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TG or not TG ....THAT is a question?


cncdoc

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I know I read somewhere about the TG of Epoxies (particularly MGS) The 285 tg was well over 200F whereas the 335 (cheaper) had a tg of 140 to 180F If I remember right, this had something to do with the post cure temps. The general idea I got from the whole thing was that if you post cure the epoxy at xxxF (temperature) then it will remained cured (hard) at or below that temperature for the rest of it's life. The "expert" in question also spouted rheotoric to the effect that cure temps over 200F were unrealistic in real life and somewhat overkill, as it would be difficult if not impossible to cure at upper tg without melting stuff (foam i'd imagine).

I tried the search engine here, but it's been drinking and wouldn't give me a straight answer and insists on making me play my "wildcard". But I had it hands down with a "full house" and a "straight"! It misdirected me on purpose and landed me square in the middle of a sanding discussion. I countered with another "wild card" and it "saw" my play and raised me into the "engine discussion" area.

I folded and lost the kitty.

 

The cards were marked.

 

I accused it of cheating and drew my "9" first!

 

I then realized I was about to shoot my laptop.

 

So I decided to circumvent the dishonest gambler search engine and plead my case here.

 

computers always win anyway.

 

 

 

unless you shoot them first.

 

:bad:

Back to building... #618 Cozy MK IV

 

My Cozy web pages, courtesy: Rick Maddy... :cool: WN9G :rolleyes:

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  • 2 weeks later...

I found the answer to my own question in the cozy builders archives!

John Slade once again giving the engineers a run for their money:D .

 

So if you're curious about the strength of your epoxy, what TG does for you and how to post cure, you can read this

It's a little long, but well worth reading.

 

So tg or not tg?

 

TG of course.. but not the highest or lowest...but just as Goldilocks said: "Just right".

 

She was eaten by bears though wasn't she?:scared:

Back to building... #618 Cozy MK IV

 

My Cozy web pages, courtesy: Rick Maddy... :cool: WN9G :rolleyes:

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Just to add another data point to your TG thoughts....

 

I've found an excellent way to post cure a cowling. Simply run the engine on the ground for about 15 minutes, get the water temps up to about 220F and then let it heat soak overnight.

 

Next day you're cowl is perfectly post cured. :D

 

This interesting scientific test has an added benefit. You can now test the new "melting temperature" of the epoxy by running really rich and letting the orange flame coming out the back curl around and play on the unprotected area of cowl inboard of and behind the exhaust. :eek:

 

I'm glad I used MGS. The safetypox would have been a heap on the floor. I wish I'd used MGS 285. Then maybe I wouldnt have to extend my turbo shield to protect the melted bit at the back. :)

I can be reached on the "other" forum http://canardaviationforum.dmt.net

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FWIW:

 

Here in the PHX area, it gets a little warm in the summer time. Along with ordering foam, glass, and epoxy, I've been scrounging up stray pieces of sheet metal to build a "hot box", about 4'x4'x12'. It will be out in the yard where it can get full sun from about an hour after sunrise until a hour before sunset.

 

What I'm hoping for is that, after the parts have "aged" a week or two from when the layups are done, I'll put them in the hot box in the AM - by 11 AM, the box should be getting to about 140* (my garage gets that hot by 13:00); it should be maxing out at about 160* around 14:00; and take

at least four hours to drop back below 110*.

 

I'll let you know in July how well it works - that is, if I can figure out a way to verify the

effects.

 

Dale R.

COZY MkIV-R #1254

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Clifford,

 

I lived in Phoenix for 18 years then Tucson for 5 years. I moved to Michigan 5 years ago.

 

I love the Michigan weather compared to the Phoenix. In Phoenix its too hot to go outside from May to the end of September. 5 months of the year are lost for outside projects unless you wake up real early. In Michigan you can't go outside from December through the end of March because its too cold. Thats 4 months of the year. Michigan gives you better weather for outside projects.

 

But maybe my memory is jaded. Spring in Michigan is assume. Also I didn't have an air conditioner on my house for the 18 years I lived in Phoenix. There was no escape from the heat. We used to go for car rides when it got too hot during the day to escape the heat using the cars air conditioner.

 

I do miss the mountains in Arizona though. Michigan is way too flat.

Mike T

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I've got family in Tucson. Over by Pantano and Speedway I think. I also have some in Phoenix, but that's toooo hot for me. I don't mind going outside and sweating from work, but I don't want to from just standing.:bad:

 

I do know someone who can sweat from talking though.:scared:

Mike LaFLeur - Cozy MkIV #1155
N68ML
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Originally posted by Dale_R

I've been scrounging up stray pieces of sheet metal to build a "hot box", about 4'x4'x12'. It will be out in the yard where it can get full sun from about an hour after sunrise until a hour before sunset.

And when it's not filled with plane parts you can use it to make beef jerky :)

 

I also like the idea of the automotive paint shop from the mailing list. rent it out over a holiday and just cook the whole bird.

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