Building The Mould - Chapelle 35' Utility Launch

The first step in building any boat is figuring out how you're going to do it. Before these pictures were taken, I had already decided I was going to build the boat w/ plywood, epoxy and fiberglass. The building method was going to be a cross between traditional plank on frame and stitch and glue. The frames would be built, and the plywood layed up against the frames for marking. Then I'd continue with something like a stitch and glue approach, -no chines or keel. No sheer clamps either. The challenge to myself: no dimensional lumber. Not sure if I'll carry through with this in the prototype, but the reasoning behind this has to do with shrinkage and rot.

I lofted the frames directly on the shop floor. The rest of the lines were also lofted, but on cheap, white, wallboard. I layed out 4 pieces at a time and built a jig on the floor to keep them lined up. I only switch one piece out at a time while drawing the curves. This means that if I want to look at the next piece to the left, I have to remove the right hand piece, move the other three over, and lay down the next piece. This ensures smooth transitions between the curves, because all curves overlap by at least 3 panels (12').

I marked the frames by hammering nails into the floor to keep the 2x4s in place. I drew the cut lines, removed and cut the pieces, then put the pieces back between the nails. Then I used pine as a gusset to keep the pieces together. Much faster to use pine then to cut plywood. None of these frames stay in the boat. They're just used as a mould. I have not broken one pine gusset to date. Everything is nailed. No screws.

For the curved frames in the stern (bit of tumblehome in the last few and the transom), I sprung a batten around some nails and let the circular saw follow the batten. This produces a perfect curve but is very time consuming. I don't do this for large panels, but the frames have to be fair, and 2x4 fir is to tough to plane. So I just cut it right the first time. No bevels needed since they're temporary frames (just put them in so that the correct edge contacts the hull at the station mark).

Once the frames are cut and assembled (I assemble them on the floor, with the nails holding them. I can even reproduce a frame if necessary from the drawing & nail holes...), they're ready to go on the building jig.

I used a bunch of 4x4 posts, plywood feet, and 2x10s to make a jig, leaving enough space for the bow so that it doesn't hit the ground, and then some. Everything is bolted together and leveled. The thing moves a bit from time to time and I have to relevel and realign as necessary. Beats digging holes and pouring concrete IMHO. Still moves anyway...

The top of the 2xs are marked with the stations, and then I use 2x4s to set them up as in the pictures. I spring some battens around (these come and go as work progresses) to ensure everything looks ok.

BTW, I used Howard Chapelle's offsets, and some of them needed to be tweaked in the stern. I think he actually got some of the numbers mixed up. I'm sure I would too if I was working with all of those measurements by hand, and on a small piece of paper. Then again, maybe I just don't see that well... Looks ok in the end though.