On Mon, 27 Sep 2010 10:57:13 -0700 (PDT), Frogwatch
wrote:

On Sep 27, 6:58*am, I am Tosk wrote:
In article ,
says...





On Sat, 25 Sep 2010 18:21:02 -0400, I am Tosk
wrote:

In article 084c9f63-3d17-496f-8a21-74c4d53f4a02
, says...

MiniCup #`1 is still sitting on sawhorses while I decide whether or
not to rebuild her. *#2 which I have been using developed cracks from
rot in the 3/16" poor quality ply I used on her even though she had
been glassed with 4 oz glass and epoxy. *While fixing this I found
more rot so ended up covering her entire rear with another layer of
glass. *Am almost done. *However, she seems to have absorbed some
water that I cannot get rid of as she seems heavy even with ports cut
in all her spaces.
Am looking over the old MiniCup plans and considering how to design a
modern version that will be much lighter. *Considering using 3mm
Okuome Ply covered with 8 oz glass all over with stiffening ribs of
foam and glass. All interior joints would be glass taped and interior
epoxied as well to seal the wood. Transom would be reinforced with
thicker ply and G10 glass composite for the rudder stresses. *Cockpit
and mast step would be self bailing and all hardware of either bronze
or SS. *Instead of being a "hardware store boat", I'd specify buying
actual boatbuilding screws and pulleys made for boats. *I'd reccomend
buying 1/8" Al tubing for the mast and 1/16" for the two other spars.
The sail should be sewn from white polytarp, none of this duct tape
stuff and visqueen. *I have devised a much improved gooseneck where
the two spars attach to the mast. *Any other ideas?

Sounds to me like you are going to use 1/8 inch ply and glass for
structure.. Glass doesn't add structure really it should be used for
protection if not laminated into a hull... Use 6mm plywood and protect
it with 4 oz tight weave if you need abrasion protection and such...

Err.. why is it that glass over plywood doesn't add structure while
glass cloth over foam does?

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

Laminated glass might. One layer over a 3mm plywood, not so much... In
most applications for small boats such as this, the glass is more as a
sealer and protection than a structural component. Especially one layer
of 4 oz tight weave...

--
OH, I could do the 105 footer, but I would hate to waste the last few
seconds of my life with my eyes closed, screaming like a little
girl...

More thoughts. Bottom would have 8 oz glass for better wear. The
cockpit would be glassed inside with 4 oz. All seams taped with 6 oz
with epoxy filets inside and out.

I'm not sure that is the best solution, although it certainly can be
argued. My own experience is that if one plans on dragging a
fiberglass boat up on beaches it is better to use some form of
sacrificial "wear strips" - perhaps wood laths glued on the bottom to
protect the bottom, although this certainly can be argued.

By the way, I'm sure that you know that 8 oz. cloth actually weighs
approximately twice that figure when installed due to the resin used.

The fillets are there to ensure that the cloth adheres to the complete
joint as glass cloth cannot be bent 90 degrees. So anywhere the cloth
is planned to be applied the surfaces must be a smooth radius. It is
"epoxy filler", by the way :-)

The center widthwise support made from 2X2" would not be used. It
only serves to stiffen the joint of two sheets and this can be done
with glass. Most of the curve of the bottom would be produced by the
fore and aft cockpit bulkheads. These would all have 3/4 X 3/4"
reinforcing at the edges just as the MiniCup does for ease of screwing
together and to yield a large glue surface. These will all be epoxy
filleted and glassed. My MiniCups made from 3/16" ply have needed
reinforcing across the wide foredeck and aft deck areas so I will
provide this.
The transom of the original MiniCup is very poor and I had to make it
stronger. I will use 1/4" ply glassed on both sides AND the G10
composite to attach the rudder pintles (or are they gudgeons?) to the
transom. The transom will be attached with 20 oz biax to the sides
and bottom.
I do not see how to make this boat as stitch and glue so will simply
update the use of "stringers" as attachments for the sides to the
bottom and deck to sides.

I have essentially stopped using fasteners in building small wooden
boats as a properly designed epoxy joint is already stringer then the
parent wood. A thought about the stringers - they might be 3/4 X 3/4
three sided stringers which would give the gluing surfaces and reduce
the requirement of fairing considerably. Epoxy is heavy and the less
one can use the lighter the structure.
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)