Subject: [harryproa] Re: Timber spar
From: "Robert" <>
Date: 2/24/2008, 7:08 PM

Consider bamboo strips. Quality bamboo has better characteristics than
most timbers. Check out the Youngs modulus and breaking strains of the
bamboo used in fly rods It makes excellent fly rods. I was looking at
making a wingmast out of bamboo, birch plywood and cedar. The idea was
a laminated beam with ceder on the inside and bamboo on the outside
for handling the side loads and the 2mm birch ply wrapping round the
lot, with some extra bamboo reinforcing for and aft. This was using
the technique for the Jarcat wooden masts, but using the bamboo to
provide the extra strength to go unstayed The numbers worked but it
was over twice the weight of a carbon one.
The Bolger masts are pretty whippy but seem to work OK from what I
have seen on a boat that I often came across sailing down the southern
coast of NSW, but again, I'd consider bamboo strips, or even a big
stick of bamboo, but they must be properly matured and of suitable

--- In, "Rob Denney" <harryproa@...> wrote:
> G;day,
> It will be heavier, possibly more expensive and will either bend
more or be
> a bigger section than a carbon one, but none of these are deal
breakers if
> you want a wooden stick. Take lots of pictures and let us know how it
> goes. Compare the righting moment of the Bolger with the proa to be
> you are in the right ball park.
> regards,
> Rob
> On Sun, Feb 24, 2008 at 2:59 PM, proaconstrictor <proaconstrictor@...>
> wrote:
> > I was wondering if any have given any further thought to a timber
> > spar. Don't freak, I know the carbon spar business is in need of
> > support. and that the carbon spar is the key to the whole design for
> > 90% of the people contenplating this design. I was just thinking of an
> > unstayed Bolger spar I have the scantlings for, and it uses an
> > interesting constrution where the back of the spar is solid timber
> > boards and the front section is light plywood. The rig was something
> > like a lug or just a leg o mutton where the loads would pull
forward on
> > the spar in a single direction. It occured to me that a similar thing
> > might be feasible on the aero rig since the spar rotates and the loads
> > could thus be kept in line with the heavier section. Not sure what
> > this would be useful for, possibly the original idea of a low
> > resistance cruiser of low cost. It would presumably just be an interim
> > rig until some time had passed and experience piled up and a move to a
> > better rig could be arranged.
> >
> >
> >

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