What is "constant camber?"

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Mindprobe - 17 Jul 2005 06:01 GMT

I've seen the phrase applied to boathulls, especially catamarans.
Seeking edification. Thanks.

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Matt Colie - 17 Jul 2005 07:29 GMT

Mind,
It means that the frames (or stations) for a plate or strake are parallel.
Translation for normal folks:
the piece that makes up that portion of the hull is done as a "flat
wrap" without any twist in it.
If I did not give you an answer you understand, I would be happy to try
again. Or, answer another question, if you have one.
I'm here a lot.
Matt Colie
Lifelong Waterman, Licensed Mariner and Pathological Sailor
(with a naval arch degree - too)

> I've seen the phrase applied to boathulls, especially catamarans.
> Seeking edification. Thanks.

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William R. Watt - 17 Jul 2005 14:50 GMT

camber is the curve in some surface, eg the deck on a sailboat. another
way of expressing it, it's often given as the radius of curvature which is
the radius of the circle which has the same degree of curve in it. a
constant camber means the radius of curvature doesn't change. on the
foredeck of a sailboat, it has the same side-to-side curvature from bow to
cabin.

there's a Basic language computer program on my website (see below) under
"Boats" then "Boatbuilding" which computes camber and displays radius of
curvature and the co-ordinates for drawing a curve which is the arc of a
circle. I think it plots a eliptical camber as well, I can't remember.
there is also a file of formuale for calculating radius of curvature.
length of arc, area enclosed by the arc, etc.

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Sam - 17 Jul 2005 18:44 GMT

I'm thinking it is a system for building hulls where you have a form
that is curved in the width and length that you can laminate a panel
on, in either fiberglass or veneered wood. You can then take 2 panels
of the same size and put them together for a hull or 4 panels of the
same size for the 2 hulls of a catamaran. Using the same form, you
could also make 1 big center hull, and then using just part of the area
of the form to make 4 smaller panels for the ama's(?) (outside hulls)
of a trimaran. The curvature (camber) of the form being constant or the
same on both sides of the center point allows the 2 panels to be
reversed, put together and the shape of the hull ends up being
symetrical.

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Tim Mueller - 19 Jul 2005 04:09 GMT

> I'm thinking it is a system for building hulls where you have a form
> that is curved in the width and length that you can laminate a panel
[quoted text clipped - 7 lines]
> reversed, put together and the shape of the hull ends up being
> symetrical.

Yes, they are called amas.

Jim "Sea Runner Trimarans" Brown built a few constant camber boats at
WoodenBoat School in the early 90's. His system was just as described
above.

One of the boats was a tri, and one was a sweet little dinghy.
Cold-molded panels for both came off the same torus mold.

If I recall correctly, Jim had been, under World Bank auspices, into the
under-developed world (Africa, Central America) setting up boat building
programs using constant camber.

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Jim Conlin - 20 Jul 2005 05:57 GMT

"Constant Camber" is a boatbuilding technique developed by Dick Newick and
Jim Brown for making sections of multihull hulls in an efficient way. In
it, there is a single standard mold, having a compound shape of constant
camber on which cold-molded panels of several layers of veneer were laid up
with epoxy. Several of these panels would be joined into a trimaran or
catamaran hull. This technique had the advantage of only requiring one mold
to be built, but required that the panels be 'tortured' into the desired
hull shape. Ultimately, the evolution of multihull hulls to have less
rocker and the emergence of strip planking methods, structural foams and
sandwich construction have eliminated its use. Kurt Hughes' "cylinder
molding" is the last gasp of the idea.

> I've seen the phrase applied to boathulls, especially catamarans.
> Seeking edification. Thanks.

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Boat Forum / Building / July 2005

What is "constant camber?"