What a difference a line can make

In June this year I wrote part 1 and part 2 of a post on Humber Yawls, in which I mentioned a design Ive been working on for my own use.

Nugget with her gaff-headed cat rig with a tiny jib set flying...

...and Nugget with her yawl rig. Some people may say this is a ketch rig because the mizzen mast is in front of the rudder, but it is very difficult to have a mizzen mast behind a transom-hung rudder! The rig is a yawl in functional terms, as the mizzen is more for balance than for drive - although it will drive strongly on some points-of-sail.

 This set of lines has been lurking in my head and on the computer since September 2011, and Ive drawn at least nineteen major versions, and countless more minor variations. Usually I get what I want in only a few intense sessions of hull modelling, but this one just wouldnt let me peg it down! You could be forgiven for saying that I have been over-cooking it, and that I should have accepted what I showed in the previously mentioned posts - or that I should have given up and moved on to something else.

??

Lines Plan of the hull shown in the previous posts - close to being good, but just not right...

Perspectives of the same hull

A few nights ago while lying in bed trying to sleep, I finally cottoned onto what I thought had been causing the problem, and the next morning I made the changes and I think Ive finally got it right - here are the new drawings...

Lines plan of the modified hull - can you spot the difference?

Well, there is no difference at all in the underwater lines, which is good because I like them very much and at this stage of my development as a designer, I cant think of how I could improve them for what I have in mind for the boat.

The only difference is that I have moved the lowest point in the sheer aft by 370mm (about 14-1/2") and lowered it by 42mm (1-5/8"), but the boat has changed from being an ugly duckling to a beautiful swan in my (biased) eyes.

Perspectives of the modified hull - a tiny dimensional difference in the sheer line, but a huge difference in the aesthetics.

So, what does all this mean in practical terms? For one thing, it means that I will probably build this boat whereas the preceding versions worried me enough for me to loose enthusiasm. Maybe the boat will get looked after better, and last longer, because someone thinks she looks beautiful long after Im gone. To me it shows the value in paying attention to detail and not just accepting something as being nearly good enough.

But the most important thing it proves to me is the astonishing effect that tiny variations in shape and proportion can have on a three-dimensional object.

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