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post #381 of Old 08-05-2013
Brent Swain
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by bobperry View Post
The Fred Flintstone school of yacht design.

I know it's done but even as a 15 year old kid I figured that balancing shapes on a, I used my triangular scale, was BS. It was just not precise. I use a calculus method with Simpson's multipliers. It takes a bit of time but the results are reliable
Far more precise than your assumptions that you can predict what very different owners will put aboard, over decades of living aboard. That assumption is incredibly na´ve. The variations in those numbers are far larger than any variations in balancing a curve of areas, model , etc. in fact huge. Herreshoff had a lot to say, none of it complementary, about the foolishness of mathematicians over the logic of practical people . He also had a good laugh about the irrelevance, and goofiness of Simpsons multipliers, over Hereshoffs own much simpler methods.
He well describes the motives of such advocates as "Exhibitionists."
Most experienced offshore cruisers come back saying "Keep it simple" not saying "Make it more complicated."
A good example is the na´ve mathematical calculations that one should put a plywood deck on a steel boat. The numbers look great , and the numbers wont tell you anything about the kind of maintenance nightmare it will result in. They wont tell you that plywood is impossible to properly insulate without introducing a high risk of dry rot, or that in cold weather the plywood will be covered in ice, inside. They wont tell you that deck hardware bolted down, instead of welded down, will leak, and pull loose a lot more, as the plywood swells and shrinks against metal, which wont, inevitably pulling any bedding compound apart.
As the hull deck joint takes most of the twisting load of the boat ,huge loads, responsible for so many hull- deck joint problems in fibreglass boats, bolts will inevitably work loose in the wettest part of the deck structure, drastically weakening it. It is the worst place on the boat for changing materials, something your calculations wont tell you. Only experience will do that.
Changing the transition to the inside edge of the deck, makes it far less structurally important, but still a bit wet, and prone to dry rot and leaks. Had leaks there in my cement boat , no fun.
As cabin sides are not all that heavy, especially when you cut ports in them, the top of the cabin side would be a far better place for any transition, something your math calculations wont tell you.
I replaced the plywood cabin top on a Colvin gazelle with aluminium, which was far lighter, and a material you could spray foam over and insulate properly, without fear of dry rot. Worked out well.
Don't expect those who believe their calculations can tell them everything they need to know about boats, with no real hands on practical experience, without living aboard in different climates, and cruising in their products over many decades, to comprehend such practical matters . Now that would be na´ve!

Bob, a friend just bought one of your boats . Nice looking boat. Could you explain the logic in stanchions so short, that all they can hope to accomplish is to make sure you hit the water head first instead if feet first? If "yachtiness" prevails , they will have on high visibility yellow boots, to maker sure you can see their feet, when they are up to their necks in murky water.
How very yotty!

Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"

Last edited by Brent Swain; 08-05-2013 at 06:52 PM.
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