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From: Tom MacNaughton
Date: 11 Feb 2008
Time: 12:20:54 -0500
Remote Name: 66.252.37.199
To give you examples of designers who paid or pay special attention to the diagonals we can cite Nathaniel Herreshoff, Colin Archer, Olin Stephens, Knud Reimers, K. Aage Nielsen, and J. Laurent Giles. I’m sure that there are others who have placed a similar emphasis on diagonals, but have kept it pretty secret. Herreshoff, Stephens, and Giles at least normally did not publish any lines showing diagonals during their working lives as I believe they considered the diagonals a secret of their success. I’m sure you will all recognize that in their respective countries and even internationally these designers would all be likely to be found on people’s lists of “greatest designers of all time”. Very early on in our career we adopted and gradually refined the process of creating lines using heavy emphasis on diagonals and we have felt that following in the footsteps of these great designers in this manner largely accounts for our rather extraordinary good luck with the performance of our own designs. I am not the only one of that opinion. Some of you may know Sven Oftedal who was taught by me and now is a partner in a design firm of his own. He stopped by a few days back and in the process of going over some thoughts he had I mentioned that I had seemed to have very good luck with my designs. He said, “Luck! Isn’t isn’t luck. Its diagonals.” While I’m told that Laurent Giles used 45 degree diagonals, I don’t know whether that is actually 100% true or whether it was just that the type of hulls he tended to design used a lot of diagonals that were approximately that angle. In any case when I say that they show good diagonals I meant that literally when you crawl under one of his hulls and run your hands along it the shape is such that the diagonals done the way I would do them would be very nearly perfect. I have experimentally done one design using all 45 degree diagonals and it actually worked out reasonably well, though you have to use a lot more judgment in the ends and it wouldn’t be suitable for all types of hull. You asked for published “support”. The closest thing to an organized presentation is in Douglas Phillips-Birt’s book “The Sailing Yacht”. He talks about it as a very easy method to develop good flow. L. Francis Herreshoff has a wonderful passage in his biography of his father N.G. Herreshoff in which he talks about his father’s model making being done by shaving away whatever kept a spline from lying smoothly on the hull in the direction of water flow and that this was like fairing the hull using ‘a thousand diagonals’, which is just what it is. Other designers have been much more cagey and, aside from our firm, the designers who use diagonals the most seem to be those who talk about it the least. I think there is a reason for this. Basically it does such a good job I think most designers who work this way kind of hope others aren’t using it! As I’ve said it is really much too deep a subject to cover in any brief article or even a chapter in a book. All in all in our Yacht Design School main curriculum we devote substantial portions of 5 lessons to the use of diagonals in solving various types of hull design problems to the best advantage. However I really think it takes about that much training to really develop a feel for this way of doing things. If you go through the whole process of studying how to do this and actually develop a number of sets of lines this way under the instruction of an experienced teacher, it then becomes pretty much self-proving in that you can see how much easier it is to get really beautiful lines this way. In that sense the best “published support” for this method is really our own lessons.