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Old Nov 30, 2012, 10:23 PM
It's a mere flesh wound!
Buddy Roos's Avatar
Woodstock,Ga.
Joined Jun 2004
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Originally Posted by electrich View Post
Will epoxy go through? Just want to clarify I was not going to use CA.
MGS epoxy goes through but I haven't had much luck getting hobby shop epoxies to go through!

Buddy
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Old Nov 30, 2012, 10:53 PM
Thermal Seeker
electrich's Avatar
United States, GA, Atlanta
Joined Feb 2011
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Quote:
Originally Posted by Buddy Roos View Post
MGS epoxy goes through but I haven't had much luck getting hobby shop epoxies to go through!

Buddy
I'll bring the wing and my epoxy up to NASA on Sunday and you can judge if I am on the right track.
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Old Dec 01, 2012, 04:44 AM
Ride, Surf, Fly, Sleep
Joined Dec 2007
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Cheers guys - I'll go with heated epoxy. Funny, I always thought CA was lighter and so have always used it for tail repairs...you live and learn

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How about a game of Whack a mole ???!!!!
Jasper Carrott - The Mole - Animated (9 min 39 sec)


It maybe from the 80s but you've got to love "The Carrot" - great comedian
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Old Dec 01, 2012, 09:17 PM
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United States, AZ, Arizona City
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I usually thinned epoxy when I'm mixing a dry mix of micro balloons. I've noticed that the cured mix is somewhat "rubbery". When the mix isn't thinned, then it's very hard.

I'd speculate that the thinner gets trapped in the mix and doesn't have a chance to evaporate.

For what it is worth.

Gary
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Old Dec 01, 2012, 10:06 PM
It's a mere flesh wound!
Buddy Roos's Avatar
Woodstock,Ga.
Joined Jun 2004
1,143 Posts
Quote:
Originally Posted by quincross View Post
Cheers guys - I'll go with heated epoxy. Funny, I always thought CA was lighter and so have always used it for tail repairs...you live and learn
Delams can be fixed with Foam Safe CA instead of epoxy. The difference is:

I started using Foam Safe CA to fix delams when I got my first HLG with a bagged wing in 1994, a DJ Aerotech Monarch. From then until last year, I fixed delams on dozens of javelin launch HLGs and DLGs and never had one of the delams come loose again. The only problem was that the areas where I fixed the delams were REALLY ugly!!

Last year I started using MGS epoxy and rebagging the wings in a vacuum bag. On wings fixed this way the repaired delam areas are barely visible!

Buddy
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Old Dec 14, 2012, 10:26 AM
Ride, Surf, Fly, Sleep
Joined Dec 2007
254 Posts
Got back home for Xmas and finally got to fix the tail - you guys were dead right, epoxy is at least as light as cyno .

No need to thin the epoxy with thinners, heating with a hair dryer is more than enough to get it to wick right through and wet nicely. Penetration through the skin was no issue, in fact you have to be real careful not to put too much on as you need to be very swift to wipe it back off before it's absorbed....this almost caught me as it's not like my heavier slope wings! That's a heavy iron milling plate on top of a wood board/foam/PTFE/FF tail/PTFE/foam/cd case sandwich...rough and ready

In the end I couldn't be bothered to get out the vac bag kit as I expect to replace the tail soon anyhow, but in the end that made no noticable difference to either the finish or strength - see for yourself. I'll be going old school on all but the highest stress repairs now as TBH bagging's a b**ch for those little jobs!

Right back to decorating the house and the insanity/stress of the Xmas run up....too much family, too little time
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Old Dec 14, 2012, 04:04 PM
Hey was that a Thermal ????
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Originally Posted by quincross View Post
Right back to decorating the house and the insanity/stress of the Xmas run up....too much family, too little time
Dude, I have been to some sort of a musical craziness about twice a week for a couple of weeks......

I hear little kids choirs and little kids bands in my sleep !!! Man do I LOVE it !!

Everyone who has their kids home with them this evening give them a big hug and be thankful they are in your arms !!!

Paul
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Old Dec 15, 2012, 03:08 PM
Ride, Surf, Fly, Sleep
Joined Dec 2007
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So true mate, even sitting through the umpty-ith kiddy nativity is sort of worth it. - love this time of year, but fear the Santa fat suit......one day they will catch me out and learn the truth..... it's only a matter of time....

Happy xmas and have a good one
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Old Dec 17, 2012, 05:23 PM
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Templeton, CA
Joined Jan 2005
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CA brittleness

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Originally Posted by kenh3497 View Post
FWIW....

In the Balsa Builders forum there was a discussion about different glues. Some of it directed at edge joining balsa sheets. Just wait I'll get to the point Anyway the discussion was how hard it is to sand a CA joint and get a smooth surface. One MFG suggested you sand as soon as the joint is cured as as the CA continues to cure becoming harder and MORE BRITTLE over time.

Ken
The point made in that forum was that CA was much easier to sand if you don't wait an hour or more before doing it. Someone then speculated that CA continues to get more brittle over time, which is not true to a significant degree. After 12 hours (usually less), CA will be as "hard" as it will ever be. Tests have shown that quality CA will loose about 15% of its strength after a ten year period.
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Old Dec 20, 2012, 04:07 AM
Ride, Surf, Fly, Sleep
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Originally Posted by Charlee View Post
The point made in that forum was that CA was much easier to sand if you don't wait an hour or more before doing it. Someone then speculated that CA continues to get more brittle over time, which is not true to a significant degree. After 12 hours (usually less), CA will be as "hard" as it will ever be. Tests have shown that quality CA will loose about 15% of its strength after a ten year period.
Both CA and Epoxy are structural engineering adhesives - and I used to use both when researching adhesion technologies for the A380.

Epoxy (in general) has better shear strength and chemical resistance, CA is very weak in shear but (in general) forms has the broadest material bonding range (it sticks anything to anything).

What matters for us is that CA cannot bond well with glass - it only forms a mechanical bond rather than a chemical one. So GF with a CA matrix already has millions of tiny cracks around each fibre in the cloth that will ultimately grow into big ones and destroy the material. Great if you're sticking on a DLG tail that needs to be replaced after a period, really really bad if you use it for a DLG peg (high stress/shear area). So use the right technology for the job.

However, glass bonding aside, it all comes down to the individual chemical composition of the system employed - not all CA's and Epoxies are equal. The epoxide number is important for epoxy's. CA actually performs well in water, if phthalic anhydride additive is used. You increase the shear strength of both with the addition of a rubberising agent etc. Guess what I'm saying is that one is only easier to sand over the other, or degrades over time or cures this way.......for a particular brand of glue. Basically always use a professional system for critical jobs (i.e. not something from hobbystore/DIY shop shelf) and always, always download and view the datasheet from the manufacturer.

I'm pretty sure the degradation you mention for CA is down to chemical degradation (probably moisture ingress) in an unprotected formula. It's the same with Epoxy and other adhesives and 15% is a very low number in any practical modelling application and 10 years is a very long time for an airframe .....at least in my stable!

(PS. if you want some fun, put some decent quality CA on a cotton wool ball and run away - just make sure everything is fireproof and well ventilated first - never use CA on cotton )
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Old Jan 06, 2013, 03:14 PM
Thermal Seeker
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United States, GA, Atlanta
Joined Feb 2011
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I took the repaired firefly out to the field yesterday and attracted a lot of attention( the field I fly at is mostly big gasser guys). It was cool and breezy but I still managed to get many flights over 2 minutes and a few of 3 minutes. My best for the day was 4:40 and could probably have eeked out 5 minutes, but I've been working on my landing accuracy so I did not make another low circuit. Very happy with the performance of the Firefly but I need a more experienced pilot to help me with my flapperon settings. Or maybe I just need more patience to adjust my mixing. I like launching and flying more than fiddling with the TX. Happy new year!
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Old Jan 06, 2013, 04:37 PM
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United States, CA, Tehachapi
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You've been pretty quiet here for a while, Paul. Any news on new developments?
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Old Jan 08, 2013, 11:50 AM
Hey was that a Thermal ????
Joined Nov 2009
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I am going to focus on just wings for a while. I am finishing up a few full kit orders but from here forward I plan to just do wings.

I don't plan to fly anymore, I am not good at it but I love to build so that is what I will do.

Paul
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Old Jan 08, 2013, 06:27 PM
Dub Cult.
Long Island NY
Joined Feb 2011
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Quote:
Originally Posted by The_Builder View Post
I am going to focus on just wings for a while. I am finishing up a few full kit orders but from here forward I plan to just do wings.

I don't plan to fly anymore, I am not good at it but I love to build so that is what I will do.

Paul

Hey hey hey those are my lines!
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Old Jan 08, 2013, 07:13 PM
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United States, CA, Tehachapi
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Paul, not being good at it is no excuse to give it up! Now if you just don't get much enjoyment out of it then that's a different story. I remember a girl that was in several of my classes my first two years, but later told me she was quitting engineering. I asked her "Why? You're one of the most brilliant kids in every class!". Her response was "Yeah, but I realized that being good at something isn't the same thing as loving it." I'm glad to hear you enjoy building, however, because your work looks great. Will you have somebody else provide fuselages and tails for your kits or do you plan to just sell wings by themselves?

B
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