Re: Plywood reefers


Greg Martin
 

In Tony Thompson's message back to Ben he writes:


As Ben Hom has already answered, the problem was in adequate sealing of
the edges of the plywood sheets. Soo Line had the same problem with box cars
having single sheathing of plywood. Rubber and metal seal strips were not good
enough. The plywood curled and cracked, and was judged (by PFE anyway) to be
inadequately weather resistant if any of the protection system (joint
sealing strips, and paint generally) failed. PFE concluded it was not worth
repairing them in kind, thus returned to T&G....<<

Likely the issue was not a plywood (or also know as Plyscore at the time)
but actually an application error... but at the time there was likely little
know of the issue of application or were not properly relayed to the end user.
When you butt plywood edge to edge and don't leave a gap the aforementioned
condition results... apparent delamination at the edge, which could have been
avoided if properly applied. The sheets must be gapped or the top veneer
can't expand and that causes the top veneer to separate from the veneer below and
causes the top veneer to wrinkle or as Tony puts it "curled" or it may check
or as Tony puts it "cracks" These are all installation errors. While the
edges do need sealed to avoid true glue-line delamination I don't see that
condition in the effects of the plywood cabooses(NYC) or Reefers that were
sheathed with Douglas Fir Plywood. Now to see why the SOO Line cabooses didn't do
this...


Dennis writes...

Tony,
Care to offer a citation to info on the Soo Line plywood covered boxcars? I
suspect you are thinking of the GN, but I'm always looking for new and
interesting facts about the Soo.<

The Soo Line did cover quite a few cabooses with plywood in the late
sixties and it held up well enough. The joints were covered with sheet metal lap
strips that had a shallow bend in the center, which tended to keep the edges
tight to the plywood between the screws. Then again, this "fix" was only
intended to last five years, until sufficient new steel cabooses were on the
property. The plywood was applied right over the ratty car siding, with a new wider
letterboard applied to cover the top edge.<

Ah Ha! We see that the installation had changed and it was done correctly
allowing the veneers to float between what Dennis describes as, "The joints
were covered with sheet metal lap strips that had a shallow bend in the center,"
a simple matter of letting the panels stay apart...

If I could hazard a guess as to what the railroads disliked about plywood
on freight cars, it is plywood's tendency to shed paint in sheets. The hard
early wood grain in Douglas fir is very resistant to paint penetration, and in
making rotary cut veneer, the hard grain becomes wide bands.<

Well, the grain is a bit of an issue but the real reason that the paint
wouldn't hold is because the veneers were constantly moving, expanding and
contracting and yes the wide grain (flat grain) was an issue but the edge grain
could be even worst in reality. But if the plywood was primed with White
pigmented shellac the paint peel issue would have diminished for the most part...
But that primer is much more expensive as well...

Plywood wasn't used for house siding, either, for the same reason until the
industry came up with what is known as T-111 siding. This plywood has strips
of rough sawn veneer on the face ply, which hold paint well, separated by
grooves to make it look like boards. It came too late to be used on freight
cars, and anyway, I can't see the car builders liking the rough sawn look on a
freight car.

Dennis Storzek<

Dennis is correct, plywood was not used for house siding until much later
than this list chooses to cover. But the one of the first sidings used was 303
T-1-11 ( it was actually referred to as 303-0,6, or 18 meaning the number of
repairs, synthetic or natural, to the face) but at first with a smooth face
and then later with a resawn face which did hold paint better. The success of
the panel was and continues to be that the panels don't but tight together...
But I have seen some repainted wood sheathed cars that look to have been
rough sawn but is just shoddy restoration work...

Greg Martin

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