Building the Strip-Plank Hollow Runner Plank

A very interesting boat showed up here at Iceboat Central last month in desperate need of a new plank. She came down from Nova Scotia, and in classic Novi style the plank was made with maple and birch. Not that there’s anything wrong with that: H.M.S. Bounty, built in Lunenberg in 1962 for the movie, was built of the same stuff. And during a re-fit on the old ship a few years ago I found chunks of birch in fine condition with the bark still on. But glue joints on the plank were failing and it weighed 110#. The old A Skeeter was built in the early 60’s by Hagarty, in Cohasset, Mass. The unique design might be from Ray Ruge, but we’re still investigating that. Buddy Melges owned the boat for a while, and there were a few more built to the same design for guys on Lake George but their whereabouts are unknown.

She looks more like an early hydroplane than what we are used to seeing on the ice, but the melonseed shape reminded me of the hollow plank that I learned how to build in Estonia. The sectional shape of the plank is very sympathetic to this particular fuselage. I believe this strip plank system would work for other large skeeters, but I don’t know about the Whizz, for example. The plank needs a certain amount of thickness for the strip planking to make sense. On the other hand, it’s often challenging to find the nice wide boards needed for building the plank so we’re gluing strips together anyway. But maybe the strips can be thinner for a smaller plank. I don’t know. The whole thing is a bit of an un-known and I’m just making it up as I go along. So we’ll build the plank and add stiffness to taste.

The old plank has a nice shape, if a bit un-fair, so I used it for a form. The building mold is set up on 1/2″ ply, and draped nicely over the old plank. I followed the Renegade thickness: 2 1/2 to 1 1/4. The chocks are twelve inches wide, same as the plank aperture in the fuselage, so there’s could be no taper in width. (Sorry, Lloyd.) The mold sections are all sections of an arc. A simple lofting yielded the arc for each station, 10″ on center.
The choice of wood is always interesting: a combination of what you want and what you can get. I wanted Doug Fir on top for it’s compression strength, and spruce for the bottom for lightness. But our local lumberyard sells a clear grade of Port Orford Cedar for decking which comes a full inch by 5 1/2. It’s actually more like a spruce than a cedar, with some physical properties right up there with Sitka spruce, but for about a third the cost. And to get it in smooth, milled boards saves a lot of millwork. Unfortunately they were out of stock on the sixteen footers so I scavenged the local boatyards for Sitka rippings and came up with just enough.

The first plank it set very carefully to an accurate centerline marked on the mold. The planks are all 3/4 x 1″milled with an 1.5 degree, which averages out nicely over the changing radius. Epoxy takes care of the rest!
Stack four or five planks together on the bench on edge and apply epoxy to all of them at once. If your mixture isn’t too thick there’s no need to wet out the other edge. I used finish nails to hold them in, and did all the planks in one session, along with the centerline stringer. The stringer isn’t part of the original design, but I though it would be a good idea.

The outside planks are just one plank ripped diagonally as most of this part will be planed away.

A couple of hours of pleasant work planing it down to the centerline and the bottom half is done. Now the whole set-up is dismantled and the old plank flipped over so we can make the new top on the old bottom. There was only 3/4″ of spring-back when the nails were pulled, and the part was surprisingly stiff. I became hopeful that the whole thing might actually work.

Stand by for part two!

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