19706Re: Observations re: Underlayment plywood from China
- Sep 2, 2009Last summer when I built my QT skiff, the local Lowe's had ultraply for $20 a sheet, and that's what I used:
--- In Michalak@yahoogroups.com, "recree8" <arvent@...> wrote:
> Sounds like a great choice David. Thanks for sharing.
> Ultraply is made in USA so I stand corrected. You got for $20 a sheet?
> --- In Michalak@yahoogroups.com, David Cassidy <d.cassidy@> wrote:
> > I built an AF3 using UltraPly (launched last fall after 2 summers of
> > building), and there is at least one other person on this list who
> > built the same or a similar-sized boat with it several years ago. I
> > found it to be really nice to work with- never found a void. I did
> > the "dishwasher test" with no change to the stock.
> > I also left an approx. 3 x 3-foot piece out in a Northern New England
> > winter -- that's about 5 months of snow, sleet and freezing temps. The
> > piece of ply was propped up a few feet away from the exhaust outlet
> > from our propane-powered boiler, which means it was blasted on one
> > side with hot, moist air several times each day. The piece of ply
> > survived this just fine - no delamination or checking.
> > I think UltraPly is made in the U.S., which may mean it is
> > manufactured under stricter controls than imported materials.
> > I took the boat on a 4-day "cruise" earlier this summer and was
> > subjected to some pretty rough poundings. I road out some pretty
> > violent thunderstorms while at anchor, sailed up onto the beach
> > several times and had a three hour downwind sleigh ride surfing down 3
> > - 4 foot waves (My gps clocked consistent speeds of 6.5 mph, with the
> > highest speed zI saw at 7.1 mph -- even if you figure the incoming
> > tide was helping me along over the ground, that's pretty good speed
> > for a 14 foot waterline and a homemade/sewn PolyTarp balanced lug
> > sail). During all of this, the boat felt solid as a rock, and I never
> > heard a crack or creak.
> > IMO, saving $200 on a project this size is worth it. That paid for ALL
> > of my epoxy supplies. I see no reason why, with proper protection in
> > the winter and normal spring maintenance required of any wooden boat,
> > it should last as long as a boat made out of $70/sheet marine ply.
> > You can check out a rather large Web site about the building of my
> > boat (including pictures and more thoughts on using UltraPly) at:
> > David C.
> > On Aug 31, 2009, at 1:20 PM, recree8 wrote:
> > > I think there is a lot of interest on the various types of
> > > underlayment plywoods that are coming from "Offshore" and carried at
> > > most big box suppliers. Sureply was one mentioned and there are
> > > other brands as well - Ultraply is another.
> > >
> > > I recently purchased some 1/4" stuff that was actually called
> > > "merranti" and has no nailing grids on it. Looks really nice. It is
> > > 3-ply with a darker, thicker middle core and two thinner ones on the
> > > exterior which are beautifully smooth and knot free with no visible
> > > voids anywhere.
> > >
> > > I cut some narrow strips off a sheet and did the "dishwasher test" -
> > > leaving them in the dishwasher for several long cycle wash loads.
> > > Then left them to dry out. In some spots I could peel off the outer
> > > layer just using my thumb nail, and there appeared to be no sign of
> > > glue at these locations.
> > >
> > > What appears to have happened is it had some glue-starved spots in
> > > it. Perhaps the inner core, being more absorbent soaked up most of
> > > the glue during the manufacturing process and left the joint starved
> > > of glue.
> > >
> > > Not saying it would not work if one is encapsulating the wood with
> > > epoxy and glassing the exterior,thus keeping moisture out, but I
> > > also am a bit leery that if you have uneven heat applied to the
> > > hull, say when storing the hull outside upside down under a hot sun
> > > and even covered with a tarp with cooler moist air underneath, you
> > > might get some ply separation inside the plywood.
> > >
> > > Is it worth the cost saving with a boat hull if using this plywood
> > > at $20 a sheet compared to real merranti at $60 a sheet? On a 5
> > > sheet boat it means a saving of $200.When you consider the total
> > > cost of the boat, including the epoxy, cloth, paint, varnish, spars,
> > > and framing, and sail I would suggest it is a risk unless you are
> > > either practicing with your first boat or only intending it to last
> > > maybe 5 years of occasional use compared to 10+ years of hard use.
> > >
> > > The difference in my view is the lack of quality control from the
> > > "offshore" stuff - if lucky you may have no problems, but the
> > > quality control of USA, European and Canadian made stuff, is much
> > > more consistent.
> > >
> > > From my understanding underpayment is intended to provide a smooth
> > > surface to lay carpet over and it is nailed down every foot or so or
> > > even less, so s bit of separation of ply's under the carpet may
> > > never be noticed. If it happens on your hull bottom it is a very
> > > large source of concern and potential head scratching on what to do
> > > to correct the separation from extending over time. Not that easy to
> > > repair either.
> > >
> > > Any other thoughts on this? Have some people done testing with their
> > > particular brand and found it to be free from separations? If so let
> > > us know.
> > >
> > > Nels
> > >
> > >
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