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Buddha

Cold curing epoxy?

29 posts in this topic

Just looking at doing some basic repairs to the boat before launch.

 

(Up in Canada) Spring can be very fickle and the weather window to get anything done is very small. I'm wondering about what are the best products to use in the cold. I'm looking for good advice on epoxies that will cure though the night in cold spring conditions.

 

When time is short - you don't want the epoxy to not harden - and start all over again.

 

Cheers. (PS> Running heaters overnight in my yard is not allowed, unless you want to babysit them the whole time)

 

- B

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How cold is cold? I've worked in temps in the 40's (F) to stay within the manufacturers specs. It's a bit thicker when mixing, I used 205 fast hardener and it's best to let it sit overnight for it to cure.

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Unfortunately heat is your friend and heat ( or the lack of it) effects the strength of the cured epoxy.

There is a lot about the length of the polymer chains that is tied up with the processing conditions, so just having hard glue left over in the pot isn't really an indication that the glue in the repair is 100%.

However, what you can get away with in cold environments depends on what you are trying to do.

For example gluing two pieces together always seems to work unless is is frigid. I always thought this was because the material insulated the glue film from the cold air and allowed it to build up enough heat to cure.

Thin films and light glass repairs need real warmth.

 

If you have to push it, the best thing to do is make sure the parts you are going to glue are good and warm before you start.

Keep the epoxy someplace warm, or make a warming box that travels to the yard with you. You can use hair driers, heat lamps and anything else as long as you are careful about it. You want to warm the repair area, not set it on fire do more damage by melting the finishes and structure nearby, so use your head. I avoid blow torches.

When you do this, you will have less open time than you would otherwise have, so planning ahead makes a mess less likely.

If you can arrange to insulate/cover the area after you finish to retain as much heat as possible, it is good.

 

Finally, you will want to be sure that the epoxy has seen enough heat for long enough before you ask it to do any real work.

If this means setting up heat lamps and running them for a day while you babysit them or do other stuff, then that is what you will have to do.

SHC

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How cold is cold? I've worked in temps in the 40's (F) to stay within the manufacturers specs. It's a bit thicker when mixing, I used 205 fast hardener and it's best to let it sit overnight for it to cure.

 

Correct - 205 will cure, albeit slowly, down to 40 F. One way to help dispense easily in cold weather is to keep the resin and hardener warm. In the boatyard it's as simple as putting a 25 watt bulb in an old cooler and keeping the cans in there. Remember, keeping the epoxy warm helps to keep the pumps working properly so the correct ratio is dispensed but as soon as the mixed epoxy hits the cold hull the viscosity will go right back up. Still, it's a good habit to follow.

 

Usually a 24 hr. cure at 40 F will give you a sandable surface but the epoxy will effectively stop curing if the temp drops lower overnight. It does then just take up curing where it left off when the temp returns to 40 F or more.

 

It always is a bitch working in the spring to make that early launch and get your epoxy projects done - it's just the nature of the beast. For me, I always launch the beginning of May and haul out the middle of November. I just came out the 17th of this month. It just seems wrong if I'm not freezing my ass of when I do either. :lol:

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no comment on the cold cure rate, i won't sail in cold waters; i'm always scrambling for the money for ice to cool the stuff down.

i do understand your dilemma costwise, that's why i won't ever have a bootstripe again..its not worth the dry time.

i would think it is worth your 'babysitting' the boat, after all..its not very labor-intensive to point a space heater or hairdryer at the area and sit around drinkin beers.

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I've never tried this, but wanted to see if anyone else thought using an electric heating pad over peel ply over the epoxy repair.

Would this work for small repair areas to keep the temps up for a solid cure?

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I once had to finish up a keel fairing job in the spring and temps were quite low 9daytime 35 -40 degreesand nights got down below freezing. I used an old electric blanket to wrap the keel with while the epoxy was curing. Seemed to work quite well and kept the lead from getting down to the outside air temp.

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Yes an electric blanket does work. Re-read Steve's post. It is all about curing temps. Warm the epoxy, 70 degrees or so, warm the work area, warm the pieces, insulate, but cold curing does not work. Cold curing effects the strength of the bond or repair and in many cases it just does not finish curing.

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Just looking at doing some basic repairs to the boat before launch.

 

(Up in Canada) Spring can be very fickle and the weather window to get anything done is very small. I'm wondering about what are the best products to use in the cold. I'm looking for good advice on epoxies that will cure though the night in cold spring conditions.

 

When time is short - you don't want the epoxy to not harden - and start all over again.

 

Cheers. (PS> Running heaters overnight in my yard is not allowed, unless you want to babysit them the whole time)

 

- B

 

Cold Cure

 

It takes longer to kick to hard than West does, but it really does cure in nasty cold weather.

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Thanks for all the advice - I'm going to get the boat prepared for work over the winter (removal/grinding/cutting) and then try to git-r-done in the spring.

 

Having epoxy not set properly due to cold is such a scare. I am not surprised that the only true solution is heat.

 

I have a back up plan that I can launch late if required (she is sitting on a trailer - so I have a real advantage... it just costs money for the tow and travel lift).

 

The work is by majority all about removing deck gear, hollowing out the hole - fill with epoxy - and remount the same gear. I'm going to take the opportunity to tidy up a couple of simple items too.

 

The other repair that I was more worried about was the keel hull joint - I couldn't think of a way to warm the lead keel until the electric blanket idea was listed - thanks so much for that.

 

I have used the brand name "cold cure" epoxy before - and I'm much happier with west system if I can get away with it. Otherwise I will revert back to CC.

 

Thanks guys this was excellent advice and I've learned something new.

 

Cheers

 

- B

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Heavy duty electric blankets are used for even for curing things such as aircraft repair patches. I like the idea of the "backyard" version, it's really not a ridiculous idea.

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Heavy duty electric blankets are used for even for curing things such as aircraft repair patches. I like the idea of the "backyard" version, it's really not a ridiculous idea.

 

 

I have used this method with two of those "Space Blanket" Mylar sheets over it on the outside.

 

13

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Hey Buddha,

 

I did some major epoxy work last fall. PM me, you know who I am. We can debate structural integrity.

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I use LTC-38 down to around 35F with good results

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Everything you ever wanted to know about working with epoxy in cold temperature

 

cold_temperature_bonding.pdf

From the pdf:

Post-cure the epoxy if possible. Post-curing can

help to complete the epoxy mixture’s crosslinking

and boost the epoxy’s physical properties even

after a week or two of cold temperature.

Post-curing simply is the process of applying heat

to complete or speed the cure after the epoxy has

reached a partial cure at ambient temperature.

Elevate the temperature of the epoxy and substrate

gradually to avoid thermal shock. Although any

temperature elevation will improve crosslinking,

try to boost the temperature to room temperature

(72°F) or warmer. The time required depends on

the hardener used, the post-cure temperature and

how much further the cure has to go. Generally,

higher post-cure temperatures require shorter

post-cure times. Do not exceed 140°F and do not

remove clamps or load the joint until after the

final cure.

 

So, what happens past 140°F, say close to 160°F?

I cooked a part in my oven, which only goes down to 170°F, although I kept the door partly open to slow the temp rise and hopefully reduce the temp further. It "feels" as stout as I intended it to be, but trying to figure out if it's actually not fit to use.

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I did some filling and fairing during last winter and had a bugger of a time when I came to sand it.....like the epoxy hadn't quite cured, even though it was hard to touch and you couldn't push your nail into it at all. Got on the gas with a mate one night and he suggested that I try vinegar as he said it was some form of catalyst. So I tried it by simply wiping it on the surface. Worked a treat and sanding no longer clogged up.

Hope this helps.

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I've never tried this, but wanted to see if anyone else thought using an electric heating pad over peel ply over the epoxy repair.

Would this work for small repair areas to keep the temps up for a solid cure?

 

 

Yup standard practice for field repairs.

electric heated pad (usually silicone rubber).. insulator blanket

 

and it all good. bunch of products on the market for this, but easy to rig your own.

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I've never tried this, but wanted to see if anyone else thought using an electric heating pad over peel ply over the epoxy repair.

Would this work for small repair areas to keep the temps up for a solid cure?

 

 

Yup standard practice for field repairs.

electric heated pad (usually silicone rubber).. insulator blanket

 

and it all good. bunch of products on the market for this, but easy to rig your own.

 

 

 

+1M

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I've never tried this, but wanted to see if anyone else thought using an electric heating pad over peel ply over the epoxy repair.

Would this work for small repair areas to keep the temps up for a solid cure?

 

 

Yup standard practice for field repairs.

electric heated pad (usually silicone rubber).. insulator blanket

 

and it all good. bunch of products on the market for this, but easy to rig your own.

 

 

 

+1M

Great product to have in the workshop for localised curing of repairs as well.

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So, what happens past 140°F, say close to 160°F?

I cooked a part in my oven, which only goes down to 170°F, although I kept the door partly open to slow the temp rise and hopefully reduce the temp further. It "feels" as stout as I intended it to be, but trying to figure out if it's actually not fit to use.

 

 

For most epoxies temperatures between 160F and 250F won't cause any significant deterioration.

 

The main issue will be that for the low temperature curing systems you may heat to above the glass transition temperature of the epoxy at which point it will soften..... and you will loose the shape.

As the material then cures it the glass transition temperature rises and 'locks in the new shape' at the nice high temperature you have selected. Even if you manage to retain the correct shape, its now the correct shape at 180F (for example) so when you cool it down again it will either warp. Or will contain some residual stresses within the laminate.

 

If you know what you are doing you can deal with all the above, but if you just stick it in the over at 170F without considering the consequences you may find unexpected results :).

 

If you cured it at 170F in the oven you would be better protecting it with insulators rather than leaving the door open. Most domestic ovens just blast heat until they reach temp and shut off, even PID controlled ovens blast out the heat to start with. By leaving to door open what happens is it gets really hot in places, and cold in other places... so you mainly loose control of the oven temp, and you have no idea what temperature the part is actually seeing.

 

If possible just use a probe thermometer on the surface of the part, control the temperature by wrapping it in glass cloth (not too much) and then take it out of the oven when it goes over 140.

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Heat is your friend.

 

Preheat the area you are working with, keep the epoxy warm.

 

Heat the area after you lay up the area.

 

For small patch areas I make up a card board oven. Point in a hair dryier into the oven. We have done keels, hulls, deck patches.

 

I place a space heater in the hull to keep it warm while I work in there. I keep the resin in the boat. That way we have a place to keep the resin from getting to cold. for hull work. I have wrapped in plastic. then place a couple of heaters in there. a propane heater blowing can keep the hull warm enough to kick the keel fairing and patching blisters. We have been able to keep the temperatures in the 50's. while the outside temps are in the teens.

 

We have also laid up the resin in a heated shop or tent area and then transfered the glass and epoxy on a piece of wax paper. This actually works pretty well if it really cold. For home jobs move you wifes car out of the garage and lay up in there.

 

 

Or you can do what everybody else does. Forget working on the boat now and go skiing! boat work can be done when it is WARMER

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Don't put vinegar on your fresh epoxy. It's a good way to destroy the bond and dissolve the epoxy (good way to clean up if you want to avoid hydrocarbon-based solvents, but bad for curing).

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Thanks for all the advice - I'm going to get the boat prepared for work over the winter (removal/grinding/cutting) and then try to git-r-done in the spring.

 

Having epoxy not set properly due to cold is such a scare. I am not surprised that the only true solution is heat.

 

x2..

 

I'm into a relatively small sump repair and I'm just going to play the spring lottery. I'm in the Northeast US. I have heater(s), but I'd prefer not to worry about it if possible. The work inside will more than likely be complete in the next few weeks or so, but the hull is going to wait. I may even put the inside off too and complete other stuff.

 

Thanks again for the advice.

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On Saturday PM I removed an old depth sounder from the hull, leaving a 2.5" counter-sinked hole.

 

I ground & cleaned the hole out, taped the bottom closed and poured a slurry of West w/ 206 slow hardener and colloidal silica. Thickness was like mayo.. filled the hole and let it set. It wasn't that cold, in the high 30s, but definitely on the colder side from everything I've read.

 

By Monday AM the plug had hardened and appeared solid. I still plan on putting heat lamps on, just to be sure, but my question is this: does the whole application eventually set and cure properly, as long as enough time elapses or the right heat is applied?

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On Saturday PM I removed an old depth sounder from the hull, leaving a 2.5" counter-sinked hole.

 

I ground & cleaned the hole out, taped the bottom closed and poured a slurry of West w/ 206 slow hardener and colloidal silica. Thickness was like mayo.. filled the hole and let it set. It wasn't that cold, in the high 30s, but definitely on the colder side from everything I've read.

 

By Monday AM the plug had hardened and appeared solid. I still plan on putting heat lamps on, just to be sure, but my question is this: does the whole application eventually set and cure properly, as long as enough time elapses or the right heat is applied?

 

 

In my mind, that's a lot of area for a filler, even a "structural fller" like CS. I have always used cloth or mat to build up a laminate when fixing holes that will "keep the sea out." I know that I'd never allow a plug repair like that in an airplane part. Standard for a full strength repair is a 10:1 scarf (or a 5" taper for a 1/2 inch laminate)for a full thickness repair. Most folks don't go that far, but you really do want the repair to become part of the hull to the limts of the secondary bond.

 

IB

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On Saturday PM I removed an old depth sounder from the hull, leaving a 2.5" counter-sinked hole.

 

I ground & cleaned the hole out, taped the bottom closed and poured a slurry of West w/ 206 slow hardener and colloidal silica. Thickness was like mayo.. filled the hole and let it set. It wasn't that cold, in the high 30s, but definitely on the colder side from everything I've read.

 

By Monday AM the plug had hardened and appeared solid. I still plan on putting heat lamps on, just to be sure, but my question is this: does the whole application eventually set and cure properly, as long as enough time elapses or the right heat is applied?

 

 

In my mind, that's a lot of area for a filler, even a "structural fller" like CS. I have always used cloth or mat to build up a laminate when fixing holes that will "keep the sea out." I know that I'd never allow a plug repair like that in an airplane part. Standard for a full strength repair is a 10:1 scarf (or a 5" taper for a 1/2 inch laminate)for a full thickness repair. Most folks don't go that far, but you really do want the repair to become part of the hull to the limts of the secondary bond.

 

IB

Thanks for the input. I should clarify: I'm re-cutting the hole to fit a different transducer that is approx 1/4" smaller in radius. So what I'll be left with is an epoxy ring that will act as a spacer, compressed against the hull by the ring/flange mechanical system on the sounder, and of course bedded in w/ 5200. This ring actually will have a trapezoidal cross section because of the counter-sinked hole, so I think it will do the job.

I'm just wondering about cure times and whether heat applied a week after the stuff was poured has any disadvantage. I've heard the answer is 'no', but want to check w/ the Anarchists...

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On Saturday PM I removed an old depth sounder from the hull, leaving a 2.5" counter-sinked hole.

 

I ground & cleaned the hole out, taped the bottom closed and poured a slurry of West w/ 206 slow hardener and colloidal silica. Thickness was like mayo.. filled the hole and let it set. It wasn't that cold, in the high 30s, but definitely on the colder side from everything I've read.

 

By Monday AM the plug had hardened and appeared solid. I still plan on putting heat lamps on, just to be sure, but my question is this: does the whole application eventually set and cure properly, as long as enough time elapses or the right heat is applied?

 

 

In my mind, that's a lot of area for a filler, even a "structural fller" like CS. I have always used cloth or mat to build up a laminate when fixing holes that will "keep the sea out." I know that I'd never allow a plug repair like that in an airplane part. Standard for a full strength repair is a 10:1 scarf (or a 5" taper for a 1/2 inch laminate)for a full thickness repair. Most folks don't go that far, but you really do want the repair to become part of the hull to the limts of the secondary bond.

 

IB

Thanks for the input. I should clarify: I'm re-cutting the hole to fit a different transducer that is approx 1/4" smaller in radius. So what I'll be left with is an epoxy ring that will act as a spacer, compressed against the hull by the ring/flange mechanical system on the sounder, and of course bedded in w/ 5200. This ring actually will have a trapezoidal cross section because of the counter-sinked hole, so I think it will do the job.

I'm just wondering about cure times and whether heat applied a week after the stuff was poured has any disadvantage. I've heard the answer is 'no', but want to check w/ the Anarchists...

 

 

Ahhhh! I misunderstood. Carry on.

 

IB

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On Saturday PM I removed an old depth sounder from the hull, leaving a 2.5" counter-sinked hole.

 

I ground & cleaned the hole out, taped the bottom closed and poured a slurry of West w/ 206 slow hardener and colloidal silica. Thickness was like mayo.. filled the hole and let it set. It wasn't that cold, in the high 30s, but definitely on the colder side from everything I've read.

 

By Monday AM the plug had hardened and appeared solid. I still plan on putting heat lamps on, just to be sure, but my question is this: does the whole application eventually set and cure properly, as long as enough time elapses or the right heat is applied?

Even if you left it for a week and then came back with a heat source, with the the right amount of time and heat it will cure properly. Some of the slow hardeners will never cure properly until they see the correct cure cycle.

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