5o5 Hull Shapes From Different Builders
from the e-mail list

I've heard a lot of people talking about one hullshape being faster than another, but I was wondering if there really is a fastest 505. I know that a finer bow is supposed to be better in waves and chop. I've heard that less rocker helps planing, but I've also heard that some Parkers have the rocker filed out to minimum and slow in light wind. So what makes a fast shape? I know from ski racing that finding skis, or in this case a boat, that fits your style of skiing, or in this case driving, in crucial. And what works for some people may not work for you. I had a pair of the latest and greatest race skis this year and thought they sucked while a friend of mine had great results with them. After reading Ali's write up about the difference between the Hamlin/Waterat shape and the Lindsay shape it seems to me that it is personal and what feels good to one person may not feel good to another.

I'd like to hear other people thoughts on this and maybe see some discussion on what makes a 505 fast shape wise, not rigging or sailing (though those may be interesting too). How do different builders hull shapes compare? Waterat vs. Rondar vs. Kyrwood vs. ??? I keep hearing everyone hulls are influenced by the Kyrwoods. How are the similar and how are they different? What are the facts and opinions?

Bill Green

While I would also like to understand the differences between various 5o5 builder's hull shapes, it is my understanding after talking to the 5o5 Class International Measurer Val May Provoost and to others who have compared hulls, that the differences are VERY SMALL. This is for two reasons. First the hulls can only vary by a small amount (either 5 or 10mm) at the measured stations. However there is more room to play with the baseline, influencing the rocker. Second, almost all current builders have tried to do similar things within the tolerances, so current hulls are generally similar. By and large, they are minimum width at the waterline and low rocker.

So... yes there are differences, but they are quite small and subtle.

Older hulls that were built in older tooling may not be minumum width at the waterline and have minimal rocker.

Hull shape is not the only speed influencing factor in the hull. Light ends are also important, and all builders have worked to make their boats as light as practical in the ends. Hull stiffness is also very important. You also want a very fair hull shape.

I don't know how you compare 505s, notice speed differences, and correctly attribute that difference to sailors ability versus hulls, centerboard versus sail shape, etc. I expect the differences due to hull shape alone are very small.

As Howard Hamlin has said (in the context of the Hamlin/Waterat and Lindsay hulls)... "it makes no difference; they all go the same speed."


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