Subject: Re: [harryproa] Re: Rotating Carbon Fiber Mast
From: "Rob Denney" <>
Date: 7/20/2007, 11:32 AM

My boat is having a wing section mast, we are part way through a full wing sail rig for a 60 footer and have a couple of other wing masts on the maybe list.  I have never seen the point of elliptical, although Eric Sponberg, who has designed a lot more masts than I have, thinks they are the way to go.  Guess we could do one if required.

On 7/20/07, Harry Tomlinson <> wrote:

Thanks for the responses; the advice seams reasonable. I found the
mast building stuff in the archives under building the split cabin
Harrygami and I found UHMWPE tube on McMaster Carr for bearing
material. I'll let yall know what I end up doing and how it works,
but it might be a long time before I do any building
(responsibilities and all).

Just out of curiosity, Rob, do you design eliptical or teardrop
masts as well as circular?

--- In, "Rob Denney" <harryproa@...>
> G'day,
> There is some information on the strip plank technique in the
archives at
> 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
> 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@...> 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
> > lb (1380 kg-m). The hull depth for embedment is about 2.5 ft
> > m). I figured this application would have some similarity to a
> > 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)
> > the lower section (say 2 meters long), overlay a thin plywood or
> > strip plank wood core overlapping the pipe (say 1 meter overlap)
> > hand lay-up the carbon fiber/epoxy composite with a combination
> > 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.
> > HDPE would therefore be the bearing material. I wonder if this
> > embedment gives too much friction for rotation.
> >
> >
> >

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