: . . .The hull
: has to hold your weight too. Getting in and out you concentrate you weight
: in one place. But I think you are grossly underestimating the strength of
: the hull once fiberglassed.

: A lot the strength and ridgedness comes from the shape of the deck. A round
: strip deck would probably be stronger than flat plywood. if your going to
: strip the hull why would you plywood the deck? Thats what is most seen and
: should look the best. Nothing personal, but I think your thinking to hard.
: Build it as designed.

Is a plywood deck a first choice for people building a woodstrip hull? Rarely. It is far more common to chose either plywood or woodstrips for a boat, and make hull and deck with the same materials. But some people chose to make a stripdeck for a plywood hull, and I can understand the reasoning behind doing the opposite. As I understand some of the thinking on this:

The prevailing school of thought is to build a "hybrid" boat with a plywood hull and a strip deck. The advantages here come from the rapid assembly of the hull, and the rather uniform curvature of the deck, which makes the stripping go quickly.

People who want hulls with complicated curves, whether to tweek performance, or for the visual appeal, are going to build them with narrow strips. These can be bent into almost any conceivable shape, so almost any conceivable hull can be built with them. This freedom in design can be matched with plywood construction, but with some additional difficulty--and generally it isn't worth the time to bother.

Consider that a kayak is a decked canoe. Canoes stay open on top because they have thwarts separating the gunwales The combination of gunwales and thwarts resists the water pressure which is trying to squeeze these boats closed. The more load in a canoe, the deeper it sinks in the water, and the more pressure applied to the sides. The more pressure, the stronger you need the gunwales and thwarts.

You can have a deck made from a very thin and weak material, such as animal skins or fabric, which will need an underlying frame for structural support, Many "tripping" canoes have fabric covers which snap over the open boat to repel waves and splases from the paddles. The thwarts serve as a frame. Another option is to build a deck which is strong enough on its own that it does not need the additional bracing. On some kayaks this is accomplished by deck beams, (basically thwarts with a bend in them) and on others it is provided by a flat or a curved panel of plastic, wood, or fiberglass. When bulkheads are used to divide the interior of a kayak into compartments, they also serve as bracing to resist the squeeze of water pressure.

If you look at a few of Tom ost's designs for aluminum-framed kayaks you'll see that many of then have flat decks over the back half of the kayak. This shape allows the paddler to bend back and lie flat on the deck to aid in rolling the kayak. You can make a flat deck on a wood boat, too. Why not use a piece of flat plywood for the job? It is fast to fit into place, and the wood grain is certainly not unattractive. Perhaps one can get artsier with wood strips, but is it necessary? An onlay of veneer can add appeal.

The shape of the fore deck is not as critical to kayak performance as the shape of the hull underwater. The only major design issue on deck shape is getting the deck high enough to hold the paddler's feet comfortably, while not serving as a sail in strong winds. Bending a thin plywood panel over deckbeams is a quick way to make the fore deck.

Depending on the materials chosen, one might use a 3mm or 1/8th inch plywood which weighs less than 3/16 or 1/4 inch woodstrips. A woodstrip deck requires glass and resin on both sides to achieve its strength as a composite material. Thin marine plywood will be durable without the added glass. You have possible savings here of construction time, weight, fiberglassing-materials, and cost.

With either a plywood deck, or a woodstrip deck, the center of the boat is going to be greatly reinforced by the shape and construction of the cockpit coaming. The shape of the coaming lip, the risers, and the deck are effectively a "c" shaped beam of a wood-cored fiberglass-sheathed composite. This not only keeps the deck from sagging, but it also serves (like a pair of thwarts) to strengthen the center of the boat. Take a look at some of the fiberglass ladders and you'll see that the sides of them are shaped like either "I" or "C" beams with a thickness of about 1/8th of an inch. A tyoical coaming we would make is going to be thicker than that, and probably as strong or stronger!

Similarly, reinforcing under the deck in the area of hatch openings will have the added benefit of stiffening the deck. This works for both plywood and strip decks.

With commercially milled woodstrips going for more than 30 cents a lineal foot a plywood deck on a woodstrips hull can represent an efficient compromise for a person who wants to devote the majority of their effort to the hull design.

Just a thought or two.

PGJ