On May 31, 11:12 pm, Bruce wrote:
I suggest that you have a look athttp://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.
I have built, lofted and spiled a few wood and wood and glass boats, I
don't think to much of it will surprise me labor wise, I am pretty
good with epoxy and glass, and I have plenty of time to do the
project.
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.
I will probably loft it out as I go, I am leaning toward a ply on
frame build the whole length of the boat, may use foam and glass to
make some pretty transititions between plywood panels. I have been
studying the many pics I have of the hull I want (13 foot whaler
sport) and I see 4 fairly defined planes that could be used, a little
smoothing inbetween strakes would make it possible to get a lot of the
nice form of the underside of the hull of the whaler. But I do see 4
panels. I am going to start on a scale half hull and see what I can
come up with.
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.
I would probably build wood into the hull at the transom and up the
seams to the bow, also I would build the boat around two or more
pretty good stringers that would tie into the transom, I have always
had a tendency to overengineer things
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.
Great point, I may not be using as much (if any) foam as I origionally
thought, If I do I will bet something like Divenacell (sp?) or
something similar.
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.
I always build with Epoxy and glass,( I am not skeered of a little
money
), most of my construction experience has been with resin as
a filler for glass or strictly as an adhesive, glass to wood, glass to
glass. I have no experience however laminating structurally critical
"skins" over foam, that is my biggest question which I think you have
addressed below.
Be sure that your foam is compatible with the resin you plan to use.
Yes, and my glass too.
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.
Sounds like I can go with just cloth? I will get some heavier cloth
and do some tests, mabey two to three layers and see if it is enough,
thanks.
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.
I have done enough glass work I kind of see that in advance and make
arrangements in advance, while forming the parts, I don't think I will
have a big problem there.
About all I've done is "hit the high places" but it may give you an
idea of what you are getting in to.
You have been more than helpful, I think I have a real direction to go
now. I did not really want to use mat, I was hoping there was a
possibliliy I could go with fabric and it sounds like I may be able
to. Also since I first posted I have been looking real hard at that
hull, I think it can be done, Thanks again everyone, I will keep you
posted.
Bruce in Bangkok
(brucepaigeatgmaildotcom)
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