Bob,
Here is a bit more detail on the question about plywood.
"exterior grade" tells that the glue is more or less waterproof. Many
of the "interior" plywoods also have this more or less waterproof glue
also, since kitchen and bath cabinets are subject to moisture and
humidity. Where "exterior grade" comes up short, though, is that these
days it may (and usually does) have voids in the inner veneers. Those
voids on the surface have been cut out and filled with the oval-shaped
filler pieces that are visible, but that effort has not been expended on
the interior veneers. When the "exterior" plywood gets wet, moisture
soaks in and collects in the voids. Then, as it dries, or worse doesn't
dry and freezes, it tends to break apart the wood fibres around the void.
Exterior ply is pretty sorry stuff. The 3/8 exterior ply that is sold
here in CT (the product can vary by market) is made of only three plies.
The inner ply is some unrecognisable wood that nobody would admit came
from his forest. Where there is a void in the inner ply, a heel can
puncture the top ply and break into the cavity. Then the opening is a
dirt trap under the carpet, and deterioration can take place surprisingly
rapidly. Three ply also fairly limber material.
"Marine plywood" may not be what it once was--once upon a time a
"mahogany" marine ply was mahogany throughout, no voids, waterproof glue,
and two more plies than would be found in regular ply. Typically today
the marine ply is mahogany for surface veneers, a stable wood for the
inner plies, no voids, waterproof glue, and the two additional plies.
The additional plies help to make it more rigid.
Plywood is a commodity these days, so a lumber yard may have plywood
from all over the USA (usually northwest) and imported stuff too. My
recommendation would be that anyone planning to use 3/8 find plywood that
is made with at least five veneers, promises no voids, and has waterproof
glue. After fitting, it should be removed from the car and all edges wet
with epoxy until no more can be absorbed. Then the new floorboards
should be at least as good as those made by MG and should last as long.
Aside from Birch plywood (birch has very low rot resistance) I don't
think it matters what the wood is, but the points of voids, veneers, glue
and sealing the edges are important.
The plywood that MG used in my TD is excellent stuff. The 3/8" used
for the back shelf of my GT also appears to be good material. There are
no voids evident on any of the edges I can see, and tapping has not
produced the sound of a void in the plywood; I doubt that there are any.
Good plywood is available, though one may have to ask the lumberyard to
order a sheet of something that the lumberyard does not stock.
Bob
>
> 1/2". If you can't find marine you might use exterior grade and do a
>
> bit of sanding. The glue is the same, the difference is in the
> finish.
> --
> Bob Shaw
> Check out Shaw's Garage at http://www.mlcltd.com/shawsgarage/
> My British Car is NOT leaky - it's merely marking its territory.
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