Re: Shaping/bending styrene.


Denny Anspach <danspach@...>
 

I submitted the original question on this
subject, and I have been most interested in the
many posts, both on and off line, relating all
of the methods that have worked over the years.
Although I asked about styrene, the fundamental
need was to fashion a radial car roof out of
whatever material might work the best for me.

With this in mind over this past week I tried
some quick and dirty experiments of my own, the
fundamental tools being a cylindrical glass
tumbler, a bunch of broad rubber bands, and 180º
F. water dispensed by a standard hot water
dispenser on the kitchen sink.

1) My first effort was to cold mold the roof out
of three layers of c. .008" Strathmore paper (a
brand of Bristol board- a very dense
high-rag-content paper). Such molding requires
slow-setting glues, and in this regard ordinary
white glue was perfect. I laminated the layers
with the white glue laid on with a small brush,
applied it around the glass before the glue could
set up, and kept it there with rubber bands. I
filled the glass with the hot water to provide
some dry heat, and an hour later I removed the
rubber bands and the molding.

2) My second effort was with a roof made of .031"
(1/32") thick scribed Northeastern wood siding.
In the same glass, filled anew with hot water,
the wood was soaked for about ten minutes. The
wood was removed, the water decanted, and the
wood was then wrapped on the surface of the glass
with rubber bands in the same manner as above,
scribed side down. The glass was then refilled
with the hot water to continue a (dry) direct
heat source. This was left for about three hours
so that the wood could thoroughly dry.

3) My third effort was with a roof made of .016"
single layer Strathmore paper applied to the hot
glass in the same manner, but thoroughly soaked
beforehand for several minutes in 180º water.
This piece was dry in about an hour, after which
it could be removed.

4) The last effort was with a roof made of .030
sheet styrene applied cold to the hot glass
tumbler. It was removed after about one hour.

Results:

1) Glued-up paper: Remarkable! The resulting
molded radial roof almost exactly mirrors the
radius of the glass tumbler, and is so stiff, one
can almost physically stand on it before there is
any deformation. The down side of this is that
unless the radius is almost right on from the
git-go, getting an accurate fit without a
force-fit will result in a lot of unrelieved
stress that is going to be difficult to deal with
(the radius of the tumbler, and thus the molded
roof as well, are both tighter than the desired
roof radius). Finishing such a roof would be
easy inasmuch as Strathmore is one of the easier
materials to fill and paint to a smooth finish.
In most installations, presuming the fit was
good, no carlines at all may be required.

2) Wood: By far the very easiest. Bending wood
with hot water/steam is a time honored process,
and as expected here, it worked well to a "T". As
stiff as the laminated paper turned out to be (as above), the bent wood turned out just the
opposite- sufficiently flexible to readily adapt
to a variety of radii. The bent wood by itself
will maintain the bend for posterity if left
alone, but in this regard it will need to be
protected by thorough sealing on both sides with
a good filler/sanding sealer. This will also be
required to gain a good finishing surface. If a
roof of this type is to be removable, carlines
will be required. If mounted permanently, either
a very few carlines, or none at all would be
required, depending upon roof size and existing
supports.

3) Paper, single layer alone: Very simple. After
a thorough pre-soaking in hot water, this also
worked quite well, and a nicely curved roof
resulted that was not stiff, and adapted well to
a variety of radii. The thickness is not as
great, and in this regard, supporting structure
(including carlines) and fasciae would probably
have to fabricated (not hard to do with either
styrene or strip wood).

4) .030" sheet Styrene: It worked, but not very
successfully (good solid bend, but way too much
"spring back"). Richard White's serendipitous
and very good post on this same subject today
points to the reason: The water I use is not hot
enough and/or the glass wall of the tumbler I use
does not transfer heat well enough. Using a
suitable metal can (excellent heat transfer)
instead of the glass would seem to be a key here.
Whether one would get his results with only 180º
F. water (v. 212º F) or not, would have to await
trial. Also, what the results might be with .020"
or .010" sheet styrene under identical
circumstances are as yet unknown to me, but I
would expect they might be much better.

Conclusions:

All of these methods used in the creation of a
curved HO car roof have something to recommend
them, as well each has some detractions. I have
yet to decide which one I will elect; much
depending upon how easily I determine it will be
to trim to size, detail, fit and finish these
roofs "non-destructively"- i.e. can I get from
here to there without ruining things!

As in most instances, what works best for one
person does not in fact work the same for
another- reflecting common individual differences
in both skills and familiarities working with
different materials over the years. Styrene is
the current lingua franca of model scratch
building, but both paper and wood as
model-building materials have long played a
distinguished role in fine model building and
should not be summarily dismissed. Each has their
own place. It is certainly not an "either/or", it
is "both", and any or all of these materials can
be used quite well with each other.

This has been an interesting exercise, and like
others I will be collecting all of the posts into
an edited compendium in WORD.

Denny


--
Denny S. Anspach, MD
Sacramento

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