Rascal Mini Airboat

We’ve built a simple airboat called the “Rascal” to demonstrate the performance you can expect from one of our Predator 22 hp reduction drive packages on a mini airboat. This is a very quick and simple boat, made entirely of 1/4″ and 1/2″ plywood, with fiberglass taped joints and edges. It is 10 ft long, with a bottom width of 5’3″ and a beam of 6’1″. It has 15″ tall sides and built-in buoyancy foam for added safety. We’ll be powering the Rascal with the Predator 22 hp engine from Harbor Freight, along with our standard V-belt reduction drive and 59″ 3-blade propeller combo. We’ll be doing some payload tests soon, so you can know what kind of performance to expect from the Predator 22 in a small airboat.

NEW! Download a free copy of the Rascal Mini Airboat plans and build your very own 1-2 person airboat!

Check out this video of the Rascal Mini Airboat in action, then scroll down to see how we built it.

Construction Photos:

These are the main hull skins laid out on the shop floor. This is inexpensive 1/4″ plywood, with the large pieces made oup of two pieces of plywood butt-jointed together with a thin strip of plywood glued over the joint for reinforcement.
The 1/2″ plywood bulkheads and transom have now been added. We use CA glue to temporarily hold the plywood parts together before we fiberglass tape the edges. It’s a very simple and easy way to build a boat, similar to the popular “stitch and glue” technique.
Another view with two transom braces bonded in place. You can see we’ve also started to bend the bottom skin upward at the front of hte boat to match the sides.
The hull is now fully assembled, interior seams have been fiberglass taped, and we’ve painted all exposed plywood with polyester resin to seal it.
We used gray rustoleum oil-based paint to cover the inside of the hull. We also added some flakes for appearance and some anti-skid powder to make the surface less slippery when wet.
A zoomed out view of the hull with painted interior.
Here you can see the rear and corner braces on top of the transom and the top deck on the very front of the hull. These elements make the hull much more rigid and provide a good place to mount lifting handles and a tow hook.
We’ve now flipped the hull to finish the underside.
We first filled gaps and corners with a polyester/glass microsphere putty, and round over all the edges.
Now all the edges have been taped and we’ve started coating the entire underside with a layer of polyester resin to seal and protect the bottom. A cheap 6″ roller with short nap works great to spread the resin.
Another view of the partially coated bottom.
The resin has now fully cured, and it’s time to trim any overhanging tape.
We scuffed the bottom with a random orbit sander to give the primer something to bite into.
The bottom hull primed and ready for paint. We used Zinsser oil-based primer, which adhered well but didn’t lay out quite as flat as we had hoped.
Now for the fun part. We chose Hunter Green rustoleum oil-based paint for the bottom. It went on very smoothly with a brush and leveled out nicely.
After giving the paint a couple days to cure, we applied two coats of min-wax oil-based polyurethane to protect the paint. This isn’t as tough as many of the slick coatings people use on airboats, but we don’t anticipate running the boat over grass or dry ground, so we mainly just wanted a little protection during trailering.
This is the engine stand and seat mount, welded up from 14 gauge steel tube, and primed and painted with matching hunter green.
Test fitting the engine stand in the hull. The shims beneath the front legs are to elevate the bottoms of the legs about 1″ above the deck so they’re never sitting in any pooled water.
The top of the transom and the rear corner braces have now been painted hunter green to match the rest of the hull.
We next drilled holes in the deck to add the buoyancy foam. After some experimentation, we recommend simply using a 4″ thick layer of extruded polystyrene foam (pink or blue insulation boards) between the hull and deck as it is lighter and easier to work with.
Test-fitting the Predator 22 hp engine for the first time!
Test fitting the reduction drive and upper pulley so we could check propeller clearance. We decided to go with a 56″ propeller and needed to raise the engine 1″ to provide propeller clearance over the transom.
This is the rear hoop of the propeller guard. We constructed the guard with 1/2″ electrical conduit. The bottom ends of the hoop are attached to the transom with conduit straps and bolts going through the transom. The 1/2″ spacers you can see between the hoops and transom are made of 1/2″ thick UHMW plastic.
We’ve now bolted on the front hoop of the guard, also made of 1/2″ conduit. We bent the hoops using the tubing roller from Harbor Freight and have had good luck with it after making a few small adjustments. Both of the hoops were too long to be made from a single piece of 10 ft conduit, so we joined two pieces at the tops of the hoops using conduit junctions.
We made to platforms from 1/2″ plywood to mount the seat, controls, fuel tank, and exhaust. We ended up relocating the fuel tank beneath the seat to place it further from the hot muffler.
A rear view showing the engine stand. We ended up hanging the Predator 22 muffler from the rear plywood platform on the engine stand.
We’ve now added braces between the two guard hoops. The top brace is positioned diagonally to reduce the tendency of the hoops to wobble back and forth relative to each other.
We’ve now added a smaller hoop going directly over the engine, with two braces two braces running upward to the front circular hoop at about the 10:00 and 2:00 positions. We also have a horizontal tube holding the upper rudder mounts. We’re using the same molded fiberglass rudders and hardware that we use on our Phoenix hovercraft.
Front view showing the nearly complete propeller guard setup.
We’ve used cable ties to attach guard mesh to the outside of the guard. We used standard 1″x1″ welded galvanized mesh. We recommend a strong mesh at least this fine around the perimeter of a propeller.
The excess mesh is now trimmed form the back of the propeller guard. Note the headers made from flexible 1-1/4″ tubing running from the exhaust ports to the muffler beneath the engine stand.
In this picture from the back, you can better see how we relocated the Predator muffler. We simply used an angle grinder to cut the exhaust flanges off the of the muffler and used our own custom exhaust flanges instead. The flexible tubing is 1-1/4″ OD.
Final installation of our reduction drive and propeller. This is the our banded V-belt economy setup, except on the Rascal we’re using the 1.9:1 reduction ration instead of the standard 1.68:1 reduction ratio so the boat will run a little quieter.
At least during testing, we’re using heavy duty nylon 2″ netting for the front propeller guard. It is very light, strong, and easy to work with. This is a picture before we trimmed the excess netting around the edges of the guard.