Early Stage Planned Build - Beach Cat

[jsheehan]

Design:
My orginal inspiration for this project
comes from Hobie Cat beach catamarans -
they've always looked like so much fun!
Looking around for existing designs that
meet my needs hasn't turned up anything
I'm prepared to run with, but has given
me some ideas. I've all but settled on a
modular catamaran vaugely similar to the
RebelCat, which uses large diameter PVC
pipe for its hulls, although I'm still
open to suggestions on this front.
As far as I'm concerned, building is easy,
knowing what to build is the tricky part -
and that's why I'm here, for some help and
input, and to avoid getting ahead of myself
in the whole process.
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Objectives:
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High Level:
Portable:
Must be reasonable for 1 person to
transport/assemble
Storable:
Disassembled storage footprint must
be as small as possible
Cost Effective:
I'm a college student, and most of
my earnings have already been allocated
to the beer fund.
Ease of Assembly:
Not as critical at this point but I'd
like for assembly time not to be longer
than 30-60 minutes for 1 able person.
Will be spending most of its life
unassembled.
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Operational:
Flexible Payload:
Will often be operated by 1 person
(~150lbs) but needs to be able to
perform well carrying up to ~400lbs
(to account for myself and 2-3 lovely
ladies).
Weather:
Most of its time will probably be spent
in light to medium winds, but I want a
design robust enough to push the envelope
and handle heavier weather every once in
a while.
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Sizing:
This is the stage I'm in now and where
I'm in search of a bit of help from the
more experienced.
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Things I Know:
LOA:
I'm using LOA as a starting point to build
upon as storage space is my biggest design
constraint.
LOA will be 10-12 feet (smaller is better
unless the extra length is absolutely
critical).
Displacement:
As noted above, displacement will vary
between boat weight + 150 to 400lbs.
Things to be Determined:
Sail Area:
Based on displacement and looking at other
small cat designs I was surprised to find
a SA of ~100 sq. ft. All of my sailing
experience has been monohull, so I don't
have a good feel for this on a cat - is
this too much sail? I'm especially concerned
with this parameter since I'll be switching
between sailing alone and with company.
Lateral Plane:
Lack of experience strikes again; I'm
familiar with recommendations of SA/LP for
monohulls, but the game is different with
cats. As I understand it, since stability is
less of a concern due to the wide beam, the
required lateral plane is smaller, but if
it is undersized the boat will drift leeward;
can anyone help me with this ratio for a cat?
Beam:
From what I've seen most catamarans this size
have a waterline beam to lenth ratio of about
0.4-0.6 - so that would put my beam around
5ft... sound good?
Rudder:
I've seen both dual and single rudder designs,
I'm inclined to believe that at this size a
single rudder will do just fine - any cautions
against this approach? Also, is there any
standard ratio of the rudder area to total
lateral plane / sail area / etc?
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I'll be tackling the design and build in the next couple months
(hopefully before summer is in full swing) once I've settled on
specs to design to. Looking forward to some input!

Cheers,
JS

[Doug Lord]

Seems to me you'd be better off from a time, money and beer perspective to go for an existing beachcat-Hobie 14's and 16's are over the place pretty inexpensively. I seriously doubt you'd save any money starting from scratch.
Good Luck!