Subject: [harryproa] Re: New test with larger board and sail
From: "Robert" <>
Date: 5/22/2008, 1:53 AM

This is what I have been rabbiting on about for years.It is nice to
see it in practice. Once the bows start to immerse, there may be even
less resistance. Compare this to a flared bow which would have a
sudden increase in resistance. Another thing I advocate is a reverse
stem to make it smoother through chop. Could you get someone to push a
board up and down in the water to see how the boats go through waves.
My ideal lw hull shape is a bit of a flare at the crossbeam, going to
vertical half way to the bow and slightly reversing as it gets to the
bow. I am not sure how easy it would be to do as I don't know how much
twist can be put into the sheets used for skinning the craft This
would give more bury for the crossbeams, a slightly wider berth and a
bit of lift in surfing conditions, while having good wave piercing
ability. Optimising the bows is made more difficult as they are also
the stern but I think a v just near the end would help with coming off
waves, allow some waterplane resistance, and allow a fine exit.
The gradual burying is much easier to handle than cartwheeling a Hobie 16
--- In, "tsstproa" <bitme1234@...> wrote:
> I did a static test a while back in the tube with the old lwh and
> weight. I think what kept the model upright was the righting moment
> vs heeling angle and extra buoyancy in reverse sheer in lwh when
> wind pressure spilled from the sail at an angle less than the
> heeling angle to cause an over turn.
> The fact that the hulls are square they due have a high prismatic
> coefficient. lwh is .801 . So I think this helps to maintain drive
> even when submerged along with the reverse sheer adding buoyancy
> gradually the deeper the bow goes under. Could be wrong here but
> seems that in combination of the two, high coefficient and reverse
> sheer. The water pressure or forces on hull are small and gradual
> nothing drastic or extreme to cuase sudden change in effect, to a
> point. Probably way off on how it works but with the right
> intention.
> Todd
> --- In, "Robert" <cateran1949@>
> wrote:
> >
> > -most impressed by how boat kept on sailing with bow submerged, and
> > then there was point where there wasn't enough weight on the
> stern to
> > keep it down. Still trying to work out why it didn't capsize but
> > stalled and fell back to start again -- In
> >, "tsstproa" <bitme1234@> wrote:
> > >
> > >
> > >
> > >
> > > Same day test with square harry full sails and main alone, along
> with
> > > crab claw model.
> > >
> > > New board on square harry has a more positive feed back not
> becoming
> > > over powered and stalling seems to hook up well even with the
> larger
> > > sail area. You can see though in the puffs the bow gets over
> powered.
> > > But when reduced to main sail alone in stronger winds it
> balances back
> > > with probably more board pressure. Don't see full sail working
> in
> > > anything over 8mph. I would reef main by 1/3 first or reef
> foresail by
> > > 1/3 and main by half, second. I thnik maybe instead of 185sq''
> better
> > > would be 150sqft on a shorter stick 0n square harry.
> > >
> > > Todd
> > >
> >

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