Model Boat Mayhem
Mess Deck: General Section => Model Boating => Topic started by: essex2visuvesi on April 13, 2015, 05:20:35 pm
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I pulled my seawolf out of the cupboard today to have another bash at it and have noticed something odd.
The epoxy that was skimmed over the tube and bayonet fixings is still tacky.... this was done at least 2 years ago! so would have thought it should be hard by now.
If I skim another layer over the top will that cure it?
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It was either an old batch, incorrectly mixed, or insufficently warm when it was initially left to set. I don't think adding additional layers is going to help, it will just mask the soft underbelly.
You should have used modified acrylics, much less fussy on mixing ratios, and they stick ABS much better than epoxies as they key themselves into the plastic.
You may want to try using a bit of heat with a hair dryer to soften the epoxy enough to let it give way. Then clean up the parts, and this time use a better glue.
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Itīs probably just on the surface and completely hardened in lower levels.
It can happen if you donīt mix enough (especially with "slow" epoxies). Some resins you have to repot (is that a proper english word?) after mixing, especially the very slow ones.
Iīd try to clean it with acetone and then check if itīs still sticky.
Normally you can clean away the resin.
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It was either an old batch, incorrectly mixed, or insufficently warm when it was initially left to set. I don't think adding additional layers is going to help, it will just mask the soft underbelly.
You should have used modified acrylics, much less fussy on mixing ratios, and they stick ABS much better than epoxies as they key themselves into the plastic.
You may want to try using a bit of heat with a hair dryer to soften the epoxy enough to let it give way. Then clean up the parts, and this time use a better glue.
Was a new bottle of Starloc's 60min epoxy.
http://www.shop4glue.com/60-min-epoxy-resin-glue-clear-set-adhesive-large-570-p.asp
Strangely the other end cap (used the same glue and from the same mixed batch) is fine
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If I do use an epoxy, I prefer JB weld. It's not cheap, but it is very, very good epoxy, and sets hard over a 24 hour period.
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This sometimes happens on full size boats, the epoxy sort of 'sweats' on the surface, it is OK underneath.
As Time Bandit says, a wipe with acetone might do the trick. After that skimming another layer might work if needed. Do a bit of Googling on 'tacky epoxy' - lots of info out there.
Colin
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E2V.......considering that other patches of epoxy from the same tube batch have cured & appear sound etc........would suggest human intervention or a form of contamination or ratio mix may have been the root cause of the non cure
However, Mr Starloc is a member here...why not ask the begging question?...... Derek
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I only mix by weight. A somewhat accurate scale (<50 or <100g) is pretty cheap on eBay these days and will let you have exactly the right amount by weight (gotta check the spec sheet as the basic instructions usually give a ratio by volume).
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I would be cautious rubbing acetone around thermoplastics, they can behave in unpredictable ways.
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Put it outside in the sun. It's worked for me in the past, don't know why though!
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Put it outside in the sun. It's worked for me in the past, don't know why though!
UV light perhaps?
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I find that too much hardener (even a very small excess) causes this effect.
Mike
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Resins can be unpredictable. A client of mine poured several model buildings in polyurethane resin, and by not measuring the two parts properly, he ended up with resin buildings that while basically cured, were quite rubbery and could be bounced off of the wall in a hillarious way.
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Too much hardener is the usual cause, but humidity or lack of airflow can cause it, the surface stays tacky due to `amine bloom , its a reaction of the hardener and carbon dioxide or moisture in the air generating Amine carbamide happens more in cool weather (even though humidity is higher in warm weather ) , should clean off with alcohol, or coat with more epoxy