JEM Watercraft

Measuring epoxy
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Author:  rodot [ Wed Nov 30, 2011 8:46 pm ]
Post subject:  Measuring epoxy

On my first boat build I used the recommended dispersing pumps to measure out the correct mix of epoxy. The only trouble was, that when I ran out of hardener, I found I still had resin left over :oops: . This was probably caused by the greater viscosity of the resin and my impatience.
I have since bought a set of digital kitchen scales and it really is so much easier. Just put the plastic cup on the scales and turn on to zero it. Pour in a guesstimate of the required resin and in my case with a 2:1 mix I just add half of that quantity of hardener. Naturally a calcution would be required for a different mix. Not only is it a lot more accurate but it is also a lot quicker, which is handy when you are wetting out fibreglass cloth. The scales are probably not a lot of difference in price to the pumps.

Author:  goanywhere [ Wed Nov 30, 2011 10:36 pm ]
Post subject:  Re: Measuring epoxy

Excellent idea. I had the same result, hardner left over when the resin was used up.

I was mixing a batch of resin once and got distracted and lost count of the pumps. I didn't know quite what to do. In the end I guessed and rounded up the hardner so that if there was an error I would have too much hardner rather than too little. Not sure if that was the right thing to do, but scales would have probably prevented that. I didn't want to throw it out, and fortunately I didn't notice any problem with the result.

Might be an idea to make sure the scales are covered by plastic though. :D

Author:  tx river rat [ Wed Nov 30, 2011 11:13 pm ]
Post subject:  Re: Measuring epoxy

I had the same experience with the pumps,I now use small paper cup like are used in the bathroom , they have designs on the cup that I use for mixing small batches . It also works as a safety for me mixing 2 to 1 I use three cups and that way I cant get confused counting.I visually look at the cups before I mix just like checking the powder in a shell you are reloading. I throw the cups away after one use they are cheap.

Author:  Wannabe [ Thu Dec 01, 2011 8:25 am ]
Post subject:  Re: Measuring epoxy

Are you supposed to mix epoxy by weight or volume or does it work out to be the same?

Author:  jem [ Thu Dec 01, 2011 9:22 am ]
Post subject:  Re: Measuring epoxy

Wannabe wrote:
Are you supposed to mix epoxy by weight or volume or does it work out to be the same?

Typically it's almost equal. But your epoxy vendor should provide that info.

Author:  rodot [ Thu Dec 01, 2011 4:41 pm ]
Post subject:  Re: Measuring epoxy

The epoxy I was using had a mix ratio by wieght of 100:48 which I considered close enough to 2:1. They also supply a different hardener I that also use which is 100:44 mix by wieght which would mean a 10% aprox. difference. The funny thing is, that when I tested the 100:44 by weight mix hardener, one pump wieghed 7 grams and one pump of resin wieghed 7 grams.
I notice that West Systems say 3:1 by volume or 3.5:1 by wieght. It's worth checking with the manufacturer.
I was advised to measure epoxy by wieght by a guy who builds ply ultralight aircraft where accuracy is critical.

PS Using metric scales makes calculations much easier.

Author:  toolman [ Mon Dec 05, 2011 1:33 pm ]
Post subject:  Re: Measuring epoxy

Were I got my supplies they cave me a graduated plastic cup and it was marked for the diffrent ratios

Author:  Oldsparkey [ Mon Dec 05, 2011 2:28 pm ]
Post subject:  Re: Measuring epoxy

You can also use clear plastic cups.

Some of the guys do this...............
Take one cup and put another in it , then fill it with the proper amount of water and mark that on the outside cup. Then do the same with another cup and the amount that needs to be in it.

When measuring out the epoxy or hardener use a cup inside the one that is marked so you know how much to put in it. Then mix the two together and the cups that are marked can be used forever since none of the liquid is in them.....They are the measuring cups. You could just mark one cup , two times ( one for epoxy and one for hardener ) then drop a cup in it and use it.

For really small , touch up batches I use plastic spoons , fill one twice and one , one time , mix and use.

Most of the time............................
I get lazy and just use the pumps which seam to work pretty good for me. One time my batch burner my hands threw the cup before I got to the boat to use it , I really mixed a bad batch , that sucker was smoking. :oops:

Author:  jem [ Mon Dec 05, 2011 3:39 pm ]
Post subject:  Re: Measuring epoxy

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