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Melted lens

LettersFromFlyoverCountry

Well Known Member
Gah.

2012-07-08_20-02-43_540.jpg


I'm guessing the 100 degree temps last week and the plane parked in the sun at Red Wing -- unpainted, possibly redirecting sunlight into a death ray of some sort -- did this (I don't use the nav light). Is there any supplier that anyone is aware of of a harder plastic than this soft stuff?

Latest flight testing details, btw, are on the blog.
 
Bob, It is very unlikely that the sun melted your lens. Do you run with your nav lights on? Are they incandescent?
It is very common for the heat of incandescent bulbs to melt these lenses.
The only practical solution is to convert to LED type bulbs.

If you don't use the nav lights, I can't explain it. The melted area is directly over the nav light bulb.
I've NEVER seen lenses melted by sunlight!
 
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Bob, It is very unlikely that the sun melted your lens. Do you run with your nav lights on? Are they incandescent?
It is very common for the heat of incandescent bulbs to melt these lenses.
The only practical solution is to convert to LED type bulbs.

If you don't use the nav lights, I can't explain it. The melted area is directly over the nav light bulb.
I've NEVER seen lenses melted by sunlight!

I don't use the nav lights at all.
 
Maybe the shape of the bulb focused the light like a magnifying glass?

I was thinking the metal frame of the light assembly redirected the sunlight. This plastic is so soft, I don't think it takes much to melt.

I suppose, around here, it also could've been a collision with a mosquito.
 
Wow - that looks very similar to mine (the melting) - I know mine melted due to the lights being on (did it the first time I sat with the lights on while on the ground). Ever since then I have made it a procedure to (try to) ONLY have the Nav lights on when I have air moving past the lenses.
 
Bob, that nav light looks to be very close to the lens. I'm sure most builders set their nav/strobe lights further back to avoid the problem of the generated heat deforming the lens. You say that you do not use the nav light, but is it possible that this occured when you were stationary and testing the lights and you did not notice the deformation at the time. The nav light can generate quite a lot of heat in a small time frame.

That lens is now cactus so it might be an idea to switch on the nav light for a while and see if the lens deforms further. That might tell you something either way.

Construction phase finished. Maintenance, repair and reinstatement phase underway. :)
 
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I had the same thing happen, Bob, when I first tested my nav lights in the hangar. Honked me off.

I replaced the incandescent bulbs with LED replacements, but then had radio noise. Sounded like the squelch on the radio. I tried a couple of things to eliminate the noise, but it remained. So, I went back to the stock bulbs and, like you, just don't use the lights. Yet. :D
 
I had the same problem - I would bet my next pay check your light was turned on at some point after installation of the lens - it only takes a minute to do the damage. If I had mounted the light a 1/4 inch further back it wouldnt have happened. Pain in the butt to fix the root problem now too. I took the easy way out and replaced the lens while making a mental note to not turn on the nav lights longer than it takes to verify that they work - about 10 secs.

erich
 
I had the same problem - I would bet my next pay check your light was turned on at some point after installation of the lens - it only takes a minute to do the damage. If I had mounted the light a 1/4 inch further back it wouldnt have happened. Pain in the butt to fix the root problem now too. I took the easy way out and replaced the lens while making a mental note to not turn on the nav lights longer than it takes to verify that they work - about 10 secs.
erich

Don't count on it. I seen quite a few that were mounted as far back as possible and they still melted the lens.
This tip design just doesn't have enough room to get the bulb far enough from the lens.
 
Replace the NAV lights with LED and you will never have any melting lens problem. These LED lights are very inexpensive, draw little power and they are bright. Even my bi-xenon HID landing lights don?t melt the lens which I have them on for extended time on day/night landings


DSC_6142 by bavafa1, on Flickr


DSC_6140 by bavafa1, on Flickr
 
I had the same problem - I would bet my next pay check your light was turned on at some point after installation of the lens

Really, there's no chance of that, especially since I just cleaned both lenses the day before the trip to Red Wing.

Interestingly enough, I took a picture of the plane as it baked that day...

2012-06-30_17-25-14_564.jpg


As you can see, the angle of the sun was beating right on the leading edge.
 
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Replace the NAV lights with LED and you will never have any melting lens problem.


It's a good suggestion, but I'm pretty much done with spending money on building the airplane for awhile, considering there isn't any left. :D

At this point, it is what it is. I think Paul Dye's suggestion is a good one if it is the bulb, however. Just don't turn it on until there's air flow to cool it.

I have seen images here where the sun shining off unpainted aluminum has melted the canopy, which is a much harder plastic. Why would that be possible and not with the soft plastic here?
 
Maybe not entirely impossible, just unlikely. Consider where the lense melted; its right onto the bulb, which is known to generate heat when powered. The simplest, most probable explanations are generally the correct ones. Said another way: When you hear hoofbeats, think horses, not zebras.

erich
 
I have seen images here where the sun shining off unpainted aluminum has melted the canopy, which is a much harder plastic. Why would that be possible and not with the soft plastic here?

What part of the aluminum airplane do you think the reflection onto the lens is coming from? I can't picture light reflecting from anywhere on the aircraft and striking the lens where it deformed. Any ideas?
 
The green lens retains or generates more heat than the red. Don?t ask me why:confused:, but the lens next to the green light will always start to deform before the red light.
 
Landing Lights?

When I saw Bob's picture, I thought he was showing off his new landing lights! I want some of those!
 
Here's one theory.
The sun heats up the dark green lens inside the wing tip,the heat builds up and becomes so hot it melts the clear plastic.
 
Here's another one: Someone else melted their lens and walked over to yours and swapped. Isn't that better?
 
Hey, thanks for the idea!

Stein looked at it tonite and said it's definitely the bulb.

The funny thing is that since I started flying this thing, I really don't care much anymore about cosmetics.
 
One of two things is certainly happening.

1. The odd shape on the wing tip is creating extra drag thus robbing you of at least two or three knots of speed.

or

2. The odd shape on the wing tip is creating an aerodynamic fence preventing the relatively high pressure air from spilling up over the wing tip thus reducing drag and giving you an extra two or three knots of speed.

The preceding was a test of internal sarcasm detectors.

Now for real,
The chances of it being anything other than the nav light are remote. It probably happened one time when you didn't even realize the lights were on. Just replace the lens and pull the breaker for the nav lights that way you can't accidentally activate them. One type of jet I used to fly had a five minute ground limit on the landing lights or they would start to burn the lens so Paul's suggestion is not out unheard of in aviation.
Been following your progress and I must say it must be irritating to be based away from your support and logistics during your test period when weird stuff always seems to pop up. Keep after it.
 
The logistical problems of driving so far every day -- not to mention the cost in gasoline -- is a pain in the neck; no question about it.

But there are a couple of things about it that I really like.

-1- Airlake (KLVN) is one of the friendliest airports I've ever been. Unlike my home airport (KSGS), people that don't know each other wave to each other (it's a Minnesota thing that people here mostly don't say "hello" to strangers; I've never understood that), and there's a lot of activity there.

-2- You can do a lot worse than having Stein and Jed for hangar mates. A LOT worse.

In other news, I found out yesterday that my 90-year-old mother has been cleaned out by con-men preying on the confused seniors, a group in which she resides. She put $50,000 in an envelope and gave it to them. I wish I had this RV out of Phase I so I can get back there to help take care of her. Soon enough, I suppose, but *this* has -- over the last few years -- has become the planned - if, likely, short -- mission of this airplane.
 
Hi Bob,

Sorry to hear about your mother being ripped of.

Your comment about Minnesota made me smile ... Its because most come from Norway... and in Norway we do not say hello to strangers ... :) ... or at least not in the way it is done in most parts of US .. You need to read Garrison Keillor to understand why ..

Jan (Norwegian living in exile in UK... slow building RV6)
 
Hi Bob,

Sorry to hear about your mother being ripped of.

Your comment about Minnesota made me smile ... Its because most come from Norway... and in Norway we do not say hello to strangers ... :) ... or at least not in the way it is done in most parts of US .. You need to read Garrison Keillor to understand why ..

Jan (Norwegian living in exile in UK... slow building RV6)

Actually, I work for the same company as Keillor. Never acknowledged other people. He calls it "shy." I call it something else.
 
Lens and things

In looking at the picture, it appears the normal wing tip light that is on a cessna is installed under the plexiglass. I thought these types of lights were meant to be installed such that they are exposed to the outside air? I think putting this type of incadesent light inside a plexiglass housing will be nothing but trouble; there will be no way to circulate air to cool the bulb. In my opinion, if you want a cover, one would need to use the low heat LED type of bulbs. JMO
 
Even with the "standard" installation, the bulb is encased under a glass lens. There is no air circulation around the bulb there either.
 
In looking at the picture, it appears the normal wing tip light that is on a cessna is installed under the plexiglass. I thought these types of lights were meant to be installed such that they are exposed to the outside air? I think putting this type of incadesent light inside a plexiglass housing will be nothing but trouble; there will be no way to circulate air to cool the bulb. In my opinion, if you want a cover, one would need to use the low heat LED type of bulbs. JMO

It's the Whelen System that Van's sold for years, before you whippersnappers even knew how to spell L-E-D. :D

There's nothing non-standard about it.
 
the sun...is just a bit hotter than a 12v bulb

Maybe the shape of the bulb focused the light like a magnifying glass?

yup, my starboard lense did exactly the same thing, and it's the sun reflecting inside the light housing. Port wing only get sun for a few hours, at a lower angle.....no problem there.
( took my builder to figure it out..... in about 15 seconds!)
 
This theory gets my vote

Here's one theory.
The sun heats up the dark green lens inside the wing tip,the heat builds up and becomes so hot it melts the clear plastic.

If Bob is sure he never turned the lights on, then this is the most likely case.
With full sun on the green bulb cover, it would reach temperatures that could melt the clear outer cover.

As unlikely as this might seem, it might be a good decision-aide in choosing which way to park an airplane at transient parking for a day.
 
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