[MHml] Bi plane rigs.

[Rob Denney]

G'day,
The biggest weight saving you will achieve with your proposed set up is to
only have one rig.

If you have 2 x 8m luff sails with 2.6m booms and a bit of roach, you get 15
sqm per sail.  The masts will be 9m long, allowing for the bury.

With two rigs, both have to be strong enough to capsize the boat.  If you
add another 2.5m to one mast, the weight increase will be much less (~10%)
than the proportional increase in mast height, as the rest of the mast will
hardly need to be changed.     You will then have one 11.5m mast, 3.5m boom
for 29 sq m sail area.    Only one hull will need to be beefed up, your
rigging costs will halve.

It will look weird (suspect you are not too concerned about this), and be a
little harder (though much quicker) to rig.  It will have a higher coe, but
the mast will be more flexible, so not such a big problem, and will have
much better light air performance, be half as hard to sail, with no
reaching/blanketing  problems.

If this makes sense to you (it obviously doesn't to most people), we can
discuss how heavy it is having two daggerboards, and how draggy daggerboard
slots are.  ;-)

regards,

Rob ----- Original Message ----- 
From: "Roy Mills" <rsirfj at shaw.ca>
To: <multihulls at steamradio.com>
Sent: Monday, September 04, 2006 9:10 AM
Subject: [MHml] Bi plane rigs.


> In support of your response Bill, as I got to the end of the book I
> found details of four of his boats. Dandy, the one that did not do
> well with a biplane rig, is shown as LOA 24' 10", LWL  23', beam
> 15'3", empty weight 2000 pounds, max loaded  2948 pounds and sail
> area 2 times 138 sq feet. Obviously not a candidate for comparison to
> a Radical Bay, other than LOA. Radical Bay has a bit less weight,
> about 25% more beam and 56% more sail area, quite a different vessel.
>
> Have to give much thought to final numbers for the camper cat,
> hulls say keep the weight way down, have to think what max beam I can
> manage on the trailer, sail area the last number to be established,
> along with mast height.
>
> All very interesting.
>
> Roy.
>
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