Mast Extension Depth

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Ashevillejanes
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Joined: 07/10/2018 - 09:23
Posts: 55
Mast Extension Depth

I have a 42 cm mast extension. If I use the full size there will be 13 cm in the mast. Is that recommended? Seems like I would want more, especially for high wind applications.

Basically seeing if I can use a 370 mast combined with above mast extension to fit a sail that requires a 430 mast.

Thoughts?

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AWD_Tiger
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Joined: 04/26/2018 - 15:50
Posts: 73
Re: Mast Extension Depth

I’ve used a 430 mast with big extension for my 7.3 sail (460 mast required). I don’t recall how long my extension is though.

That being said, I ended up getting a 460 mast to be on the safe side.

-Clayton

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Ashevillejanes
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webguy
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Joined: 12/31/2000 - 22:01
Posts: 11443
Re: Mast Extension Depth

I've used a 48 cm extension raised to 44 without issue. Chinook puts the holes as far as they feel comfortable and no more. Keep in mind that most of the pressure at the bottom is in compression, not bending. The big bending pressure is in the middle of the mast and that's where you see them break.

Now, a separate issue, a 370 in a sail that calls for 430. The luff curve is cut assuming the bend characteristics and stiffness of the recommended mast. When the sail is under load, the mast will bend way too much which will balloon out the sail exactly when you want to keep it flat - exactly the opposite of what you want in a higher wind situation. It's like adding downhaul to a sail and not adjusting the outhaul to compensate. tLightweight sailors can, and often do, go down one mast size because they put less bending pressure on the mast (less weight on the harness) but hardly anyone can get away with two mast sizes.

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AWD_Tiger
Ashevillejanes