Thread: west system

This is a mechanical problem. When working in very small amounts, a small difference in measurement a big difference in ratio.

For example, lets say you're working with drops (not that you would, it's just a handy word) and you put in 1 drop of 206 and 5 drops of 105, but the last drop was little (small) for some reason, being only half the size of the others. The mixture is now short resin by 10%, which is enough to screw up some batches. Now think of this in reverse and the single drop of 206 is for some reason half the size of the drops of 105. Now the mixture is short hardener by 50%. Viscosity alone can cause this to occur.

Epoxy is fairly good about ratios being off a little. I've screwed up ratios by as much as 10% and gotten a cure.

Now lets take the example up in size. You mix one ounce of 206 to 5 ounces of 105 resin. If you are slightly off on the resin say using only 4.9 ounces, it's only off by 2% and within the window of a full cure. The same is true of the hardener, you wouldn't screw up on a half ounce, but you could use .9 of an ounce. This will toss of the mixture too, but not enough to get worried about.

Viscosity can be a problem too, on small batches. On these occasions, I'll use a syringe to pick up resin and hardener, because it's very precise. Also you have to mix really well on small batches, because any little bit not mixed, will screw the ratio.

In the end, you can only work batches that are so small, before minor errors become huge changes in mixture ratio. I very rarely use less then a few ounces of goo and you have to be fairly careful with these.

This assumes you aren't making a fundamental mistake, such as mixing 403 into the resin before the hardener or using a contaminated measuring or mix container.

Howdy,

the normal reason it doesn't work is that either it is not measured properly or not stirred properly (scraping the sides or the bottom carefully enough).

As you are an old hand and it is a sudden problem I would suspect you are not at fault, but I have been caught not being careful enough too.

Another possiblity if you are using pumps is that one has become a bit gummed up or is partially broken.

It is very unlikely to be the epoxy itself - I've only seen a couple of cases of that over some thousands of boats.

I would ring up West with the batch numbers and ask them if there have been any problems. They will give you the same advice I have given you above (again!) but will confirm that either there was or was not a problem with the batches.

I would suggest going back to basics and measuring without trusting the pumps to make a trial batch. You can weigh it using a digital scale (the two components have slightly different weights so you need to calculate that out.

Or get a clean dry flat bottomed tin like a baked bean tin. Mark a stirring stick with 30mm from the end then an additional 6mm above that. This gives you your 5:1. Pour or pump carefully and make sure the stick is vertical.

I suspect if you are mixing very small quantities it might be quite difficult to meter out the right amount of hardener because of the very small quantity involved. But if mixing several I would have expected you to get some right even with this problem.

Best wishes
Michael.

Thanks fellows,
Back to basics it is. Will start with all new mixing containers and re-calculate everything. The very small amounts of epoxy must be the problem so I'll go for a larger amount and save up the jobs to do all at once. Can't waste anymore than i am now . Thanks again for your prompt replies

I purchased a cheap (<$10 including postage) 1000 gram electronic scale off ebay - accurate to 0.1 grams (tested its claimed accuracy by cutting, folding and weighing a sheet of paper) to use when doing small batches of epoxy.

Splinter beat me.

I use electronic scales for small batches and it works brilliantly. In fact, for some time there (much of Redback's build), I was did all my mixing that due to a couple of pump failures removing my confidence in them.

Nowadays though, I just use the pumps and am 'happy' to waste what's left of a one pump mix. I find I waste more with larger mixes due either to overestimating what I need or the amount of ooze out of the joint (I tend to be 'liberal' when spreading the stuff).

But for small batches - electronic scales - measure by weight in the same 5:1 ratio

On the question of does poxy go off in the pot. I've only one experience to report on. My first batch of Bote Cote was never finished and sat in the pots for a couple of years - it turned a horrid orange colour and I was well past the point where I was tempted to just toss it out. When it came to building Toad, I decided that seeing that mongrel boat was being built out of anything I could find and would be painted with the cheapest paint I could get, I decided to try this ancient Bote Cote - it still worked as before and the boat's five years old now. Maybe I was just lucky (Toad's been a remarkable boat in many ways, even the elcheapo patio paint is still hanging in there).

Richard

Wow ... that old hardener was a looooong time ago! I think they went to the clear one about the mid '90s.

Actually I think earlier than that.

MIK

Originally Posted by Boatmik

Wow ... that old hardener was a looooong time ago! I think they went to the clear one about the mid '90s.

Actually I think earlier than that.

MIK

Well Mik, I bought it from you (literally)
You tried to talk me into building a GIS too
And you tried to talk me out of building Redback, along with a couple of other professional boat builders

Richard

Richard, you goo hasn't "gone off" but it has aged in it's can. Epoxy, particularly some types of hardeners will go "amber" in about a year's time, once you open the can. I've used really old West 209 once, that came out looking like I'd just poured mahogany stain into the resin. It was dark reddish brown and made a pretty cool looking tint when applied to the very light colored Ocoume. It cured normally, though if the coating was tested, I'm sure it had degraded to some degree.

A method I have found to work well for small quantities is to store the resin and hardener in a couple of different coloured plastic sauce bottles, and leave a plastic syringe in the spout as a plug. I have a 30ml syringe in the resin and a 10ml syringe in the hardener.

I just invert the bottle and suck out the amount I need. I figure that if it is accurate enough for medical injections, it should be good enough for 2:1 Bote-Cote epoxy.

I have often mixed 1ml of resin and half a ml of hardener without any problems.

Actually I measure all my resin that way, even the 100ml batches I use when glassing kayaks.

Originally Posted by PAR

Richard, you goo hasn't "gone off" but it has aged in it's can. Epoxy, particularly some types of hardeners will go "amber" in about a year's time, once you open the can. I've used really old West 209 once, that came out looking like I'd just poured mahogany stain into the resin. It was dark reddish brown and made a pretty cool looking tint when applied to the very light colored Ocoume. It cured normally, though if the coating was tested, I'm sure it had degraded to some degree.

That's more or less what I thought ... which is why it was used on an ultra cheap and crappy Mouseboat rather than on Sixpence

That old Mouseboat still remains a wee gem. She was the second Rowing Mouse built (my son and I built the first after Gavin redesigned the basic mouse for rowing - see, even in those days I preferred going backwards).

Richard

have we answered the OP's question sufficiently to safely indulge in thread drift?

Originally Posted by anewhouse

A method I have found to work well for small quantities is to store the resin and hardener in a couple of different coloured plastic sauce bottles, and leave a plastic syringe in the spout as a plug. I have a 30ml syringe in the resin and a 10ml syringe in the hardener.

I just invert the bottle and suck out the amount I need. I figure that if it is accurate enough for medical injections, it should be good enough for 2:1 Bote-Cote epoxy.

I have often mixed 1ml of resin and half a ml of hardener without any problems.

Actually I measure all my resin that way, even the 100ml batches I use when glassing kayaks.

I think that is the tip for the day, week and maybe year for people mixing small amounts like modellers.

MIK