anoccasionalyachtsman
Well-Known Member
Yes, even the cheap digitals are pretty accurate, just make the range covers your need.
How much epoxy at once?
- Thread starter slawosz
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thinwater
Well-Known Member
^^ The scale must weight to the nearest gram, minimum, but 0.1 gram is better. basically, each component must be weighed withing about 5%.
coopec
N/A
Why not use measuring flasks to measure?
William_H
Well-Known Member
As said I don't think exotherm will be a problem once epoxy is in place. What you will need to think about as also said is that you need to keep the epoxy and glass in place while it hardens. Horizontal with a backing is best. However backing with cling wrap for release then cling wrap over the job on the outside might help. If all this is too difficult then perhaps several goes with layers might be easier to manage. ol'will
thinwater
Well-Known Member
Because those are cups, not flasks.
The problem with 5:1 epoxies is that measuring the minority component is a little tricky. IME it is too easy to miss. But I do like disposables like that (100 ml is probably handier). I bought a case of 1200 considerably heavier duty ones for $10 at a lab GOOB sale some years ago. I'm farther into that case than I would have thought. Suprising how often you can reuse them by popping the hardened epoxy out.
coopec
N/A
Because those are cups, not flasks.
The problem with 5:1 epoxies is that measuring the minority component is a little tricky. IME it is too easy to miss. But I do like disposables like that (100 ml is probably handier). I bought a case of 1200 considerably heavier duty ones for $10 at a lab GOOB sale some years ago. I'm farther into that case than I would have thought. Suprising how often you can reuse them by popping the hardened epoxy out.
I believe measuring epoxy in a graduated cup/flask would be more accurate than weighing.
For larger jobs of course you can buy 100ml disposable cups!!
(Incidentally the epoxy I use is in the ratio 2:1)
coopec
N/A
I've only ever used epoxy (or polyester over a mold to keep its' shape.
I'd worry about the use of cling wrap as it would stop any cooling effect of breezes (air movement) over the work.
Fiber-glassing right down inside the keel of a yacht is a worry as there are no air currents to carry the heat away. On those occasions I've always had a bucket of water on the ready "just in case" or alternatively I used n electric fan to get rid of the heat..
coopec
N/A
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rotrax
Well-Known Member
I can assure you overheating has NEVER been a problem with any epoxy job I have ever done in the UK.
My work is normally carried out in late March or early April.
Tee shirt, shirt, sweater and overalls are my normal wear for the average temperatures experienced in these months in the UK.
Last job was the base for the Genset I installed. Two layers of epoxy bonded 12mm marine ply with the mounting bolts for the genset chassis pre fixed in place. The edges were given a shallow chamfer. The base was sikaflexed, screwed and glassed in place, the glass tape tri directional and of several layers, rollered to expel air bubbles.
Oh $H1t - two days later, overnight temperatures as low as 2 degrees C, still tacky!
Spoke with the yard GRP expert, very experienced. He said " Pretty normal mate - get a bit of 'eat on it. Be OK in a day or so "
And it was.
Phew!
My work is normally carried out in late March or early April.
Tee shirt, shirt, sweater and overalls are my normal wear for the average temperatures experienced in these months in the UK.
Last job was the base for the Genset I installed. Two layers of epoxy bonded 12mm marine ply with the mounting bolts for the genset chassis pre fixed in place. The edges were given a shallow chamfer. The base was sikaflexed, screwed and glassed in place, the glass tape tri directional and of several layers, rollered to expel air bubbles.
Oh $H1t - two days later, overnight temperatures as low as 2 degrees C, still tacky!
Spoke with the yard GRP expert, very experienced. He said " Pretty normal mate - get a bit of 'eat on it. Be OK in a day or so "
And it was.
Phew!
PilotWolf
Well-Known Member
Also if you're working in an enclosed space be aware of the fumes. I did some work in an anchor locker a few years ago, I didn't realize how high I was until I try to have my lunch!
W.
W.
coopec
N/A
Well right now in Lancelin West Australia it is 41.7 ° C (107.06 ° F) and I wouldn't dream of doing fiber-glassing today.
For cold days to speed up the curing I use one of my wife's discarded hair dryers (blowers?)
If you are laying up in full sun it will go "off" very quickly (too quick to do a decent job) so I prefer to lay-up in the shade. It will also go "off" quickly if there is no breeze.
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anoccasionalyachtsman
Well-Known Member
Time to change your beliefs then. A cheap digital scale reading tenths of a gram is accurate to two drips of water - how do you do that with your cups?
anoccasionalyachtsman
Well-Known Member
Here in deepest Surrey last May I was mixing about 300mls of SP106 epoxy with microballons and racing to get it up into the boat and down to bed my new keels floors. Nightmare, despite getting it straight out of the pot onto a ventilated 600x300mm steel plate to mix the filler in. Such a problem that I'd taken the 106 home and had it in the 'fridge the night before and still only just got the things bolted down before it was solid - and very very hot. I'm sure that the microballons add insulation and exacerbate the the heat build up, but problem it certainly was.
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coopec
N/A
Get real! Two drips of water wouldn't wet the sides of a container ?
I'm building a boat and I don't measure resin to 1/10 of a gram!!! Geeez!!
(1 ounce (oz) is equal to 28.34952 grams)
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coopec
N/A
As a matter of interest I built a 43ft hull using polyester resin. I used 2L ice-cream containers to mix each batch of resin. (That is standard practice in Australia)
What do you guys use in the UK?
What do you guys use in the UK?
Stemar
Well-Known Member
For polyester, it doesn't much matter what you use. The hardener is a catalyst, so any sensible amount and it'll go off sooner or later. Epoxy's far more critical because the hardener provides a chemical necessary for the hardening. Too much or too little and you've got a problem.
I learned my GRP skills with a series of rusty old bangers and polyester. If I had a lot to do, I wouldn't put much hardener in so I had a good work time, on a cold day (why was it nearly always a cold day when doing stuff like that?), it'd get a bit more so it went off quicker. When I started using epoxy, that didn't work so well...
I learned my GRP skills with a series of rusty old bangers and polyester. If I had a lot to do, I wouldn't put much hardener in so I had a good work time, on a cold day (why was it nearly always a cold day when doing stuff like that?), it'd get a bit more so it went off quicker. When I started using epoxy, that didn't work so well...
anoccasionalyachtsman
Well-Known Member
Exactly. You made the statement that cups were more accurate than scales. You see a bit of wet in the cup, I can tell you how many drips it was.
coopec
N/A
Geez that would be really handy! (I didn't think of that!) ?
lw395
Well-Known Member
I use syringes for measuring epoxy.
I've found it's worth measuring the catalyst for polyester, I use disposable dropper / pipettes which can get a fraction of a ml reasonably close.
Epoxy is expensive in my book, and the best way to not waste any is to work in fairly small batches.
Also line up a few simple jobs like filling chips in the Laser rudder, to use up any you've got left over....
I've found it's worth measuring the catalyst for polyester, I use disposable dropper / pipettes which can get a fraction of a ml reasonably close.
Epoxy is expensive in my book, and the best way to not waste any is to work in fairly small batches.
Also line up a few simple jobs like filling chips in the Laser rudder, to use up any you've got left over....
coopec
N/A
I always line up a few extra jobs if I have any epoxy left over.
As far as catalyst for polyester is concerned I would never use a measure because the amount of catalyst you require depends on:
- The amount of resin you are planning to use. and
- The ambient temperature. You might need 25ml in early morning when it is cool but only 15 ml later in the day when it is warm. I just use judgement.
We usually express this in terms of percentage ie:1% catalyst to resin = 10ml of catalyst to 1kg of resin. A rule of thumb for polyester laminating resin is between 1% and 2% i.e. 1% for summer (to give maximum wetting time) and 2% for winter (Fiberglassresinsales)
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