Strip Construction


Strip Construction
by Bill Durham
(Excerpted from The Mariner's Catalog - Volume 4)

I can congratulate myself in hindsight for deciding to build the right kinds of boats with strip construction. This technique is not suitable for most boatbuilding projects, and I think should rarely be chosen unless there are strong secondary reasons beside the fact that it's "simple" and cheap.

I built a careful replica of a 26-foot dugout canoe, using 2" X 1-3/4" strips on the bottom, 1-1/2" X 1" strips up the sides, epoxy-glued and nailed at 4" intervals with 16d galvanized casing nails on the bottom, 8d on the sides. I used tough 3/4" Philippine mahogany planks as stem and sternpost, with the strips simply beveled to a feather edge and glued and nailed to them.

On launching, the canoe leaked not a drop, and no seams opened or wood shifted during five or six years of careless treatment — left waterlogged in a polluted lake winters; sun-baked each summer. A purchaser set out for the Inside Passage several years ago, and I haven't seen the canoe since. Of precisely the same scantlings as a 1928 prototype, and indistinguishable from a dugout at ten feet, I felt that the strip-built hull was a much stronger and more durable fabric than dugout construction could provide. The canoe was structurally 100 percent successful, primarily because of the virtues of western red cedar and gap-filling epoxy, and the suitability of a dugout-canoe prototype.

I chose strip construction for a 20' X 54" elliptical stern launch partly because I wasn't interested in learning all the skills and acquiring all the materials necessary for building such a hull in the traditional way; partly because I planned to use the hull as a plug for a fiberglass mold. I used 3/4" X 1-1/4" red cedar strips, resorcinol-glued and nailed at 3" intervals with 6d galvanized nails, with much extra clamping.

Strip construction made it easy to achieve an almost perfectly fair and smooth surface for the fiberglass work. The 3/4"-thick hull required frames, and I found that inserting frames and fastening them securely to a thin softwood skin is not easy.

On launching, the seams wept quietly in dozens of places before they took up. "Absolutely waterproof" resorcinol glue is rarely handled in just the right way, or given enough clamping pressure, by amateur boatbuilders. I think ordinary water-mix Weldwood will give better results for most amateurs, if only because it can be slathered on more liberally.

I think that the questions usually asked about strip construction — How do you fit the strips? How do you scarph the butt-ends? How can I get clamping pressure? — are not the questions that need to be asked. The main thing is to use a completely stable and glueable wood such as western red cedar, and epoxy glue if you can afford it or know where to get "Boeing surplus," and to select a project entirely suitable for strip construction. A traditional plank-on-frame boat hull, imitated in strip construction, does not look very authentic.

In my experience, strip-building is phenomenally sparing of materials costs; wasteful of builder's time. My canoe took 600 hours to build; the 20-foot launch 1,000 hours. Neither hull had $100 in it prior to painting or decking.

I'll leave it to a professional boatbuilder to explain the several reasons why most professionals regard strip construction as an amateur aberration.

—Bill Durham-