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  #1  
Old 01-28-2012, 01:27 PM
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RVG8tor RVG8tor is offline
 
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Question Resin Not curing

10 day ago I mixed up slow hardener and resin (West systems) and rolled it onto my canopy skirt (inside). Due to snow and ice storm and power outages I am just now getting to sanding this coat down to do another. Three days after the coat the power went out for 3 days so the temperature in the garage dropped from the normal 58-60 but not by much, maybe down to 45. I did bring the skirt inside the house for two days after the first 24 hours in hopes of getting it to set, but I took it back to the garage.

Well now 10 days later it is still slightly tacky and gums up when I try to sand it down. Normally I just get dust when sanding. So I am guessing I messed up the mixture of resin and hardener (West pump system) and there is not enough hardener or is this all temperature related? Hard to believe the pump system failed me but I did read having the product at a cold temperature can effect how much comes out of the pump.

Now what to do, can I re-coat as is and if not how to get the gummy stuff off. This is the inside of my skirt so I am not concerned about looks as the plan is to have cloth cover over the visible part of the inside skirt. I am basically using the inside to practice technique, and a good thing too. I know warmer temperatures will help. I have a propane heater going in the garage now and I can get it close to 68 in a few hours.

Cheers
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  #2  
Old 01-28-2012, 03:00 PM
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Default

Quote:
Originally Posted by RVG8tor View Post
10 day ago I mixed up slow hardener and resin (West systems) and rolled it onto my canopy skirt (inside). Due to snow and ice storm and power outages I am just now getting to sanding this coat down to do another. Three days after the coat the power went out for 3 days so the temperature in the garage dropped from the normal 58-60 but not by much, maybe down to 45. I did bring the skirt inside the house for two days after the first 24 hours in hopes of getting it to set, but I took it back to the garage.

Well now 10 days later it is still slightly tacky and gums up when I try to sand it down. Normally I just get dust when sanding. So I am guessing I messed up the mixture of resin and hardener (West pump system) and there is not enough hardener or is this all temperature related? Hard to believe the pump system failed me but I did read having the product at a cold temperature can effect how much comes out of the pump.

Now what to do, can I re-coat as is and if not how to get the gummy stuff off. This is the inside of my skirt so I am not concerned about looks as the plan is to have cloth cover over the visible part of the inside skirt. I am basically using the inside to practice technique, and a good thing too. I know warmer temperatures will help. I have a propane heater going in the garage now and I can get it close to 68 in a few hours.

Cheers
THe slow hardner really likes 70+ degree temps. If you are going to work in the cold, you'll need to get the fast hardner. I don't have the numbers or the temp ranges handy, but they are on the West Systems site.

I would probably bring the parts (if you can) into a warm area to finish curing, then sand as appropriate.
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  #3  
Old 01-28-2012, 03:06 PM
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Default Scrape old stuff

That gummy mass need to go Mike. Remove it completely don't even try to cover it or heat to cure. It will stay soft even when temps are higher. Scrape off take your time on it. Use utility knife razors or similar. Do it again in proper temps with right mix. I had that experience. Chemistry gurus may explain the process.
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  #4  
Old 01-28-2012, 03:17 PM
Bob Axsom Bob Axsom is offline
 
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Default I Agree with just waiting in a warm environment for it to cure

I typically use EZ-Poxy brand wirh 24 hour cure hardner but I have mixed some off nominal combinations and they have always hardened eventually. I would bring it inside and let it warm for a few days and I think it will harden and sand normally. When McDonnell was first getting into composites with the skins on the F-15 tail surfaces and speed brake I had to do the initial certification of the new the facility. It has been a long time but I remember that one of the refrigeration temperatures that was used for storage of the prepreg material to prevent it from starting to cure was 40 F deg.

Bob Axsom

P. S. I just read Vlad's post and he obviously had a different experience. I would suggest both approaches may be tried - try to let it cure in 70 F minimum temperature and if it doesn't cure follow his remove and replace procedure. Since you have used the material and process before I doubt that you can be uncureably far off but he has experienced this failure.

BA

Last edited by Bob Axsom : 01-28-2012 at 03:26 PM. Reason: P.S. added
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  #5  
Old 01-28-2012, 04:10 PM
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Default I took it off

I called a local guy who had built sail planes and he recommended taking it off with acetone or MEK. It actually did not take long. I took it off with the acetone I had on hand, gave a an additional wipe with denatured alcohol and then sanded it down real good, no more gummy bits.

I have not had any issues with the West systems curing in my 60 degree garage up to now, so I am guessing I mixed the batch up wrong and that is what caused the problem. I just put on another coat and the garage is nearing 69 with the heater going so time will tell. I do have some of the fast cure on hand I guess I should try that next.

Can you put a mixture with fast hardener on top of a partially cured slow hardener? I want to do a second coat after this one is partially cured in a few hours and wondered if I should use the fast cure hardener for the second coat.

Cheers

BTW thanks for the advice and inputs
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  #6  
Old 01-28-2012, 06:39 PM
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Default Why Not....

Why not ask the Gougeon Brothers? I prefer going to the source for tech questions... but hey, what do I know....!

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Last edited by flyingriki : 01-28-2012 at 06:54 PM.
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  #7  
Old 01-28-2012, 07:03 PM
Ron B. Ron B. is offline
 
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One thing I find is if you are working with cooler temps is to have the resin kept in a warm place before use.
Ron
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  #8  
Old 01-28-2012, 07:15 PM
Wayne Gillispie Wayne Gillispie is offline
 
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Default

Thin layers of epoxy take much longer to cure, especially when cool.

Unvented kerosene or propane heaters can inhibit the cure of epoxy and contaminate epoxy surfaces with unburned hydrocarbons. I use a heat pump or portable electric heater with fast hardener.
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  #9  
Old 01-28-2012, 07:30 PM
rockwoodrv9 rockwoodrv9 is offline
 
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Default don't cover it up

I have built several sail boats with West Systems epoxy. One think i know for sure is, do not cover up sticky - poor mixed or cured epoxy. Scrape, scratch, grind, or sand it off. It will come back to haunt you once sun hits it, cold, pressures, whatever, it will pop or something. Just my 2cents, but an hour or two now could save you many hours later.
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  #10  
Old 01-28-2012, 07:32 PM
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Default

Once you realized that the ratio of the mixture wasn't per spec then you did the right thing by removing the epoxy.

Rockwoodrv9 and Vlad gave you good advice.
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Last edited by rv6rick : 01-28-2012 at 11:05 PM.
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