On 30 May 2007 22:22:16 -0700,
wrote:
On May 30, 11:22 pm, Bruce wrote:
On 30 May 2007 19:52:36 -0700, wrote:
I am determined to have smooth lines on the small Whaler clone I am
thinking of building. If I were to carve the shape of the outside hull
into foam, and then laminate an outside skin in it with resin and
glass, what kind of layup would I use, how many layers, what material?
Any guidelines or educated guesses, tia.
Be a bit more specific.
Do you mean make a mold from foam, laying up a fiberglass skin and
then removing it from the mold?, or
make a foam boat, for want of a better word, and sheath it, inside and
out, with fiberglass?
To calculate thickness of fiberglass you will need to specify the
length and breadth of the hull, how many and where any reinforcement
will be located, the intended use of the boat, anticipated life of the
boat, and probably a number of other specializations that I didn't
mention. Not a trivial task.
Bruce in Bangkok
(brucepaigeatgmaildotcom)
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Here is a link to the boat I want to use as a starting point. I would
probably be looking to make my hull very similar to this boat, size,
length, etc.
http://cgi.ebay.com/ebaymotors/13-Bo...20493171QQrdZ1
I hope the link works. If not, and if you wish you can go to ebay,
type in "Boston Whaler" and look at any of the several 13" Sport
models that show up. I would probably build a flatbottom skimmer type
vehicle and then use foam to build up the tri hulls. I could but
bulkheads in the forms every 12-18 inches and then cover with laminate
of some sort to form a skin. I would leave the foam in the hull, the
floor would be flat and come up in the bow like a scow as is the case
in these whalers too. I imagine they leave the foam in there too. So I
need a laminated skin that would need to support itself over the foam
in maybe 12 X 18 inch surfaces. The tri hulls would be made in this
manner, everything above the floor including the sides and transom,
floor etc, would be made in traditional (heh, seems funny calling S+T
traditional) stitch and tape with Ocoume plywood, resin and cloth.
Thanks for your interest, hope this gives you enough info to get me
pointed in the right direction. I know some of the kayak guys use
methods like this, and I do remember one "bullet proof boat" a few
years back, think it was this group.
I suggest that you have a look at
http://continuouswave.com/whaler/reference/13/
Much better information about the Whaler 13.
Down toward the bottom of the page there is a picture of a whaler with
the stern cut off to show the construction which appears to be
essentially a foam boat with inner and outer skins.
First of all I think you are starting on a much more complicated job
then you realize but having said that here is the way I'd do it.
First you need to design the boat and loft it, full size if possible.
This lets you plan things like transitions between thicker and thinner
layers of glass cloth, reinforcing wood inlays, etc., accurately.
Next, build the "upper hull" which would be a flat bottomed structure
consisting of the "floor" and top sides of the boat. This could be a
stitch and tape structure.
Turn the upper hull over and shape and glue foam blocks to the hull
and fair to the shape you want. You do not need bulkheads.
You will, of course, need to incorporate a solid transom to mount your
engine and build in strong points, where needed, from solid wood, to
mount whatever...
Once every thing is completed the entire hull is covered inside and
outside using glass cloth and epoxy resin.
Several things you should be thinking about
:
As the topsides are fairly thin plywood and the base/keel is a thick
foam sandwich the top sides may be more flexible then you want. You
may have to inlet "ribs into the foam bottom that reach to the top of
the sides to stiffen them.
You DO want to use closed cell foam for your construction. Invariably
these foam composite structures get damaged. If you do not use closed
cell foam and you get a crack or hole below the water line your hull
will absorb an amazing amount of water.
You DO want to use epoxy resin and glass cloth that is designed for
epoxy. It is possible to build a composite structure like this with
polyester resin but you would definitely need to take more pains in
order to have a solid structure. But, of course, the polyester resin
is much cheaper then the epoxy.
Be sure that your foam is compatible with the resin you plan to use.
In real life, whether you use chopped mat or woven cloth is pretty
much immaterial but the chopped mat will take more filler to fair the
boat.
Here in Thailand we use Grams/M2 and my figures for Ounces/Yd2 are
estimates. I would probably cover the bottom with about 1/8 inch of
glass, something like 2400 Gm/M2, about 72 Oz/Yd2 and the plywood
structure with about half that. These are estimates only and might
well be changed as the building progresses.
You will have to make a transition between the thicker glass on the
lower part of the hull and the thinner on the plywood by tapering the
foam on the lower part of the hull.
About all I've done is "hit the high places" but it may give you an
idea of what you are getting in to.
Bruce in Bangkok
(brucepaigeatgmaildotcom)
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