Transom complexities and other pieces

I'm still catching up on my blog. This posted activity actually happened prior to and over the Christmas holiday.

Besides the frames, there are several other key pieces to make.  The stem, breast hook, chine block and a knee are constructed of 3/4" marine plywood glued together.  The breast hook and chine block get attached to stem and form the front, pointed part of the boat.  The knee forms a strong brace that support the transom to the keel.  Here are pictures of these pieces.

You'll see them later when the pieces are assembled to the building form.

The transom is the final piece and caused a lot of analysis and review before actually cutting the wood.  The transom is not straight up and down but tilts back 12 degrees from level.  However, the bottom of the boat is not level so the actual angle between the keel and transom is 13 degrees.   The other key point is that the outline of the transom is on the outside of the transom.  So, this means that when you cut at 13 degrees, the inside dimension is larger.  Frame members are also attached to the inside of the transom and they must be larger still, since they are also cut at 13 degrees.   Here's diagram of what I'm trying to explain.

How do you get this right?  Well, I drew a level and center line on the outside of the plywood piece I had for the transom.  On this I traced the transom outline using the templates I had made from the full size plans.  I carefully continued the center and level lines around to the other side of the plywood and traced the transom outline on the "inside" of the transom.  The two outlines should coincide.   The oak frame pieces that go along the bottom and side of the transom I made oversize on the outside.  I then temporarily screwed these to inside of the transom in their correct positions based on the level line and published dimensions.  I'm now ready to cut.

I turned the plywood over so I'm cutting on the outside and the lines I follow are the correct outline for the transom.  Since the bottom consists of two straight lines converging at the keel, I used a circular saw set at 13 degrees and a guide to cut both the plywood and the oak frame pieces at the same time.  I used a jig saw set at 6 degrees to cut the two side cuts and I cut the top of the transom with no tilt.  I guesstimated on the sides because they have a slight flare but the angle isn't critical since the transom will get faired along with the rest of the frames, chines and sheers.

I disassembled the frame pieces and used my table saw to cut the slots for the battens, keel, chine and sheet.  These cut-outs are in the frame and not the transom so they have to be done before the frames are attached to the transom.   Also attached to the inside of the transom is another piece of 3/4" plywood to thicken and reinforce the transom for the motor.  The could now all be glued and screwed together to complete the transom.

One final detail, the oak framing is 13/16" while the plywood is 3/4".  The knee that braces the transom needs to fit flush against it from the keel on up.  You can do one of two things: put a notch in the knee or trim out the frame to match the plywood.  I took a 1/16" out of the middle of the bottom frame above the keel to get it to the same thickness as plywood I attached.   Here's a close-up.   The keel goes in the notch in the lower right and the knee will attach to the keel and go up the inside of the transom along that centerline.