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Old 31-03-2018, 00:13   #1
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West System Epoxy help

I'm new to this fibreglass epoxy stuff and making a bit of a mess.

PROBLEM 1.

The instructions tell me only mix at 5-1. At that, the mixing pot gets too hot to hold, and goes off before I have put on a single coat in about 6-8 minutes. It actually melts the plastic cup.

So I used some of my creative licence and altered the mix down to 8-1 which extended the cure rate to around 10-12 minutes and not as hot but the epoxy I applied takes much longer to cure than the mix in the pot ??

PROBLEM 2

I'm assuming this is my next problem anyway.
Tomorrow I am going to mix the epoxy with a West System filler and do some filling of holes and some tidy up of the glassing I have done. All of this is on a 45° slope and I am worried it will just run. At its thickest it may be 8mm 5/16" thick.
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Old 31-03-2018, 00:54   #2
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Re: West System Epoxy help

Are you using too fast catalyst? Also what is the ambient temp? Epoxy will heat up much faster if the temps are much over 70F/20C. How much epoxy are you mixing? Too much will produce significantly higher temps and faster cure times. Counter intuitive but that's epoxy for you.

I haven't used West in a while as I found it to be too unforgiving if the mixing ratio is off. I use industry sold stuff which I buy from a local carbon mast manufacturer. He says his stuff is so much more forgiving about the mixing ration that it could be mixed at anywhere from 3:1 to 3:2, by weight not volume. Plus it is about 1/2 the price of West.
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Old 31-03-2018, 01:06   #3
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Re: West System Epoxy help

In the case of Epoxy you should never alter the mixing ratio unless a different hardener specfies it.
It would result in a much less than optimal performing laminate or bond when glueing.

Thats just different than using polyester.

In case of epoxy you modify curing times with a different hardener.

Mix smaller quantities in a wide open plate rather than a cup, so exothermique heat can built up less quick.

Also check if you perhaps mix by volume instead by weight.
(Verify what tge manufacturer specified).

Hope that helps.

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Old 31-03-2018, 01:23   #4
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Re: West System Epoxy help

To avoid the runaway exothermic reaction, use a wide shallow metal pan and place the pan on a container of ice water. In fact I think I remember seeing such a setup for sale. As mentioned above, ambient temperature can be a factor. WEST has information available about use of its products.
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Old 31-03-2018, 02:24   #5
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Re: West System Epoxy help

Thanks all

It was 27° today and I had a tall narrow mixing cup. Only mixed about 70ml each time.

It was the slow set hardner, they say 25-30 minutes at 25° so it must have been my mixing bowl. I'll get a flat bowl and sit it in some water (ice might not be so easy) got lots of water around.

Nothing in the instructions about that.

Thanks again.
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Old 31-03-2018, 02:37   #6
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Re: West System Epoxy help

Dispensing (Mixing) without Mini Pumps (Weight/volume measure)
To measure 105 Resin and 205 Fast Hardener or 206 Slow Hardener by weight or volume, combine five parts resin with one part hardener.
To measure 105 Resin and 207 Special Clear Hardener or 209 Extra Slow Hardener by volume, combine three parts epoxy resin with one part hardener (by weight, 3.5 parts resin-1 part hardener).

The key to slowing down epoxy’s cure is to create more surface area, exposing more of the mixture to the air. Epoxy will build up heat unless it is spread into a thin film or quickly poured off into multiple small containers. This allows the epoxy’s heat to dissipate, extending the working time.

Because working time is shorter with large batches, it makes sense to use a slower curing hardener such as 206 Slow Hardener. To further extend the epoxy’s working time in warm temperatures, we recommend 209 Extra Slow Hardener.

From ➥ https://www.westsystem.com/instructi...ensing-mixing/

See also ➥ http://epoxyworks.com/index.php/big-...ixing-methods/
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Old 31-03-2018, 02:38   #7
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Re: West System Epoxy help

Quote:
Originally Posted by Dave_S View Post
Thanks all

It was 27° today and I had a tall narrow mixing cup. Only mixed about 70ml each time.

It was the slow set hardner, they say 25-30 minutes at 25° so it must have been my mixing bowl. I'll get a flat bowl and sit it in some water (ice might not be so easy) got lots of water around.

Nothing in the instructions about that.

Thanks again.
Have the canisters in a cooler place helps, a fridge if there's nothing else. Water bath while mixing is a bit late IMO. As said earlier never change the ratio as the hardener is the other part of the reaction. West epoxies mix ratio 1:5 is by volume. Any additive as silica, microfibers and such makes the mix kick in faster. You can mix in a cup as have but pour it immadiately after mixing to a paint tray.

BR Teddy
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Old 31-03-2018, 02:53   #8
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Re: West System Epoxy help

What's been said above, and absolutely don't alter the mixing ratio. Epoxy doesn't use a catalyst like polyester does, it is a two-part adhesive with a specific mix ratio that cures as a chemical reaction between part A and part B (as opposed to a catalyst that does not react, but instead drives the polymerization). Some brands may be a little forgiving but WEST, in particular, is not. WEST is amine-based and a mix ratio that is off will leave unreacted amines that will just cause numerous problems down the road.

Keep it thin, chill the components to about 10C before mixing, use 209 instead of 206. If you are putting in fillers it is critical to spread them out into a thin layer after mixing, as some of them will insulate and retain the heat even better than neat epoxy (try the thermoplastic fairing filler in a test batch, that stuff cuts pot life by about 75% when mixed to peanut butter consistency).
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Old 31-03-2018, 02:57   #9
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Re: West System Epoxy help

I've found West epoxy gets hotter than other brands. Might be the combination of heat and humidity? Anyway, shallow pans work. I always keep the cake trays from Coles to use as pans. Mix in the cup, then poor straight into the pan. Refrigerating your epoxy prior to mixing will also help as will the ice bucket set up as suggested earlier.

Also, this might be stating the bleeding obvious, but you need to mix by volume and not by weight as the density is different between resin and hardner. If you mix by weight using the volumetric ratios you will always add excessive hardner.
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Old 31-03-2018, 03:45   #10
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Re: West System Epoxy help

Quote:
... Also, this might be stating the bleeding obvious, but you need to mix by volume and not by weight as the density is different between resin and hardner...
Quote:
Originally Posted by GordMay View Post
Dispensing (Mixing) without Mini Pumps (Weight/volume measure)
To measure 105 Resin and 205 Fast Hardener or 206 Slow Hardener by weight or volume, combine five parts resin with one part hardener.
To measure 105 Resin and 207 Special Clear Hardener or 209 Extra Slow Hardener by volume, combine three parts epoxy resin with one part hardener (by weight, 3.5 parts resin-1 part hardener)...
Sort of.
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Old 31-03-2018, 04:43   #11
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Re: West System Epoxy help

Quote:
Originally Posted by GordMay View Post
Sort of.
Interesting that the volume and weight ratios are supposedly the same. I'd have to check which resin I've used in the (recent) past (only ever use 205 hardener in this warm climate) but I can tell you from unfortunate experience that if you mix by weight you will run out of hardener well before you run out of resin.

I gave West the flick because it had far too much tendency to run hot and kick. More than once we had to eject a cup of epoxy from the boat because it was in danger of catching fire. It just seems that it doesn't take much to upset the applecart with the stuff. The brand we use now seems much better behaved in this regard. I still mix by weight, but have a conversion table for reference as this product does have a density differential between resin and hardener.
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Old 31-03-2018, 04:47   #12
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Re: West System Epoxy help

Good advice upthread

Quote:
Originally Posted by Dave_S View Post
I'm new to this fibreglass epoxy stuff and making a bit of a mess.

PROBLEM 1.

The instructions tell me only mix at 5-1. At that, the mixing pot gets too hot to hold, and goes off before I have put on a single coat in about 6-8 minutes. It actually melts the plastic cup.
So the first problem here is that 6-8 minutes is usually all you get in the mixing pot. You have to work faster, or make smaller batches. Generally, if you're applying to a large area, you want to get it out of the mixing pot as quickly as you can, because it will kick off much faster in the pot than on a larger surface.

Quote:
So I used some of my creative licence and altered the mix down to 8-1 which extended the cure rate to around 10-12 minutes and not as hot but the epoxy I applied takes much longer to cure than the mix in the pot ??
As others have said, don't change the mix ratio, use what they recommend.


Quote:
I'm assuming this is my next problem anyway.
Tomorrow I am going to mix the epoxy with a West System filler and do some filling of holes and some tidy up of the glassing I have done. All of this is on a 45° slope and I am worried it will just run. At its thickest it may be 8mm 5/16" thick.
You are correct, you can't fill an area that thick on a slope without filler. West sells a whole bunch of fillers for the purpose. They work great.
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Old 31-03-2018, 04:53   #13
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Re: West System Epoxy help

Problem 2 won't be a problem if you mix the filler so that you end up with "peanut butter" consistency. Mix the epoxy first then mix the filler in bit by bit until you get the desired consistency.

Has anyone mentioned how much epoxy to mix in a batch? I find that mixing no more than 250 ml at a time also helps prevent premature kicking. In fact batches of 150 ml are probably best this time of year.
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Old 31-03-2018, 05:14   #14
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Re: West System Epoxy help

Even when I was coating sheets of plywood with West Systems, I only mixed one pump of resin and one pump of hardener. That's what, 30 mL total? I never had a problem with heat, but I use it fast at small quantities. I also use the special clear hardener to preclude the amine blush, and that may make a difference. I have no experience with their other hardeners.
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Old 31-03-2018, 05:22   #15
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Re: West System Epoxy help

When using west system or most other epoxies only mix what you can use or require in a few minutes
NEVER change the mix ratio only ever try using differing hardness (part b) get everything ready and mix quickly then always spread out your mix on a board or a piece of glass and trowel it out quickly over the largest area you can this keeps the exotherm as slow as possible given the hardner and the temp while you are working
If you feel it's going off too quickly use smaller batches but always mix the correct batch ratios, the 8..1 you said you used might not work it may set but may not have other exothermed (cooked) correctly if you used this on anything structural I would remove it

Just experiment a bit and you will understand that any big volumes will heat up quickly (exotherm) so much so that it will start a fire in large volumes
With the powders or fillers some are glues and set very hard making it so hard sanding is difficult some powders are made for topping off and are easy to sand on slopes I use both types and normally use glue to fill holes then top with the softer top coat,if left too long these coats need sanding between them also lookup the material (looks a bit like silk) peel ply it is used to lay on the epoxy coats then peeled off leaving a smooth and easier surface to sand ATL have this info on their site.
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