Hull Construction
Lift Duct Thrust Duct
Before you begin building the hull you will want to read the "General Hovercraft Construction" booklet that comes with your plans. This booklet was written by Bob Windt. It would be difficult to understand the steps that must be taken in the blueprints if you don't read the book. I began my UH-13P by building the prop & fan, then the rudders, and several of the small parts on the blueprints. I did this because I knew that when I got close to completion I would be VERY anxious and not want to take the time to build the parts properly. I bought the Styrofoam at Menards. It was about $14.00 per sheet for the 2". I then ordered 7 sheets of 1/8" OKUME marine plywood, delivered to my door was $38.00 per sheet. I wanted it here when I was ready for it. I ordered 1 more sheet than the plans called for in case I made a mistake, I did not want to be short.
Styrofoam Layout: Follow the plans as far as lapping so you don't get 2 seams on top of each other. Styrofoam has many imperfections that to not allow perfect contact with the two surfaces. When I build the next one I will sand the entire piece to take the "sheen" off and would sand the edges square. Once you have it dry fit, mark the pieces on the edges before you dissassemble and epoxy both sides that will be mating. I used about 20 concrete blocks for weight. This worked OK. Next time I would vacuum bag this to provide pressure throughout the hull. You can use epoxy (I did) or I have heard of some using expanding foam between the sheets. ( this may cause an uneven surface due to expanding. (Just my theory)
If it isn't perfect don't worry. It is easy to become fixed on everything being perfect. For allot of this stuff it just doesn't matter.
Picture above should be a hull with screws showing the layout of the nose of the craft.
Laying out the bow. I used a string and used 3" screws to keep halving the distance between them. I placed one at the tip Dead center and one on each side where the taper begins. (Plans) Then by using the 3" screws I would twist them in with my fingers at the midway point between the side & nose. I continued 1/2 ing the distance until you see the picture above. Then I used a fine tip marker to draw the line. When I measured the line I was within a 1/16 ".
Cutting it out. I used a sawsall. A keyhole saw or a jigsaw with a long blade would work good too. Do not try to get to close to the line. I used #60 grit self stick sandpaper stuck to a 2X4X12". This sander will remove allot of Styrofoam fast & accurately. Bring it down to the line by hand.
Another tool that is an absolute must is a carpenter's Rasp. It is a metal file for wood. I used it to shape many different parts on the hull. It removes allot of material faster than the sandpaper but cannot be used on large flat areas.
The shape is done. This took about 1.5 hrs to layout the bow, cut and sand. Do not worry about little holes, bumps, small gouges, etc. in the styrofoam.
You can see the wood block with the sandpaper on the hull.
Epoxying the 1 3/4 tack strip to the outer edge of the foam. I used twine to wrap and hold the wood in place. With one person on each side of the craft toss the twine over the top then under and back to the other person, one guy hold pressure on the twine while the other passed the twine. Once the passer grabs tension the other guy can release and grab the twine and pass. The bungees at the rear are to attach the rear tack strip and as a bonus they also hold tension on the rest of the twine.
On the bow I used screws every 8" or so to hold the twine from slipping forward.
Bottom of Hull. Landing skids 3/4" X 1" are attached with epoxy and placed 11" in from outer attach strip. The more accurate the 11" is the easier to install the skirt later.
Bottom of craft
This shows the 1 1/2 " rear inside tack strip for the skirt.
Need to add another 1 1/2" pine to the front of the craft. I could not find this in the plans.
You can see the board added to the front here. It ends where the taper comes together.
The bow should be ground down from the bottom of the top 1 3/4" board and tapered back. I did not do this. I did not understand until I was to far into it. It has not made any noticeable difference in the performance.
The blocks here are used to hold in place while I finish epoxying the rest of the ply. I will remove them when I bag it.
I used 8' house wrap plastic, 3 mil. I laid it lengthwise and folded it over at the rear and taped it at the sides and left the opening at the bow for the vacuum.
Ignore the vacuum pump looking thing...It did not work. I used the vacuum hose attached to it with a sears vacuum.
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