Here are some directions on how I build my homemade hovercraft.
Supplies
1-piece of 3/8 plywood. This was the thinnest I could get. If you can find some thing thinner
or lighter use it.
Some 2x3's
Some Marine grade vinyl for the skirt. I got this at a local fabric store for under $20.00.
A seat. I used a milk crate.
Chicken wire. Home depot. 1/4" holes.
Two small engines:
For the lift I used my backpack leaf blower. As is unmodified. I just took the tube off.
For propulsion I used a 2-cycle snowblower engine. I think its about 2.5 H.P.
A model airplane prop. I got it of Ebay for $12.00 with shipping. Its 22" with 10 pitch. You will
have to experiment with this. You want your engine to run at full RPM at full throttle. If the engine is running to fast you
want a higher pitch or longer prop. If the RPM's are too low you need a lower pitch or shorter prop.
Some misc hardware
You can click on any image to make it larger.
Frame
I cut the ply-wood to 6 1/2' x 4'. This turned out to be a little too short for me. This depends on the amount of space
the engines and the seating area take up. You want the craft balanced from end to end. Mine is a little too heavy at the back.
If it was a little longer I could move the seat a little foward to compensate.
I cut two 2x3's the length of the ply-wood (6 1/2') and two about 20" for the cross pieces. This is for the top frame
rails. I'm using a milk crate for the seat so these pieces are designed to support it. You can see in the picture the two
cross pieces are directly under the crate for support. I was originally going to use an old aluminum ladder and just cut it
down. This would probably be lighter than the wood. This frame was then attached to the top of the ply-wood. You can then
mount anything you need to along this frame.
I put four holes in the plywood for the lift air to get through. I used a plastic container upside down over the holes
and fed the back pack leaf blower into this container. These holes can be anywhere. You can use wood to build a box or just
PVC pipe to get the air from the leaf blower to under the hovercraft. I just used what I had around. I also didn't want to
modify my leaf blower. It is just stuck into a hole in the container and screwed to the deck with two sheetrock screws so
I can use my leaf blower if I need to.
I've done a lot of reading and experimenting with building this hovercraft. In my opinion a cage blower type unit is
the best for the lift. They move a lot of air at a low pressure. There are books I've found on Ebay that explain how to make
them and the formulas for specific needs. The leaf blower I'm using has no problem liftiing a 200lb+ person 6" off the ground.
Rudders
The hovercraft rudders aren't too difficult to do. I just used some thin plywood, thin threaded rod, thin rope and
some small pulleys. I attached some small blocks to the plywood and drilled holes through it for the threaded rod. Then the
threaded rod goes through holes in the engine stand. There is also a connecting rod accross the top rear of the rudders to
keep them together. There is an arm sticking out the front of the bottom of one rudder to connect to the control rope. It
has a little eye hook on the end and I tied the control rope around it.
The control rope then goes through the pulleys to the control stick. The control stick is attached to the deck with a
basic hinge. You can connect the control rope right to the stick but I would recommend putting springs on the end of the control
rope and attach them to the stick. This will provide a little play and prevent damage if some thing gets jammed. The length
that the arm sticks off the rudder and the distance you connect the control rope to the control stick away from the pivot
point will affect the response of the rudders. You can easily experiment with this. You want the rudder to move to full deflection
in both directions while the control stick moves side to side in reasonable distance.
I think it would be easier to mount the rudders using hinges than the threaded rod route I used. I just didn't have them
and had the other stuff on hand.
The skirt in some of the picture is just a shower curtain that was reinforced with duct tape. I used this to experiment
and it worked better than I expected.
This is the bottom. I just cut two 2x3's for the skids. They are directly under the top rails and short enough so the
skirt can't go under them. The Hovercraft will land on these so you don't damaged the skirt when its sitting on the ground.
This is the Propulsion engine. I built a little table like stand for the engine. This is all mounted to the rails. I
then built a cage around the prop. For safety reasons I wouldn't think of not doing this. I was originally going to just use
a box fan for this. A new box fan is about $15.00. Just remove the motor and blade and mount it so its around the prop. I
broke the grills on mine before I finished it so I just built a frame and covered it with chicken wire. Using a box fan frame
would be a lot lighter.
The engine is from a snowblower. I believe it about 2 1/2 H.P. It came with a shaft about 6" long with a pully on the
end. There was also a threaded hole in the end of the shaft. I bought a model airplane prop on Ebay and used a bolt to mount
it to the end of the shaft. Make sure the prop is spinning the right direction. I've tried several prop and motor combos and
this one worked the best. For the throttle I used a throttle lever and cable from an old lawn mower. Connect it directly
to the butterfly on the carb. Don't use the governer on the engine. To make sure the engine runs right, try to mount the gas
tank in the same height relation to the engine as originally done. Some engines have a fuel pump, a pressure line to the tank
or just use gravity to feed the gas. Changing this configuration too much could affect it. I also put the engine shut off
switch where it could be easily reached.
Skirt
The Hovercraft skirt I used on this craft is just a simple bag skirt. This is by far the easiest to make but it does
have disadvantages. It will only go on a smooth surface. I live on a lake and use this on the ice during the winter and I've
used it on pavement just fine. This type of skirt will even have trouble on grass.
To make it I laid it out under the craft flat. I traced out the outside of the hovercraft with a marker. Then I measured
out from this mark an equal amount all the way around and marked it. You can experiment with the measurement. You can always
make it smaller but if its cut your stuck at this size. I think I measured out about 3" all around from the original
mark. Then the outside mark on the skirt is the mark I used to attach the skirt to the hovercraft. Some pictures show that
I attached the skirt by screwing small wood strips around the top of the hovercraft. The other pictures I just stapled the
skirt to the hovercraft deck. These have lasted a lot longer than I thought they would.
After the skirt is attached to the hovercraft I marked out an oval on the bottom of the skirt in the center. I cut it
out and then tested it. Start up the lift engine and see how it looks. I cut my oval several times at 1" intervals till it
looked good. If the hole is too small be ready to shut the lift engine fast. It will blow out the skirt or buldge the pylwood
to the point of cracking. After experimenting with the hole I managed to get it to the point that the hovercraft would just
barely hover with the leaf blower was at idle and raise up completly without buldging the plywood at full throttle.
Whenever you've got a good size and shaped hole you want to make sure the Landing skids will be clear of the skirt.
