D4 Dinghy?

[Guest]

I built a D4 dinghy out of ply wood and fiberglass. I was considering using the boat as a female mold and make a total fiberglass boat. Would this work as long as i use something to get the hull out of the mold. Any ideas on this would be appreciated
Thanks,
Tom

[Tim B]

I'm not an expert on the subject by any means, but it is possible, by the method you mentioned, to mould a new hull. You must be careful, though, to make sure that your female mould fits every part of the boat that you want to copy in GRP. There are also a few questions about such things as joining the hull and deck. For example, with a wooden boat, an inset deck, or a deck lapped to the outside of the hull is simply a question of a bit of glue and screwing it down, on GRP it's not so easy. If that is a problem, you can either bond the hull and deck together and put a reinforcing weave inside. Alternatively copy the LARK/LASER method, and mould a flange in both the hull and the deck so they neatly mate together, then just bond them together with the appropriate resin. The second method will also increase the stiffness down the length of the panel during building, and consequently the stiffness down the sheer-line when built.
Remember, though, that you will still need severel bulkheads and stiffeners over the length of the hull. In most boats this means a forward bulkhead, a central wood (usually maghogany) stiffener, and a full transom. the central wood stiffener, which is screwed or bolted to a hard-point on either side of the boat, also serves to help support the center board case.
Further to that, before laying in any gel-coat or cloth, make up a keel (obviously built around the centerboard slot) which is just shorter (or will fit when raised the thickness of the layup) than the internal mould length. Leave enough room at the aft end for the transom layup. To this I suggest you add a small triangle say 4"long by 4"high (10cm by 10cm), then when the gel-coat is in and dry, and the layup is in place(hull and transom), fit the keel, bond on the triangle and glass it all in place(remember to wet out the bottom corners of the centerboard slot well. This will make the hull much stiffer longitudinally. The full or half bulkheads can be fitted and glassed in much the same way at the the same time.

Hope this helps, I'll post a few sketches in a minute.

Cheers,

Tim B.

[Tim B]

Here we are, to illustrate what was said before (I hope)