On Jun 5, 10:34 pm, NSS wrote:
I'm looking to build a 20' v-bottom spritsail skiff, using stitch and
glue. Pretty much straight from the NC Maritime Museum plan #5:

http://us.st11.yimg.com/us.st.yimg.c...00216_1952_134...

This will be an open boat - structure will include short deck at the bow
(a foot or two long), with a bulkhead at the aft end of it; a thwart at
the mast, centerboard trunk, thwart at aft end of trunk, and thwart in
rear, in front of removable sternsheets. No side decking, just a strong
rail/gunwale. I will probably make gussets on either side of each
thwart, extending from rail to chine, and box in under the thwarts
(flotation filled). As per the traditional skiff, there will be a
relatively heavy deadwood starting at the aft end of the centerboard
trunk and extending to the rudder. No keelson forward, probably a
minimal one aft to bolt the deadwood through to.

I will epoxy/glass the exterior, and possibly glass the interior too
(haven't decided yet). Ply will be Okoume BS1088.

I'd like to make this boat as light as possible for maximum speed; it
will be basically a toy for the Beaufort NC area, Bogue Sound, etc.

I'd like it to be as stiff as possible for maximum performance, moreso
than for great seaworthiness. Note the rig will be a bit taller than
that shown in the plans; the norm for the museum built boats has been
15' or so mast height, vs. the 12' spec'd for the workboat in the plans.

So my question is, what thickness plywood should I use? The original
boats were planked with 7/8" juniper, with quite a few frames holding
the planks in place. With S&G I will have no frames, other than the
aforementioned structure.

I was leaning toward 3/8" for bottom and side panels, but am wondering
if I should make the bottom panel 1/2" just to stiffen things up, and
for walking around on (hoping to get away without any floorboards).

Any opinions?

Thanks in advance,

NSS

Well, if you run thin stringers inside the floor, maybe 14 inches
apart and bulkheads evey 2 feet you could probably get away with 6mm
(1/4inch"). A sheet of 6 oz. glass over the bottom for scratch
protection. Certainly with curved sides like that I would use the 6mm
for the sides. And if you are nervous, 9mm (3/8") inch on the bottom
with a lighter sheet of glass, maybe 4 oz tight weave. The two biggest
mistakes folks make with s+t is overengineering it, and over coating
it. Remember, thickness of epoxy really does not add strength on it's
own. Do a test or two with a a 2foot x 18" piece of 6mm, glass it,
support it on all four sides (like stringers and bulkheads) stand on
it. see what you think! And two, using glass and epoxy instead of wood
for structure. Hope this helps.