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  #16  
Old 05-22-2007, 09:54 AM
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Found it

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Originally Posted by eracer113 View Post
I would like to add some information about the color of paint on the composite AC. I have had dark violet pearl paint on the leading edge of my E Racer wing, canard and winglet for 10 years now. I have read all the reports about the effects of colors other than white paint and find the reports hard to believe. In the process of modifying my AC with blended winglets, I cut off about 12 inches of the wing and 9 inches of the lower winglet both with the dark violet paint on them. I examined the blue foam just under the outer skin and there was absolutely no deterioration of the foam either on the wing or winglet. I put the wing section in the sun Sat 34.2C for two hrs. I have a digital temp tester, white 114o , hot pink 125o dark purple 144o. The temp inside the hanger with the door open checked within 1o of the actual os temp.at the airport. I went to the rear bumper of my truck to the black top step pad which had been in sun for 4 hrs, it registered 149o. I also checked the black side tinted edge of the truck glass in direct sunlight, because it was a high gloss, it only registered 121o. I will in my spare time test to see at what temp. the blue foam deteriorates. I would think it would be above the 160o number mentioned. Every product has a safety margin figured into it to protect the manufacturer. I just thought I would run this by everyone because I have seen first hand that the colors I have on my AC have absolutely no effect on the foam core caused because of high outside temps.

Jack
E Racer113
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  #17  
Old 05-22-2007, 02:25 PM
spg_76013 spg_76013 is offline
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Default Black Paint Scheme followup...

Hi Again,

Concerning my black-on-white paint scheme, I will have a custom fitted cover made for the wings, and it will be part of the aircrafts manifest during hot months. So, if I am caught out on a hot Texas tarmac for longer than say, 30 minutes, I will cover the wing leading edges. The cover will only weigh a few pounds. I may also do the same for the vertical parts of fuselage which are black.

Thanks for the idea of a surface thermometer... I have a Radio Shack digital thermometer which will work perfectly. I think I'll attach it's sender to my forward/upper nose access panel (4 ply BID), which will always be in direct sunlight and so should get the worst of the heat.

When the temperature warms up a little more this spring, I'm going to run some *internal* temperature tests on some spare wings I have, just to see if the internal temps (inside the foam core) far exceeds the surface temps. I'll do same for both white and black colors.

Regards,

SPG1
Arlington, Texas

p.s., I got my first backseat ride in a LongEz a few days ago. What a blast!
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  #18  
Old 05-22-2007, 02:32 PM
spg_76013 spg_76013 is offline
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Default Black Paint Scheme - Epoxy

Hi Again,

FYI, I'm using the 105 West System Epoxy (www.westsystem.com), which has a rather low Tg temp of about 130 to 140 deg. See attached.

So, while potential heat damage to the underlying foam is of concern, damage to the glass itself is also a big factor.

SPG1
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  #19  
Old 05-22-2007, 02:37 PM
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Quote:
Originally Posted by spg_76013 View Post
..a rather low Tg temp of about 130 to 140 deg. SPG1
Yeay - agree - rather low, too late to switch?
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  #20  
Old 05-23-2007, 12:53 AM
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Quote:
Originally Posted by spg_76013 View Post
FYI, I'm using the 105 West System Epoxy (www.westsystem.com), which has a rather low Tg temp of about 130 to 140 deg. See attached.
Rats. That's the max Tg you can expect from West, too, even after a full post cure . It's great stuff and super easy to use, but it's certainly worth keeping a close eye on here in the TX heat (... where hangars make GREAT ovens in August).

FWIW, we've seen West 105/206 parts that weren't post cured get a bit soft/gooey in the 120 F range (around the published HDT, I believe). If/when you do your post cure just be very sure your structure is well supported.

D
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  #21  
Old 05-23-2007, 09:22 AM
Wayne Hicks Wayne Hicks is offline
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Careful, mind what you're reading. The Tgs in the WEST literature are for ROOM TEMPERATURE cures after only two weeks. Room temperature in this case is 72 degrees. Do some post curing and the Tgs go way up. You folks in Texas get your post-curing done for free (hot Texas hangar in the mid-summer).

(I'm wrong about this. Read post #24 and #25. Sorry.)

Yeah, you're right. WEST is just crap. That's why they sell tons of it. I've met Jan Gougeon. One of their consulting physicists is a close friend of mine. They have a good chuckle when I tell them that our builders are afraid to use WEST for fear that the epoxy is not good enough.
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  #22  
Old 05-23-2007, 12:18 PM
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Wayne - that is what i was thinkin, a call to gougen bros tech center for post cure procedures and resultant tg's may be in order
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  #23  
Old 05-23-2007, 12:22 PM
Wayne Hicks Wayne Hicks is offline
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Be my guest.
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  #24  
Old 05-23-2007, 12:59 PM
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OK, just got off the phone with them.

the west system is a room temp system and DOES NOT BENEFIT FROM POST CURE. THE TG is 129F and that be it, no improvement available.

His advice was to go to proset for Black parts because they gonna bend and get soft at 129F
Gougeon Brothers Inc
www.gougeon.com

100 Patterson Ave
Bay City, MI 48706
(989) 684-7286

My GUESS is that this is the reason scaled went to pro set
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  #25  
Old 05-23-2007, 01:05 PM
Wayne Hicks Wayne Hicks is offline
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Hmmmm... That flies in the face of everything I've been told before from Gougeon, my physicist friend, and Gary Hunter. Did you talk to the tech rep or the lawyer?

=====

Addendum: Okay, I called and spoke with Jeff. Dust is correct in that WEST doesn't benefit greatly from post-cure. It's because of its chemical formula. Post-curing will raise its Tg by a few degrees, but not by the amounts (tens of degrees) we've all come to expect.

But....let's tell the more complete story! There's more to it than Wayne's wrong, Dust is correct.

When it comes to Tg, there is onset Tg and ultimate Tg. Onset Tg is the temperature at which the strength properties start to decline. It is nowhere near gummy, and we as casual observers would never notice the difference. Ultimate Tg is the temperature at which the epoxy exhibits its lowest strength properties. The Tg curve looks like a ski slope. Onset Tg is at the top of the hill just when you push you and your skis over the edge and gravity takes over. Ultimate Tg is near the bottom after you've finished your ski run. Pretty much flat lines there.

Now, for WEST, Gougeon only publishes the onset Tg. They know that the chemical formula they're using for WEST doesn't benefit greatly from post curing. So they've not done the comprehensive testing to fully characterize ultimate Tg. So they don't publish it. Many of Gougeon's competitors publish only ultimate Tg. Jeff says he wouldn't be surprised to find that WEST's ultimate Tg would be in the ballpark with other room temperature cure epoxies. (140-160 degrees if he had to guess.)

That is why you builders can use WEST with confidence.

The Pro-Set system uses a different chemical formula. It benefits greatly from post-curing.
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  #26  
Old 05-23-2007, 01:19 PM
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Tech Rep, talk to your buddy on the west system versus pro set.

He was adamant that they did not even like the 140F number that was from standard industry tests

129F is it
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  #27  
Old 05-23-2007, 04:32 PM
spg_76013 spg_76013 is offline
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Default West Tg's

Quote:
Originally Posted by Wayne Hicks View Post

...Now, for WEST, Gougeon only publishes the onset Tg. They know that the chemical formula they're using for WEST doesn't benefit greatly from post curing. So they've not done the comprehensive testing to fully characterize ultimate Tg. So they don't publish it. Many of Gougeon's competitors publish only ultimate Tg. Jeff says he wouldn't be surprised to find that WEST's ultimate Tg would be in the ballpark with other room temperature cure epoxies. (140-160 degrees if he had to guess.)...
Thanks for your research/input Wayne. You mentioned that West only published onset Tg, not ultimate Tg. Please see the attachment to post #18 or West's website: FYI, they do publish onset and ultimate Tg. (129 and 142 respectively for the 105 epoxy.)

I'll be monitoring my VE's 'worst-case' black-panel temp, and if/when it approaches 125-130, I'll put on the wing leading-edge & fuselage covers or put it in the hangar.

Regards,

SPG1

Last edited by Dust : 05-23-2007 at 05:36 PM. Reason: Sintax
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  #28  
Old 05-23-2007, 04:52 PM
Wayne Hicks Wayne Hicks is offline
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Okay. I guess that's what I get for going off half-cocked. Just too busy with the day job. Sorry.
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  #29  
Old 05-23-2007, 11:06 PM
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I wasn't going to post this before but...

I once had a set of LongEz wings that I had acquired but had no use for... They were ~military surplus, painted very light gray (urethane). One wing was stored outside in the sun with ambient temperatures over 100 degrees in the southwest.

Somewhere over the course of one summer the top surface of the wing developed dozens of delaminations. Destructive examination revealed that the glass was intact but that there were, essentially, "bubble pockets" at each of the delam sites.

I attributed this situation to a gas-expansion of the foam itself. The Tg of the epoxy is irrelevent in this situation.

Now, dark colors on a foam/glass substrate may not make much trouble in an Ez that is hangared, or one that is in a cooler area of the country. Having had this experience, I would never paint an Ez any dark color unless I new the airframe would be protected from heat. It's not the epoxy, it's the foam.

For what it's worth, I was under the impression that these wings were built by Ronnenberg [sp?] for a govt contract.

Regarding the original post, I wouldn't personally "keep the black black" for an Ez based in Texas. Should you ever develop a problem, the fix is more work than any pleasing asthetic would ever be worth. But, to each there own.
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  #30  
Old 05-23-2007, 11:29 PM
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The wings were urethane! interesting.

After talking to the tech person and having sat in the shade in scottsdale AZ when ambient was 118, i would not use the west system ifin you paid me

Course, i am not a fan of the west system anyways as it is the only glue that i have had problems with in woodworking and they were big and multiple.

Just realized - you were talkin about the paint, not the foam, heh heh heh
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