Re-shaping fiberglass parts with heat

[JJ Sinclair]

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

[[email protected]]

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"

[[email protected]]

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

[[email protected]]

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.

[[email protected]]

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

[John Galloway[_1_]]

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

http://www.jonkersailplanes.com/video/Jet_Test_Stand_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
>
>
>
>

[bagmaker]

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

http://www.jonkersailplanes.com/video/Jet_Test_Stand_320x240.wmv

John Galloway



yahhoooooooo!

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

Bagger

[Paul Hanson]

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/video/Jet_Test_Stand_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