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Sport C Tunnel Race Boat Plans
Page Two
Bulkheads and Beams

Bulkheads #2 through #5 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.

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 plwood scraps cut 42" long. I also used the bow beam to help shore up the structure which is very unstable at this point.

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 Bulkheads #3, #4 and #5 are positioned forward of their station lines; Bulkheads #1 and #2 and the Transom lie aft of their station lines.

Attach the inner bulkhead 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 notched for those tunnel battens that will extend beyond the beam and form the tunnel extension. Notches are only 1/2" deep and will later be matched to 1/4" notches in their respective tunnel battens.

The other five battens deadend at the beam. Attach a cleat, 3/4" from the edge of the beam, for these battens to attach to.

Alternatively, you could notch in all the beams, trimming off these central five at the aft face of the beam.

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

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