Re-shaping fiberglass parts with heat

I knew the concept was valid from Schempp-Hirth instructions on how to
heat up an early Cirrus wing and put in the twist that Cirrus's after
s/n 175 had. I have a badly twisted gear door (corner stood proud a
good 5mm), so I thought I'd give it a try on a much smaller scale. I
held the gear door in front of an electric space heater for a good 8
minutes, until it was too hot to leave a finger on the surface. Then I
put it in place on the wheel-well (fuselage inverted) and held the
ends with two 25# shot bags. I slipped in a 5mm shim to achieve over-
twist for the expected spring-back. Let it cool for an hour and it
fits like new!
Anybody else have experience heat-twisting epoxy/fiberglass parts?
What's the yield temp?
JJ

On Oct 29, 3:28 pm, JJ Sinclair wrote:
I knew the concept was valid from Schempp-Hirth instructions on how to
heat up an early Cirrus wing and put in the twist that Cirrus's after
s/n 175 had. I have a badly twisted gear door (corner stood proud a
good 5mm), so I thought I'd give it a try on a much smaller scale. I
held the gear door in front of an electric space heater for a good 8
minutes, until it was too hot to leave a finger on the surface. Then I
put it in place on the wheel-well (fuselage inverted) and held the
ends with two 25# shot bags. I slipped in a 5mm shim to achieve over-
twist for the expected spring-back. Let it cool for an hour and it
fits like new!
Anybody else have experience heat-twisting epoxy/fiberglass parts?
What's the yield temp?
JJ

Lots of experience here !
Yield temp is just a bit lower than when it starts to turn brown ;-)
Last time I did this I just used a hair dryer and gradually increased
the heat until the part gave a little easier.
There's got to be a better way to quickly judge it though ?
Maybe Bumper can recommend one of those nifty strips that
changes color at just the right temperature ?
See ya, Dave "YO"

On Oct 29, 3:28 pm, JJ Sinclair wrote:
I knew the concept was valid from Schempp-Hirth instructions on how to
heat up an early Cirrus wing and put in the twist that Cirrus's after
s/n 175 had. I have a badly twisted gear door (corner stood proud a
good 5mm), so I thought I'd give it a try on a much smaller scale. I
held the gear door in front of an electric space heater for a good 8
minutes, until it was too hot to leave a finger on the surface. Then I
put it in place on the wheel-well (fuselage inverted) and held the
ends with two 25# shot bags. I slipped in a 5mm shim to achieve over-
twist for the expected spring-back. Let it cool for an hour and it
fits like new!
Anybody else have experience heat-twisting epoxy/fiberglass parts?
What's the yield temp?
JJ

Doesn't seem to work as well on ships made with newer resins like
current production ships
that have been post cured to 50 C or so.
T1(yield) temp is just above whatever it was post cured to from my
experience.
Seems to make sense.
UH

On Oct 29, 1:06 pm, wrote:
On Oct 29, 3:28 pm, JJ Sinclair wrote:

I knew the concept was valid from Schempp-Hirth instructions on how to
heat up an early Cirrus wing and put in the twist that Cirrus's after
s/n 175 had. I have a badly twisted gear door (corner stood proud a
good 5mm), so I thought I'd give it a try on a much smaller scale. I
held the gear door in front of an electric space heater for a good 8
minutes, until it was too hot to leave a finger on the surface. Then I
put it in place on the wheel-well (fuselage inverted) and held the
ends with two 25# shot bags. I slipped in a 5mm shim to achieve over-
twist for the expected spring-back. Let it cool for an hour and it
fits like new!
Anybody else have experience heat-twisting epoxy/fiberglass parts?
What's the yield temp?
JJ

Doesn't seem to work as well on ships made with newer resins like
current production ships
that have been post cured to 50 C or so.
T1(yield) temp is just above whatever it was post cured to from my
experience.
Seems to make sense.
UH

I've used hot tap water to "adjust" fiberglass parts. It conducts the
heat to the part better than air, and I don't think you could over
heat it that way. I maxed out the thermostat on my water heater to do
it. I've been able to do significant "shaping" this way. I've also
gotten scalded more than once.

On Oct 29, 12:28 pm, JJ Sinclair wrote:
I knew the concept was valid from Schempp-Hirth instructions on how to
heat up an early Cirrus wing and put in the twist that Cirrus's after
s/n 175 had. I have a badly twisted gear door (corner stood proud a
good 5mm), so I thought I'd give it a try on a much smaller scale. I
held the gear door in front of an electric space heater for a good 8
minutes, until it was too hot to leave a finger on the surface. Then I
put it in place on the wheel-well (fuselage inverted) and held the
ends with two 25# shot bags. I slipped in a 5mm shim to achieve over-
twist for the expected spring-back. Let it cool for an hour and it
fits like new!
Anybody else have experience heat-twisting epoxy/fiberglass parts?
What's the yield temp?
JJ

Depends on the resin.
When we reshaped the trailing edge of my ASW22 Rudder, Larry M. built
a foam box and used hair dryers to maintain it at 175F
The part was Kevlar lay up not plain glass.

Your experience might vary

Regards

Al

Looks like the Jonkers sustainer will have this capability
built in - a least for the fin and tailplane:-)

http://www.jonkersailplanes.com/vide...nd_320x240.wmv

John Galloway

At 09:30 30 October 2007, wrote:
On Oct 29, 12:28 pm, JJ Sinclair wrote:
I knew the concept was valid from Schempp-Hirth instructions
on how to
heat up an early Cirrus wing and put in the twist
that Cirrus's after
s/n 175 had. I have a badly twisted gear door (corner
stood proud a
good 5mm), so I thought I'd give it a try on a much
smaller scale. I
held the gear door in front of an electric space heater
for a good 8
minutes, until it was too hot to leave a finger on
the surface. Then I
put it in place on the wheel-well (fuselage inverted)
and held the
ends with two 25# shot bags. I slipped in a 5mm shim
to achieve over-
twist for the expected spring-back. Let it cool for
an hour and it
fits like new!
Anybody else have experience heat-twisting epoxy/fiberglass
parts?
What's the yield temp?
JJ

Depends on the resin.
When we reshaped the trailing edge of my ASW22 Rudder,
Larry M. built
a foam box and used hair dryers to maintain it at 175F
The part was Kevlar lay up not plain glass.

Your experience might vary

Regards

Al

Looks like the Jonkers sustainer will have this capability
built in - a least for the fin and tailplane:-)

http://www.jonkersailplanes.com/vide...nd_320x240.wmv

John Galloway



yahhoooooooo!

Man do I want one of those!
Or Two, hang the expense!

Bagger

At 13:48 05 November 2007, Bagmaker wrote:

-Looks like the Jonkers sustainer will have this capability
built in - a least for the fin and tailplane:-)

http://www.jonkersailplanes.com/vide...nd_320x240.wmv

John Galloway
-


yahhoooooooo!

Man do I want one of those!
Or Two, hang the expense!

Bagge




--
bagmaker

HpH has is also going to have the option on the new
304S's see:http://www.hph.cz/ (second item down on
news page) As you can see, they are pretty far along,
and it should be available soon.

Paul Hanson
"Do the usual, unusually well"--Len Niemi