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Epoxies in the winter...

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I need to take advantage of our indoor storage this year to get some old hardware holes filled in. The problem is the indoor storage is not heated. I am initially thinking I might be able to follow a process like this...

1. Keep the resin on a heating pad or something of that sort.
2. Warm up the glass where the repair will be done just before filling
3. Mix the catalyst on the upper side of hot. 
3. Fill, fair, and then keep steady heat on the spot until it kicks off and hardens  (20 minutes or so?)

Some suggestions would help. Thoughts?

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Heat lamps. I recently watched the boatyard install a thruster outdoors in very low temperatures using heat lamps - worked fine.

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Catalyst?  Mix the catalyst on the upper side of hot? 20 min hardening time?  Sounds like you are talking about polyester rather than epoxy.

With epoxy, the resin/hardener ratio is fixed.  You can only speed up the reaction by using a "fast" hardener.  Stepping up on the hardener only creates a weakened epoxy, it does nothing to speed up the hardening process AFAIK

20 min hardening time is only possible with a big cup full of epoxy, and there will be a lot of smoke.  Under normal curing conditions, a typical epoxy takes about 8 hours to get to a solid state - and even then it is not fully cured, so you shouldn't be sanding it for at least a day - preferably more along the lines of a 3 day cure before sanding

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Localized heating can work well. Mini tent with carboard/alum. foil + small 1.5 kW fan forced heater. 

Heat lamps can set stuff on fire so use caution.

Halogen work lights can produce a lot of heat too.

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I have used heat lamps before with good results.   The warming blankets sound like a good idea.

Warm the area before layup.   keep the materials warm and mix in a warm place or over a heating pad (saran wrap over pad?).   Use a non contact thermometer to see if everything is up to temp.

--Kevin

 

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In addition to warming the victim during cure, it's good to have your resin & hardener and victim warm ahead of time.  It makes dispensing, mixing, saturating, etc. easier.

Also remember that epoxy resin that sees cold temps can crystalize which poses other big problems, like it can't be dispensed or mixed accurately.  Always store your epoxy in warm conditions, i.e., indoors.

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If it crystallizes - which it can do over time even at room temperature - simply putting the container in very warm water will liquefy it in minutes.

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5 hours ago, 12 metre said:

Catalyst?  Mix the catalyst on the upper side of hot? 20 min hardening time?  Sounds like you are talking about polyester rather than epoxy.

Yes, I would actully prefer polyester because it's easier to laminate with. I probably should not have used the word "epoxy"... My bad

Sounds like keeping the repair areas heated and locallized will work acording to everyone's feed back. Thanks m8s.


 

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Well, polyester is faster, but as a DIYer, I don't know if I would say easier to work or laminate with.

Also, keep in mind that polyester shrinks more than epoxy.  I've had a few polyester plugs in my deck (done by a PO) pop out without too much or any effort.

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I've done structural repair with epoxy in 10 deg weather. You just need to keep in warm enough for long enough to cure. I would get everything to a reasonably warm temp - near what you are going to cure at - before starting, because the viscosity of the epoxy will thin as it warms, so if you lay it up pretty cold then heat, you may end up with it all running off onto the floor. Best not to have it changing radically during the process so you know how it will behave. 

Heat lamps, cardboard boxes with heaters or heat guns running into them, old style halogen work lamps, propane infrared heaters - all can work, just monitor carefully unless the boat is well insured against fire. 

If it's just some small holes, with some patience and a heat gun you can have it gelled in 20 minutes. But for a full cure you want it warm for a few hours. 

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You might want to talk to the resin manufacturer if you are doing anything structural or safety related. 

I am more familiar with epoxy work but the cure process takes days not hours.

Yes there is a green stage where it sets' but it is flexible and can deform . The full cure takes much longer

I don't know what happens if you get the full cure interrupted with a period of cold

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West for example says 1-4 days, but that is at ordinary temperatures. They also say that once "solid" it has achieved about 90% strength, with the additional 10% in the final cure. They claim their fast hardener will cure at temps as low as 35 deg. System3 makes a cold cure version that is supposed to do the same. From experience, I know that a period of cold followed by heat will continue the cure - whether that has an effect on ultimate strength, I don't know. 

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If you are just filling screw holes try Marine Tex epoxy Preheat the holes with a hot air gun.

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Hint:  If it is 45F or below, do not go for it without your own supply of heat.

Been there, done that, got the t-shirt with a photo of a really ugly cure job and more sagging than a 70 year old lady. 

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Never pre-heat the resin, other than to 70F for mixing. Heat it up and it will exotherm in the pot.

It will warm up the instant it hits the surface.

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The most important thing is to keep the hardner & resin(epoxy, vinylester, polyester) at 24-27C(75-80F). Don't be concerned that the warm resin will not bond to the cold substrate. The resin temperature is more important when it comes to the chemical bonds within the resin and the viscosity. Adhesion is a totally different issue. The colder temps will make the resin very thick and hard to apply. It will also take a long time to harden to the point it is sandable.

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One of my favorite stories of perseverance was a boat that broke its mast at a particularly cold  KWRW, maybe a low of 45 overnight?. they found some carbon battens, laid the mast out, and went to work repairing it, lots of heatlamps etc. At some point in the night the power went out, and a mad scramble to find generators and fuel ensued. Ultimately, they made it work and got the rig back in the boat two days after the failure. Far as i know, that mast is still standing... (story told 3rd or 4th hand, so i may have missed a step or two along the way). 

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