Subject: Re: [harryproa] Reducing beam afloat
From: "Peter Southwood" <peter.southwood@telkomsa.net>
Date: 5/15/2008, 4:35 AM
To:
Reply-to:
harryproa@yahoogroups.com.au

Hi Arto,
The swing beams can be simplified by having the hinges at the ends only, there were a few trimarans built with this type of system in the early days I think Westell was the builder. I think maybe Dragonflies were also built this way. The hard deck and dinghy ramp could fold up when the ama is swung inboard (or down if it doesnt matter if they hang in the water.
The usually used wire stays to lock everything in place for sailing. If the stays are for and aft of the akas then they will put big stresses on the lee hull, so it would be better to have them diagonally between the akas or more convenient but heavier, to use locking mechanisms on the beams. It would only be necessary to lock one end of each beam though. For a harry proa it would make sense for the lock to be at the lee hull as there is more space and a bulky mechanism wouldnt get in the way of anything else, though if the windward hull has a lee pod, that might be a good base for mounting a locking device.
This arrangement would work best if the WW hull is short enough not to extend beyod the LW hull when folded.
Cheers,
Peter
----- Original Message -----
From: Arto Hakkarainen
To: harryproa@yahoogroups.com.au
Sent: Thursday, May 15, 2008 7:21 AM
Subject: Re: [harryproa] Reducing beam afloat

--- Mike Crawford <jmichael@gwi.net> wrote:
>
> Rafael Francke at Cat2fold has a very interesting
> design for a folding
> catamaran that can reduce its beam while on the
> water.
>

In
> addition, he as a
> fold-down hard deck to span between the beams.
>
> http://www.cat2fold.com/index.php?page=videos
> http://www.cat2fold.com/index.php?page=pictures
>
> You can see from the video how the scissors-action
> akas allow the boat
> to fold and unfold while stable, while also keeping
> each hull vertical
> (no stained/blistered topsides like with the Farrier
> method).
>
> This design would obviously make it tough to have
> a full-beam solid
> walkway. That would either have to be removable,
> foldable like the
> Francke design, or left out entirely.
>
> It wouldn't be a classic trailering solution,
> either.
>
> By putting the wheel in the cockpit, though, or
> using tillers, you
> could have a system that gets the beam down to 12'.
> That's narrow
> enough for a marina berth. 12' is also the maximum
> trailering width in
> the United States for getting a wide load permit
> that doesn't require
> escort vehicles with signs to lead or follow the
> main vehicle.
>
> There are problems with the design. It could add
> 50 to 100 kg to the
> boat weight, it would add expense, and there
> wouldn't be room for the
> wheels and walkway in the existing location. But if
> you want to fold on
> the water while keeping both hulls level, Francke's
> design is a workable
> solution.
>
[lot of text snipped from between]

Mike,

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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