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Laker 14 Tunnel Boat Plans
Page Seven
Coaming

The coamings for the "racing" cockpit are integral parts of the structure of the hull, helping to strengthen the wide expanse of stringers and plywood between the tunnel sides. As such, from bulkhead three to the tunnel extension, they must be accurately fitted to the curved shape of the tunnel plank and firmly attached to the tunnel battens located eleven inches either side of the centerline.

Coamings for the side-by-side cockpit, on the other hand, are attached directly to the inner face of the tunnel sides and have limited structural value. The centrally located beam, as suggested by the plans, serves the structural role that the "racing" version coamings otherwise would.

"Racing" Coamings:

The bottom profile of the coaming does not come from the drawings, but directly from your hull. There is certainly more than one way to do that, but this is the one I use.

Start with a strip of plywood 8 feet long and 8-12 inches wide. This will be long enough to reach from the tunnel extension to somewhere between bulkheads three and four. With the plywood resting on top of the beams and held snug to the carlin, mark the locations of the beams.

Now you want to make a series of measurements along the length of the template -- for instance, one at each station and a couple between stations. At each point, measure the same distance (say, 4") up from the tunnel plank and make a mark on the template.

Bend a batten along these marks and draw the curve. Make the cut-outs for the beams, cut out the profile and test-fit your template. Make adjustments as necessary.

A similar, but shorter, piece of plywood does the same job in the bow. Long enough to overlap the first template by a couple of inches.

You may find it a bit trickier here since the plywood must be bent along the carlin. It is very important that your template be snug to the carlin along its entire length to ensure an accurate profile.

The coaming extends 12 inches forward of the bow beam. The bottom edge of the extension is taken directly from the tunnel plank.

If you wish to scarf together the two parts of your coamings, you will want to join the two parts of your template and remove them from the boat as a single unit.

Otherwise, cut the coamings as two separate pieces to be joined with butt blocks at final installation.

Starting with a full-length piece of plywood that is somewhat wider than the finished coaming, transfer the aft template to the bottom edge. Remember that the coaming extends aft of the tunnel extension enough to include the angled motorboard, plus another 2" for the cleats behind the motorboard -- and I'd add at least another inch to make certain you don't come up short.

NOTE: Depending on the engine you intend to use for your Laker, you may want to set your motorboard at greater angle than is called for in the plans. I found that my own Laker, powered by a 70hp Merc 700, could have used more angle in order to achieve deeper down-trim.

As with the template, cut the forward portion of the coaming long enough to creat an overlap of about two inches. Then strike a line along the edge of one piece and onto the other. Cut along this line and the two parts of your coaming should meet nicely, ready to be joined with a butt block when they are permanently installed.

Test fit the templates on the other side of the cockpit and make any necessary adjustments, then cut the second coamings same way as the first.

I found it useful to add a small bulkhead right on the leading edge of the bow beam to hold the coamings in proper places.

Use the plans (or follow your own notions if you prefer) to determine the finished top profile of the coamings and cut them to their final shape.

I added a second layer of plywood to the aft 4 feet of the coaming.

Since the type of luan plywood I am using has most of its thickness in the middle ply, I installed this layer such that the grain of that middle ply is oriented fore-and-aft.

DON'T FORGET: You will need to cut two notches in your coamings to avoid blocking the limbers that lead water to the sponsons.

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