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Mini Tunnel (Redesigned Version) Boat Plans
Page Eight
Upper Sides, Deck & Flotation

The general rule is one cubic foot of flotation will support 60 lbs. For GT Pro racing, three cubic feet are required, and this is a good amount for non-racing uses as well -- enough flotation to support the motor, the battery and a small amount of hardware. Most everything else should be bouyant.

I used high-density foam insulating board for the Laker 14, shown here. I loaded the foam into the hull before installing the upper sides.

The other option is two-part pour foam. For this you will want to install the upper sides first (see below) to help contain the foam.

Line the space with plastic sheeting. I have discovered, to my shagrin, that pour foam shrinks some after it cures. If it is poured directly into the hull it will grip the plywood and lumber with enough tenacity to distort your hull as it shrinks.

Also, make certain that bilgewater can drain past the foam and does not get trapped in the forward area of your sponsons.

Installing the upper sides is straightforward. Again, the joint can be scarfed or butt blocked.

The inner and outer decking meet at the tunnel side. The inner deck, which is installed first, extends from the carlin to the inner-most deck stringer, but does not overlap the edge of the tunnel side.


... over the tunnel extension where a little extra plywood is needed.

Forward of station three, the two parts of the deck diverge, the inner deck descending to the bow beam.

Although the edge of the inner deck is straight, the edge of outer deck is gently curved where the two meet.

Use a block plane, sanding block or belt sander to bevel the edge of the outer deck. Perfection is not required. Any gaps can be readily filled with epoxy sanding filler.

The outer deck completed. As with all other plywood joints on this project, scarfs or butt blocks are used.

As mentioned before, I prefer to install the deck first, then the coaming. This way I am able to clamp the deck plywood to the carlin, instead of using fasteners, and I can easily trim the deck along the carlin for a nice neat deck/coaming joint.

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