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  #1  
Old 10-01-2016, 09:09 AM
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Vlad Vlad is offline
 
Join Date: Oct 2008
Location: Utah
Posts: 8,440
Default Heliograph

For couple years I was puzzled how my brand new glare shield got a burnt spot. I didn't solder anything in the cockpit and my passengers usually don't smoke. Then I got another a bigger one. Then one day I returned to my aircraft to see a touch of smoke coming out of the cockpit. Now I know why. Ever heard of a heliograph or sunshine recorder? Your RV bubble canopy can be one of these.





Watch the sun at your six thirty.





Your bubble canopy (tip up in my case) becomes a powerful magnifying glass. Your finger won't stay like this for too long you feel the heat right away.





These marks I acquired through 4 years of flying without even knowing the cause. Only last year I was able to figure it out after seeing a smoke. Did anybody experienced something similar? What would happen if your glareshield is other then aircraft designed part?


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Не имей сто рублей, а имей сто друзей.
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  #2  
Old 10-01-2016, 09:31 AM
cmmguy cmmguy is offline
 
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Location: North Carolina
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From your experience, would you say that your RV should be parked in a certain direction if outside or rather to NOT park it facing a certain direction.... (such as never park facing north during the day)?
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  #3  
Old 10-01-2016, 11:40 AM
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drill_and_buck drill_and_buck is offline
 
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Vlad,
Fascinating!

You have one smoking hot airplane! You'll just have to fly inverted to avoid additional burn marks while in cruise.
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  #4  
Old 10-01-2016, 12:13 PM
N15JB N15JB is offline
 
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There is another variation of this. IIRC it was Dave Saylor who had a polished -10, until the reflection off of his wing melted one of his side windows. His wing is now painted.
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  #5  
Old 10-01-2016, 12:22 PM
RVDan RVDan is offline
 
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This is a common problem for gliders with tip up canopies. Often find a spot burned in the glare shield if not careful and the sun shines through the tipped up canopy.
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  #6  
Old 10-01-2016, 12:31 PM
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Vlad Vlad is offline
 
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Quote:
Originally Posted by cmmguy View Post
From your experience, would you say that your RV should be parked in a certain direction if outside or rather to NOT park it facing a certain direction.... (such as never park facing north during the day)?
Certainly. If possible avoid sun position between 5 and 7 o'clock with tip up canopy open or propped.


Quote:
Originally Posted by drill_and_buck View Post
Vlad,
Fascinating!

You have one smoking hot airplane! You'll just have to fly inverted to avoid additional burn marks while in cruise.

A good one Mike! But why are you getting all awards and trophies?
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Не имей сто рублей, а имей сто друзей.
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  #7  
Old 10-01-2016, 12:38 PM
BillL BillL is offline
 
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Location: Central IL
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Well, the science is well known, but the discovery of it in an RV is amazing. I guess that the sun comes in at that angle frequently. I have a tipper, so it looks like parking in the sun without a cover is not recommended.

What is declination and heading (relative to the fuse) of the sun to create this issue? Any way to avoid it?

Edit: Good timing on the answer above. Thanks
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Last edited by BillL : 10-01-2016 at 12:41 PM.
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  #8  
Old 10-01-2016, 07:42 PM
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bhester bhester is offline
 
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Location: Hopkinsville, KY
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Exclamation Meske tip-up/slider mod also

I saw the Meske tip-up/slider mod being demoed at Sun-n-Fun some years back, when someone pointed out to the owner that the sun was burning a hole in his seat. Same thing the angle of the canopy was a big magnifying glass.
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  #9  
Old 10-02-2016, 08:57 AM
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airguy airguy is offline
 
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Haven't seen it happen in an airplane (yet) but my brother in law lost a pickup to this. He had some 5-gallon jugs of clear glass full of water in the bed of his truck sitting on a rubber bed mat, it smoked and eventually ignited the rubber bed mat, which ignited the two fuel jugs also sitting in the bed of the truck, and it was all over but the cryin'...
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  #10  
Old 10-02-2016, 10:01 AM
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DanH DanH is offline
 
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Just to clarify, the canopy is believed to focus the sun's energy (a) like a parabolic reflector (sunshine reflects off the inside of the canopy to a focal point), or (b) by refraction (sunshine passes through the plexiglass at an oblique angle, probably twice, to a focal point, much like a magnifying glass)?
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