Round Bottom Boats

Round Bottom Boats

In the last post I said that your client had changed his mind, what I intended to do was to modify the power dory to take an outboard. However whilst I have been taking a break from posting, primarily because I actually have to create the design from scratch, I was contacted by a follower who wanted more rounded boats, so here we go,

Several years ago I designed a rowing boat which I called Sally Blank, (white hall=salle blanche= Sally Blank, I told you I liked puns) she looked like this,

 I called her the poor man's Whitehall skiff. However she was hard chined, here are the lines.

So to satisfy the request for a round chined boat, I redesigned her. The process is much like that described here and here. However in order to create a fair hull more lines are needed. Here are the almost finished lines of the new Sally Blank.

You can see that there are far more defining lines than in the drawing of the hard chine version. In the first version you have only one waterline, which you don't even draw in, here you have four which must be drawn in. Those lines give you the hull shape looking at it from below.

Then you have buttock lines, those are the lines in the section drawing parallel to the centerline. When transferred to the profile they give the hull shape from the side.

There are some extraneous lines to be removed and a last set of lines drawn in.

If you carefully compare the hard chine version and the round chine version you'll notice that the chine line and the keel line from the hard chine version are shown in the new version, that's because I used those lines to establish the new hull shape and the location of the chine and curve of the bilge You'll also notice that the stem is still straight which it can't be in the new boat. So we'll remove the extraneous lines, alter the stem and draw in a keel.

You'll notice two new lines in the sections drawing, those are a diagonal which will give us an idea of the flow around the hull. If we've done this right that diagonal, which will show as red line on the profile, will also be a fair curve.

C'est bon, n'es pas (yes I know I fractured the language).

So there you have it from a hard chine row boat to a round chine skiff. The work is not difficult, just tedious however, as I said here, using a computer speeds up the process.

Maybe we'll start something more ambitious next time.