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General control line discussion => Open Forum => Topic started by: Dick Pacini on October 03, 2015, 05:54:23 AM
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Anyone here familiar with Araldite, a form of epoxy said to be exceptionally strong?
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Dick,
Araldite is an epoxy that is made by Huntsman. I believe it was formulated for the bonding of advanced composite materials. I have some friends in Australia that use some of Huntsman's products. Huntsman used to be CIGA-Geigy.
Alan Resinger
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To all of us here in England, Araldite has traditionally been THE epoxy. The original, which took 24 hours to cure at room temperature, first became available on the High Street some time in the second half of the 1950s, and soon became the first choice for glueing engine bearers to plywood formers and nose doublers - and any other high-stress applications. We'd simply never seen anything like it; and when we discovered that you could thin it with methanol and brush it on as a super protection against oil soakage, the fact that it cost about ten times as much as balsa cement became a minor consideration, since our models lasted so much longer before they fell apart. To this day, you'll hear people of my generation say 'Araldite' when they mean epoxy, just as they'll say 'a Biro' when they mean a ball-point pen, or 'a Hoover' when they mean a vacuum cleaner.
Regards
John
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Anyone here familiar with Araldite, a form of epoxy said to be exceptionally strong?
It's a quality slow set two equal part epoxy. Good, but probably no better than other epoxies available in your country. Also available in a "5-Minute" mix which doesn't have the high strength properties of the former.
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Also available in a "5-Minute" mix which doesn't have the high strength properties of the former.
And which isn't as strong as you might expect after 5 minutes. I found this out as a kid, while trying to fly a freshly-repaired model. The noisy end of the model parted company with the rest of it, travelled a surprising distance, and narrowly missed my flying buddy. Happy days. :)
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I don't have the patience for using a 24 hr. epoxy. Even the 2 hr is stretching it.
You forgot "bonnet." I had a Morgan +4 for 35 years. Also many other British sports cars.
Charles
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And then there's the "boot" H^^
and also "running in" as opposed to our breaking in.
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And then there's the "boot" H^^
and also "running in" as opposed to our breaking in.
I was talking about the minor sin of using a Trade Mark in place of a generic term. (I used to be a Trade Mark Agent, and that sort of thing was the bane of my life - it can destroy a Trade Mark's value.)
Regards
John
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Hi.
Slow Araldit is a good glue for hardwood but basically all epoxys with slower than 1/2h curing time are strong enough for anything we glue.
Once I had access to a machine for pull-testing differend things, so I made lots of shear-strenght tests for differend glue joints.
The main conclusion was that when cured in room temperature, epoxies faster than 30min were allways weaker,
this is due to the fact that the glue starts to harden before it has impregnated the wood deep enough.
In elevated temperatures (60..70C) all joints got a lot stronger and difference betseen slow and fast epoxies were no longer so big.
With slow Araldit the joint strenght doubled when cured in elevated temperature.
It's not only about the impregnation, also the mechanical properties of glue improve in elevated temperature.
So, I recommend to heat the parts allways when it is possible. You can use an oven, hairdryer or a light bulb for heating, for example.
The 24h Araldit cures in about 30 minutes in 70C.
The only problem with Araldit is quite bad temperature resistance, it starts to loose its strenght quite dramatically allready in 60C, so it is out of question in more serious aeromodels. But good for everything in our stunters.
A much better slow epoxy that is easily available at least in Europe, is UHU Endfest 300. It remains strong up to 180C, and you can manipulate the mechanical properties by changing hardener:glue ratio. Less hardener results in a harder glue with best temperature resistance. Put more hardener, and the joint remains more flexible. L
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Hi....Less hardener results in a harder glue with best temperature resistance. Put more hardener, and the joint remains more flexible. L
I guess the same is true of ordinary HW store epoxy. This week I thought I had mixed a bad batch because it was unusually slow to set, and I suspected too little hardener. But I checked my test puddle today, and after 36 hours it was very hard and surprisingly brittle.
Rusty
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Yes I guess so, UHU is just the only one I've seen who explains it in their manual.
But all the 1:1 mix epoxies have something added to the hardener just to inrease volume, to make 1:1 mix possible. That *something* affects the technical properties of glue, and is propably one big reason why some glues are better than others. It seems that UHU got it right.
For best results, it's better to use good laminating epoxy and build up the viscosity with something like colloidal silica or microballoons, or chopped fibers. L
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Araldite is common here in New Zealand. I like their slow cure, have used it for a long time and found it works great.
Only thing is the price, it's quite expensive, $15 for a large syringe. A friend uses another brand for his boats, buys it in 4 litre buckets. Much cheaper and works just as well.
I've recently started using "Gorilla" polyurethane glued for high stress areas and have found it works great. Time will tell how well it holds up I guess.
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That is kind of funny, since Araldite is how people in general refer to epóxi glue here in Brazil...
You walk into a hardware shop and ask for epóxi glue, one may not know what you're talking about, but you say Araldite, everybody knows...
Marcus
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Further to Steve Thomas' story about 5-minute Araldite, a mutual friend built two examples of the same model using laser-cut short kits that I had—one for him, one for me.
He used 5-minute Araldite to 'glue' in the hinges on the elevators—there were no flaps. Mine was totalled when I was completing consecutive loops and the last one turned into a figure 9.
The elevator connected to the pushrod was hanging off and the other one was about 10 feet away. On close inspection, there was no evidence of adhesive on the nylon hinges and certainly no balsa stuck to the hinges. The model was on its third flight.
I took the remains to the field the next week so our friend could see it. He had his example with him—which had completed two flights—and he checked the hinges. They were all in place but loose. He came to the conclusion that, as he was using 5-minute Araldite on a hot day, there must have been an issue.
Anyway, his model would probably have crashed on its third flight as did the one he built for me.
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Further to Steve Thomas' story about 5-minute Araldite, a mutual friend built two examples of the same model using laser-cut short kits that I had—one for him, one for me.
He used 5-minute Araldite to 'glue' in the hinges on the elevators—there were no flaps. Mine was totalled when I was completing consecutive loops and the last one turned into a figure 9.
The elevator connected to the pushrod was hanging off and the other one was about 10 feet away. On close inspection, there was no evidence of adhesive on the nylon hinges and certainly no balsa stuck to the hinges. The model was on its third flight.
I took the remains to the field the next week so our friend could see it. He had his example with him—which had completed two flights—and he checked the hinges. They were all in place but loose. He came to the conclusion that, as he was using 5-minute Araldite on a hot day, there must have been an issue.
Anyway, his model would probably have crashed on its third flight as did the one he built for me.
Geoff old boy! Now you know why they give us a plastic mixing stick with that 5 minute "liquid lead" in each pack. The epoxy peels off the stick easily ready for the next mixing session. 5 minute epoxy has it's uses but sticking nylon hinges isn't one of them!
HH
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It's been said that 5 minute epoxy, is good for about that length of time.
Any glue joint for me that will carry stress, like engine mounts is slow epoxy.
I find 5 minute epoxy perfect for wrapping lines, it stays relatively flexible.
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I find 5 minute epoxy perfect for wrapping lines, it stays relatively flexible.
I'd suggest heat-shrink tubing instead. I like to butt a small tube up to the wrap and overlap with a larger size that fits over the wrap. After shrinking, they are "conjoined" and do a nice job of spreading the stress concentration. The hardest part of this is remembering to put the sections of heat shrink tubes on the line before binding. :-[ Steve