- There's been some discussion of UHMW plastics for bottom
runners/sheathing for small boats; I just spoke with Pete, a product
guy at Crown Plastics: http://www.crownplastics.com/ 513-367-0238.
They have noticed that boatbuilding may be a pretty good market for
UHMW, and want to understand it better; they've had a lot of interest
from manufacturers of drift boats, air boats, etc.
In the past, you had to use at least 1/4" thick sheets, to allow for
countersinking the screws. Since this isn't great in boats - too
much weight, and lots of screw holes - they've developed two UHMW
product lines that fit the bill - a pressure sensitive adhesive
backed sheet, and a "treated for bonding" sheet. They think 3/32
(.093") may be the best thickness for sheathing the bottom of a boat,
in 12 or 18" widths.
Pressure-Sensitive-Adhesive: Crown applies a 20 mil foam acrylic
adhesive (mfd by Avery Denison) to one side of the sheet. You peel
off the backer sheet (a little at a time) and use a firm roller to
apply about 2' at a time, applying pressure, and rolling out air
bubbles. This adhesive is supposed to be pretty good in a marine
environment, but can be removed (with some difficulty) at a later
Treated-for-Bonding: One surface is roughed up (my
oversimplification) to allow a mechanical bond with epoxy or other
glues. This sounds ideal for boatbuilding, but Pete warns that
it's "permanent" - no removing it later, for any reason. At first,
this sounds good, but what if it does wear out, or you need to make
repairs on the underlying plywood... This system is used in
snowboards, where you just discard the whole assembly...
In either case, thermal expansion can be an issue (a real problem
with thick sheets and screw fastenings); they recommend leaving an
expansion gap (1/16") between pieces, and have processes in
manufacturing to minimize later expansion/contraction.
I pressed Pete for a ballpark cost, and he estimated $5-10 per square
foot, depending... I'd assume more for a small (one-boat) order.
Finally, they are looking for a local (Cincinatti) boatbuilder
willing to work with them to test out products and methods.
Sounds to me like there may be some great new products coming out,
and I'm sure people will find creative new uses for them (a high-tech
alternative to copper-plating for antifouling, anyone?).
- A very nice looking example Ken!
How does she row? I like your colour scheme. Where are you? And don't
listen to anyone, you're not pazzo, I am!