G'day,

There is some information on the strip plank technique in the archives at www.harryproa.com.  The technique works, but we have made improvements since then. 

 

First you need to determine how strong the mast needs to be.  Either pay for an engineer (ours charges $1,000 per mast) or do it yourself from first principles.  I am happy to comment on any calculations you do.  We can sell you plans and instructions for building it for anything from $1,000 for the bare tube upwards, depending on what other information you need. 

 

All very expensive for a small mast, but the drawings and calculations are the same regardless of length. 

 

Bonding to alloy would be a mistake, for the reasons mentioned, and others such as electrolytic corrosion..  We use UMPWE bearings and use them as a mould and thickened epoxy  to make the mast round.  Works well. 

 

Bonding a tube into the boat does solve the deck leak problem but at the expense of more weight and cost, plus you cannot see the top bearing.  Too big a price for too small a gain in my opinion. 

 

regards,

 

Rob

 

On 7/19/07, harry_tomlnson <harry_tomlnson@yahoo.com.au> wrote:

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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