Hull Construction

The UH-10F trailer loaded with the raw materials for the Rip Tide hull, including 8 sheets of 2″ thick extruded polystyrene foam and 6 sheets of 1/8″ plywood.
Laying out the foam for the first layer of the hull. A 3/4″ square strip of wood is being used lay out the desired hull profile.
The first layer of the hull foam has now been cut out.
Using the first layer of foam to mark the outline on the second layer of foam. The sheets have been arranged so that joints between sheets in the two layers are as far apart as possible. This eliminates the possibility of a weak point in the hull.
Laminating the two foam layers one sheet at a time using weights. Vacuum bagging results in a superior bond, but moving fast enough to vacuum bag a hull this size without help is very challenging.
Using cinder blocks to hold the outer skirt attach strip in place while it is epoxied in place. The strips were made by planing down 1×4 boards to 3/8″ thickness.
The top of the hull tapers down on the sides, giving the hull increased longitudinal strength due to the stressed plywood skin.
Another view of the hull, ready for the 1/8″ plywood skin to be bonded to the top. Four 1×4 boards have been bonded into routed pockets in the hull as anchor points for handholds and tie downs.
A thin but uniform layer of epoxy has been spread over part of the foam with a squeegee. The edges of this glue operation have been taped to reduce problems cleaning up squeeze out.
Laminating one of the 1/8″ birch plywood sheets to the top of the hull. Special care and added weight were necessary near the sides where the plywood had to conform to fairly sharp curves.
The decked hull. The hull is very rigid despite being 17.5 feet long and consisting of only two layers 2″ pink foam and a single layer of 1/8″ plywood.
An additional layer of 2″ foam is added to the bottom for added rigidity and buoyancy, and to provide anchor points for the lower skirt attach strip.
Two pieces of 3/8″ plywood are bonded into routed pockets on the rear underside of the hull to provide a solid underside anchor for the bolts that will eventually hold the engine stand in place.
An additional sheet of 1/8″ plywood on the rear underside of the craft, and a thin 1/8″ plywood strip has been run around the perimeter of the craft to anchor the lower skirt attach strips.
Unfortunately, epoxy squeeze out prevented me from getting smooth plough plane cuts with a hotwire, so I instead cut the plough planes with a hand held belt sander.
A reciprocating saw is used to cut the hole for the lift duct.
After the lift duct has been bonded in place, the underside edges are sanded into a smooth transition into the hull and fiberglassed.
More fiberglass covering the remaining exposed pink foam on the underside of the hull.
A single layer of 6 oz fiberglass also covers the tapered inside edges of the plenum.
3/4″ square wooden skirt attach strips are now bonded in place and held temporarily with brads.
The front landing skid.
There are also two skids in the middle of the craft and two skids at the rear of the craft.
The completed hull with engine stands temporarily in place.