Cold temp and fiberglass?
Peter D. Brown
Can anyone provide some information on how fiberglass responds to cold, both
in static storage on the ground in winter and during wave flights to
altitude?
Here in Anchorage, our normal winter temperatures run from about 20F (-6C)
to -10F (-23C) with some occassional dips to -40F (-40C). We are about at the
same latitude as Stockholm, Olso, and Leningrad so reponses from other nordic
pilots will be appreciated.
Will unheated storage of glass ships (birds ranging in age from an old
Diamants to a new S-10) result in accelerated gelcoat damage? What about
repeated wave flights?
Thanks,
--
Pete Brown, ASEL/CFIG C-170B
Anchorage, Alaska SGS-1-23G
907-345-7529 (home) 907-564-0223 (fax) Frank Zaic Thermic 18
Michael Gregor
Peter D. Brown wrote:
>
> Can anyone provide some information on how fiberglass responds to cold, both
> in static storage on the ground in winter and during wave flights to
> altitude?
Here in Hamar/Norway, about 120 km north of Oslo, we fly through the
winter with temperatures between 0c and -30c. The temperature seems
ususally to rise at higher altitudes. I have often experienced -25c on
the ground and -5c to 0c at 600m. Our planes are stored cold in a hangar
or in their trailers and seem not to suffer from the cold. Moisture
however can be a problem during abrupt temperature changes. Particulary
for those stored in trailers. Instruments can get clogged. Assembly can
also be quite difficult.
We do not do much waveflying around here but when such conditions do
occur the temperature does rise somewhat.
Michael Gregor
--
- itha...@online.no
CWatters
Peter,
> Can anyone provide some information on how fiberglass responds to cold, both
> in static storage on the ground in winter and during wave flights to
> altitude?
Epoxy and Polyester resins become more brittle at cold temperatures. I wouldn't
expect more damage in dry storage but that stone thrown up by the tug is more
likely to craze the gel coat than if it's nice and warm.
Colin
F. L. Whiteley
Michael Gregor <itha...@online.no> wrote in article
<3473EA...@online.no>...
> Peter D. Brown wrote:
> >
> > Can anyone provide some information on how fiberglass responds to cold,
both
> > in static storage on the ground in winter and during wave flights to
> > altitude?
>
> however can be a problem during abrupt temperature changes. Particulary
> for those stored in trailers. Instruments can get clogged. Assembly can
> also be quite difficult.
High temperatures can also make assembly difficult on some GRP sailplanes.
Makes sense assuming factory rigging layup is probably 20-25c.
F. Whiteley
Krister Engvoll
Marc Till wrote:
> CWatters wrote:
> >
> > Peter,
> >
> > > Can anyone provide some information on how fiberglass responds to cold, both
> > > in static storage on the ground in winter and during wave flights to
> > > altitude?
> >
> > Epoxy and Polyester resins become more brittle at cold temperatures. I wouldn't
> > expect more damage in dry storage but that stone thrown up by the tug is more
> > likely to craze the gel coat than if it's nice and warm.
> >
>
> I do have some experience with the use of fiberglass-expoxy composites
> at cryogenic temperatures ( down to liquid helium boiling temperature,
> i.e., 4K or -269C or -452 F - please don't flame me if the last figure
> is wrong ! ).
>
> Generally speaking, the tensile strength of these composites _increases_
> with _decreasing_ temperature and they are not subject to embrittlement.
>
> So, you should be more concerned about freezing your feet than breaking
> your wings ;-)
>
> Marc
Correct, but..The methyl-acrylate that most canopies are made of does become (more)
brittle (in fact it IS brittle all the time) in freezing temperatures. It also
contracts much more than epoxy and glass (or carbon) when cooled down, thus creating
stress between it and the frame. Canopies may fit well on the ground, and leak and
shriek all over up in the wave. There are also stories of canopies that have cracked
for no apparent reason except stress and brittleness in the cold.
Gelcoat is polyester and also contracts more than epoxy/glass, it is also brittle.
This induces stress between gelcoat and underlying glass/epoxy structure. If the wing
is stressed additionally, from turbulence or hard manouvring (or that rock from the
towplane), the gelcoat may crack.
Now gelcoat also becomes brittle from excess sunlight so if we dont mind flying in
sunlight why mind flying in the cold :-) ?
Just glad the Poles knew what to paint the Jantar with (not gelcoat).
--
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Krister Engvoll
Laboratoriet for Radiologisk Datering
Sem Sælandsvei 5
7034 Trondheim
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e-mail: eng...@phys.ntnu.no
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Basilhome
In article <347443...@sympatico.ca>, Jean Richard <j.ri...@sympatico.ca>
writes:
>It's exact that temperature (and probably moisture) affect composites.
>Our Grob Twin canopy is more difficult to close on those hot and humid
>July days when temperature rises near 30 degrees and dewpoint above 15.
>On dry and cooler days, no problems with it.
>
But this is the perspex of the canopy expanding in the heat. Not the glass
fibre.
Andreas Maurer
On Thu, 20 Nov 1997 22:50:09 -0800, Marc Till <mt...@club-internet.fr>
wrote:
>Generally speaking, the tensile strength of these composites _increases_
>with _decreasing_ temperature and they are not subject to embrittlement.
Tensile strength is not the problem - it's thre elasticity.
>So, you should be more concerned about freezing your feet than breaking
>your wings ;-)
Well, actually the "working" of the gelcoat on the Laminate surface is
the problem: Changing the outside temperature too fast will cause
immense forces on the gelcoat because it's expansion over temperature
is slightly different from the one of the laminate. Adding a loss of
elasticity at low temperatures leads to cracks - I personally had to
discover this problem last year in the Alps... :-(
The cure is simple: Climb slowly and sink slowly. Hard to do in a
strong wave...
Bye
Andreas