Epoxy - A batch gone off

Problems, how to use. Also see: "EPOXY", in the left-hand column of the Home page.

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Jones
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Post by Jones »

Bruce Dow wrote:The West System pumps are calibrated at 5:1 and work fine. (except for the West System "Special" Hardener which is 3:1 - be careful to use the right pump)
Sorry, not trying to split hairs, but "work fine" because the product went on ok or "work fine" because you've compared the pumps to a reliable scale? I mention this because the engineers who perform stress tests to evaluate bonding strengths weigh out the ratios.

You could have a joint that looks fine, but just as in steel welding, could fail w/o visual sign of defect.
Avoid Haste.

HouTexBBC
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Post by HouTexBBC »

So why not just use a less complicated epoxy. If you believe, as I do, that the quality is not that much different between the "top" brands, (unless you buy off on the advertising) why go through all the frustration?

Dennis

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BruceDow
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Post by BruceDow »

Jones wrote: You could have a joint that looks fine, but just as in steel welding, could fail w/o visual sign of defect.
I have used West System products, using West System instructions. Though I never tested the pumps against a scale, I have never had the epoxy fail to cure, or had a glued joint fail.

Do you have a source for that claim that a joint that looks fine could fail?

My understanding is that "Cured is Cured". There are not degrees.

That's the sort of thing that will keep a guy up at night when he is 2000 hours into a build, and a few months from launch. If you are suggesting that the boat could disintegrate at the first sign of stress because I didn't use a scale, I'd like that backed up before I sweat this anymore.
Bruce.

~~ Do what you love, and love what you do. ~~
~~ To me - only my boat is not yet perfect. Everybody else's is to be admired for I know the path they have walked (Dave Lott, 2010) ~~
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Bill Edmundson
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Post by Bill Edmundson »

I've always used the pumps. Anytime that I made a mistake and had to back up the wood failed, not the epoxy.

I've always been amazed at what a stir this is every time it comes up!

My time is limited. The pumps allow me to measure and mix a batch in about a minute. Three pumps of this three pumps of that. Stir until you don't see color swirl marks start using.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
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Fifty Plus
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Post by Fifty Plus »

Bruce,

I wouldn't sweat it anymore. I have 45 gal of West in Fifty Plus, all done with pumps. I have checked my pumps with volume and by weight on several ocassions and they are accurate.
On a plant tour at West, Meade Gougeon told me that they modify their own pumps, and that's why they work.
I never had a batch not cure, even ones put aside because I lost count on the pumps.
I put 5000 hrs. into my build, and after 2 yrs, 430 engine hrs, and 2800 mi under the keel, I have found no evidence of any problems with the epoxy anywhere on the boat.

Carl

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Bill Edmundson
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Post by Bill Edmundson »

Hey! Bruce!

Doesn't that belong in Miscellaneous - Fear & Anxiety? :lol:

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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BruceDow
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Post by BruceDow »

Bill...

That's exactly what I was thinking... but couldn't figure out how to co-joint the threads...

:roll:
Bruce.

~~ Do what you love, and love what you do. ~~
~~ To me - only my boat is not yet perfect. Everybody else's is to be admired for I know the path they have walked (Dave Lott, 2010) ~~
Dow's Monaco Project

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Rich Coey
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Post by Rich Coey »

Bruce,
Have you ever tried to get this stuff off anything? don't worry it will hold.

Rich Coey

Jones
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Post by Jones »

Bruce Dow wrote:

My understanding is that "Cured is Cured". There are not degrees.
I happen to trust scales, nothing I said implied that your work was less than satisfactory.

Here is the reasoning behind getting an accurate ratio:

1. All glues, in order to be received by the host wood for a good bond, require a reduced viscosity so the wood can be penetrated. That takes time.

2. If the epoxy (or any glue for that matter) is in an advanced state of cure before being applied (and for some compressed) the glue does not have ample time to penetrate, hence the joint appears perfectly sound to the eye but and will not reveal inherent weakness. For other glues this is listed as "open" or "working" times. Epoxies also must follow suit, naturally.



"Epoxies, in general, will cure at lower temperatures than most other marine adhesives. Many are available with hardeners that will set fast or slow to compensate for ambient temperatures. NEVER vary the proportions of hardener to resin. Always measure accurately, don't guess at the proportions" - Glen L. Witt, Naval Architect.

"Catalyst ratio can be varied to speed up or slow down the cure. Do NOT use less than 1% or more than 2% catalyst to the resin." TAP Plastics, Inc.

Incorrect amounts of resin & hardener can cause incomplete curing and/or too much heat build-up. Incomplete curing can cause a weaker final product as well as yellowing of the epoxy. John Soller, Soller Composites.

In working with epoxies, the resin to hardener ratio is very important and should never be adjusted in an attempt to slow down or speed up the curing process. ITW Evercoat, Inc.
Avoid Haste.

HouTexBBC
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Post by HouTexBBC »

There's no doubt that the mix ratio has to be accurate but getting it right is not that hard to do, with or without pumps. I just don't understand the sense that it is all that complex. If your supposed to pump an ounce and the pump is giving you 3/4 oz then you definitely have a problem, a problem that you will realize rather quickly. And if for some reason the mix is off by a droplette that is not going to affect the mix. A pump is not a complicated piece of machinery and in all the time I have been working with the stuff I have never had an inaccurate pump. And I have never had an inaccurate batch.

If the answer is that its just more difficult when your mix ratio is 5:1 vs 2:1 than again I ask, why use a 5:1 epoxy? Switch to something easier to use. I still don't understand that part.

There are a lot of things to stress about when building a boat but there is no need for epoxy to be one of them. There is no reason why you should have to get an ulcer every time you mix a batch.

Dennis

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BruceDow
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Post by BruceDow »

Jones:

Thanks for the sources. I concur that the mix needs to be acurate, but believe quality pumps will do that. I will not sweat this any more.

Dennis:

I don't have ulcers when I mix, so I'm happy with the 5:1. But I concur that if someone was really hung up on this, a 1:1 or 2:1 mix would be less prone to error.

Others:

Thanks for the reassurances.

B.
Bruce.

~~ Do what you love, and love what you do. ~~
~~ To me - only my boat is not yet perfect. Everybody else's is to be admired for I know the path they have walked (Dave Lott, 2010) ~~
Dow's Monaco Project

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leakcheck
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Post by leakcheck »

Phew ! ! ! I am sure glad this epoxy thing is all cleared up...I was about to undo everything I have already not done. You saved me !!

Steve :roll:

GeorgeD
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Post by GeorgeD »

I just got a batch of slow hardener in the post this morning :)

Trouble is the temperature has dropped back to fast hardener conditions! :x
What's the rush? Getting it finished?!
Zip project started: January 2008
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Falcon
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pumps

Post by Falcon »

I have just finished the "Caroline" lots of epoxie work, in over a year an 1/2 never lost a batch. i mix in as said above low pie tin. also i use hand soap pumps! they work great you can mix very very small amounts an really never any gets tossed out. also don't bother cleaning the pie tin just turn it over an use next time. also i use the toss away brushes over an over. i wash them in 3 different glass jars with asitone an store till next use in nearly clean acetone. (if you let them dry you'll get dry epoxie dusty chips in fresh epoxie.
Falcon
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Rational Root
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PICS ?

Post by Rational Root »

You can't tell us you have just finished your boat, and not post pics !!!!!
:D :D
Falcon wrote:I have just finished the "Caroline" lots of epoxie work, in over a year an 1/2 never lost a batch. i mix in as said above low pie tin. also i use hand soap pumps! they work great you can mix very very small amounts an really never any gets tossed out. also don't bother cleaning the pie tin just turn it over an use next time. also i use the toss away brushes over an over. i wash them in 3 different glass jars with asitone an store till next use in nearly clean acetone. (if you let them dry you'll get dry epoxie dusty chips in fresh epoxie.
Falcon
Hey! I built a boat ! No Really, I did !
http://davesboat.blogspot.com/

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