Lexan Bend Radius

On Tue, 5 Dec 2006 17:05:39 -0500, "Capt. Geoffrey Thorpe" The Sea
Hawk at wow way d0t com wrote:

"J.Kahn" wrote in message
news
Whats' the minimum bend radius for 1/8 and 3/16" polycarbonate sheet?

Bending hot or cold?

I've seen references that suggest using a sheet metal brake which is an
almost negligable radius (and I assume a cold bend)

Hot you should be able to form it at will.

I don't think lexan lends itself to hot bends, however I have made
several three panel winshields in a sheet metal brake. I bends
beautifully, however don't ever spill gasoline on it, especially if it
is stressed or it will craze and shatter almost immediately.

"Ed Sullivan" wrote in message
...
I don't think lexan lends itself to hot bends, however I have made
several three panel winshields in a sheet metal brake. I bends
beautifully, however don't ever spill gasoline on it, especially if it
is stressed or it will craze and shatter almost immediately.

I have had two aircraft with Lexan windshields - an Ercoupe and an Emeraude.
Both of the windshields were gently curved and installed cold. Both of them
were unsatisfactory as they developed internal crazing which rendered them
unusable when flying into the sun.

I would not use Lexan for this application again.

Rich S.

I don't think lexan lends itself to hot bends, however I have made
several three panel winshields in a sheet metal brake. I bends
beautifully, however don't ever spill gasoline on it, especially if it
is stressed or it will craze and shatter almost immediately.

I have had two aircraft with Lexan windshields - an Ercoupe and an
Emeraude.
Both of the windshields were gently curved and installed cold. Both of
them
were unsatisfactory as they developed internal crazing which rendered them
unusable when flying into the sun.

I would not use Lexan for this application again.

Rich S.


Every now and then, I get the nutty idea that Lexan would ake a great
windshield material because of its impact strength. About halfway through a
thread like this one, I start to remember a lot of the problems and learn a
few new ones. The two that always come to mind are the difficulty of
polishing out any scratches and inability to tolerate shock cooling: IIRC,
Steve Wittman tried a lexan windshield on one of his aircraft only to have
it shatter when he pulled it out of his heater hangar and into the cold for
a flight to Florida.

Peter

On Wed, 06 Dec 2006 00:38:10 GMT, Ed Sullivan
wrote:

On Tue, 5 Dec 2006 17:05:39 -0500, "Capt. Geoffrey Thorpe" The Sea
Hawk at wow way d0t com wrote:

"J.Kahn" wrote in message
news
Whats' the minimum bend radius for 1/8 and 3/16" polycarbonate sheet?

Bending hot or cold?

I've seen references that suggest using a sheet metal brake which is an
almost negligable radius (and I assume a cold bend)

Hot you should be able to form it at will.

I don't think lexan lends itself to hot bends, however I have made
several three panel winshields in a sheet metal brake. I bends
beautifully, however don't ever spill gasoline on it, especially if it
is stressed or it will craze and shatter almost immediately.


Or ANY hydrocarbon. Don't even think about wiping with a varsol
dampened rag. Even some waxes and polishes have a hydrocarbon solvent
base and can/will damage lexan.

--
Posted via a free Usenet account from http://www.teranews.com

You can hot bend lexan but you have to preheat it for some time at just
below 212* F to drive the moisture out of the material before raising
the temp to the bend temp.

I don't recall the time nor temp I used, though. This was done about 18
years ago for my landing light on my RV-6. The lexan did craze
somewhat. Would not have been good used for a windshield or window.

John

Ed Sullivan wrote:
On Tue, 5 Dec 2006 17:05:39 -0500, "Capt. Geoffrey Thorpe" The Sea
Hawk at wow way d0t com wrote:


"J.Kahn" wrote in message
news
Whats' the minimum bend radius for 1/8 and 3/16" polycarbonate sheet?

Bending hot or cold?

I've seen references that suggest using a sheet metal brake which is an
almost negligable radius (and I assume a cold bend)

Hot you should be able to form it at will.


I don't think lexan lends itself to hot bends, however I have made
several three panel winshields in a sheet metal brake. I bends
beautifully, however don't ever spill gasoline on it, especially if it
is stressed or it will craze and shatter almost immediately.