[Ravensfort] showers / Re: [rfofficers] Gundy's Find

[SF Tester]

On Sun, Oct 12, 2008 at 6:34 PM, byzytym <byzytym at att.net> wrote:

>  Would you spell out FRP please ?
>

Fiberglass reinforced plastic.


> Michelle suggested plastic sheets as well, but I didn't mention it because
> of the drawbacks.
> Both fiberglass and plastic breakdown and get brittle in the sun after a
> few years.
>

Not entirely true for fiberglass. That all depends on exactly what resin the
panel is fabricated with. Polyester will break down, epoxy can if it's a low
grade and/or doesn't have a UV inhibitor, vinylester will last virtually
forever, as will urethane. Properly selected polyester or epoxy, with the
right UV inhibitor or gelcoat, will last longer than the steel it's attached
to.


> The stress of moving the showers could crack an old panel... especially in
> cold weather.
>

ABS gets brittle at somewhere around 0 degrees. UHMW or nylon aren't an
issue. Delrin would last until the SCA is considering the 20th century
period ;)


> If it fades or scratches it could start looking pretty bad.  It is hard to
> get paint to sick to it in long range terms.  It peels after a few years and
> has to be completely scraped off.  That can be a nasty job.
>

Latex paint will stick to fiberglass better than you can get anything to
stick to steel. Fiberglass, scuffed like I mentioned before, doesn't even
need primer. It's a perfect substrate for painting.


> Ten pounds a sheet is still heavy compared to thin sheet metal, but not
> overly.
>

A 4x8 foot sheet of steel that weighs 10 pounds would be 35 gauge, which is
roughtly .008" thick. No chance that'll hold up. I'd guess that the minimum
we could get away with would be 24 gauge, which is .025" thick and around 32
pounds/sheet. Steel on building walls and roofs is around 18 gauge, .050"
thick and 64 lb/sheet.


> How much is the cost of a 4x8 sheet.  Can we get larger sheets that
> cover an entire side ?
>

 It's been a few years since I bought any, and I wasn't the one paying the
bill, so I don't really want to give my guess. Cheaper than steel, though.
Last time I bought steel was a very long time ago, and $80 for a sheet of 16
ga. Steel has gone waaaaaaay up since then.


> I'm not trying to be negative.  I'm just trying to look at all sides of
> suggested materials.
> Wood is too heavy, expensive and rots after a few years
> Fiberglass or Plastic becomes brittle in the sun and does not like paint.
> Metal rust.
>

Metal dents, too, and doesn't like paint any more than plastic. The stuff
that will stick is expensive and has to be put on with stuff we can't handle
at the site (air compressor, HVLP gun, lots of nasty chemistry, and so on).



> What ever we use should be light weight and be able to withstand being
> loaded onto a trailer and moved to a different site if need be.
>

Most of that will be in the design, not specifically the material. What we
do at the shop is come up with what we want it to do, figure out how to make
it work, pick suitable materials, and use a (not "the") correct fabrication
process for the project. We know what we want it to do, now we need to
decide on a design, then pick the materials. We can take the last step out
of order and use that as a factor in deciding on materials.
--
Gundy, who is good at this stuff :)
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