Mark V 36 Commuter

The Mark V 36 Commuter is my submission for the WoodenBoat/Professional BoatBuilder Design Challenge II. The design parameters are:

Must be trailerable, max beam 8’, max length 40’ trailer weight less than 3,500 lb.

Must burn less than 2 gallons an hour at 10 knots in a 2’ chop and 15 knot breeze while carrying 800 lbs (family of 4)

Must include at least spartain accommodations (berths, head, galley) for two adults and two children.

Since the boat is supposed to be fuel efficient, I figured that the potential owner would also be concerned about the initial cost. I designed the boat to be as inexpensive to own and operate as possible.

Plywood on frame construction was chosen to be the quickest and cheapest for amateur construction. It was chosen over stich-and-glue because I think in larger sizes it is no more labor, and easier for a solo builder, since the largest piece that the builder has to deal with is a single sheet of plywood. The boat does not have to be lofted; the actual dimensions of all the bulkheads are on the plans. Dimensional lumber will be standard sizes of pine, which can be picked up at any lumber yard. The bottom is cold-molded with two layers of plywood, since there is quite a bit of twist forward. Epoxy is used for gluing, and the exterior will be sheathed with Xynole-Polyester cloth. The windshield frame, roof supports, rub rails, and trim are varnished hardwood. I stated Mahogany on the plans, but other hardwoods would be suitable.

Outboard power was chosen, because it is much simpler and cheaper than an inboard diesel. Since two gallons an hour would be 20 hp with a gas engine, I used that as a starting point. 20 hp would push this boat at about 10.8 knots in a calm, so it should be able to meet the design parameters. A 25 hp high-thrust four stroke would be adequate, but I chose a 50hp outboard, which should give a top speed of about 14 to 15 knots. At 10 knots, it would be running at less than half throttle, so it will be a lot quieter and smoother than the 25. Two 24 gallon fuel tanks give a range of over 200 miles at 10 knots. The outboard could probably be enclosed in a box, but I decided to leave it in the open. The box would have to be as high as the aft cabin, and extend to the transom. There would also have to be a large ugly cutout in the transom so the motor could tilt up. The motor is not very conspicuous as it is, and 50 hp four-strokes are very quiet, especially if run at lower speeds

Styling was from the 1920’s, because I think that was when power boats were the most elegant. The somewhat boxy styling is also simpler to build. The hull is straight-sectioned V-bottom, which is a good shape for moderate speeds. It will slice through the water cleanly, and will look very elegant at cruising speed. I once was passed by a 70 or so foot 1920’s commuter on the ICW. It was cruising at over 20 knots, and I was impressed by how cleanly the boat sliced through the water. I was hoping to get that effect with a smaller and much less expensive boat.

The cockpit will be able to be completely enclosed in canvas, and it was assumed that most of the time, that is where the crew will be. There is 6’ 6” headroom in the cockpit. The roof is only ¼” plywood, so it is not intended to be walked on, however, a couple of kayaks could be carried up there. The cockpit is not self-bailing, but the canvas should keep rain out. The forward cabin has four feet of headroom, and would mainly be used for sleeping. The headroom is a bit tight, but I didn’t want to raise the freeboard any more, as it would increase the weight and windage. The head was put in an aft cabin, keeping the portable toilet separate from the sleeping area. It also moves the cockpit forward, putting the crew weight closer to the center of buoyancy. The aft cabin will also block the sound of the outboard.

In order to get the boat light enough, there is almost nothing built into the interior. The galley will consist of a portable camp stove and cooler. Water will be in jerry cans, stored under the V-berth. Seating will be folding canvas chairs. The electrical system will be very simple, one starting battery, and one house battery, lights, and a few electronics.

There is a self-bailing anchor locker forward. Anchor handling will be done while standing in the forehatch, so no lifelines will be needed. The working anchor will be 22 pounds, so no anchor cathead is shown.