Subject: Re: [harryproa] Rotating Carbon Fiber Mast
From: "David Howie" <>
Date: 7/18/2007, 4:29 PM

I'm no engineer but wanted to ask this before.

Why not a fixed tube from the bottom of the boat , through the deck and up say 3m. Then the wing can slide down over that and the bearings are all above deck and the deck is watertight. Did that make sense??

------ Original Message ------
Received: Wed, 18 Jul 2007 10:56:40 AM MDT
From: "harry_tomlnson" <>
Subject: [harryproa] Rotating Carbon Fiber Mast

What's a good method to home build carbon fiber masts? Also, for a
freestanding and rotating mast, what's a good design for the
bearings/embedment. My specific interest is in a freestanding
rotating rig with a wishbone sprit boom with about a 25 foot tall
(7.5 meter) mast on a boat with a max righting moment of 10,000 ft-
lb (1380 kg-m). The hull depth for embedment is about 2.5 ft (0.75
m). I figured this application would have some similarity to a uni-
rigged Elementarry.

Is there a free, written description of the Harryproa strip plank
carbon tow method I have seen reference to?

For those with experience, do you think the following idea has
merit? Use a structural aluminum pipe (T6061 4-in schedule 40) for
the lower section (say 2 meters long), overlay a thin plywood or
strip plank wood core overlapping the pipe (say 1 meter overlap) and
hand lay-up the carbon fiber/epoxy composite with a combination of
biaxial and uniaxial cloth. I have thought through the details of
this process, especially how to get the wood/carbon/epoxy to hook up
real good with the aluminum stub, but I won't try to explain it
here. The aluminum stub would then insert in a high density
polyethylene (HDPE) pipe solidly attached to the hull framing. The
HDPE would therefore be the bearing material. I wonder if this
embedment gives too much friction for rotation.

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