View Full Version : Epoxy Cure Temperature in Cold ??
10-05-2004, 09:09 PM
I have seen and read several similar threads on this subject but I am writing to see if anyone can give specific expectations given my specific situation.
I have a 24'x40' insulated shop (1" rigid styrafoam) with an industrial ceiling fan to keep the heat moving downward. I use a 200,000 BTU propane heater and have adequate air exchange to eliminate fumes from wreaking havoc on the epoxy. Outside air temperature at night will not be lower than 20F.
I want to laminate a boat hull using West System epoxy and their fast curing hardener. I will be using four layers of 1/8" cedar veneer to deliver a 1/2" final thickness. Vacuum bagging will not be used and instead the veneer will be stapled with staples removed the next day. Each contact surface will receive a rolled on layer of epoxy.
Given the above info, if I get my shop up to say 60F and apply a single layer of veneer by 10AM and hold my 60F temperature until 6PM at which point I shut off the heat and lay an electric blanket over the hull with a medium temperature,
can I expect an acceptable product upon final cure?
Sure, I could plank on frame her but I want to try laminating a job (I have never done one before) and my concern is the cure temperature. I have built a sample lamination over a small portion of my mold and it works great but then the temperature outside right now is nowhere near 20F but winter's coming...
Thanks in advance for your feedback
10-05-2004, 10:21 PM
My boat was put together with a lot of epoxy during the Winter from Hell (2002-2003) up in New Brunswick using a smaller shop and a wood stove. The temperature in the shop was run up into the 70's for glue up. The builder also added temporary partitions to cut down the volume of shop to be heated.
EDIT: I disagree with the 4 @ 1/8" scheme, but it's your boat.
In the Swamp. :D
[ 10-06-2004, 01:51 AM: Message edited by: Venchka ]
10-05-2004, 11:44 PM
For a project of this scale I would highly recommend talking to the tech people at Gougeon Brothers/West System. They should be able to tell you whether your planned procedure on the shop temperature will be adequate...
[ 10-05-2004, 11:46 PM: Message edited by: Bruce Hooke ]
10-06-2004, 12:02 AM
Cure times are usually stated at 70 degrees. I seem to recall that typically for every 18 degrees the temp drops cure times double. But my experience has been that at somewhere around 45 the process pretty much stops. This is definitely true for the FGCI products I favor.
To be sure, I'd use a cold-cure epoxy, or plan on heating the shop through the process.
10-06-2004, 12:07 AM
Yes, do seek the Gougeons' advice.
If your heater is not vented to the outdoors, I fear that the humidity level could be a problem. Mention that to them. I'd worry about the CO2/oxygen mix, too.
You say "Outside air temperature at night will not be lower than 20F. ". Not in the Portsmouth, NH I know.
The 1" styrofoam (r=5?) sounds chilly even if ambient is 20F.
[ 10-06-2004, 12:28 AM: Message edited by: JimConlin ]
10-06-2004, 01:26 AM
One month minimum, I think. Temperature matters, but I think 'time' matters more.
It is the hissing of the sandpaper that describes the level of the cure. Three month after the epoxy is on the boat, that's when you're in for a shock ... six months later the freakin' stuff is still shocking ... but far more effecting by then.
[ 10-06-2004, 02:14 AM: Message edited by: Wild Wassa ]
10-06-2004, 09:22 AM
Like mentioned above -if your heater fumes aren't vented then Gougeons say the residue from the propane fumes causes a problem coating the resins surface.
Otherwise you're OK .
I've also got a 15 by 40 ft plastic covered shelter.
I'm using Low Temp Cure epoxy from Progressive Epoxy Polymers.I compared the LTC to Cold Cure a few days ago and found the LTC better than CC for my use.LTC flows better so I can roll it on.They have similar pot life -about thirty minutes at 65F.I'd use them at lower temps to get a longer pot life which is what I need for my Richard Woods Eclipse Cat build.
For heat I'm using Delonghi electric oil filled radiators from Sears/Cdn Tire .They work for me because I've got a male mold and place two of them inside the mold .They take the edge off for late Fall and early spring work.
The LTC is good down to 35F/2C as is the CC.
[ 10-06-2004, 09:29 AM: Message edited by: Jim Mathieson ]
10-06-2004, 09:30 AM
Even the *cold cure* epoxies are only rated down to 34 deg per manufacturer instructions.
I have never tried it - but I'm guessing at 20 deg, the stuff will freeze instead of cure.. In fact - the epoxy manufacturers tell you to keep the resin and hardners from freezing period. (if I remember correctly)
During glueups - I'd try to keep the glue area as warm as possible - Your electric blanket idea will work. The air doesn't need to be warm - just the glue and the materials in contact with it.. You don't need to be too concerned about overheating it with the electric blanket - crank it right up so it will cure.
I third the recommendation to call the manufacturers
10-06-2004, 11:01 AM
In addition to the perennial question of whether a given epoxy system will cure at whatever temperature, you should also consider other effects of temperature.
Any of the epoxy materials i've worked with are miserably viscous at temperatures below maybe 60F. It's near impossible to pour, pump, mix or wet-out with epoxy at cooler temperatures. This could affect the quality of the bonds or the resin-richness (weight) of your work. Heat lamps on he Googe bench or other warmed storage approaches are a help. It take a long time for a 5-gal. jug to be warmed up.
Second, I find that the quality of my work declines (further still) when the temperature gets cooler. I just can't do careful work if i'm uncomfortable.
Consequently, i try to have my workspace, the victim, and the materials at or above 60F. If the shop temp goes lower after layup, that's a lesser problem.
[ 10-06-2004, 11:05 AM: Message edited by: JimConlin ]
10-06-2004, 11:30 AM
I froze a small patch job of Cold Cure epoxy one night when temps dropped a few degrees below freezing.It just looked clear but for sure the chemical process was stopped.
I took a hair drier and heated the area for five minutes and it flowed again .Held the hair dryer there for a few hours down at the storage area and it set up .The temps didn't drop below freezing again ,it set up rock hard.
I have come close to poisoning myself with propane heat in a garage with poor air exchange a few times. I may have suffered but the epoxy was just fine. Wasn't using West, though. Like others say you should talk to West but at 60 degrees a cold cure should be fine. The ceiling fan is a good idea. I also invented clever ways to jack the boat up as high as possible during curing to take advantage of the the higher temps higher up, which can be significant working off a cold garage floor, or rigging tarps or whatever to keep the heat close to the boat.
10-06-2004, 01:41 PM
Has anybody tried making up a "curing oven", something like a tent made up of urethane insulating foam, just enough to hold in the heat of an electric heater? Seems as if you could hold a reasonable temperature this way for curing even a medium-size hull.
10-06-2004, 02:00 PM
I sell a lot of marine epoxy, including the low temp stuff, 'normal' temp stuff, and hot weather stuff.
In yoiur case I would recommend the 'regular - normal' epoxy. Save the low temp stuff for temps in the 40's and 50's during application. Besides the 'regular' epoxies are cheaper. Also, low temp means short potlife at 60 degrees when you are applying it.
A light bulb hanging 2 or 3 feet away from your work surface will probably keep that surface at 70 or 80 degrees for a few pennies of extra electrical power.
If surface temp drops to freezing for a few hours in the morning, no problem - it will continue to cure when the temps increase.... Look at it this way --- you get a longer recoat window!!
progressive epoxy polymers
I spent this winter restoring a 1958 Amphibi-ette Sloop in a 2.5 car garage. I bolted some 18' pallet boards together attached them to the ceiling, draped plastic sheeting over that and covered the sheeting with drop-cloths , "Old" blankets, and whatever else I found not being used. Put carpet on the concrete floor, sealed the edges of the "tent" with blocks and used a 12" electric space heater inside the cocoon. Once temps would hit 50-60 inside I turned off the heater and did my business. then I would keep the temp up for the remainder of the day. Follow the product guidlines as exact as possible, and your results should be great. Gougeon has a great guide on this topic
10-07-2004, 10:56 PM
I regulary use Clamp on heat lamps. The electric blacket is a good idea. It doesn't cost that much to leave the heat lamps on all night and I do it often in the winter. As said the heat lamps on your epoxy in the jugs way before time will help a lot.
10-07-2004, 11:24 PM
In January one year I was building laminated frames for a boat. I had the West epoxy inside where it was 65-70. Outside was about 30. I mixed it up in the house and brought it outside to paint or roll on the lamination strips. Then I clamped them up in the jig to make a frame. I then brought the whole mess inside where it warmed up and cured. The cold weather gave me a good long work window and the epoxy cured with no effect. Later with temps in 40s at night I used epoxy outside and mixed it up and it cured ok. Most of the curing occurred during the day when temps got to 50s or 60s then it stopped at night only to pick up the next day. I've never had a problem with weak or uncured epoxy.
10-08-2004, 07:17 AM
You might find that the hull is still too sticky to put a heating blanket on it after 8 hours. But what is the hurry? I had one project wherein I never heated the garage and about a month later it got up to 52 degrees F and the whole thing cured out in one day. The longer cure time meant the epoxy soaked in farther. That hull you are building sounds like a winner to me. I made a 1/2" thick hull with 3/8" ply and 3/8" spruce strips and it is built like a tank.
10-08-2004, 07:19 AM
And my hull got sanded and scraped down to 1/2".
10-08-2004, 02:58 PM
Don't forget that the temperature of the workpiece matters as much as the ambient air temperature. Even though you may have gotten the air temp up to 60F, your boat hull may still be down in the 30s from the night before.
[ 10-08-2004, 02:59 PM: Message edited by: Nicholas Carey ]
10-09-2004, 05:18 PM
being a chemical reaction the potlife and cure time will double or half every 10 degrees C or 18 degrees F
10-10-2004, 10:35 AM
Use Cold Cure epoxy instead of West system, and bite the bullet and use electric heat. Either that or buy a used propane/gas furnace that exhausts outside.
As was said, burned propane is wet and poisonous.
I assume you're building the boat upside down. In that case a baseboard heater underneath will trap the rising heat and warm the hull. (And you won't glue the blanket to the planks!)
I've used this stuff. It seemed to work as well as any epoxy.
10-10-2004, 10:40 AM
If electricity is extra expensive, another alternative is to heat the place and all its contents up quick and hot with the big burner, then shut it off, open the doors and flush the air once. Then close them and carry on with electric. The fact that you pre-heated the walls and all the items in the shop will make it quick to re-establish the temp with electic.
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