Ooops...Epoxy Mistake

[DALukens]

Hello All:

I think I may have made a mistake when mixing epoxy. I think I mixed in far too little hardener. (Don't ask how, it would be a long story.) The pieces epoxied were gunwales and inwales. They are still slightly sticky after 24 hours.

What should I do? Strip off what I applied -- and how do I do that? Or, apply a correctly mixed batch?

Thanks,

Dana Lukens

[NewLou]

Hello All:

I think I may have made a mistake when mixing epoxy. I think I mixed in far too little hardener. (Don't ask how, it would be a long story.) The pieces epoxied were gunwales and inwales. They are still slightly sticky after 24 hours.

What should I do? Strip off what I applied -- and how do I do that? Or, apply a correctly mixed batch?

Thanks,

Dana Lukens

If it were me id get rid of it and start again. Sand of the epoxy ................ if needed heat i'll make it let go (butaine torch is the go). get some sort of electric sander (My choice would be an electric file sander) strip it off n re do join strictly following epoxy manufacturers mixing instructions to setup the epoxy...................

Regards Lou

[Boatmik]

Howdy Dana,

Before pulling out the blowtorch (! - and a hot air gun is a better alternative anyhow ... less chance of charring something) I would see what progress you can make with other methods!

Heat would be a very last resort.

The good thing is that it is on a heavily shaped part of the boat. When it is on a flat panel, it can be quite a difficult problem.

The general rule too ... is if you think you counted out the number of pumps wrongly and you don't know whether it is the right mix ... the only thing to do is leave the container where it won't set fire to anything and throw it out when it is cured. I know this may not be the problem here ... just mentioning it as part of the general education process!

Did you use the Wet on Wet application method in the plan?

Sanding won't work if the epoxy is sticky as the sandpaper will just clog.

Finding the right approach is important and I would recommend just trying some of the following methods in the following order to see what works best on different parts of the gunwale and inwale.
_________________________________________________

FIRST - check for amine bloom
Now ... if it is possible that you got the mix right ... the epoxy may have cured ok and the stickiness could potentially be an amine bloom or waxy layer that comes to the surface as the 'pox cures. Way to check is to wash down a section of gunwale with water and a plastic scourer (scotchbrite) - just a foot or 300mm. let it dry and feel it to see if is sticky. If the scotchbrite gets cheesy .. it does mean the epoxy has not cured properly.

If not sticky now, it was amine bloom and you can wash the whole gunwale and inwale with copious amounts of water and a plastic scourer and mop it dry before sanding ready for the next coat of whatever.

The most likely causes for amine are a temperature drop or higher humidity than the rest of the building so far.
__________________________________________________

If that didn't work then it probably means the epoxy was measured out wrongly.

NOT QUITE ENOUGH HARDENER
If you think it was only a little bit out and if it was too little hardener rather than too much (it makes a big difference) then it might be worth waiting another couple of days ... particularly if you have other things to do too - get on with the mast or rudderbox or ...

After 48 hours you will have some idea if it is changing or not.
__________________________________________________

STILL NO DIFFERENCE ...

The right method will depend on just how hard the epoxy is.
try a couple of methods on small areas .. to find what works best

1/ ACETONE WASH (was my old standard method
Try this on a small section -
I have washed down the sections with acetone and lots of rags

BUT

2/ CABINET SCRAPER or very fine set plane (the direction you do it in is critical .. wrong way and it will bite deep or raise the grain
There was a similar problem with a Eureka about a year ago and it was flat panels! But someone suggested using a cabinet scraper and it sounded like it worked very well.

With gunwales or inwales a fine set plane will work because they are the right shape to remove very tiny amounts of the surface.

If using a plane you will have to disassemble it during and after to make sure there is no epoxy jammed insided somewhere that will glue or block the plane.

Best wishes
Michael Storer

By now

[joe greiner]

Have a squint here: http://www.woodworkforums.ubeaut.com.au/showthread.php?t=69227&highlight=loctite

Joe

[DALukens]

Mik/All:

Thanks -- as always -- for the detailed suggestions. I have been away on a business trip and the boat has sat for 3 days. If the inwale/gunwales are still tacky when I get back tomorrow then I'll go with the acetone or cabinet scraper approach. I too am a bit wary of blowtorches, and I don't even have one. Agree that sanding would be useless.

Thanks again. I guess this is all part of the learning process. You have all been wonderful with the promptness and thoroughness of your responses!

Dana

[coogzilla]

Pox needs 80f+ to cure. It will most likely cure if you keep it hot enough.
Give it a week or so before tearing it apart and see if sets up.

Regards, Coogs

[Boatmik]

Sounds a bit high Coogs (I might be having a problem with conversion though!!).

Just checked .... same as 25C.

No ... epoxy will cure well below this temperature. Though if I can do all my gluing on 25 degree days I will be a happy man!

Usually an epoxy brands will specify minimum temperatures, but I have done successful work down to about
12C = 53F (maybe a bit less) but it ain't easy .. another 3 or 5 degrees under each system respectively makes it a lot easier.

MIK

[m2c1Iw]

A note on mixing, if your using a pump and 2:1 ratio count 2 pumps of pox then 1 of hardner then back to 2 pumps and 1 hardner. That way you don't loose track.
Small thing that I have read somewhere (probably one of Miks posts) that makes a big difference to confidently mixing correctly especially when if like me you start thinking of the next steps instead of the mix.

Mike

[Boatmik]

With larger quantities and the normal small capacity pumps for retail packs I will usually find a tin can and use the stick method to measure the epoxy.

I am really crap at counting. I use a parallel sided tin. Baked bean, dogfood.

For example, bote cote is a 2:1 mix.

Mark a stirring stick with one mark 20mm from the end of the stick then another mark 10mm above the first mark. Of course you can use any height you like ...
160 and 80
40 and 20
56 and 28
anything that FITS THE RATIOS OF THE EPOXY THAT YOU ARE USING - THESE NUMBERS ARE ONLY FOR 2:1 EPOXY RESINS!


Pour or pump in resin until it touches the first mark. Then hardener to the second.

Simple, accurate and verifiable!

Best wishes
Michael

[coogzilla]

Heres another way that's pretty foolproof.
Get some clear plastic throwaway cups. Measure the mix ratio and
mark one with a felt tipped pen. Then put another inside and use the marks.
Keep the original and use it again as a guide. Then you have beer glasses
too! Coogs

[Daddles]

Hello All:

I think I may have made a mistake when mixing epoxy. I think I mixed in far too little hardener. (Don't ask how, it would be a long story.) The pieces epoxied were gunwales and inwales. They are still slightly sticky after 24 hours.

What should I do? Strip off what I applied -- and how do I do that? Or, apply a correctly mixed batch?

Thanks,

Dana Lukens

Welcome to boat building - you're only a pretender if you haven't stuffed up at least one epoxy mix :2tsup:

And you were smart about it, you chose something relatively fixable :wink:

Use a pair of electronic scales and they work a treat - a good accurate mix and you don't have to worry about the pump not doing the right thing, something they are really bad at (half pumps, air bubbles, general stupidity, etc). The problem with scales is that you have to do some mental arithmatic but that's okay. I use West which is 5:1 so do my counting in fives. Bote Cote is 2:1 so you count in twos. The other beauty of scales is the ability to do really, really small batches with confidence, something you can't do any other way.

And the big pain in the neck with scales? Getting halfway through the mix and having the rotten things turn off (thanks to the automatic timer) :((

Now, I'm going to offend people here so Mik and other serious boat builders should look away. Having watched a lot of people get successful mixes with pumps, I'm convinced the ratios are nowhere near as critical as people think. This observation is backed up by watching the differing weight squirts that come out of the pumps (one of the joys of using scales). Having said that, I always work as though the mix is critical because there are so many things to go wrong in mixing that you do NOT want to take risks.

But yeah, getting the wrong number of pumps - been there, done that, had smoking pots of poxy as well as one or two that stayed stubbornly yucky ... hence the scales. As I said earlier, a bad mix or two is compulsory ... a bit like having a hard glue spot on your best pair of jeans :doh:

Richard

[Dyf Nurgler]

I'll second those comments Daddles. I use electronic scales to measure my WEST System epoxy. It only measures to the nearest 5 gram but I haven't had any problems although I must admit my smallest batch has been 100 grams of part A and 20 grams of hardener. Does that make the scales accuracy plus minus 2.5 grams or 5 grams, it's been a while since I had to think about that sort of thing?
I suppose someone with highly accurate scales should do some mixtures and some strength testing to see what difference it really makes to the batches. I would suspect a slight drop off in strength but some boffins should test that in the lab.

Dyf

[Boatmik]

Many pros do use scales ... but I am strongly from an amateur background ... so I always measure volume using a stick.

When doing repetitive batches ... you can use the same stick - just use a saw to cut some grooves.

No probs with scales either!!!

MIK

[Theodor]

I was mixing some pox yesterday on Koala's electronic scales for our PDR rudder cases. The local bought stuff we have is 100:45 by weight. Little did I know that his scales only go up in increments of 2! So when I couldn't get 15g of resin, I had to do some serious mental arithmatic to figure out how much hardener I needed. Fortunately it was just a small amount for a second coat (of 3), so I doubt any miscalculation I made would be detrimental to the build.

Hmm .. we did use the leftovers to make some glue for the tiller laminates .. I wonder if they'll still be sticking together....

[b.o.a.t.]

A note on mixing, if your using a pump and 2:1 ratio count 2 pumps of pox then 1 of hardner then back to 2 pumps and 1 hardner. That way you don't loose track.
Small thing that I have read somewhere (probably one of Miks posts) that makes a big difference to confidently mixing correctly especially when if like me you start thinking of the next steps instead of the mix.

Mike

Amen to that Mike (and MIK)
I rarely mix more than a dozen pumps at a time, & often less than a single pump
(combined) so other methods are of limited use. Often Mk.1 eyeball is only suitable
measuring instrument available. So far, no disasters. touch wood it stays that way.
cheers
AJ