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Laker SC12 Tunnel Race Boat Plans
Page Two
Bulkheads and Beams

Bulkheads #2 through #6 and the Transom consist of two parts -- the outer part which lies outboard of the tunnel sides, and the inner part which spans the distance between the tunnel side and the coaming.

Bulkhead #1 and the Transom consist of only the outer part, while the Tunnel Extension Bulkhead has only the inner part.

Begin layout of a bulkhead by drawing a Centerline and a Reference Line, making certain that they are precisely at right angles to each other.

The bottom edge of the inner part will lie directly on the lower edge of the beam. The beam location must be drawn onto the outer part to assure proper placement.

Note the "limbers" cut into the sponson batten notches. These allow bilge water to flow aft to the transom.

Set up the tunnel sides upside down. Correct spacing is initiated with some plywood or lumber cut 42" long. I also used the bow beam to help shore up the structure which is very unstable at this point, but a third temporary plywood spacer would work here as well.

Make certain the tunnel sides are parellel to each other and otherwise perfectly aligned. It may help to temporarily install a couple of bulkheads, along with their beams.

Note that some Bulkheads are positioned forward of their Sta. Lines, while others are positioned aft.

Attach the inner bulkheads to the tunnel side with a 3/4" x 3/4" cleat. Make certain the bulkhead is aligned with the station line, and the Reference Lines on bulkhead and tunnel side are aligned.

Align the lower edge of the beam with the lower edge of the bulkheads. Make certain the Tunnel Sides remain 42" apart.

Attach the outer bulkhead to the Tunnel Side with 3/4" x 3/4" cleats, again making sure it is aligned with Station and Reference lines.

The beam should line right on the line(s) you drew on the bulkhead.

The Transom Beam is the only beam that is notched for the tunnel battens.

Slide the Bow Beam into the slots you've cut for it.

Add an angled cleat to the aft face of the Beam, ready to receive the Tunnel Battens and the Deck Battens and Stringers. (See Drawing "Bulkhead #1")

Install temporary braces to hold the sponson tips properly aligned. These can be removed once the hull is turned over.

But that's not enough. A brace between sponson tips holds them vertical.

Both of these sponson tip braces should stay in place until after the sponson pads and the sides are intalled.

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