Epoxy questions

[PabloPicasso]

Ok I'm doing an epoxy repair but have some ordering questions

What influences choice of cloth (I.e, 200g close we've cloth,280 g satin weave, 450g biaxial glass etc)?
How much epoxy resin would wet out, say, 1meter square of cloth?

So 5 layers of repair of 200g cloth at 1 meter square=how much resin to order? Would 500g & hardener be enough?

I'm trying to get an idea of the amounts to order for my repair. Is there a guide to how much resin wets out how much cloth?

Is it better to use neat epoxy on flat areas and only thicken when working vertically or overhead, or is thickening on flat horizontal surfaces advisable?

I've read the west booklet which was very helpful, but didn't seem to give specifics I need to order materials

 

[nemodreams]

The tabbing I have done with epoxy - many yonks ago, was fraught with problems.
I was using SP epoxy - which is a sort of 2/3 - 1/3 mix. resin/hardner.

Trouble was I was trying to treat it like grp layup - and the stuff takes hrs to cure off to a gel.
In that time it was deciding to dribble everywhere.
I understand now why carbon fibre lay ups are vacum bagged - its to keep the stuff in there.

Even on the flat - it runs sideways. Not fast - too slow to notice its doing it.

Unless you can stand there for hrs on end to keep spreading it back in - or apply heat to speed up the gel - or maybe there is a quicker acting product ?

If thickned to stay put it not ideal for wetting into the weave ( I would have thought ? )

All I know of the cloth is that it has to be woven - not chopped strand - as chopped strand has a binder holding it together which is not compatable. That said - I did some stuff back then with chopped strand and it seemed ok ?

Just my experience !

 

[G12]

You can use chopped strand matt with epoxy but it MUST be the powder bound type. If you use the normal stuff then the binder doesn't dissolve and you end up with a load of junk.

www.cfsnet.co.uk - Phone these guys, they'll sort you straight out and they're very used to dealing with people who aren't quite sure exactly what or how much they need. I've used them many times. No connection other than happy customer.

 

[VicS]

Ok I'm doing an epoxy repair but have some ordering questions

What influences choice of cloth (I.e, 200g close we've cloth,280 g satin weave, 450g biaxial glass etc)?
How much epoxy resin would wet out, say, 1meter square of cloth?

So 5 layers of repair of 200g cloth at 1 meter square=how much resin to order? Would 500g & hardener be enough?

I'm trying to get an idea of the amounts to order for my repair. Is there a guide to how much resin wets out how much cloth?

Is it better to use neat epoxy on flat areas and only thicken when working vertically or overhead, or is thickening on flat horizontal surfaces advisable?

I've read the west booklet which was very helpful, but didn't seem to give specifics I need to order materials

I went through the same sort process 3 years ago when I had to mke good a 55mm hole left after removing an old "Ball Hed" toilet

If found all the necessary info by searching the West web site an the suppliers websites although I cannot now remeber which sites provided what info

I ended up buying 600g biaxial cloth ( far, far, far more than I needed but its cheap enough) ( it looks like I bought just over 2 sq m )

Any thinner would have meant rather a lot of layers but there were no problems wetting it out and working with it ... Id buy the same weight again for a similar job

I bought a 1.2kg West 105/205 ( fast) resin pack. Again far more than I needed but I was afraid a small repair kit might not have been enough.

( IIRC you need about the same weight of resin as glass so 1kg of resin will wet out 1 kg of glass mat ... but check that out .. dont rely on my memory

I also bought some peel ply, pumps for the resin and hardener, fillers, pigment various other bits and pieces i thought would come in useful but did not


My advice would be to study the methods and procedures described in the various West documents and follow them Techniques, not always the most obvious, and use of fillers to thicken the mix etc

I bought all my stuff for various reasons from East Coast Fibreglass Supplies.

 

[PabloPicasso]

So is it 50% mix of resin to mat?

Helpful replies so far

 

[prv]

I also bought some peel ply, pumps for the resin and hardener, fillers, pigment various other bits and pieces i thought would come in useful but did not

Are you including the pumps in the "thought would come in useful but did not"? Because they're definitely in that category for me. I persisted with them for several years, but they were always messy and wasteful. Nowadays I use a small electronic scale which is far more convenient. Put the pot on, press tare, pour in hardener straight from the bottle, note the actual number of grams, press tare again, then multiply by the proportion your epoxy needs and add the appropriate amount of resin. No dribbles, no squitty half-pumps that throw the ratio off or have to be binned, nothing to leak in the box or bung up and need cleaning.

Pete

 

[paul-essex]

I think it is 1 kg of resin to 1 sq meter of mat at 1,000 g
so if you use 500g matt 2sq mts to 1 kg of resin
250 g mat 4sq mts to 1 kg of resin
witch is 1 kg resin to 1 kg of mat

 

[laika]

You can use chopped strand matt with epoxy but it MUST be the powder bound type. If you use the normal stuff then the binder doesn't dissolve and you end up with a load of junk.

That's the accepted wisdom but unless you know otherwise from personal experience I'll suggest that that's not completely true.

Here's my post from last year outlining what I discovered when I found that the boatwrights in the yard I was in a few years ago were using ordinary CSM:
http://www.ybw.com/forums/showthread.php?422478-Can-Chopped-Strand-Mat-(CSM)-be-used-with-EPOXY&p=5174063#post5174063

Bottom line: It actually doesn't make that much difference according to West.

 

[VicS]

Are you including the pumps in the "thought would come in useful but did not"? Because they're definitely in that category for me. I persisted with them for several years, but they were always messy and wasteful. Nowadays I use a small electronic scale which is far more convenient. Put the pot on, press tare, pour in hardener straight from the bottle, note the actual number of grams, press tare again, then multiply by the proportion your epoxy needs and add the appropriate amount of resin. No dribbles, no squitty half-pumps that throw the ratio off or have to be binned, nothing to leak in the box or bung up and need cleaning.

Pete

The pumps worked for me.

A squirt of resin and a squirt of hardener..... done!

None of this frigging around ........"Put the pot on, ......press tare,.......... pour in hardener ........., note the actual number of grams, ...........press tare again, ......... multiply by the proportion your epoxy needs .......... add the appropriate amount of resin.

Waste ful/ probably but at the end of the day a very large proportion of that £110 worth will just go in the bin anyway. There's just one little job to do first on my old Mirror dinghy before I give that away. Then I'll dump the rest.

 

[VicS]

I think it is 1 kg of resin to 1 sq meter of mat at 1,000 g
so if you use 500g matt 2sq mts to 1 kg of resin
250 g mat 4sq mts to 1 kg of resin
witch is 1 kg resin to 1 kg of mat

Thanks for confirming what I said was correct. I was not sure but I though that was what I could remeber

So is it 50% mix of resin to mat?

Helpful replies so far

what paul-essex says.


In my case i bought about 2 sqm of 600 g ( dont know why the odd dimensions on the list) That 1200g so a 1.2kg packshould be the right amount to wet it all out. Its only a rough guide though.

BTW the biaxial cloth is easy to work with because its stiched together ......... It keeps its shape and does not all fall apart while you are working like CSM does..

 

[lw395]

So is it 50% mix of resin to mat?

Helpful replies so far

That's what you are aiming for in a good layup, for best strength/weight.
In repairs, it's common to use more resin.

Choice of cloth is often affected by the nature of the repair, heavy cloths are prone to showing a pattern on the finished gel surface if that's applicable.
Vic's bill of £100+ for filling a 2 inch hole seems OTT by a factor of about ten. Half a litre of polyester and a couple of metres of mat from my local place would have equally done the job.

 

[crisjones]

A very experienced GRP guy (he also lectured at Uni on the subject) I worked with reckoned the ideal resin / matting ratio is 1:1 by weight to get the strongest possible layup - as stated above by a couple of other posters.
However he also said that getting 1:1 with normal hand layup techniques, especially small repair areas is almost impossible, you are likely to end up with 2:1 at best and maybe even worse. The reduction in strength of the layup is not likely to be important for most DIY jobs since it is likely we will use more resin and grp than actually required.
It is more of an issue for production builders who are trying to minimise material costs and maximise strength - hence the common use of vacuum bagging which is much more easy to control and therfore achieve the optimum 1:1 ratio.
Bottom line for DIY jobs is probably to buy at least double the weight of resin compared to matting.

 

[vas]

Are you including the pumps in the "thought would come in useful but did not"? Because they're definitely in that category for me. I persisted with them for several years, but they were always messy and wasteful. Nowadays I use a small electronic scale which is far more convenient. Put the pot on, press tare, pour in hardener straight from the bottle, note the actual number of grams, press tare again, then multiply by the proportion your epoxy needs and add the appropriate amount of resin. No dribbles, no squitty half-pumps that throw the ratio off or have to be binned, nothing to leak in the box or bung up and need cleaning.

Pete

I also bought (initially) the West system and pumps, gave them away soon after, too messy for my liking and anyway changed brand with different hardeners according to job and weather.

However, I've gone through a few barrels of epoxy putting the resin first and the hardener afterwards, am I missing something?

cheers

V.

 

[prv]

However, I've gone through a few barrels of epoxy putting the resin first and the hardener afterwards, am I missing something?

The chemicals don't care which way round you do it. The reason I put the hardener in first is that I might not always pour a 100% accurate quantity, and by basing the measurements off the smaller one, the ratio ends up more accurate.

With West at 5:1, let's say I decide I want 10g of hardener and 50g of resin for a small job. I put in the hardener first, and maybe an extra drip or two from the rim of the bottle means I actually end up with 12g of it. No problem, I just add 60g of resin instead of my originally intended 50g, and I'm still at exactly 5:1. Of course, I might then be a gram or two under or over with the resin, but that matters five times less than the same error with the hardener.

Probably more relevant for small jobs than for your entire barrels of epoxy

Pete

 

[prv]

The pumps worked for me.

A squirt of resin and a squirt of hardener..... done!

None of this frigging around ........"Put the pot on, ......press tare,.......... pour in hardener ........., note the actual number of grams, ...........press tare again, ......... multiply by the proportion your epoxy needs .......... add the appropriate amount of resin.

Shrug; I've tried both and I know which I prefer. If you think you won't like the one you haven't tried, that's no skin off my nose.

Pete

 

[lw395]

The chemicals don't care which way round you do it. The reason I put the hardener in first is that I might not always pour a 100% accurate quantity, and by basing the measurements off the smaller one, the ratio ends up more accurate.

With West at 5:1, let's say I decide I want 10g of hardener and 50g of resin for a small job. I put in the hardener first, and maybe an extra drip or two from the rim of the bottle means I actually end up with 12g of it. No problem, I just add 60g of resin instead of my originally intended 50g, and I'm still at exactly 5:1. Of course, I might then be a gram or two under or over with the resin, but that matters five times less than the same error with the hardener.

Probably more relevant for small jobs than for your entire barrels of epoxy

Pete

I use syringes for measuring epoxy and plastic pipettes for polyester hardener. Both cheap enough on ebay.
Alternatively, get a set of digital scales, and work by weight. The scales can be in a polybag to keep them clean.

Measuring the catalyst with polyester seems to help, compared with guessing 'a few drops'.

 

[VicS]

I use syringes for measuring epoxy and plastic pipettes for polyester hardener. Both cheap enough on ebay.
Alternatively, get a set of digital scales, and work by weight. The scales can be in a polybag to keep them clean.

Measuring the catalyst with polyester seems to help, compared with guessing 'a few drops'.

The mixing proportions of epoxy are critical because it cures by reaction between the two components. Accurate measurement by weight, calibrated dispensing pumps or syringes is therefore necessary.

The mixing proportions for polyester are not critical because the curing process is catalytic. It therefore lends it self to simple / less accurate measuring methods such as marked mixing cups and teat pipettes. Curing can even be slowed down in warm weather by using slightly less hardener.

 

[PabloPicasso]

A very experienced GRP guy (he also lectured at Uni on the subject) I worked with reckoned the ideal resin / matting ratio is 1:1 by weight to get the strongest possible layup - as stated above by a couple of other posters.
However he also said that getting 1:1 with normal hand layup techniques, especially small repair areas is almost impossible, you are likely to end up with 2:1 at best and maybe even worse. The reduction in strength of the layup is not likely to be important for most DIY jobs since it is likely we will use more resin and grp than actually required.
It is more of an issue for production builders who are trying to minimise material costs and maximise strength - hence the common use of vacuum bagging which is much more easy to control and therfore achieve the optimum 1:1 ratio.
Bottom line for DIY jobs is probably to buy at least double the weight of resin compared to matting.

Ok, so for each 1kg of mat I need 2kg of resin mix?

 

[crisjones]

Ok, so for each 1kg of mat I need 2kg of resin mix?

That would be a good place to start - let us know how it actually works out when you have done the job.

 

[VicS]

Ok, so for each 1kg of mat I need 2kg of resin mix?

Buy more than 1kg but you should aim to use only 1kg resin mix per 1 kg of cloth