Fiberglass Still tacky

[PilotjohnS]

Originally Posted by scsmith

I suspect your epoxy has cold-inhibited and will never cure. I have had this happen a few times with West.

I found that I could put a part that had cold-inhibited in the oven at 175F for several hours and it wasn't tacky anymore, but it was rubbery. It never got hard. I scrapped the part.

In your case, I suggest removal. warm it with a hair drier a small area at a time and scrape it all off.


Folks - the hardener systems used with epoxy are not a "catalyst". It is not a matter of enough heat for enough time for a catalyst to bring about a chemical reaction to harden the resin, such as happens with polyester and vinyl ester resins. The hardener system in epoxy becomes an integral part of the final chemical compound. But whether or not that compound properly cross-links into the intended structure depends on the temperature at the time when the basic compound is formed.

If it hasn't cross-linked, it is not going to. Ever.

Darn.

Double Darn.

lesson Learned: trying to save a minute may cost you a month.....
Thanks for the feedback

[Taltruda]

I must have gotten lucky.. I used Jeffco epoxy, I mixed up some micro that wouldn't harden for over a week. I knew it was throughly mixed, but cold. I gave it a couple of heat cycles with a heat gun, and it did harden up.

[wirejock]

Just curious and not trying to hijack but interested.
Those who have had issues with epoxy not curing, was it mixed with a scale by weight?

[PilotjohnS]

Originally Posted by wirejock

Just curious and not trying to hijack but interested.
Those who have had issues with epoxy not curing, was it mixed with a scale by weight?

In my case, yes, always.
I am going to try and put a blanket over it with a temperature controlled heater.

[rmartingt]

Had this happen with the "skim coat" I tried on my canopy skirt. Never cured, just stayed gummy. Had to sand it all off.

One more of many, many reasons I hate this [expletive deleted] fiberglass.

[lr172]

Originally Posted by rmartingt

Had this happen with the "skim coat" I tried on my canopy skirt. Never cured, just stayed gummy. Had to sand it all off.
.

Same here. Tried the skim coat recommendation for pin hole covering. Total disaster, as it wouldn't harden. Even left it in the sun for several hours and no joy. I mostly use the West or Total Boat (west copy) with the slow activator and have otherwise never had something not cure, even in temps below 60. I do know that they have a recommendation not to use the Fast when temps will not stay above 60 or something like that. They say slow is good down to something like 45.

[PilotjohnS]

Seems others have a similar problem with a skim coat. Maybe the skim coats need a higher temperature cure?

I have got my cowl under a heat source about 90F. Lets see if there is a change after 24 hours. Otherwise peel it off, and redo, but let it set up under a heat source. Seems like in thin layers, the epoxy performs differently then in a glass epoxy matrix.

[9GT]

Well, I am not familiar with the epoxy system that JohnS used. I only use MGS for fiberglass lay-ups and West for any fill that will require sanding. Early in the Cozy MKIV build, I was very interested in the prepeg fiberglass available. As an experiment, I was laying up fiberglass taping with the MGS. After it was wet out, I immediately placed it on a frozen plate right out of the freezer and put it in the freezer for a couple days. After removal and thawing, the wet out tape was slightly pliable with a touch of tackiness. The next day, that tape was fully cured. I did that experiment in hopes that I could save some time making the taping in advance. MGS does benefit from a post cure per manufactures specifications, It may or may not work with JohnS epoxy but it is certainly worth a try.

Originally Posted by scsmith

I suspect your epoxy has cold-inhibited and will never cure. I have had this happen a few times with West.

I found that I could put a part that had cold-inhibited in the oven at 175F for several hours and it wasn't tacky anymore, but it was rubbery. It never got hard. I scrapped the part.

In your case, I suggest removal. warm it with a hair drier a small area at a time and scrape it all off.


Folks - the hardener systems used with epoxy are not a "catalyst". It is not a matter of enough heat for enough time for a catalyst to bring about a chemical reaction to harden the resin, such as happens with polyester and vinyl ester resins. The hardener system in epoxy becomes an integral part of the final chemical compound. But whether or not that compound properly cross-links into the intended structure depends on the temperature at the time when the basic compound is formed.

If it hasn't cross-linked, it is not going to. Ever.