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Sport C Tunnel Race Boat Plans
Page Eight
Upper Sides and Deck

The upper sides can be made from the same 5mm plywood I've recommended for all part up until now. Or, if weight is a concern, 4mm or 3mm can be used.

Step one is to bevel the upper edge of the lower side.

This drawing illustrates the steps from rough lower side, to beveled lower side, to installed upper side with its lower edge finish trimmed.

The middle part of this drawing is at the same stage as the photo above.

Installing the uppper sides. If you have enough clamps, no fasteners are required along the deck stringer.

Now is time to seal the inside surfaces of the hull. Use epoxy, or varnish, or paint, taking care to avoid surfaces to which the deck will be glued.

Before installing the deck, the two-part pour foam flotation must go in.

The area to be filled must first be lined with plastic. Because: 1) The foam will adhere to the structure of your boat as it expands and cures; and 2) As it fully cures, it shrinks somewhat, and, as I've learned from unhappy experience, will distort your boat in the process.

Racers: Four cubic feet of foam are required for Sport C boats.

If the expanding foam rises above deck level, the excess can be cut off with a handsaw and further trimmed with a belt sander or disc sander.

IMPORTANT: If you do cut into the foam, seal the cut surfaces with epoxy to prevent water from soaking into the foam.

Start laying out the deck plywood by cutting the split where the sponson deck departs from the main deck.

(NOTE: This (and the next) picture came from the Pro Tunnel in which the tunnel sides are extended to form air traps which theoretically help direct air across the deck. I didn't include this feature on the Sport C.)

To reach under the plwood and strike a line along the carlin, I made the sophistacated tool shown here -- a pencil taped to a stick. Actually, you probably can't get a very accurate line this way, but close enough to cut away most of the scrap, after which you CAN get a good line to cut to.

It will not be possible to seal the underside of the deck plywood after it is installed. So either pre-finish before installation, avoiding areas where the plywood will be glued to the hull, or (as I prefer), seal it with epoxy at the time of installation.

Screws and/or staples install the deck, although clamps can be used along the edges.

Once the deck is permanently installed and has been trimmed along the carlin, you are ready to install the coaming, the motorboard and other associated parts.

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