"Bewert" wrote in message
news:P5Q1d.417122$M95.119342@pd7tw1no...
I'm working on a project in Vancouver BC in which the client wants an
exterior deck in which they want 3/4"x2 3/4" solid teak strips epoxies
to
2
laminated 3/4" shts of Marine plywood. They want the joints between the
strips to be bonded with Sikyflex caulking with no seems as on a boat
deck.
I was wondering if you could use regular biscuits joiners exteriorly,or
would they swell to much more than the teak & create problems as this
is
a
very wet climate,also what is the best epoxy?I thought the biscuits
would
help keep the planks even as I can't use screws to keep them down to
set.Thanks



You can do the epoxy part using a method descibed in the W.E.S.T system
epoxy booklet entitled "Fiberglass boat repair and maintenance" page 45.
Basicly you use screws inserted in the space between boards to clamp the
teak while the epoxy is curing. After cure they are removed and their
holes are filled with epoxy. The spaces btween the planks are filled with
sikaflex or something similar.

Here's the problem. It sound like your customers are asking that the teak
be laid up tight without any significant joint between the planks.
Assuming that this is a horizontal outdoor surface of unvarnished teak,
this arrangement is guaranteed to fail. The problem is that the teak will
expand and contract with varying moisture levels. Percent of shrinkage of
teak is about 4% from winter wet to summer dry. That means that a 4' panel
of teak will grow about 2" when wet in the first winter after
installation. This incease in dimension must have some place to go. In a
tight installation, it will result in pressure on whatever bounds the
edges and you will see cupping in the center planks which will probably
result in breakage of the epoxy bond. This is the entire rationalle behind
the 1/8" plus sikaflex joint between teak planks/strips on boats. Each 2
3/4" strip will only move 0.1" seasonally. The adjacent sikaflex seam can
easily handle that kind of movement without transmitting the force to the
neighboring strip. Additionally, the epoxy bond on the bottom of each
strip is unlikely to rupture as the movement is distributed accross the
entire bottom face of the strip. Your 2 3/4" are the widest strips I would
use in this sort of application. Narrower strips of about 1 7/8 are vastly
superior.

Let us know what you do and how it comes through the first winter. Never
underestimate the power of expanding wood. It was used to split the stones
that built the pyramids.


David
S/V Nausicaa