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Laker 14 Tunnel Boat Plans
Page One
Tunnel Sides & Bulkheads

Construction begins with the tunnel sides.

Since the tunnel sides are longer than a single sheet of (typical) plywood, a panel must be constructed.

The joint can be scarfed. Or, as I prefer, you may use a butt block. The butt block must be on the outboard face of the plywood -- that is, the surface that faces the interior of the sponson. The butt block can be glued in place with weights. Alternatively, you can use screws.

You will want to make sure that your butt blocks do not end up on a station line (see below) where they would interfere with bulkhead installation.

Draw reference line, secondary reference lines, and station lines onto the tunnel side blank. (After cutting out the tunnel sides, carry the reference and stattion lines onto the opposite face.)

Find the edges of the tunnel side by measuring above and below the reference line at each station. Bend a batten through these points and draw the lines. Note that the bottom edge of the tunnel sides are a straight line from Bulkhead #3 to the transom.

More about drawing curves HERE.

Once the first tunnel side is cut out, it can be used as a template to cut the second one.

Locate the cutouts for the beams at each station. Note that the bow beam is located aft of station line #1, while the beams at stations 2-6 are located forward of the station lines. The transom beam is located 3/8" forward of the transom station line.

Beam cutouts can be cut slightly oversize to make installing the beams easier.

Layout and cut the lightening holes as suggested in the plans, or as you see fit. Not much weight will be saved here, but these openings allow the free flow of air through your hull to help keep it dry.

The narrow-cockpit "racing" layout requires outer bulkhead sections (outboard of the tunnel sides) and inner sections. The side-by-side layout requires only outer sections.

All points on the bulkheads are measured horizontally from the centerline, and vertically above or below the reference line.

For each bulkhead, start by drawing two lines exactly at right angles to each other. The horizontal line is the reference line; the vertical is the centerline. Locate the several corners of each bulkhead section, and draw the edges.

Layout and draw the notches for the stringers.

Also, draw a line that shows where the bottom edge of the beam crosses the outer bulkhead section (the inner section's bottom edge is exactly aligned with the lower edge of the beam).

SUGGESTION: After laying out a section of bulkhead, cut it out very roughly, staying, say, an inch outside the lines. Then I screw it to a second piece of similar size and cut then out together.

After cutting out, carry the reference line around the edge and to the other side.

Cut lightening holes in the bulkheads as space allows -- generally, below the beams on the outer bulkheads and above the beam on the inner bulkheads. Again, weight savings will be minimal, but they will facilitate air circulation through the hull.

After accurately locating the stringer notches cutting out the bulkheads, I cut away some of the edges, partly so that the plywood would not be in the way when beveling the stringers later on. But also, along the bottom edges of the outer bulkheads drainage is provided.

Glue cleats (approximately 3/4" x 3/4") to the edge of each bulkhead section where it will be attached to the tunnel side.

Make certain the cleats on opposite side of the bulkhead from the beam. EXCEPT at the transom, where the cleat and beam must be on the same side. Therefore a shortened cleat must be used on the transom so that it does not block the beam notch in the tunnel side.

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