Subject: Re: [harryproa] Re: Reducing beam afloat
From: "Peter Southwood" <>
Date: 5/15/2008, 11:16 AM

Hi Robert,
I think it could go either way depending on the engineering. Farrier has had great success with his hinged system, but there are not many sliding systems that get used a lot (as far as I know, correct me if I am wrong) I will agree a poorly designed hinge/folding system  is easier to achieve by accident or lack of skill, and the devil is in the details.
----- Original Message -----
From: Robert
Sent: Thursday, May 15, 2008 11:53 AM
Subject: [harryproa] Re: Reducing beam afloat

G'Day Peter,
Hinges are a pretty high stress concentration. I have my doubts that
it is lighter than a sliding system. The sliding system has really no
extra weight other than a bit of bearing surface. Maybe a few
kilograms at the most. Rob and Mark had no problems with Elementarry's
sliding system with slightly thicker beam at full out and full in
allowing easy movement at other points. I would have thought this was
easier to handle the racking loads as the highest stress is at the
beam/lw join where the scissor folding system has a hinge and the
sliding system is no different from the usual system. Controlling the
sliding in and out could be done with two simple winches and about six
small snatch blocks or a continuous line system.
-- In, "Peter Southwood"
<peter.southwood@...> wrote:
> Hi Robert,
> Hinges for swinging are easier to get to work smoothly while still
keeping stresses and play small than sliding beams, unless you have
developed an improved sliding system that hs no play, can take racking
loads, slides easily without jamming on both beams, and prevents one
beam sliding in or out more than the other, which could lock
everything up, and still has fewer moving parts and critical failure
points than swing hinges, and locks easily and reliably when deployed
for sailing. Also should weigh less.
> Cheers,
> Peter
> ----- Original Message -----
> From: Robert
> To:
> Sent: Thursday, May 15, 2008 9:50 AM
> Subject: [harryproa] Re: Reducing beam afloat
> -A simple sliding in telescoping beams is pretty simple.There is
> plenty of bury available. three metre wide ww hull and only narrowing
> by less than two metres, leaves a metre to play with. There is a bit
> of fiddling to anchor the the ends but not insurmountable. The
> advantage, is there are no fancy hinges , just simple beams and
> sockets I don't see too many problems with sealing the crossbeams, as
> the sockets could be separated from the inside volume, or just wrap a
> boot around the point of insertion. I looked at folding systems and I
> worked out how a folding system to trailing is possible. Just a bit of
> drama in removing the mast, but not insurmountable. I felt that if I
> had to trailer, then I can simply take the beams out, but I could see
> situations where I would like to quickly narrow and still be able to
> gently sail.
> Robert
> -- In, "Rob Denney" <harryproa@> wrote:
> >
> > G'day,
> >
> > Cat to fold is an interesting solution. To get 3560 degrees on the
> tillers,
> > mount the rudders on the beams, although this may mess up the
> scissoring.
> > Could also put the rudders in the hulls in daggerboard cases, if you
> really
> > wanted to scissor it.
> >
> > regards,
> > Rob
> >
> > >
> > >
> > > I am aware of cat2fold desing and actually thought it
> > > would be the best solution for a folding big proa.
> > > Trailering is not an issue for me. Accessing marinas
> > > is. The scissor-like mechanism of cat2fold design
> > > would probably offer most reliable and solid solution
> > > to folding while afloat. To get reasonable beam while
> > > folded steering wheels should be in the cockpit
> > > (tillers would be better but I haven't been able to
> > > figure out how to get 360 degrees rotation functional
> > > with tillers). Rigid walkway and optional dingy ramp
> > > would be hard to fit to folding option though. They
> > > would be very nice but I haven't been able to figure
> > > out those details yet. One monohull design had
> > > removable walkway part of cockpit bottom that doubled
> > > as gangplank. Perhaps removable/folding walkway and
> > > dinghy ramp that can be lowered while folded. Two
> > > gangplanks that can be attached between hulls as
> > > walkway? Or perhaps just live without the added
> > > complexity... Just remembered the KISS principle
> > > again.
> > >
> > > Arto
> > >
> > >
> > >
> >
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2008/05/14 04:44 PM

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