QUOTE (philstubbington @ 22 Feb 2013, 19:56) <{POST_SNAPBACK}>I'm trying to make the SE Finecast white metal kit of the GWR Metro. I attempted to assemble the first few parts using the SE Finecast recommended two-part araldite (don't have the name to hand) but despite following the instructions to the letter the glue doesn't seem to set hard.

Any ideas what I may be doing wrong? Should I use more hardener than the instructions suggest, or is this going to cause other problems?

Thanks,
Phil
I use the equivalent to araldite called devcon.Its much better and its about the same price aswell.Most good model/craft shops should have it.

 

There are two types of Araldite (epoxy resin) in general use, if your one is "whitish" in appearance it is likely to be of the quick set variety and in my experience it never sets quite as hard or as strong as the straw coloured slow-set stuff.

Both types when freshly set tend to be a little tacky on the surface but the quick-set sort never seems to get quite so hard, a compromise to get the fast setting time I suppose.

The adhesion of the "normal" Araldite can be improved by baking at 70°-90°C when just before it sets it becomes quite fluid and will creep into all nooks, corners & crevices. The down side is of course that you are getting fairly close to the melting point of the whitemetal which might cause problems and you would certainly need to have accurate control of the temperature for peace of mind if nothing else!

For my part Araldite would not be my fixative of choice on whitemetal, low temperature solder is probably the best and strongest but Loctite 480 is pretty good too, a bit expensive maybe but it goes a long way.

 

Are you using real 'Araldite' or an epoxy 'like', recently used some similar to find it did not harden, so assumed gone off with age. Araldite Rapid Steel used after was OK. Epoxies normally better if you can 'heat' even on top of a radiator. high heat will make liquid and so fall apart after epoxy runs out of joint . I originally use 'Devon 5 min Epoxy some 30 yeras back and mine still hang together, but oil can 'undermine if not careful Beeman.

 

high heat will make liquid and so fall apart after epoxy runs out of joint

True, but if you keep an eye on it and remove from the heat when the Araldite becomes clear there is little risk and in any event the parts being fixed should be otherwise supported until the Araldite is fully set and if heated, cool. Common & garden Plasticine will seal up gaps, prevent leaks and support although it'll be degraded by the heat so it is a "one shot" job but at least it cleans off easily.

I would agree about using the "proper" real Araldite, I'm sure there are cheap knock-offs from you-know-where being sold.

"Proper" Araldite has a good shelf life, the chemists at the firm I did my time with used to make up what they claimed was a special two part epoxy. I rescued a pair of part used tubes from the clean-up crew, 50 years later I've just used up the last drop of it so it can last!

 

Apologies for spelling error in my previous post should be DEVCON 5 MIN EPOXY was USA made. fortunately still available so should say something about its quality Beeman.

 

I found that Rapid Araldite worked well on some white metal figures.

Dave

 

I'm using Deluxe Materials Speed Epoxy - comes in two bottles (adhesive and 4 minute hardener). Think I might try something else!

Thanks for your help everyone.

 

Hi Phil,

Interesting thread and quite a few pointers to the answer ... your last post somewhat summed it up.

Those a/c modellers who tried to use the faster Epoxy, found out quite quickly, that it remains slightly flexible. If you glue a tail-plane on with it, the model becomes slowly more difficult to control, with odd manoeuvres, not input from the pilot. This is eventually followed by the tail departing it's intended location and a resultant instant a/c matchstick kit ......

The more rapid the curing process, the more flexible the joint remains and the less the strength.

There are times when speed is important and also when a little "give" in a joint may be desirable. I guess in your case, you might prefer to use something much longer curing. ..

NB. As a sort of aside, you might look at some of the longer curing, thicker, Cyano glues on the market now. It might need a bit of internet searching to find what is useful to your kits but may well be worth it. There have been lots of developments around that scene and it may well give you a faster solution, with sufficient strength too.

J

 

QUOTE (philstubbington @ 11 Mar 2013, 16:23) <{POST_SNAPBACK}>I'm using Deluxe Materials Speed Epoxy - comes in two bottles (adhesive and 4 minute hardener). Think I might try something else!

Thanks for your help everyone.

A good few years ago I tried Deluxe Materials epoxy,utter rubbish wouldn't set even firm.I've tried other products of theirs over the years and come to the conclusion that their products are best avoided.

Allan

 

Bought some DevCon 5 minute epoxy at the Ally Pally show yesterday. Will report back whether it works for me or not! A few exhibitors recommended superglue - as I've not done a kit for about 30 years (and even then, didn't finish it) I am not that confident

 

Hi Phil,

QUOTE Bought some DevCon 5 minute epoxy

QUOTE Those a/c modellers who tried to use the faster Epoxy, found out quite quickly, that it remains slightly flexible. If you glue a tail-plane on with it, the model becomes slowly more difficult to control, with odd manoeuvres, not input from the pilot. This is eventually followed by the tail departing it's intended location and a resultant instant a/c matchstick kit

I assume that the kits you are making require to remain together for some time after completion.
It would be a shame to make a model and experience gradual disappointment later, for the price of 4 hr Epoxy .......

J

 

Just a thought but how much are you mixing at a time? It might seem a bit wasteful but it is easier to get equal quantities of adhesive and hardener if you mix up a larger amount. I have used Milliput epoxy filler quite a lot and every so often find it doesn't harden even though it is from the same pack, usually when I only mixed a very small quantity.

 

Hi

Only time I have had a real issue with 2 part epoxy was when I mixed in some green paint with it (to colour it), and it took about a week to set.

Most of the time I use Devcon. Works well, although one of the components really does stink.

All the best

Keith

 

Hi

This might help, from R/C a/c blog RCGroups

QUOTE The slower the epoxy set up time, the stronger it is. When epoxy cures it builds a molecular chain and the slower the cure, the longer the chain which increases strength. It has nothing to do with the soak in bit as that is a function of viscosity, the lower the viscosity the more apt to penetrate deeper into a medium. The strength is not a matter of penetration but of the molecular adhesion between the molecules of the glue and the structure it is binding to.

and this seems better than guessing

QUOTE One of the better sources is "Handbook of adhesive technology" by Antonia Pizzi & K.L. Mittal. Adhesives can be a lot of different things so there is a gigantic amount of data to try to describe all types. The epoxies are one of the ones more dependent on molecular structure and attraction than many of the others.

As I said before, it rather depends whether the price difference of longer cure Epoxy is really worth the risk to your hard work building. ...

J

 

*** Loctite 480 is a very, very good alternative - about 20 seconds work time, it is a black rubber filled Cyanoacrylate glue (superglue) and also has useful gap filling properties - incredibly strong (much stronger than other similar glues) and unusually for the type of adhesive, thanks to its rubber filled nature it also has very good shock resistance. Clean up with MEK or Butanone (both safe solvents body wise). Buy from a specialised retailer who understands how to store glues properly and who has fast sales - it should be kept in the fridge. not cheap, but no good glue ever is.

Richard

 

Thanks Richard,
That sounds very interesting.

I can see a number of applications where a little "shock absorbency" might make for smoother running and some quicker build times too.

Off topic, I know but it sounds as though it might work well for R/C a/c Main Spars and Dihedral joints, though perhaps not for Tail-planes - given the flexibility. Even though it contains rubber, can I assume that the quantity doesn't make it a weight issue for flying models?

J

 

*** It's only enough to add the shock resistance - we used to use it glue the magnets on huge concert subwoofers, so its certainly rigid and tough enough for anything... there is no "flex", just a removal of the weakness that's inherent in many so called superglues.

Richard

 

Thank you Richard,

That's interesting stuff .... The Cyano weakness was always a problem, although if it was well soaked into Balsa frames etc it made a very good joint. Anything non-porous was quite weak.

It sounds worth a try for Spars though ...

J