Kayak Build: Strongback 2.0

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Originally uploaded by TimsPottery

The weather got cooler, and school began, so work on the kayak stopped for the winter. Now the sun is beginning to shine, and I'm ready to get back to the boat. I ended last year's work with the forms on a new strongback. This post will describe what went into that. I urge you to learn from my mistakes...I mean insights.

Before you go any further, you should check out the videos in Nick's blog at http://www.guillemotkayaks.com.

After deciding that the first strongback was not constructed well enough, I decided to go ahead with a single length of 2x4 extruded aluminimum box beam. I bought this at a local metal supply place. I cut it to the length of the untapered part of the strongback as outlined in the kayak plans. For the tapered ends of the strongback, I trimmed 2x4 sections of wood from 2x6's and trimmed them to fit into the ends of the aluminum box beam. I inserted them about 8 inches into the boxy beam. The wooden parts were narrower than the inside dimension of the box beam, so I secured them with wedges on either side.

Once I had the ends in, I used a nylon line to trace a straight line down the strongback. About every foot, I used a dab of hot glue to hold the line in place so that I could more easily draw the line. If you do this, be careful not to nudge the line to the side as you put the glue down.

In his videos, Nick does the cutouts in the center of the form so they just fit over the aluminum strongback. By the time I got the strongback built, I had already cut holes too large for this method. An additional issue (probably not too hard to deal with on future boats) is that my aluminum beam has a slight bit of torsion, so forms would have to be adjusted to line up.

Since the form holes were oversized and the beam had torsion, I decided to use cleats to anchor the forms. For every form, I drilled 2 holes in the side of the beam and in the top of the beam. I then tapped the holes. To anchor the cleats to the beam I used machine screws. Yes, this was a bit of work, but it was not as bad as I thought it would be.

The photo shows one end of the strongback. The tapered portion is wedged is held tight in the box beam by wedges (after the forms were all on, I secured the tapered insert with screws through the box beam and into the wood). At the top of the end of the box beam is a small horizontal cleat. on the side of the box beam are two tapped holes waiting for the vertical cleat. I predrilled holes into the cleats and made sure they were square with the beam so that the forms could go on them. Each cleat was attached after the previous form was slipped onto the strongback.