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Old 09-01-2010, 10:39   #31
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18 m catamaran

A friend of mine put such an aluminium mast on deck of his self built 18,1 x 9,4 m aluminum catamaran 'blu:kat'. Mast length: 21,4 m, weight: 700 kg.
He uses the same technique for boom and front beam. All parts are selfmade. The mast was calculated by the German engineer:
Bernd Tiedemann,

The boat is in the moment in charterwork in the Caribbean after it's first Atlantic crossing. If someone interest, I believe the owner will gave informations about.

A report of that boat, and the building process you will find at the homepage: blu:venture - Katamaran Segeln
Texts are all in German, but a lot of pictures shows all.
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Old 09-01-2010, 14:26   #32
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Originally Posted by multihuller View Post
A friend of mine put such an aluminium mast on deck of his self built 18,1 x 9,4 m aluminum catamaran 'blu:kat'. Mast length: 21,4 m, weight: 700 kg.
Was ist das here, KAT? Schaut wie a trimaran.

I like the center section, it's out of the water but works as a wave breaker, similar to an old Grainger design.

blukat Film

This guy is a expert welder in aluminum. Mein Deutsch ist nicht sehr goot BUT I"m willing to bet the fabricated masts are heat treated (stress relieved).

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Old 12-01-2010, 02:21   #33
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Less turbulence in leech?

First: There is an around 40 feet cat lying in Dintelmond in the Netherlands with such a mast. Triangular shape, pointing to the rear. The cat looks at least 20 years old in design, so the owner must have some experience with reliability issues. I'll make pictures next time I visit that marina, our Mahe 36 is there as well.

I wondered about one advantage I did not see mentioned on this thread: wind can blow through the mast. This might reduce the turbulence and efficiency loss caused by the wind shadow of standard masts at the leech of the mainsail (which can alternatively be reduced by using a rotating mast).

Fact is that you don't see this construction on racers, and they will do anything (and accept high cost) to make a boat go faster. Still, there may be advantages for a cruiser.
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Old 12-01-2010, 11:03   #34
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Jeff & Marin Windage was my original question. What will this mast perform like. I'd guess a rotating wing or mast will out perform it, but will this truss out perform a typical stationary mast.

As a former racer I agree with your point but I figure the big performers go the rotating mast route. Others go for reliability, KISS principal. And I'd guess again that others don't want to go out of the box or take a chance on an unproven concept, (ridicule is an issue here too). Then there's the one design factor where racers want to test their skills on similar boats, (except they, I, do buy new sails when able to).

It would be interesting to see what designers think. Maybe someone's done studies on this in a wind tunnel, low speed of course. How about crane designers. Anyone with real experience out there?

I see this mast every day and its grown on me. But I don't want a performance or reliability penalty.

Thanks again for all these posts.

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Old 12-01-2010, 11:35   #35
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Strong- yes, if proper welding practices are followed.
Turbulence -yes. No doubt with all of those open spaces to flow around and upset things.
Noise in a breeze - yes.
To my thinking it would sail best with a gaff rig. But who does that. Pappy
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Old 16-01-2010, 13:18   #36
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I suspect there is no chance for laminar flow over the sail. Rather, the mast serves as a turbulence generator, and I suspect that sailtails will quiver at a fairly high frequency, but appear to be steady. In addition to the structural issues of that many welds, the issue of windage is serious in a gale.

Remember, escaping from the struts and guy wires of the biplane era was a major advancement in the performance of all aircraft; the only biplanes flying today are collector's items and crop dusters, where drag and turbulence are a plus!

Boat buyers are for the most part extremely conservative. Radical designs such as this must demonstrate undeniable advantages to catch on, but changes do happen when that case is met. With this many examples already out there that long, there probably aren't any great advantages. However, this sample doesn't even fill the number expected of the lunatic fringe! If it doesn't work that great, and doesn't really appeal to the lunatic fringe, it's a curio.

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