Do any of you guys heat your hangars with the overhead infrared heaters? If so, have any of you noticed your white fabric aircraft yellowing? We've had 2 through the shop recently that are both showing te same discoloration/yellowing on the fabric, but the taped and metal portions are still fairly white. Top and side of plane only. One is a Husky and one is a supercub. The ony thing that we can think of that is the same for them both is that they are both stored in hangars that are heated with infrared heaters. So what do you guys think?
Here's a picture


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Not sure it helps but the electric ones I've installed yellow walls with certain types of paint others don't for some reason, especially white obviously as well but that's just cheap paint. No experience with the big gas ones but you'd think the plane would need to be pretty close to affect it like that and they're in a lot of hangers. Strange the tape lines held up so well next to the fabric though hey, or is it just the photo? You think maybe it could have something to do with the silver/UV coat maybe?

IR heaters emit a lot of radiation, about 95% of the heat comes off as radiation, if memory serves me correctly.

Leaving the plane under a IR heater kinda the same as leaving your plane out in the sun, except you don't get the radiation from visible wavelengths and UV wavelengths etc. It could very well be killing your fabric at an accelerated rate, compared to normal hangar-kept aircraft.

Although that said, I think it's the UV radiation which does most of the damage. I think the IR is a lot more benign. I am not an expert, been a decade since I knew this stuff properly...

Fluorescent lights are another way to accelerate the ageing process for fabric planes using UV-B radiation. LED lighting is a much better choice.

Rogue wrote:Not sure it helps but the electric ones I've installed yellow walls with certain types of paint others don't for some reason, especially white obviously as well but that's just cheap paint. No experience with the big gas ones but you'd think the plane would need to be pretty close to affect it like that and they're in a lot of hangers. Strange the tape lines held up so well next to the fabric though hey, or is it just the photo? You think maybe it could have something to do with the silver/UV coat maybe?

Ok, that is interesting that they yellow walls. The tape lines have definitely retained the white better, it's not just the picture. And any part that is metal has also held the color fine.
One plane is a Husky with original factory from the early 90s, and the supercub is one that we covered. So I'm pretty sure neither is a silver coat issue.
Battson, very interesting about the fluorescent light. And we are a bit concerned about the fabric degrading at an accelerated rate, which is the reason for my post. Thought I'd see if anyone else has noticed it or not. Seems like not many planes are hangared with those types of heaters though, or so the lack of responses would suggest...

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Remembering my college physics this makes a lot of sense to me.

Will the discoloration buff out?

A1Skinner wrote:

Rogue wrote:Not sure it helps but the electric ones I've installed yellow walls with certain types of paint others don't for some reason, especially white obviously as well but that's just cheap paint. No experience with the big gas ones but you'd think the plane would need to be pretty close to affect it like that and they're in a lot of hangers. Strange the tape lines held up so well next to the fabric though hey, or is it just the photo? You think maybe it could have something to do with the silver/UV coat maybe?

Ok, that is interesting that they yellow walls. The tape lines have definitely retained the white better, it's not just the picture. And any part that is metal has also held the color fine.
One plane is a Husky with original factory from the early 90s, and the supercub is one that we covered. So I'm pretty sure neither is a silver coat issue.
Battson, very interesting about the fluorescent light. And we are a bit concerned about the fabric degrading at an accelerated rate, which is the reason for my post. Thought I'd see if anyone else has noticed it or not. Seems like not many planes are hangared with those types of heaters though, or so the lack of responses would suggest...

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Some of us poor folks are lucky to have our airplanes in hangars at all, let alone in heated hangars! I've given some thought to using my tent heater in the hangar--might raise the ambient temp a couple of degrees if the wind doesn't blow too hard.

Cary

Cary wrote:

A1Skinner wrote:

Rogue wrote:Not sure it helps but the electric ones I've installed yellow walls with certain types of paint others don't for some reason, especially white obviously as well but that's just cheap paint. No experience with the big gas ones but you'd think the plane would need to be pretty close to affect it like that and they're in a lot of hangers. Strange the tape lines held up so well next to the fabric though hey, or is it just the photo? You think maybe it could have something to do with the silver/UV coat maybe?

Ok, that is interesting that they yellow walls. The tape lines have definitely retained the white better, it's not just the picture. And any part that is metal has also held the color fine.
One plane is a Husky with original factory from the early 90s, and the supercub is one that we covered. So I'm pretty sure neither is a silver coat issue.
Battson, very interesting about the fluorescent light. And we are a bit concerned about the fabric degrading at an accelerated rate, which is the reason for my post. Thought I'd see if anyone else has noticed it or not. Seems like not many planes are hangared with those types of heaters though, or so the lack of responses would suggest...

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Some of us poor folks are lucky to have our airplanes in hangars at all, let alone in heated hangars! I've given some thought to using my tent heater in the hangar--might raise the ambient temp a couple of degrees if the wind doesn't blow too hard.

Cary

Cary, my plane sits outside as well. Didn't mean anything derogatory by my comment. But I think those types of heaters are less common than other types.

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Long wavelength light (red, infra red, etc.) if far less energetic than the shorter wavelengths (UV or any blue). Think of lots of waves arriving in a given time. IR wavelength 700nm-1000nm UV 10nm-400nm. Or Light energy goes up as wavelengths do down.

My guess is that it is pigments in the paint react w/ IR , but as pointed out it is usually the UV that does most damage.

One thought, however, is that IR penetrates much farther than UV. The short wavelengths get absorbed in a very short distance (one reason they are so damaging) while the reds tend to penetrate more deeply. Possible IR is detrimental to fabric but have no idea if this is true.

Light geek signing off.

The discolored areas you describe are the same areas I see collect dew when I camp out with the plane...makes me think it may have something to do with moisture. Maybe some combination of the moisture byproduct of radiant propane heat, and particulate matter in the air such as lingering ash from all the fires? Seems like there would have to be some sort of temperature variation that would give moisture a chance to condense on the fabric though...unless the humidity created by the heaters is close to saturation.

CFOT wrote:The discolored areas you describe are the same areas I see collect dew when I camp out with the plane...makes me think it may have something to do with moisture. Maybe some combination of the moisture byproduct of radiant propane heat, and particulate matter in the air such as lingering ash from all the fires? Seems like there would have to be some sort of temperature variation that would give moisture a chance to condense on the fabric though...unless the humidity created by the heaters is close to saturation.

The hangars are dry. And up in northern BC where the smoke hasn't been terrible until this summer. But they were showing this before that. Lots of other planes we work on that are in other hangars in the area show nothing like this. It really seems specific to the heaters. Like I say it's the only 2 planes we work on that are stored under them.
Who knows. Might have to do some more testing with scraps of fabric...

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Just a thought; maybe the tape & tubes act as heat sinks and transfer away some of the IR energy, whereas the rest of the fabric cooks,
thereby yellowing the paint?