Wednesday, March 3, 2010

Side Plywood Installation

Prefitting the side involved getting a 8' x 18" piece of plywood in place from the front of the boat back to where it ended just forward of the middle frame. Once it was bent in place and rough fit, a countersunk screw hole was put midway along the chine and one midway along the shear. These screws provided a repeatable location so the panel could be removed for trimming and re-fit in the same location. Once this piece was fit, then it was removed and put on the other side to determine if the fit was close enough to use as a template. The picture is of this trial fit on the other side of the boat. It was a decent fit, so it was traced onto another piece of plywood and cut.

Going back to the first side, towards the rear of the boat, 4' x 18" piece was fit and aligned to match up to the 8' long piece. An angular cut was made to establish a butt joint between the two pieces of plywood. Lines were traced onto the back side to show it locations along the chines, shears, transom and stem. Then the pieces were removed and laid out on a long make-shift table. Screw hole locations were determined for placing screws every 3" along the chine and shear. Location holes were drilled from the backside (which had the traced lines) every 18" or so. Then the pieces were flipped over and the final holes were marked on the face side and all holes drilled with a countersinking bit.

Butt joint bonding: A piece of plastic was put on the table and then a piece of painters tape adhered along the underneath side of the joint to prevent epoxy from flowing everywhere. One side of the board was screwed to the table using the predrilled holes, the second piece was butted tight and also screwed in place. A liberal application of clear epoxy was applied and a 4" wide strip of fiberglass tape was laid into the joint. After sqeegeeing the epoxy, a piece of plastic sheet was laid over the whole mess, a plywood piece of wood laid on top and clamped down.

The next day, after removing the clamps, the area over the fiberglass tape was fairly smooth but other areas had too much epoxy needing sanding. The second picture is my second panel for the other side of the boat and it did not come out as nice as my first one. It took quite alot of hand sanding to get this one smoothed down, but eventually it started to look better. Then I flipped it over and applied epoxy and fiberglass tape, but kept the tape shorter so it would not interfere with the fit to the chines and shear. A little more squeegee action and tighter clamping helped smooth it out. The whole surface of the plywood was epoxied as it will be on the inside of the boat and this is the easiest way to get it coated. This inside surface is the one shown in the prior picture showing the butt-joint clamping.

Securing to the boat: It was a marathon session gluing and screwing the plywood to the side of the boat. After mixing up a batch of epoxy, the frame surfaces and bonding area on the plywood was rolled and brushed with epoxy. Then a colloidal silica filler was added to the epoxy and this thickened goo was brushed onto frame members back to the middle frame. The panel was located to the frames with the previously mentioned locator screws. I rigged up a chain from the ceiling to support the rear of the long panel while I began clamping and screwing the front portion.

After clamping forward to the stem to ensure proper location, then clamps were placed adjacent to each screw hole and redrilled to put a pilot hole into the frame member and a #8 7/8" long silicon bronze screw was screwed into the hole. Progress was from the front of the boat rearward, removing clamps from previously screwed areas and re-clamping and drilling and securing three screws at a time. When I got to the middle of the boat, another batch of thickened epoxy was made and applied to the frames from that area rearward. In the forward and rear portions of the boat where the wrap is severe and a screw head may have pulled through, small blocks of wood were used with 1 5/8" drywall screws to secure the plywood in place until the epoxy cured. After 100 screws and almost two hours of non-stop action it was done. I worked up a good sweat and needed a beer.

The next day, the screw blocks were removed and replaced with a silicon bronze screw one at a time. Everything held in place. The overhanging plywood was trimmed off with a hand saw and planed and filed smooth with the chine, stem and transom. The portion along the bottom of the pictures will not get trimmed until the boat is flipped over. The last picture is at the transom after trimming off the excess side panel and sanding smooth with the surface of the transom. The way the side of this boat twists and rolls into the transom ("tumblehome" as its known in the auto and boat design community) is really cool. Since the boat is upside down, this roll is towards the bottom of the picture.


  1. thanks for sharing your work with us
    Jack Fisher

  2. Hi there great boat I just bought the same motor with the remote steering, shifter and throttle but came in pieces. Could you send me or post another picture of how the shifter assembly connects together. Thanks Paul