Monday, January 26, 2015

A dinghy to row. Galifreya

Most dinghies today aren't designed to row, Even ones that you might think are. I was lucky to grow up with two nice rowing dinghies and no outboard motors.

Part of the decision to go for a bigger boat was to be able to get a bigger dinghy on deck that will row much better than the 8 footer on Snow petrel. I can fit a 12 footer onto Snow Petrel II.

Anyway, A good friend was going to build an Auk for his beautiful atkins cutter. I couldn't help myself designing a 8.5x4 foot rowing dinghy that was more suited to him.

Here's the result. I called it Galifreya to go with his yacht Galifrey.

 It had to look good, especially upside down on his deck, And fit under the boom.
The dinghy also had to row exceedingly well, He has a bolger light dory and that was the standard that it was being judged against. But more stability was needed, and better towing. He wanted high freeboard to get a comfortable rowing position,
I chose to pull the quarters up to reduce wetter surface and transom drag when heavily loaded. The waterline beam is also pretty narrow, but wide enough to carry the weight and give about twice the initial stability of the bolger light dory. Most small rowing dinghies have broader low sterns to carry more weight and give more stability. Good for outboards and sailing but very very bad for rowing, especially when loaded.
The bow is fine underwater but rapidly flares to a fuller bow to lift it over any waves and stop bow steering when towing. Coupled with the high freeboard the dinghy is very dry, The sheer is pretty flat to give the comfortable rowing position he wanted, And to give more capacity for deep loading.
 The keel is long and straight with a big skeg. It makes it track very well. possibly two well for my liking, I would probably take 25mm of the skeg and 10 mm of the keel to make it more nimble. But it is a joy to row, You don't need to focus on keeping it going straight. Even when gliding or with a beam wind. It surfs well down the smallest waves. And is stable enough to stand up in.
 Happy! A smooth wake and nice curl to the bow. The dinghy rowed better than any other I have tried in this size range. Next we need to do some speed trials against other dinghies and row it in all sort of conditions but our first trails were better than I could have hoped. Just needs some paint and a few finishing touches and she's done.
The lines plan, the waterline shown is roughly with two light to medium weight people onboard and no gear. It was not a quick and easy dinghy to build, but it is within the capabilities of most people. I generated offsets for the hull planks which where mostly pretty close, except at the bottom of the bow, where they were about 10mm off. It is 6mm ply over bulkheads and temporary stations.
video