epoxy curing temps.

[Josh9685]

hi,<br />I just recieved some epoxy, and reading the instructions it gives all the examples at 70+ degrees.<br />I live in northern michigan, and its cold! the boat is in my pole barn, and with my propane heater I can get it to 55 degrees or so. Is that gonna be warm enough?

 

[fishingdan]

Re: epoxy curing temps.

I built my boat through the winter in New England. with a medium speed hardener My garage temps were often in the high 30s or low 40s. <br /><br />55 degrees in the work space is fine. The key is to keep your epoxy at room temps. The epoxy needs to be about 70 degrees. You can put it in a old fridge with a light bulb for heat or keep it inside a heated space like a basement or a closet with a small heater.<br /><br />Plan your work around the fact that it will take time for the epoxy to cure. There were times when it would take 4-6 days for the epoxy to fully cure.

 

[imported_bjs]

Re: epoxy curing temps.

most all paint and epoxy and glue will dry at any temp epoxy is a little touchy about drying wont to call manafacture.somtimes the epoxy may not cure or stick at lower temps.dry times are all rated at 70 degrees.meaning that if it cures in 24 hrs the manufacture room was 70 degrees.thats saying you cant use the glue at a low temp .hope this makes sense

 

[bigbad4cyl]

Re: epoxy curing temps.

try a fast hardener . i just baught some fast hardener for my west ststems because its rated for a lower working temp...

 

[qaztwo]

Re: epoxy curing temps.

When I epoxy in my transom I kept the temps in the garage around 50 degrees. Wanted to prolong set up time, allowing me to apply the epoxy and place the transom in the correct postion.

 

[BillP]

Re: epoxy curing temps.

A couple things to be aware of...<br /><br />When kick time is extended from cold temps the resin has more time to run off or soak into the wood, foam, etc. That can leave a dry and weak glassjob. On vertical surfaces it means you may have to baby the job until the resin gels enough to stop sagging. <br /><br />If you heat epoxy to make it kick faster the resin thins out and can run too.

 

[fishingdan]

Re: epoxy curing temps.

Originally posted by BillP:<br /> If you heat epoxy to make it kick faster the resin thins out and can run too.

No one said to heat the epoxy. That would be bad. However, you do want it close to room temps for a number of reasons. If it is too cold, it will not start to cure. If it is too cold, it will be difficult to saturate fiberglass.

 

[BillP]

Re: epoxy curing temps.

Originally posted by fishingdan:<br />

Originally posted by BillP:<br /> If you heat epoxy to make it kick faster the resin thins out and can run too.

No one said to heat the epoxy. That would be bad. However, you do want it close to room temps for a number of reasons. If it is too cold, it will not start to cure. If it is too cold, it will be difficult to saturate fiberglass.

I mentioned heating because people do it all the time to make it kick faster or penetrate better. There is nothing harmful about heating it. I do it on epoxy and polyester with a heat gun after it is down and not kicking quickly. Epoxy gets very thin and poly doesn't.<br /><br />Keeping the resin at "room temperature" only helps for mixing and glassing. If the glassed surface is cold the resin can get cold quickly and take a long time to kick. Like I posted earlier, resin can run off and out of the glass if you let it take hours or days to gel. Try keeping uncured resin on the side of stringers for a few hrs without touching it...you have a puddle of resin with a dry glass job.

 

[Pogo123]

Re: epoxy curing temps.

Big subject, but as brief as I can make it ...<br /><br />For years, Josh, I did research into epoxies and application methods for the Golf Club industry.<br /><br />What I (and others) found that was, for the average user of medium to slow cure epoxies, 70F was the minimum to give the curing times and strengths listed by the manufacturor ... but ... the higher temperature you cure epoxy, the stronger it gets ..up to about 170F. Sheer and impact strengths of 3500 to 4000# are not uncommon with good quality epoxy and the higher the curing temps, the higher the melting point once cured.<br /><br />These numbers are for metal to metal. Bonding anything porous enough to give a good surface "tooth" will provide an even stronger bond.<br /><br />These were important because, first, a golf club sees about 2500 to 2700# of force over 1/10th second at impact and the trunk of a dark car (where most golfers store their clubs) in the summer sun can hit over 200F. If you doubt that, contact your local SCUBA dive shop and have them show you picturs of tanks that have exploded from being stored in a car trunk during an August afternoon. At those temps, epoxy cured at 70F often melts and runs away from the bond site.<br /><br />While curing, epoxy does create some temperature rise of it's own by chemical reaction, but not for long enough to overcome low ambient temperatures.<br /><br />Low curing temps do slow the curing process and give you a longer pot life, but it also yields a weaker bond ... not all resin reacts with all the accelerator.<br /><br />I'd suggest rigging some sort of enclosure and getting the ambient temp to AT LEAST 70F and anything near the 125 to 140F range would be even better.<br /><br />Just my $0.02 worth, fyi ...

 

[Pogo123]

Re: epoxy curing temps.

Josh ... I just noticed your other posts relative to this project and came back to pass on that, in epoxy thickness ... more is NOT better.<br /><br />For any joining, a good mechanical fit is important, no matter what the bonding material. You ideally want the two pieces to fit together well before you glue them. Epoxy layers of 1/64th to 1/32nd" is O.K. and a bit thinner is even better. Any more and you are "filling" rather than gluing and fillets are not as strong.<br /><br />I suggest making your new piece fit snugly before you epoxy. Apply some epoxy to both surfaces and squeeze the new piece in place. If there is ANY epoxy on both surfaces and they contact well, you should end up with a bond stronger then the original material.<br /><br />Prep is also very important with epoxy. Each surface should be clean, dry and NO oil. Roughing with sand paper, then wiping with an aromatic like acetone, denatured alcohol or similar assures a good bond. <br /><br />You can always, if only for cosmetic reasons (and some added strength), mix up some "filler" (epoxy and stuff like finely chopped glas, Aerosil, Cabosil, aluminum dust (fine filings) or even fine sawdust) to the peanut butter consistency you mentioned and smooth around the finished seams. <br /><br />Again ... barely $0.02 worth ...

 

[Chief101]

Re: epoxy curing temps.

That's a good point, and the single largest mistake that I see amateurs commit. Speaking of the resin thickness, of course.

 

[surlyjoe]

Re: epoxy curing temps.

athother good reason to use the "peanut butter" is to fill in anything that could be a potential air pocket in your layup

 

[BillP]

Re: epoxy curing temps.

In boat applications I personally think worrying about 1/32 - 1/64 gaps is borderline paranoria with epoxy. The only place you see fits that tight in the boating industry is where they aren't using epoxy. Unlike most other glues and resins, gap filling without fillers is one of the things epoxy is known for.

 

[Pogo123]

Re: epoxy curing temps.

I think you missed the point here, BillP. We were approaching it from another view, not with "gap" as the primary question, but ...

 

[18rabbit]

Re: epoxy curing temps.

Originally posted by Pogo123:<br /> Low curing temps ... yields a weaker bond

Anyways, Josh, that's what you need to know. If you have a 55-deg enviroment, you need to be using an epoxy designed to cure at 55-degs.<br /><br />Also, mucking around with the mix ratios to affect the curing speed isn't necessarily a good idea, either.

 

[BillP]

Re: epoxy curing temps.

Originally posted by Pogo123:<br /> I think you missed the point here, BillP. We were approaching it from another view, not with "gap" as the primary question, but ...

Here's a few points for you...If you glue properly prepared wood to wood with 70F epoxy at 55F with a 1/4" gap the bond will be stronger than the wood. Glue the same with 55F epoxy and the bond will be the same but the kick time will be shorter. Strength will be the same.

 

[Josh9685]

Re: epoxy curing temps.

well guys, <br />I did it. I put the new transom core in today. <br />I heated the wood and outer hull with heating lamps for about an hour before applying.<br />I had a problem though.<br />I made the first batch up, and I had to do some filling along another part of the boat. so I figured 2 birds with one stone right?<br />I then realized as I began spreading the epoxy to the wood that I wouldn't have enough. So I had to make a second batch up.<br />I then bolted parts of the transom/outer shell together with through bolts that I pre drilled and I clamped other parts of it. <br />I think I used to much becuase it was squeezing out all over the place along the borders.<br />I used a dummy transom on the outside of the outer hull that I ran the bolts through to help evenly distribute the clamping forces. I peaked underneath the wood and there were several streaks of epoxy manaise slowly running out of holes where the exaust runs though. I don't know how im gonna get this stuff off the hull once it cures...<br />my main worry is that I just checked on it, and the temp. in the building came down to 56 degrees. I do have several space heaters blowing at the transom though. <br /><br />now..<br />How do I know when it is done curing? how do I know if I did it correctly/it will hold?<br /><br />thanks

 

[BillP]

Re: epoxy curing temps.

It's going to get tacky, then rubbery, then hard. I've had epoxy take 2 days in cool weather to get past the tacky stage. Dig into some of those places that squeezed out with a screwdriver and see how hard they are. Ultimately they will get too hard for you to do much of anything but a scratch. There is no way to practically measure the cure strength...but 1000s of people use "70F" epoxy on boat work evey year at low temps and it never shows up as inferior. I won't go into all the empiracle testing I've done with epoxies but all I can say is don't worry about your glass job...once your epoxy is hard it will take a sawzall, crowbar and sledge hammer to get it apart.