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I am Tosk

In article ,
says...

On Mon, 27 Sep 2010 06:58:45 -0400, 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...

Agreed that a layer of glass on one side is inferior to glass on both
sides but I would argue that it is far more then simply a sealer.

Not what I said at all, for smaller boats, glass on both sides only
invites more rotting and moisture retention...

In
fact if it is simply a sealer there would be no sense in applying the
cloth as glass cloth is far from being water proof, quite the contrary
in fact.

Of course there would be "sense" in applying the glass. To understand
you must first understand that glass it to hold resin, resin is to fill
glass.. They work together, it's just the way it is...

If sealing were the sole purpose then all the boat designers wouldn't
be recommending "glass over...." .

Sure they would, cause glass it to hold resin...

The layer of glass actually makes the 3 mm ply substantially more
resistant to bending then bare ply would be. A parallel might be
fabric covered aircraft where the airframe is covered with a cloth
which is perhaps less strong then a bed sheet, which is then
reinforced with coats of cellulose dope.

Don't know much about airplanes but I bet the framework is substantial
under that skin. Either way, a 4 oz layer of glass over 6mm Occoume does
not all all that much stiffness. Glass is good for adding structure when
laminated into fillets, but trying to use it to stiffen a plywood hull
is a waste of time and poor design.

The guy who taught me to use glass and resin had over 40 years in the
shop, fabricating with glass, resin, and other combinations of
materials. He knew more than either of the two distributors I bought
from as to be expected as his experience was all hands on in the shop.
Most boat builders I know don't really understand as much about glass
and resin as they think they do, but I know how my ideas are taken here
and not to be an ass, I know how you are about being challenged on such
issues so I will leave this as my last post to this thread..

Take it for what it's worth... I will note that I have built over 50
plywood, glass, and resin, stitch and tape, tack and tape, and glue and
screw type boats in my day...

Cheers to you too

Scotty from SmallBoats.com

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

--
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...