassed 'em.
						The three rudders and the trim wing are fully glassed and ready for the control horns to be installed. Then they'll be painted and mounted.
						After constructing the trim wings and rudders, I soon discovered that I had placed the trim wing pivot point too close to the rear of the duct. I hadn't even considered this when I was building the trim wing mounts as I was just happily building the craft to the plans which offered no dimensions for the location of the pivot point in relation to the duct. I measured the plans to get the position (and converted from 1/12th scale) rather than actually think about it. The result of my folly was that I had to hack off the existing mount and reattach an extension using a 3" overlap dovetail joint and epoxy.
						I filled the imperfections and drilled the hole and after it's painted, you shouldn't be able to see my mistake.
						The next job was to make the aluminium lower rudder mounts shown here two phases of construction. The lower unit has been marked and drilled and not yet angled and the the other two have been angled. I cut the shapes out using a hand-held jigsaw with a metal cutting blade.
						The tough part involved drilling a 3/4" hole in the business end of the mount. This was tough since I didn't have a 3/4" bit that could chew through aluminum. I solved the problem with my jig-saw and a narrow blade. Only took a few minutes to make each hole. Next, I had to press a 3/4" diameter by 3/4" long piece of EMT into the hole and epoxy it in place. The extension you see attached to the bottom of the mount is due to another miscalculation on my part as well as an ambiguity on the part of the plans. It ensures the mount is far enough out to allow the rudders to clear the back of the thrust duct.
						Here's one of the lower rudder mounts mounted to the back of the craft.
						The next job was to make and attach the upper rudder pivot/mounts to the trim wing which also acts as the upper rudder support.
						This is how the trim wing and a rudder look when mounted.
						This is a close-up of the upper rudder mount in action if you're curious.

2010-02-22T10:59:00.000-08:00

Construction of the thrust duct

						My next big job was/is the Thrust duct. This proved to be the most intimidating part of the construction for me thus-far. Construction consists of making two 48" diameter disks, attaching the disks together via 3" blocks and then wrapping the disks with 1/8 plywood to serve as the duct wall. The plywood is then wrapped with two layers of 1" polyurethane foam. I used that urethane foam that comes in spray cans to glue the foam together and to the plywood.
						The second layer of foam was glued to the first layer with a 3/8" overlap to form the duct lip. You'll see pictures of the formed lip a little later. This view is useful to see the disk attached to the plywood attached to the foam layers as well as a plywood joint (I used epoxy to join the sections of the duct wall together).
						I mounted the 48" diameter duct assembly on a 1" shaft which I mounted to my bench via 2 pillow block bearings (which I bought to use in the finished hovercraft to drive the propeller shaft). I affixed a 12" swamp-cooler pulley to the shaft and drove the contraption with my old Maytag washing machine motor via a 58" belt and 1 1/2" sheave.
						This is a closeup of the drive motor which I strapped to the bench with plumber's strap. This motor spins in either direction at 1750 RPM. The shaft spins at around 146 RPM, and the outside edge of the duct is moving at around 15 fps and has a massive amount of inertia. Why did I want to spin the duct at 146 RPM? Because then I can shape the foam like a lathe. I borrowed the idea from http://www.hoverclubofamerica.org/fmduct.html.
						This view shows how the shaft goes through a 1" hole in the plywood disks...
						...to this side where it spins a small pulley which then spins the thrust duct. The arrows are pointing at the adjusting devices I used to adjust the duct's balance on the shaft. The balancing gadget consists of a 1.5" hole in this disk and 4 'clamps' that allow me to straighten the duct on the shaft by moving a piece of wood in or out and tightening a screw. Once I acheive the proper alignment, I insert another screw in each of the 4 clamps thus affixing it in a set position. Why did I need to adjust the alignment? Well, even I'm not perfect... sigh
						Finally, I could start shaping the duct. Before I started sanding, I rough cut the basic shape I was trying to get with a hot-wire which saved me alot of sanding. When that was done, I spun the duct up and started sanding on it with 50 grit. The lines you see are the uneven spots I had marked while the duct was spinning.
						This is what the duct looked like when I finished smoothing it out with 100 grit. The sanding block was a 2x4 about 18 inches long to make the angled backside of the duct as straight as possible.
						I basically just free-handed the lip by just holding a piece of sand paper against the foam and shaping the lip with my fingers kinda like using a potter's wheel. I would occasionally shut down the spinning motor and check the shape with a template I cut out of 1/8" plywood (Hmmm... a little more off the top).
						And this is how the duct shaped up when I was done.
						When the sanding is finished, it's time to glass. This is a major hassle that's only slightly improved by having the duct mounted on a spindle. Nope, I didn't spin it up while glassing on account of it would toss all my hard work right back in my face... literally. This job took 2 layers of 1.45 oz./sq. yd. fiberglass cloth (Good stuff to work with compared to the 6 oz cloth) and about 5 coats of Epoxy resin. I recommend West resin available from St. Louis Hovercraft. Get the handy-dandy measuring pumps too. Makes the job of measuring resin to hardener easy and precise.
						Duct is done. Time to make the duct support fins that keep the duct stable when mounted on the hull. The fins are constructed by cutting the shape out of 1/2" thick piece of foam, sanding the foam to a fin shape, and then epoxying a rounded piece of wood to the leading edge.
						Finally you slap on two layers of 6 oz glass and sand them to perfection... well, use your imagination. I'll actually need 4 fins but decided to make just two at this time because I haven't decided how to attach the final two fins to the craft since the plans make it look like I'm supposed to cover one of the thrust bearings with a permanent plywood structure which I really don't feel comfortable doing for maintenance reasons. More on that later.
						To mount the duct, the first thing that has to be done is to carve a flat spot on the duct where the duct is to be mounted on the hull. I accomplished this by mounting the bearings and shaft that I had used to spin the duct where the prop shaft and bearings will be mounted on the rear of the craft. Before doing this, I had to find the true center of the hovercraft regardless of where I placed my bearing mounts. Turns out that center was about 1/2" to starboard of where the bearing mount centerline is... sigh. After mounting the bearings and shaft, I fitted the duct with discs in place back onto the shaft. I could then sand off a portion of the duct, slide the duct forward until it contacted the hull, slide it back, sand some more, etc. This was actually a difficult task since the _inside_ of the duct was to be aligned with the prop shaft and the back of the duct is slanted one way, and the back of the craft is slanted down the other... shiver. This picture is taken straight on at the flat spot. You can see the shaft and rear bearing (and mount) to the right. The duct has been slid back for sanding.
						This is what the duct looked like when it finally fit where it was to be placed. There was a slight bit of error but I think I'm happy with it in general.
						After I mounted and epoxied the duct to the hull, I installed the two fins that I'd constructed earlier and kicked out the discs that had been used to form the duct. Holy cow! It's starting to LOOK like a hovercraft!
						Here's a view of the duct from the front with my experimental cat-o-matic thrust system. After several hundred man-hours (and cat-hours) of training and experimenting, my crew of engineers and I just couldn't get Snowplow to spin his tail fast enough to provide the necessary thrust so the project was scrapped (scratched? heh).
						The plans called for a couple of 10" diameter discs made out of 1/4" plywood to be glued to the rear bearing mount and a piece of wood at rib 5. The discs were to be covered with 1/8" plywood on top of which the top duct support fins were to be mounted. This troubled me because I felt that the dome would get in the way of maintaining the thrust bearings and engine. I decided to build a higher dome made out of 3/8" ply. I'm confident that this assembly will be just as strong and not much heavier than the original and it will provide good access to the engine, bearings, and shaft. I will post pictures of the finished dome and top duct support fins very soon.
						Since I've added quite a bit more weight to the hovercraft, I felt it necessary to beef up the gear used to hang the craft from the ceiling. I bought some 3/8" steel cable, ferrels, and heavy-duty clamps and replaced the nylon rope previously used to connect the hovercraft to the lower pulley. This is a bad picture of the craft hoisted to the ceiling so my car can use the garage too.

2010-02-19T09:53:00.002-08:00

Making the hull

						This is a shot up into the nose of the hovercraft where you can see the lift ducting.
						The cockpit sides where then attached and the seam between the side and deck was glassed.
						Here's a view of the inside. Those two boards are where the tandem seat will be after the steering rod is mounted between them.
						Fore and aft shots. Notice in the aft shot the green steering cable that will be attached to the rudders. The thrust duct will be centered around the thrust shaft which will be just barely above the rear thrust shaft bearing mount visible here. The duct will be 48" in diameter. The rope is used to hang the aft end of the craft from the ceiling of the garage via a pulley. Is it me, or does this beast look kinda like Frankenstein's monster?
						A hovercraft picture that really turns me on. Full frontal nudity! (Get it? No paint.) ;-)
						A rear view.
						a side view.
						Since the plans are very vague about the position and location of Rib 1 (the piece of wood at the very front of the craft), I took a close-up head-on of the front...
						And the side.
						Here's a picture of the dome that supports the duct supports. Notice the easy access to the rear bearing mount and thrust engine that will sit beneath it.
						As the plans leave it, the floor of the 12R is not very strong and wouldn't tolerate much use or general wear and tear for very long especially for someone of my... uh... weight class. So, after conferring with a gentleman by the name of Rob who is also building a 12R (and is almost done after only a few months!), we decided that floor reinforcement stringers would be the best and simplest solution. The stringers are 1" pine strips screwed to ribs 3, 4, and 5 edgewise with more screws fastened from the inside of the craft to the stringers. Also, the stringers are glued to the bottom. After walking on the floor the past few days while working on the craft, I'm gaining confidence that no further reinforcement will be necessary at this time.
						The seat simply consists of a piece of 1/4" plywood spanning two 1x4's. Also, I think I'm going to bolt one o' them boat or airplane seats to it for cruising comfort.
						So, anyway, I sat there on my new seat looking out over the top of the craft and decided that I needed a windshield. I opted for a simple windshield consisting of a hoop of 1/2" EMT, a sheet of 1/16" Lexan, and a plywood strip to screw the lexan to the top of the craft. I selected a simple angle of 45 degrees and a height of around 15" from the top and then built this contraption to find out how far out on the nose the windshield would have to be mounted.
						I then measured the top of the nose from side to side and calculated an arc of a circle that would extend out the correct distance and end at each corner of the cockpit. I set my jigsaw at about a 27 degree angle and cut 2 arcs out of 1/4" ply. I glued the first arc to the nose and the second arc to the top of the first arc to get a rise of about 1/2". The reason I didn't just use 1/2" ply is that it's difficult to bend and would easily disfigure the 1/8 ply on the nose.
						Next, I drew an arc on a piece of cardboard that extended 18" (15" tall windshield with 3" rise on the nose) with each end ending at the edges of the cockpit. I used that drawing as a template to bend the 1/2" EMT. I then flattened then ends and bolted the arc to Rib 3.
						I then used a straight edge between the EMT and the plywood arc to find the true angle at which the outside edge of the plywood arc must be set so that the 1/16" sheet of Lexan lays flat against the angled side of the arc. I used my Dremel tool with a sanding attachment to quickly form the correct angle. I then filled any gaps with filler so that water couldn't seap under the windshield mount.
						Finally I was able to primer the entire craft with several coats of a primer that the paint guy at the local Kwal-Howells said would stick to anything. You see, since what I don't know about paint would fill a book, I had a mental delimma about what type of paint to use because I used polyester resin to seal the bottom and epoxy resin to make all of the ducting and controls. The problem is that I heard that epoxy doesn't stick to polyester and thus epoxy based paint won't stick to the bottom. "Like I care", I said to myself and went ahead and selected the epoxy paint... that is until I found that the epoxy paint available locally only in a couple of colors (black, white, red). Finally, I decided on a simple, cheap, alkyd enamel. The paint guy said that with this super primer, the enamel will stick to anything and it did. However, it also was sucked into the wood (great for sealing) but caused the tiny grain cracks in the ply to expand making for a rather ugly finish at close inspection. Looks good from a couple of feet away though. Heres my recommendation: Seal the top with polyester resin or epoxy resin (I'd go with polyester next time myself), prime over that, and then paint with enamel. This shot of the craft is in bad light and doesn't really reflect the true Teal color. The bottom was painted yellow since I had an extra can sitting on a shelf. That way, when I can tell onlookers that if the craft turns from teal to yellow, send help.
						After painting the entire top and sides of the craft teal (the colors were of my wife's choosing), I asked my friend Jack to come up with a design for the sides. He laid out a design on paper and I made a scale drawing of the design in Autocad and printed it out on my dot-matrix printer to use as a template allowing for 1/2" of masking tape to form the lines. I taped the design on the sides and covered the areas surrounding with newspaper to protect against stray splatter and spray.
						I sprayed on 3 coats of Royal Plum, pulled off the mask and this is how it turned out. The colors are a little odd but it doesn't look bad... not bad at all.

2010-02-19T09:53:00.000-08:00

Construction of the lift duct

2010-02-19T09:52:00.001-08:00

Construction of the frame

						Construction starts with buying about $50 worth of #2 grade (or better) lumber, cutting it, and gluing into the rib shapes specified in the plans. When the ribs are complete, they are aligned on a jig so that they may be attached together via stringers. This picture is of the ribs aligned on the jig from what will be the front of the hovercraft.
						After the ribs are aligned, the stringers are glued and stapled into place. My father-in-law's air stapler has been the most valuable tool on this project. This view is from what will be the aft end of the hovercraft (Sorry that the photo is so dark, my camera was having problems... couldn'ta been the photographer). Notice that the jig is different from the above pics. Truth is, I changed the jig at least 3 times finally deciding upon two solid core fire doors which I covered with 1/2" plywood into which I screwed guides so that I could make sure the ribs were straight and level before attaching the stringers. This was the most exciting part of the construction to this point because the hovercraft became 3-Dimensional. Now, where was I gonna keep it?

2010-02-19T09:41:00.001-08:00

This page is dedicated to a model hovercraft I'm building based on the last model hovercraft I built. The last one was successful enough but too heavy. This one is built from 1/2" 'pink' foam. I was a little more hasty building this one than the last and thus didn't pay as much attention to detail.

The small pictures below can be clicked on to see a larger image.

						As you can see, this model looks strikingly similar to the previous. In fact, it's pretty much identical in dimension. It's driven and controlled by the exact same equipment that drove its predecessor which I cannibalized for parts... not a pretty sight (RIP).
						This has the same dimensions as the last but I still had to make everything for the body from scratch such as the skirt, the motor mount, and the top. After contemplating for days how to attach a nylon skirt to a foam hovercraft, I finally decided to simply masking-tape the skirt to the hull. I've had this model running for some time and haven't had a problem with this method. That foam step you see in the middle of the craft is what the servo compartment rests on. I cut the foam parts with a hot wire and glued them together with epoxy. When the hull was complete, I glassed the outside with 1.45 oz/sq. yd. cloth and epoxy resin.
						I had to completely redesign the motormount to be foam-friendly. Basically, that required attaching it to a piece of 6"x6"x1/8" plywood with screws and then epoxying the assembly to the foam. Notice that the rudders are now mounted directly to the motor mount instead of on a seperate mount (one less part to break).
						This is a bottom view showing the base of the skirt attached to the hull via 1/8" x 1/4" basswood sticks used as the skirt attach strips. Currently, I epoxy a strip to the hull, lay the skirt over it, and then screw another strip to that strip. The problem is that the strips total over 1/4" high when I'm done. I'm probably going to modify this system by epoxying a 1/16" strip to the hull and screwing a 1/16" plastic strip to it to hold the skirt.
						This bottom view of the front-left corner of the model shows the 5/8" diameter air feed holes for the serial airflow system. I used contact cement to attach a circle of screen to the inside of the skirt so that debris is not allowed in.
						I made the top by cutting a styrofoam plug in the shape I wanted for the top with a hot-wire, glassing the plug with epoxy resin and one layer of 1.45 oz/sq. yd. fiberglass cloth. I then ran a strip of 6 oz/sq.yd. fiberglass tape around the outside edge of the outside edge to form a strong lip. After it had fully cured, I hacked the foam out with various sharp instruments and disolved the foam that remained with Acetone (nasty fumes... use a respirator and do it outdoors).
						This frontal view shows the large gash that I had to repair on the starboard side of the craft. The fiberglass is very light and rather strong but not strong enough to stop a falling hot-wire power supply. ;-)
						I forgot to take a picture of how I fastened the top to the bottom. I cut out pieces of plastic tubing, sliced them long-ways, and then 'clipped' the lip of the bottom to the lip of the top and stuck a pin through the tubing, top lip, and bottom lip to keep the clip from popping off. Seems to work.
						Here's a couple of views of the engine and engine mount. Notice that I'm using nyrod to actuate the rudders this time rather than a push rod.
						This is the fuel/electronics compartment. The servo on the right actuates the rudders and the servo on the left is for the throttle.

2010-02-19T09:40:00.001-08:00

This page is about the model hovercraft I've built recently. It's 24 inches long by 18 inches wide and is powered by an OS .40 FP nitro engine. The prop is a standard 10x6 model aircraft prop. The bottom is made from 1/4" marine plywood. The sides are made from 1/8" 'Masonite' board, the top is made from fiberglass, and the skirt is made from neoprene coated nylon (just like the big guys). Sorry, I'm not making the plans available at this time.

The craft utilizes an integrated lift/thrust system which passes air by 3 rudders while also into serial-feed bag skirt. The craft weighs in at just over 10 lbs wet.

I designed it to be as simple and easily as maintainable as possible. It uses standard model airplane starter, glow plug lighter, fuel system, servos, etc. I learned this lesson after trying to design my first few models too cleverly and would spend most of the time fixing things on them. With this one, I just crank it up and play. The only time it's really needed repairs is when I was flying it up a road and a wind gust blew it over... ouch! I haven't calculated the top speed or anything but I would estimate that it goes around 20 - 30 mph.

Nope, doesn't work on grass but Eric Goldstein is working on that problem. ;-)

Below are some pictures of the doo-hicky. Note that the pictures show that it doesn't have a propeller guard. These were taken during testing when I didn't have one installed. This craft will NEVER fly around the public without a propeller guard.

Here's where it all began. Notice the big-heavy duct which it won't have and the one rudder which is now three. Everything else actually went according to plan as you can see below. I even used the Autocad drawing to print out full-sized templates which I used to cut the sides and the styrofoam plug from which I made the top.

Here's a picture from the top. Notice the rudder push stick on the port side of the craft. The radio is an older Futaba 6 channel. Now, what am I going to do with the other 4 channels? Hmmmm... ;-)

This is a view of the receiver/servo/fuel compartment. I made it a recessed area in the hull which will theoretically be the last place to flood if the craft gets swamped or starts to sink for some reason. If I were ever to get really serious about using it over water, I would probably outfit this comartment with a sealed top and make it as watertight as possible. Notice the two servos. The one on the left is for the throttle and the one on the right is for the rudder control. The battery is to the upper right of the fuel tank and the receiver is to the lower left . The left line from the fuel tank is attached to the muffler to pressurize the tank while the right line goes to the engine carburator.

This is a view of the rudder assembly. The center pivot goes to the pushrod via an 'L' arm at the left rear of the craft. Each rudder control arm is just a regular collar used on model aircraft landing gear (to hold the wheels on) with an arm soldered to it. Simple and effective. The collars are pushed up hard against the rudder mount while the bottom of each rudder rod is set into a depression in the bottom of the craft. This keeps the rudders from moving around or coming out. You can see where the fuel tank lines attach to the engine.

This picture of the inside of the craft shows the white styrofoam which serves not only as flotation but also to direct air within the hull. Notice all the little holes in the sides? That's to feed air into a segmented skirt in the future (probably not gonna happen though). ;-)

This is a picture of the bottom of the craft which shows the holes through which air is fed into the cushion from the skirt. Also, you see the landing skids that keep the craft from tearing up the skirt when it comes off-cushion. The skirts are attached by using old windshield wiper inserts (with the wiper removed). The inserts are glued around the top of the sides and the perimeter of the bottom about 1/2" in from the edge. The skirt material is then placed over the insert and a wire is pressed into the slots thus trapping the skirt material. You can see one of these wires that I pulled up for the photo. at the lower left of the craft. A closeup of the corner is shown below.

Here's the closeup of the corner. The old glue spot just above the skirt attachment point is where I attempted to glue the skirt before. Forget it!

Here's a side view of the craft in action. The antenna is just a tube with the receiver's antenna wire fed through it.

Here it is coming at us at about 20 mph. My wife took this one so it's a little fuzzy (heh.. just kidding honey... ouch!).

Here's the one time the little craft has ever seen water. Skimmed right over it like there was nothing there. I feel pretty confident that it'll work on the real thing.

And it did! I took it up to Vega Reservoir and turned it loose from land where it hovered right onto the water and started skimming along nicely but making sluggish turns as compared to land. I then set it down on the water and then took off from a dead stop and found that it took quite a run to get over hump. This is most likely caused by the model being overweight and/or underpowered. Can't do much about the power since I'd like to stay with the current engine so I'm rebuilding the craft out of much lighter materials such as 1.45 oz glass fabric instead of 6 oz and 1/8" ply instead of 3/8" ply.

Transitioning from water to an island to water again.

Making a sharp turn.

Skimming straight towards us.

2010-02-19T09:28:00.001-08:00

HOVERCRAFT FAQ (Frequently Asked Questions)

By: Alex Olshove

V. 1.33

This FAQ will be updated as required and posted to ALT.REC.HOVERCRAFT 
at least once a month.  It is meant to be used as general reference 
by those not familiar with the hovercraft.  If you reproduce this in 
any way, I only ask that you give me some credit (unless it's bad). 
:-)


Contents:

1 This FAQ is completely sucky... how can I make repairs to it?
2 What is a hovercraft?
3 The Skirt
 3.1 What's the big deal about the skirt?
 3.2 What types of skirts are there?
  3.2.1  The bag skirt
  3.2.2  The segmented skirt
  3.2.3  The juped skirt
 3.3  Comparison between skirts.
4  The Engine
 4.1  How many engines does a hovercraft need?
 4.2  What types of engines can a hovercraft use?
5  Okay, a hovercraft sits on a cushion of air but where does the air 
come from?
 5.1  How many fans does a hovercraft use?  
  5.1.1  Single fan design
  5.1.2  Dual fan design
 5.2 What types of fans are there?
  5.2.1 Axial fans
   5.2.1.1 Ducted fans
   5.2.1.2 Propellers
   5.2.1.3 Propellers vs. Fans
  5.2.2 Centrifugal fans
6  How much does a hovercraft cost?
 6.1 What are some good sources for buying a hovercraft?
7  Where can I find plans to build a hovercraft?
8  Do you need a pilot license? Driver license? Any US states require 
licenses? 
9  Are there associations and conventions for hovercraft owners?
Clubs
 9.1  Conventions
  9.1.1 U.S.A.
  9.1.2 France.
10  Are hovercraft allowed on public roadways?
11 What companies manufacture hovercraft?
 11.1  Australia
 11.2  England
 11.3  Canada
 11.4  Holland
 11.5  U.S.A.
12  Where can I get more information about hovercraft on the 
Internet?
13  Can you recommend good hovercraft books to read?
14  Can you make a hovercraft stop and back-up?
 14.1  Reversible pitch fan
 14.2  Reverse bucket
 14.3  Transmission
 14.4  Puff ports
15  Can I insure my hovercraft?
16  Aren't hovercraft ‘handicapped’ when it comes to control
(stopping/steering)?
17  Do Hoverboards like in ‘Back to the Future’ really exist?
18  Where the heck to do I find 1/8” marine plywood!?!
----------------------------------------------------------------
 
>1. This FAQ is completely sucky... how can I make repairs to it?
 
 Just e-mail me at .  I'm not claiming to be an expert so 
there may very well be errors in this and I'll be happy to fix them 
or add more information if you want to set me straight. ;-)
 
>2. What's a hovercraft?
 
 I'm going to answer this question with a description of newer, 
popular hovercraft.  Perhaps I'll add a history lesson later with 
descriptions of peripheral jets, etc.
 
 A hovercraft is a vehicle which is suspended upon a cushion of air.  
The cushion of air is generated by a fan which is attached to an 
engine which is attached to the hovercraft.  The cushion of air is 
contained by a flexible sleeve called a 'skirt' that is attached 
around the perimeter of the craft to hold the air under the craft and 
thus upon an air cushion.  The craft is then propelled by whatever 
means is necessary to carry it forward.  A majority of craft simply 
utilize a ducted fan or a propeller attached to a small 2 or 4 cycle 
engine.  Be assured that pretty much every mode of propulsion known 
to man has already been tried from jet engines to sails.
 
 Control of a hovercraft is accomplished primarily through the use of 
rudders like the type used on aircraft.  The main difference would 
be, however, that hovercraft generally utilize many rudders rather 
than just one.  Another method of control is through 'puff ports' 
(see 13.1.4) or dual thrust fans where you would slow one down and 
speed up the other to turn in the direction desired. 
 
 
>3. THE SKIRT
 
 >3.1. What's the big deal about the skirt?
 
 The skirt is one of the most important parts of a hovercraft as it is 
the part that allows the hovercraft to clear obstacles.  Generally 
speaking, the higher the skirt, the larger the obstacle that the 
craft will clear.  However, if the skirt is too tall, the craft will 
'slide off' the cushion and the cushion will deflate or the craft 
will become extremely unstable.  This is not a FAQ on hovercraft 
design so I won't go into this in any more detail.  On larger craft 
(> 1 or 2 tons) the skirt is made of heavy, rubberized fabric.  On 
smaller, recreational craft, the skirt is made of neoprene coated 
nylon that weighs >= 8 oz/sq. yd.
 
 
 >3.2. What types of skirts are there?
 
 There are several types of skirts but the most common are the bag 
skirt, the segmented skirt,  and the jupe skirt.
 
  >3.2.1.  The bag skirt:
 
 The bag skirt is basically just that... a bag.  The bag skirt should 
probably be called a tube skirt because it consists of a tube that 
encircles the perimeter of the craft.  The bag is inflated which 
serves to lift the craft off the ground and more importantly, to 
contain the air cushion.  There are two methods of inflating the bag 
skirt, the first being serial feed and the second being parallel 
feed.  The serial feed method requires that air be directed from the 
lift fan _through_ the skirt and then out into the cushion.  The 
parallel feed method requires that a certain amount of air be split 
off of the lift fan into the skirt (about 10%) and the rest  into the 
cushion.
 
  >3.2.2.  The segmented skirt:
 
 The segmented skirt is also called a 'finger' skirt because it 
consists of several separate nylon segments that, when inflated, 
press together to form a shape that looks like fingers of a hand that 
are pressed tightly together (place your hand into a fist and then 
look at your knuckles).  Although much more complex to manufacture 
than a bag skirt, the segmented skirt offers much less resistance to 
obstacles and much more ease of repair when damaged since you only 
need to replace one or two damaged fingers instead of an entire 
skirt.  Segment skirted craft, however, are less stable than bag 
skirted craft (not necessarily a bad thing if you race hovercraft).
 
  >3.2.3.  The juped skirt:
 
 The jupe skirt (a.k.a. cell skirt)  consists of several cells that 
look like cones with their tops cut off and have their bases attached 
to the bottom of the craft.  When inflated, these cones readily 
support the weight of the craft upon a stable cushion.  A jupe 
skirted craft generally utilizes a minimum of 2 or 3 cells surrounded 
by a large jupe that encompasses the perimeter of the craft.  
Although a jupe skirted craft is very stable, it will experience 
difficulty when attempting to inflate the jupes on a rough terrain 
such a tall grass or deep gravel.  Jupe skirts also tend to scoop 
water in rough conditions and drag on grass.
 
 >3.3. Comparison Between Skirt Type (excerpt from 'Light 
Hovercraft Design' by Christopher Fitzgerald and Robert Wilson):
 
   Bag       Segment        Jupe
 
 Cost                low            high           low
 Labor               low            high           medium
 Drag
  smooth water       same           same           same
  Rough water        high           low            very high
  Mud                high           low            low
  Grass              high           low            medium high
  Ice                same           same           same
  smooth snow        medium         low            low
  rough snow         high           low            medium
 Reparability        hard           easy           hard
 Life                good           moderate       good
 Durability          good           poor           moderate
 Stability           good           poor           Excellent
 Plow in             same           same           same
 Roll ability for 
  turning            slight         excellent      none
 Dust and spray      poor           good           poor
 Colors available    limited        unlimited      limited
 Ease of attachment  moderate       easy           moderate hard
 Weight of skirt     low            moderate       low
 Hump performance    moderate       good           poor moderate
 High speed          good           moderate       moderate
 Bulkiness           poor           poor           good
 Appearance          moderate       good           moderate
 Bounce              poor           good           good
 Performance when
  damaged            moderate       good           poor
 Potential for
 development         good           good           good
 Over water rapid 
  take off ability 
  from long time 
  floating mode      poor           good           excellent
 Obstacle capability poor           good           poor
 Complexity          low            high           moderate
 
 
>4. THE ENGINE
 
 >4.1. How many engines does a hovercraft need?
 
 With the exception of human powered craft, a hovercraft needs at 
least one engine.  With a conventional hovercraft, air needs to be 
supplied to lift (to make the cushion) and thrust (to propel the 
craft).  The supply of air to lift and thrust can be accomplished 
using only one engine  by either powering a single fan and then 
splitting an amount of air off to lift (about 33%) and the rest for 
thrust (called an 'integrated' system) or the one engine can be used 
to power separate lift and thrust fans.
 
 Most hovercraft, however, use a dual engine system where one large 
engine is used for thrust and another, smaller engine is dedicated to 
lift.  Unlike the integrated system, this allows the craft to remain 
hovering while the thrust engine is turned off.
 
 Larger, commercial craft may use as many as 6 or 8 engines for power 
of the lift and thrust systems.  Engines types range from diesel to 
gas turbine.
 
 >4.2.  What types of engines can a hovercraft use?
 
 A hovercraft can use (and probably has used) any type of engine you 
can think of.  The main point of concern about the engine to be used 
is weight.  Obviously a high weight to power ratio is bad for a craft 
that is supported by a cushion of air.  Although an air cushion can 
support a massive load, that load must still be moved and accelerated 
from a dead stop (and then stopped again when need be).  Also, drag 
becomes more imminent as the weight of the craft increases.  So, you 
must try to keep the engine light and powerful.  Currently, the 
engine with the best power to weight ratio is the 2-cycle engine 
which is the primary engine used for racing hovercraft.  
Unfortunately these things are _generally_ noisy and temperamental.  
Also, they generally require a gear, belt, or chain reduction system 
to match the fan or propeller they are powering.
 
 A large majority of hovercraft utilize the heavier, but quieter, 4-
stroke engines.  Although these engines put out less power than a 
similarly sized 2-stroke engine, they are much quieter, don't require 
a special fuel-oil mix, and sometimes don't require a gear-down 
mechanism.
 
 Large, military or commercial craft will sometimes utilize jet 
turbine engines that put out thousands of horse power as well as 
large diesel engines.
 
 
>5. Okay, a hovercraft sits on a cushion of air but where does the 
air come from?
 
 The answer is 'fans'.  Fans are a very important part of a hovercraft 
whose primary purpose is to inflate the cushion contained within the 
skirt beneath the craft as well as to provide thrust with which to 
propel the craft forward.  For all intents and purposes, 'fan' in 
this text will be used to describe any air moving device.
 
 >5.1. How many fans does a hovercraft use?
 
 A hovercraft can use as many fans as the designer wishes.  In fact, 
the larger military and commercial hovercraft like the Bell Aerospace 
AALC Jeff (B) uses six lift fans and two thrust fans.  In the 
recreational hovercrafting world, however, most craft function on two 
basic designs. The single fan or the dual fan design.
 
  >5.1.1.  Single fan design
 
 In the single fan design, one engine powers one fan (or propeller).  
Most of the air generated by this single fan is directed rearward as 
thrust while a moderate percentage of the air (c. 33%) generated is 
split off and thrust below to charge the air cushion contained by the 
skirt.
 
  >5.1.2.  Dual fan design
 
 In the dual fan design,  one or two engines are used to power two, 
separate fans.  One of the fans is dedicated to the generation of air 
for the maintenance of the air cushion beneath the craft while the 
other is dedicated to the generation of air to provide forward 
momentum for the craft.  Typically, this configuration utilizes two 
separate engines but occasionally, you will see a system devised 
which uses only one engine to power both fans.  This often proves to 
be a more daunting task than using two separate engines as the 
mechanics involved may become very complex.  After all, you need to 
provide a constant speed to the lift fan while allowing the thrust 
fan's speed to be moderated. If not, the basic advantage of using two 
fans is lost.
 
 >5.2.  What types of fans are there?
 
 There are several types of fans that may be used  but the two main 
types of fans are axial fans and centrifugal fans.
 
  >5.2.1  Axial fans
 
 Axial fans are those that propel air parallel to their axis.  Of the 
axial type of fan, there are propellers and ducted fans.
 
   >5.2.1.1. Ducted fans
 
 Ducted fans typically utilize several blades that are generally wide 
at the tip and  taper towards the base.  A ducted fan may contain as 
few as 3 blades and as many as a dozen or more.  These fans need to 
be contained within a duct to realize their peak performance.  Some 
advantages of ducted fans include the ability to mount reversing 
mechanisms such as reverse buckets which direct air forwards when 
placed in the column of air generated by the fan.  Also, ducted fans 
are generally of a smaller diameter than propellers which can allow 
several fans to be placed side by side thus allowing for better 
control of the craft (speed one up and slow one down and the craft 
turns).  One more major benefit that comes from using fans is that 
fans are readily available from ventilation companies.  Ducted fans 
can be used to provide either lift or thrust.
 
   >5.2.1.2. Propellers
 
 Propellers typically utilize between 2 and 5 blades that are quite a 
bit longer than those used on ducted fans.  Although propellers are 
generally more efficient (and safe!) when placed in a duct, ducting 
is not a necessity as propellers will function well in open air.  
Propellers must be replaced if damaged by debris whereas a blade is 
replaceable on a ducted fan.  Propellers are generally noisier than 
ducted fans.  Propellers can be used to provide either lift or 
thrust.

   >5.2.1.3  Propellers vs. Fans.  (Note: This was 
taken from James Perozzo’s ‘Hovercrafting as a Hobby’ and is best 
viewed with Courier 10 font.)
 
    PROPELLERS  FANS
    
    More thrust/HP  No blade edging
    Less costly  More costly
    Noisy   Quiet
    Rotate fast  Slow Rotation
    Edge blades avail. Less blade erosion
    Large Diameter  Smaller diameter
    Must have a guard Duct is also a guard
    8’ and more diam. Only to c. 48” diam.
    Fast throttle resp. Slow throttle resp.
    Replace whole prop. Replace indiv. blade 
 
 
  >5.2.2.  Centrifugal fans
 
 Centrifugal fans are those that propel air perpendicular to their 
axis.  That is, they draw air in the center and 'fling' it out the 
side similar to the type used in hair dryers.  This type of fan is 
generally limited to use as a lift fan due to their orientation and 
relative bulkiness although some craft have been built that use 
centrifugal fans exclusively.
 
 
>6.  How much does a hovercraft cost?
 
 Depends on several factors.  A hovercraft could be build for less 
than $300 if you don't mind that it may only support 100 lbs and only 
goes 5 MPH.  However, if you need a craft that will support 2 adults 
over water at around 30 MPH, then you will probably spend in the 
neighborhood of $5000 for a pre-manufactured recreational craft.  If 
you can stand something that's used, you can get a good deal for 
between $1000 and $5000 for the same craft which will probably get 
you a trailer as well.  If you're handy with a saw and screwdriver 
then you could build one for less than $1000 or as much as you want 
to spend.  All in all, the cost boils down to the materials used to 
manufacture the craft (fiberglass or plywood?), the time spent, the 
engine(s) (Rotax 503 or B&S 12 HP?), the fan(s), the skirt (bag or 
segmented?), and the gadgetry (Radio? electronic actuators? 
elevons?).
 
 
 >6.1. What are some good sources for buying a hovercraft?
 
 The HoverClub of America's bi-monthly publication called 'The 
HoverNews' lists several good deals in the classifieds section in the 
back.  Also, there are a few hovercraft related pages on the Web that 
have a classifieds section.  You can also order a brochure directly 
from the manufacturers listed below.
 
 
>7. Where can I find plans for building a hovercraft?
 
 Why not design your own?  If you're not feeling that confident, then 
try the dealers listed below: 
 
 Sevtec Inc.
 PO Box 846
 Monroe, WA  98272.
 794-7505
 sevtec@aol.com
 Models:
 Scout  ($29)
 Vanguard ($44)
 Prospector ($48)
 Explorer ($62)
 Mariner ($92)
 http://members.aol.com/sevtec/sev/skmr.html
 
 Universal Hovercraft
 3rd Street Box #281w
 Cordova, IL 61242
 Phone / Fax (309) 654-2588
 Complete Catalog $2.00
 Too many plans to list
 http://www.hovercraft.com
 
 Databoat International, LTD.
 PO Box 1073, 8609 Fissile Lane
 Whistler, BC Canada V0N 1B0
 databoat@whistler.net
 Models:
 Neoteric Neova 4 ($143.50)
 http://www.databoat.com/27hover.htp
 
 Robert Q. Riley Enterprises
 Box 12294
 Scottsdale, AZ   85267-2294
 Phone: (602) 951-9407
 rqriley@netzone.com
 Models:
 Tri Flyer ($45)
 Pegasus ($35)
 http://www.netzone.com/~rqriley/plans.html
 
 
>8. Do you need a pilot license? Driver license? Any US states 
require licenses?
 
 Nope.
 
>9. Are there associations and conventions for hovercraft owners?
 
 Yes, here is a list of Clubs followed by some annual conventions.
 
 >9.1.  Clubs
 
 Australian Hovercraft Federation
 Michael Nell
 17 Fegen St.,
 Huskisson, NSW 2540, Australia
 Email: nell@mpx.com.au
 Title of Publication: Australian Hovercraft News
 Frequency of Distrbiution: Quarterly
 Cost of subscription: Australia AUS$20.00; USA US$25.00
 Contact: Tim pryor, Editor, Australian Hovercraft News [tpryor@mail.fairfax.com.au].
 38 Barnes Road, Frenchs Forest, New South Wales 2086, Australia
 
 Hovercraft Club of Canada
 10 Gold Crescent
 Russell, Ontario
 CANADA K4R 1B4
 Tel / Fax: (613) 445-3139 
 Bob Rennick  
 Title of publication: 'Hovercraft Club of Canada Newsletter'
 Frequency of distribution: Four times a year
 Cost of subscription: Membership in the club ($15/yr)
 http://www.peaceregion.com/hover/
 
 
 Hoverclub of America
 PO Box 908
 Foley, AL  36536-0908
 Phone: (334) 943-3279
 Title of publication:  'HoverNews'
 Frequency of distribution: Every two months
 Cost of subscription: Membership in the club ($30/yr).
 Http://www.hoverclubofamerica.org/
 
 
 Hoverclub of South Africa
 5 Marais Street
 Somerset West 7130
 SOUTH AFRICA 
 Title of publication:
 Frequency of distribution:
 Cost of subscription:
 
 
 Belgian Hoverclub
 Blvd St. Michel 78 1040
 Brussels
 BELGIUM 
 Title of publication:
 Frequency of distribution:
 Cost of subscription:
 
 RHONE ALPES AEROGLISSEURS
 Jean CLAUDE DELORME
 RUE DU MONT CINDRE ST 
 CYR AU MONT D'OR
 FRANCE
 Title of publication:  "POTIN d'AEROS"
 Frequency of distribution: bi-monthly (once every two months)
 Cost of subscription: 12 (Francs?)
 
 Hoverclub von Deutschland
 Lechfeld Str. 2
 Mering
 GERMANY 
 Title of publication:
 Frequency of distribution:
 Cost of subscription:
 
 Hoverclub of Great Britain
 Secretary: Mrs Brenda Kemp 
 Long Acre, Bingham, Notts, NG13 8BG 
 Title of publication:  Light Hovercraft
 Frequency of distribution: 
 Cost of subscription:
 Editorial contact: Jeremy Kemp 
 Long Acre, Bingham, 
 Nottingham, NG13 8BG 
 
 The Netherlands Hovercraft Club 
 Uiterdijksehof 5, 
 JK Nederhorst den Berg 
 HOLLAND 
 Title of publication: Hovercraft Sportnieuws
 Frequency of distribution:
 Cost of subscription:
 
 Japanese Hovercraft Association
 C/o SOREX Co. Ltd.
 KOUMENAKA
 Kumenan-cho, Kume-Gun
 OKAYAMA-KEN, 709-36
 Title of publication:
 Frequency of distribution:
 Cost of subscription:
 
 Hovercraft Club of New Zealand
 David Van Bysterveldt 
 Robinson Rd, 
 4, Paeroa 
 Phone 64-7-862-4793 
 NEW ZEALAND 
 Title of publication: Hover News
 Frequency of distribution:
 Cost of subscription:
 
 Wellington and Wairarapa (New Zealand) Hover Club
 Kerry Workman
 Harvard Grove
 Totara Park
 Wellington.
 New Zealand
 Phone: (04) 5267655
 http://www.voyager.co.nz/~arthurg/
 arthurg@voyager.co.nz
 
 Swedish Hoverclub
 Ollonvaegen 17
 Akersberga
 SWEDEN 
 Title of publication: Hover News
 Frequency of distribution:
 Cost of subscription:
 

 > 9.2. Annual Events
 
 There are many annual events around the world.  Here are some of them 
listed by country.  For more specific information, visit 
http://www.hoverclubofamerica.org/events.html courtesy of the 
Hoverclub of America.
 
   >9.2.1. U.S.A.
 
   What: West Coast Hover-In and Cruise
   When: July
   Where: Long View, Washington
 
   What: The U.S. National Cruise on the Wisconsin River
   When: August
   Where: Muscoda, Wisconsin
 
   What: Scioto River Hover-In & Cruise
   When: August
   Where: Chillicothe, Ohio
 
   What: Tennessee Hover-in
   When: October
   Where: Big Spring, Tennessee
 
   What: Texas Hover-In
   When: October
   Where: Dallas/Ft.Worth Texas
 
   What: 23rd National Annual Hoverally
   When: June 12,13, & 14, 1998
   Where: Troy, Ohio
 
 
   >9.2.2.  France
 
   What: The World Hovercraft Championship
   When: August
   Where: Luçon in the Vendée, France
 
 
>10. Are hovercraft allowed on public roadways?
 
 Nope.  And you probably wouldn't get very far if they were since most 
roads are 'humped' up in the middle to allow for water run-off.  
Unfortunately, this also causes air cushion vehicles to slide off to 
the side of the road since there is no friction to hold 'em on there.  
If you're a skilled driver, then you can counteract the sliding 
affect by directing the nose of the craft towards the center of the 
road and 'crab' sideways like you would during heavy wind. 
 
 
>11. What companies manufacture hovercraft?
 
 The companies listed below are categorized by country.
 
 >11.1.  Australia
 
 Airlift Supercraft (Aust) Pty.Ltd.
 Olsen Avenue
 ASHMORE, 4214
 Queensland
 Australia
 Phone: Australia 07 5527 8111 
 Fax: Australia 07 5527 8016
 Models:
 AS 400 Thriller
 AS 560 Hoverflyer
 AS 560U HoverUte
 AS 600C Mustang
 AS 600A Mustang Ambulance
 AS 8900 Pioneer
 AS 10600 Pioneer L(ong)
 AS 1200 Challenger
 
 TURBO Hovercraft Pty. Ltd.
 Vortex Hovercraft Pty. Ltd.
 Models:
 Turbo 235 Superwedge
225 Wedge
Vortex 245
Turbo 265 Super
Turbo 265 Hyper
Rocket
 
Revolutionary Technology
11 Mulberry Court
Eltham 
Victoria, Australia, 3095
(Owen Ellis designer of Rocket)
Models:
Rocket (seen by many at the last world championships)

 
 >11.2. England
 
 Pegasus Aviation
 Elm Tree Park
 Manton, Marlborough, Wiltshire, SN8 1PS
 ENGLAND, UK. 
 Tel. + 44 (0)1672 861578
 FAX. + 44 (0)1672 861550 
 pegasus@cccp.net
 Models:
 Cyclone PRIMO
 http://ayla.avnet.co.uk:80/pegasus/caprimo.htm#primo
 
 Bill Baker Vehicles
 
 Eagle Hovercraft
 
 Ingles Hovercraft Associates Ltd.
 Ingles Manor
 Castle Hill Avenue
 Folkestone, Kent CT20 2TN
 ENGLAND, UK
 Models:
 River Rover
 
 
 >11.3. Canada
 
 AeroTour Canada
 1279 boul. Hurtubise
 Gatineau, Quebec, J8P 7C2
 Tel.: (613) 762-3167
 Voice and fax: (819) 669-8454
 http://www.angelfire.com/biz/aerotour


 Canair Hovercraft Inc.
 O. Box 478
 Carleton Place, Ontario
 K7C 3P5
 Telephone: (613) 257-8332
 Facsimile: (613) 257-7948 
 Models:
 Canair 504L
 http://local40.pr.incentre.net/~hover/canair.htm
 
 
 Surface Effect Boats (S.E.B.) Enterprises Inc.
 Models:
 AirCat 7
 
 >11.4.  Holland
 
 Hovertrans B.V.
 Keizersveer 9
 LD HANK
 The Netherlands
 Telephone: +31 1622-3062
 Tel/Fax: +31 1622-3075
 hovertrans@pi.net
 Models:
 Colibri
 Hurricane
 
 HP Design 
 Uiterdijksehof 5 
 JK Nederhorst den Berg 
 NETHERLANDS 
 Models:
 Sprinter
 
 >11.5.  U.S.A.
 
 Hovercraft America
 N114 W18605 Clinton Dr.
 Germantown, WI 52033
 Phone: 414.253.9979
 FAX: 414.253.9033
 hover@execpc.com
 Models:
 HA-5
 http://www.execpc.com/~hover/index.html
 
 Hovercraft Concepts
 13910 SW 139 Court
 Miami, FL 33186
 305/256-8696
 FAX: 305/256-8698
 Contact: William Flett
 Models:
 SA 580
 Aerocruiser SA 1100 (price: $12,995)
 
 HoverDynamics
 JAKenney@aol.com
 Models:
 Starcraft RX2000
 
 GPL Enterprises
 Contact: Gary Lutke 
 Tangelo Terrace #A13 
 Delray Beach, FL 33444 
 Phone: (407) 274-2247 or (800) 541-7228
 Fax: (407) 276-4159 
 Models:
 Air Commander
 
 Neoteric Hovercraft Inc.
 Tippecanoe Street, Dept.. 12
 Terre Haute, IN  47807-2394
 Telephone: (800) 285-3761 
 Alternate Phone: (812) 234-3217 
 Fax Phone: (812) 234-3217 
 Hovercraft@delphi.com
 http://www.sapphire.com/UNCAT/uncat135.html
 
 Oregon Hovercraft
 27612 Crow Rd.
 Eugene, OR 97402
 Telephone: (541) 485-0588
 hiblerp@continet.com
 http://www.continet.com/hovercraft/
 
 Sevtec Inc.
 PO Box 846
 Monroe, WA  98272.
 sevtec@aol.com
 Models:
 Scout
 Vanguard
 Prospector
 Explorer
 Mariner
 http://members.aol.com/sevtec/sev/skmr.html
 
 Hovertechnics Inc
 Contact: Hugh B. Firminger 
 Box 257 
 St. Joseph, MI 49085 
 Phone:(616) 925-0025 
 Fax: (616) 925-6940 
 Models:
 HoverJet
 
 Weber Hovercrafts
 28728 Crabtree Corner Road
 Cuba City WI 53807
 vweber@mhtc.net
 Phone: (608) 744-3678: Verdon
 Fax: (608) 759-5704: Vernon
 Models:
 StarCruiser 1-4
 Price: $3400 +
 
 SCAT Hovercraft of Washington
 PO Box 4838
 Federal Way, WA  98063
 voice (206) 838-5005 or (888) NEW-SCAT
 
 New Mexico Scat
 P O Box 90575
 Albuquerque  NM  87199
 Dan Morris
 Phone: 505-828-2273
 
 St. Louis Hovercraft Rides Inc.
 P.O. Box 73
 Chesterfield, MO  63006
 Michael Murphy (MURHOVER@aol.com)
 Models:

 HoverStar
 HoverJet
 http://members.aol.com/MURHOVER/index.html
 
 
>12. Where can I get more information about hovercraft on the 
Internet?
 
 When I first started the Hovercraft Homepage, there was no, none, 
zip, zero, nada information about hovercraft on the Internet.  Now 
there are hundreds of web pages to access.  If you're too lazy to do 
an Alta Vista search, here are what I consider to be the main pages:
 
 http://www.olshove.com/HoverHome My Hovercraft Homepage.
 
 http://www.hovercraftersresource.com/  Kelly Jernigan's Hovercraft Resource.

 http://members.aol.com/sevtec/sev/skmr.html Barry Palmer's Sevtec 
page.
 
 http://www.hoverclubofamerica.org/ The HoverClub of America's 
Official Homepage.
 
 http://www-personal.umich.edu/~untitled/hover.html HoverTechnic's 
Page.
 
 http://www.ozemail.com.au/~ahf/index.html The Australian Hovercraft 
Federation Page.
 
 http://www.ils.nwu.edu/~eric/hover.html Eric Goldstein's page. 
 
 http://www.innotts.co.uk/~pault/hcgb.htm The Hoverclub of Great 
Britain Homepage.
 
 http://www.hovercraft.com  Universal Hovercraft.
 
 http://www.peaceregion.com/hover/ The Hovercraft Club of Canada 
Homepage.
 
 There is now one newsgroup relating to hovercraft called 
alt.rec.hovercraft.  If you don't see it on your local news server 
then please e-mail root@ (root@xoom.com or root@netcom.com, 
etc) and request that they start carrying alt.rec.hovercraft on your 
news server.
 
 An easy way to read and post to alt.rec.hovercraft is through a 
service called DejaNews.  You can get to this service via your web 
browser by entering http://www.dejanews.com as the location.  When 
you get there, you can simply enter ‘alt.rec.hovercraft’ in the edit 
box marked ‘Type a specific question or topic:’.
 
 I have the capability to start a mailing list but I want to see how 
the news group does for awhile before I consider maintaining such a 
pain in the hoo-ha.
 

>13. Can you recommend good hovercraft books to read?
 
 Sure thing.  In fact, these were the primary sources for this FAQ 
(other than from my noggin that is). ;-)
 
 Title:  Hovercrafting As a Hobby
 Author: James Perozzo
 Subject:  All aspects of hovercraft design for recreational use.
 Available From: Twin Peaks Publishing; 30455 Kent-Blk Diamond Rd., 
Auburn, WA 98092. (253) 631-7347.
 NOTE: The author has passed away and this book is out of print.  If 
 you can get a copy, it’s a good book for beginner to intermediate.
 
 Title:  Jane's Surface Skimmers
 Author: Jane's USA
 Subject:  General hovercraft reference.  Lists darn near everything 
 ever built.
 Available From: http://www.janes.com/.
 Your best bet for getting your hands on one of these rather expensive 
references is to search for a used one through a book exchange.
 
 Title:  Light Hovercraft Design
 Author(s): Christopher Fitzgerald and Robert Wilson
 Subject:  General hovercraft design reference.
 Available From: The Hoverclub of America.  See above for contact 
information.
 
>14. Can you make a hovercraft stop and back-up?
 
 Yes, although it requires some mechanical wizardry since no part of 
the craft is in contact with the ground.  This is generally 
accomplished via reversible pitch fan, 'reverse bucket', 
transmission, or 'puff ports'.
 
 >14.1.  Reversible pitch fan
 
 A reversible pitch fan (or propeller) is a fan that allows the 
operator to physically reverse the pitch of the fan blades thus 
reversing the flow of air forward thus slowing and/or reversing the 
direction of the craft.  These are mechanically complex and are not 
useful in a craft of single fan design (see 4.1.1.a) since the 
reversing of the airflow would essentially create a vacuum in the 
cushion and suck the craft to the ground.
 
 >14.2.  Reverse bucket
 
 A reverse bucket is placed, mechanically, directly rearward of the 
thrust fan to redirect it's airflow forward via a curved surface when 
the operator wishes to slow the craft or stop.  Although this method 
is much simpler than a reversible pitch fan, the bucket adds weight 
to the rear of the craft in addition to the engine, duct, fan, and 
rudders.  Also, reverse buckets are only useful with smaller diameter 
fans.
 
 >14.3.  Transmission
 
 A transmission is sometimes as complex a solution as a reversible 
pitch fan.  As in an automobile, a transmission reverses the rotation 
of the fan and is attached to the driveline between then engine and 
the fan.  A transmission may utilize gears as in an automobile or 
belts as in a 'mule drive'.
 
 >14.4.  Puff ports
 
 Puff ports are apertures through which air is redirected from the 
lift or thrust system to the front or sides of a hovercraft.  When a 
puff port is opened, the air is allowed to flow out of the craft in 
whatever direction the operator desires.  Realistically, puff ports 
are only useful at slow speeds since they often lack the ability to 
pass air at a sufficient velocity to counteract a craft with much 
momentum and are used primarily for low speed maneuvering.
 
 
>15.  Can I insure my hovercraft?
 
 Currently, insurance for hovercrafts is very difficult to obtain (in 
the USA anyway).  Most insurance companies don't even know what a 
hovercraft is but may insure your craft as a boat
 
 
>16.  Aren't hovercraft  ‘handicapped’ when it comes to control 
(stopping/steering)?
 
 Nope, we prefer to see those as "limitations of frictionless motion".  
It could as easily be said that automobiles suffer from the handicap 
of not being able to move over water or that boats suffer the 
handicap of not being able to transition to land travel.  The primary 
advantage of the hovercraft is that you can fly them over any 
relatively flat surface on land, snow, mud, water, swamp, peat bog, 
river, etc.  They are being used more and more often for rescues, 
ferrys, and general grins (_big_ grins).
 
 Advances are gradually being made in control.  We've learned, for 
instance, that a tighter, more controlled turn at speed can be made 
by tilting the hovercraft to one side and banking it through a turn. 
This can be accomplished by operator weight shift, elevons, or 
cushion control mechanisms.  The resulting control starts to approach 
that of your average speed boat on full plane and exceeds that of 
your basic automobile on an icy highway. ;-)
 
 Braking is accomplished fairly effectively through the use of thrust 
reversing mechanisms such as reversible pitch propellers, and reverse 
buckets.
 
True, hovercraft don't offer the best response times for braking and 
steering as water plows (boats) and automobiles but owners/operators 
of hovercraft would agree that the advantages of hovercraft travel 
outweigh the disadvantages which, by the way, are adjusted to as the 
operator gains experience.


>17. Do Hoverboards like in ‘Back to the Future’ really exist?
 
Figure it this way.  An axial fan puts out only so much lift 
per horsepower.  In hovercraft terms this is measured in pounds per 
square foot.  A good lift system will produce 10 lbs per sq. ft.  
Multiply the the area of the hovercraft by the lbs-sq-ft for a rough 
idea if it will work or not.  How big is the hoverboard?  1' x 4' ?  
That is 4 square feet.  With a good lift system you will have 40 lbs 
of lift total.  Now, how much do you weigh?

Note:  This explanation was graciously provided by Dave Galka who is 
the editor of HoverNews for the Hovercraft Club of America.  In 
summary, a 1’ x 4’ board is capable of supporting about 40 lbs.  
Unfortunately, most humans weigh much more than this.  Sorry, but 
hoverboards will not be a possibility unless a seriously powerful 
power source can be devised.  Preferably one that can supply at least 
40 lbs per square foot and still fit within the confines of 1’ x 4’.

>18. Where the heck to do I find 1/8” marine plywood!?!

Okoume is a fairly common mahogany 3-ply marine plywood available 
from numerous sources. It is light, bends easily and is moderately 
durable.  Below are some suppliers:

M.L. Condon Co., Inc.
260 Ferris Ave.
White Plains, NY  10603
914-946-4111 
914-946-3779 (fax)
Marine grade okoume - 3 mil, 4x8 $40 / sheet

Edensaw Woods, Ltd.
800-745-3336
PortTownsend, WA
www.olympus.net/edensaw/
Marine grade okoume - 3 mil, 4x8 $37 / sheet

Boulter Plywood Corp.
24 Broadway, Dept WB
Somerville, MA  02145
617-666-1340 
617-666-8956 (fax)
Marine grade okoume - 3 mil, 4x8 $39 / sheet

Harbor Supply
1401 Russell Street
Baltimore, MD  21230
800-345-1712 
410-752-0739 (fax)
Exterior grade okoume - 3 mil, 4x8 $24.68 / sheet
Marine grade okoume - 3 mil 4x8 $53.20 / sheet

2010-02-19T09:27:00.000-08:00

This page is dedicated to the construction of a simple and inexpensive hovercraft that can be built as a science project at your school. It supports a reasonable amount of weight and operates indoors using an electric leaf blower for power. I am not the original designer but received the instructions to build this from students from several schools that have built this hovercraft as their science project. This hovercraft was demonstrated recently by 'Bill Nye The Science Guy' on a morning show called Kathy Lee and Regis.

Materials: 1/2" plywood sheet 4.0' X 4.0': 6.0 to 7.0 mil plastic sheet 5.0' X 5.0': 3/8" carriage bolt 1.0" long: roll of duct tape: large washer such as a plastic lid: Lift air supply (a leaf blower): propulsion system (optional):
CLICK ON THE IMAGE TO THE LEFT FOR A LARGER IMAGE.
						Cut the plywood into a 4.0' diameter circle.
						Drill a 3/8" hole in the center of the plywood for the carriage bolt.
						Drill a second hole 1 foot from the center of the plywood to fit the air supply nozzle.
						Sand all sides and edges of the disk to remove splinters and sharp edges.
						Lay plastic sheet on plywood disk and cut about 6 inches larger than the disk.
						Use your plastic lid as a washer and place the bolt through the lid, the plastic sheet, and the plywood disk (through the center hole) and place a nut and washer on the other side to secure all the parts together.
						Tape the edge of the plastic securely around the outside edge of the disc and then staple through the plastic into the edge of the plywood disc to secure the plastic.
						Cut about 6 2" holes in the plastic about 6" from the center of the disk. These are to allow a small amount of air to escape on which the craft rides.
						Secure the air supply nozzle in the hole you made for it in the plywood disk.
						Turn on the leaf blower and have fun! ;-)
						WARNING: IF YOU USE AN ELECTRIC LEAF BLOWER, DO NOT ATTEMPT TO OPERATE THIS PROJECT ON WATER! OPERATING ON WATER WILL PRESENT A SHOCK HAZARD THAT COULD RESULT IN DEATH.

After skinning the bottom, next was the construction of the lift duct. The actual duct was made by wrapping 1/8" ply around two plywood disks. The duct lip was constructed by forming styrofoam into a shape that pleased me while clinging to the ambiguous description in the plans. A belt sander was used to form the styrofoam. The plans called for blue, closed-cell, styrofoam which was $25/sheet compared to white bead styrofoam at $15/sheet. Budget tight... white styrofoam cheaper... White styrofoam it is! Kind of made a mess but came out okay in the end.

The duct was then 'glued' to the styrofoam using that canned expanding styrofoam. Works great and fills gaps that might have occured in the mating. At this point the duct was just hanging off the styrofoam and had no other support.

Oh yeah... that rope hanging down attached to that green cable was where I decided to store the thing. Hanging from the ceiling of my garage as seen in the pic to the right.

This is a view from the bottom of the duct after cutting and fitting 1/8 plywood from the bottom of the duct to the main stringers and rib 3. This serves to give the duct support. The pulley apparatus I use to store the craft also serves to support the craft for jobs like this.

The plywood strips where then fiberglassed to each other, rib 3, and the main stringers. In this shot, notice that the landing skids are in place and the seams on the bottom have been fiberglassed to seal them against water. Also, note the inside skirt attach strips visible here.

Next is the attachment of styrofoam blocks around the outside edge of the duct to serve as the rest of the duct lip. Then the inside of the craft was painted to protect it against standing water and the flotation jugs were installed.

The top of the nose was then glued and stapled over the lip and the lip was sanded smooth. After the lip was sanded, the disks were kicked out. It's not perfect but I think I did a pretty dog-gone good job. :-)

Finally, I Installed the lift motor mounts and the air splitter and fiberglassed over the styrofoam.

2010-02-19T09:22:00.001-08:00

This page is dedicated to the Universal Hovercraft UH-12R that I built in my garage way back in 1995. It all started when I purchased Universal Hovercraft's catalog for $2 August 20, 1995. I then decided on and purchased the plans for the UH-12R shortly thereafter and started contsruction in early March of 1997 and put $40 into the project every two weeks.

The small pictures below can be clicked on to see a larger image.

The 12R's Performance Data (from catalog)

 Capacity:  1 to 2 persons
 Payload:  500 LBS
 Length:   12 1/2 ft.
 Width:   6 ft.
 Empty Weight:  375 lbs.
 Flotation:  1400 lbs.
 Hover Height:  8 inches
 Speed:   60 MPH
 Climb Gradient to: 60%
 Thrust:   200 - 350 lbs
 Const. Cost:  $500 - $1500
 Const. Time:  100 - 200 hours
 Engines:
  Lift:  8 HP Briggs
  Thrust:  Polaris 440 twin cylinder (55+ HP)
 Thrust Prop:  48" UH
 Lift Fan:  30" UH

The 12R's Construction

						This is a partial scan of the 12R plans and only shows the side view. The full sized plans show a top view, a front view, and a side view as well as rib layouts on the first sheet and a second sheet containing details on mechanical structures. I've run into some ambiguity on the plans regarding the layout/shape of the lift duct, the location of the skirt attach strips, and the attachment of the rib 1 at the front of the craft. In my opinion, the plans need to show more detail of the front of the craft.
						Construction of the Frame.
						Construction of the lift duct.
						The Hull.
						Construction of the thrust duct.
						Construction of the control surfaces.
						Construction of the lift system.
						Construction of the thrust system.
						Miscellaneous contruction details. Hot-wire, lift engine, etc.
						Pictures of the 12R in action.