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Old 04-01-2010
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seeking advice on tapering an aluminum mast

Greetings folks,

I am hoping that I can gather some knowledge here on tapering an aluminum spar.

I am re-rigging my boat and will be converting a mast section from mast head to fractional rigged. The hardware to do this is readily available from Sparcraft so that part should be somewhat easy.

I would really like to put a taper in the mast and would like to hear pros/cons of doing this and any advice on how to do it.

I have excellent welders and both mechanical and welding engineers assisting me to do the project so am not completely entering into this blindly.

Thanks All.
Jay
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Old 04-01-2010
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Well

On and orginal J24 mast its easy to see were they cut out the front section and closed it back up to form the taper

I would think there would be a LOT of hit amd miss AS TO THE END RESULT
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Old 04-01-2010
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I'd point out that most modern spars are heat-treated grades of aluminum alloy and gain much of their strength from the tempering process. Cutting and re-welding the spars are going to cause them to lose much of their strength unless you can re-heat-treat the spar....which I doubt.
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Quote:
Originally Posted by sailingdog View Post
I'd point out that most modern spars are heat-treated grades of aluminum alloy and gain much of their strength from the tempering process. Cutting and re-welding the spars are going to cause them to lose much of their strength unless you can re-heat-treat the spar....which I doubt.
Understood, but as I understand it, the top 5-6 feet of the spar is under mostly compression load. The strength lost won't matter as long and as there is a fully penetrated weld things will be good.
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Old 04-01-2010
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Quote:
Originally Posted by sharedwatch View Post
Greetings folks,.....I am re-rigging my boat and will be converting a mast section from mast head to fractional rigged.
I'd be interested in what boat you're doing this to and what dimensions you are going to vis-a-vis the original rig. This could significantly shift the C of E of the sailplan if the mast isn't relocated at the same time. Details?....

As far as putting the taper in, strength/wisdom issues aside I believe it's usually done by cutting a vertical wedge in the leading edge, squeezing the section together again and welding the resulting seam.
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Old 04-01-2010
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Actually I have seen it done many times on Soling masts and unless my memory fails me, which it often does, they cut a tapered slit along each side and pinched them together and welded it up.

Did not seem to be overly difficult but there may be some thing to the heat treating. They may have shipped the spars out for anodizing and it could have had some form of heat treatment then ??
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Old 04-02-2010
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I'd be interested in what boat you're doing this to and what dimensions you are going to vis-a-vis the original rig. This could significantly shift the C of E of the sailplan if the mast isn't relocated at the same time. Details?....

As far as putting the taper in, strength/wisdom issues aside I believe it's usually done by cutting a vertical wedge in the leading edge, squeezing the section together again and welding the resulting seam.

Alden Caravelle. I'm not too worried about negatively effecting the CE. -quite the opposite actually. I'll be adding about 6 feet to the rig and changing to fractional rather than masthead. It has been done before to a sister-ship and I have consulted with a naval architect about the rig change.
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Old 04-04-2010
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We may have had one of those taperd Soling masts on our boat. It was certainly anodized after the welding was done, and held up fine. Sharedwatch has not yet advised the size of his mast or boat, so we have no way of kowing the loads associated with it. Up to a Soling size, rough guesstimates may be good enough. When you get much bigger, more precise info might be a good idea if you don't want the top fraction of your fractional rig to crack off the second time you crank in the backstay.
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Old 04-04-2010
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Quote:
Originally Posted by sharedwatch View Post
I would really like to put a taper in the mast and would like to hear pros/cons of doing this and any advice on how to do it.
Jay,

Not trying to be smart here, just curious -- what's the benefit of tapering the spar?
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Quote:
Originally Posted by sharedwatch View Post
Alden Caravelle. I'm not too worried about negatively effecting the CE. -quite the opposite actually. I'll be adding about 6 feet to the rig and changing to fractional rather than masthead. It has been done before to a sister-ship and I have consulted with a naval architect about the rig change.
Ah.,.... Clever - all your headsails will still fit! That's great, I was just concerned that some ill advised butchery was ahead but obviously you're going about this the right way!

Best of luck.
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