Tiny bubbles.....

[Oscar]

On the glass (6 oz cloth) that I'm putting on the inside of the laminate on top of the balsa. Not too many, just a few here and there. Am I doing something wrong? Or just sand and put the second coat on it. (I've been doing the latter)

[BALANCE]

That's what the ragged edged piece of plastic is for, you run that along what you're woking on to spread it and break the tiny bubbles. Bubbles are not great for the integrity.

[Quetzalsailor]

Always best to bubble-bust to the best of your ability and patience. Since you hadn't grumped about this before, perhaps you recently tried laminating in the morning and the day grew warmer, or some such temperature change was going on, more an issue as the season advances. The air in the balsa could be expanding before the cure.

I've enjoyed this pleasure even when simply coating out porous wood. Endless tipping is the only cure if I've forgotten to do the coating on a falling temperature. This is particularly a problem on end grain.

Some core mfrs precoat their core so that excessive soaking in, attendant excessive weight and resin starvation does not occur. You could do the same, perhaps by precoating and sanding, or by timing successive lamina so that they're applied over partially gelled coating.

Current Professional BoatBuilder has an article about precoating before adding tabbing; their issue was resin starvation rather than bubbles. They reminded the reader that it's much easier to wet out fabric if the lamina below is already wet out.

Going down to the barn now to work on the FD: plenty of acreage to deal with this issue (but not today).

[Collin.Harty]

Assuming your application technique is good, and you're rolling or squeegeeing out the excess resin and air from your laminate, another thing to look for is the temperature trend durning the time your glassing. An unsealed porous substrate, such as balsa or plywood, will outgas if the air temperature is rising, potenially causing the bubbles you describe. The best way around this is to seal the wood with resin first. Let it kick, give the piece a quick sanding (and/or scrub with a Scotchbrite pad and water, if your using epoxy, to remove the amine blush), then proceed with your laminate. If you absolutely must apply the laminate to unsealed wood it helps a great deal if the ambient air temperature is falling during the period your resin is kicking off.

Collin

[Hirilondë]

If you absolutely must apply the laminate to unsealed wood it helps a great deal if the ambient air temperature is falling during the period your resin is kicking off.

Yup. As a matter of fact, help it get warm and then apply the resin in the late afternoon or evening.

[Oscar]

Thank you all.

[bcooke]

The best way around this is to seal the wood with resin first. Let it kick, give the piece a quick sanding (and/or scrub with a Scotchbrite pad and water, if [you're] using epoxy, to remove the amine blush), then proceed with your laminate.

Why would you want the epoxy kick to the point of being sand-able? If it is still green it will bond chemically as well as mechanically. Wouldn't that be a good thing?

And what do you mean, "if [you're] using epoxy"?

[Oscar]

And what do you mean, "if [you're] using epoxy"?

No blush with polyester?

[bcooke]

Unless you are building new hulls, polyester is never acceptable. Even then it is only 'good enough'.

[Oscar]

For the record, I am using epoxy. I will pre-wet the next batch of balsa with a thinned mix before I apply the cloth and report back here.

[Hirilondë]

For the record, I am using epoxy. I will pre-wet the next batch of balsa with a thinned mix before I apply the cloth and report back here.

You will thin the epoxy with a solvent? I know of no brand of epoxy that was formulated to be thinned. I see no good coming of this.

[Oscar]

How about heating? These are the two ways of reducing viscosity and improve penetration...

[LazyGuy]

Every time I see this thread.... I think of Don Ho. (may he rest in peace)

Now you will have that song in your head for the rest of the day.

[Hirilondë]

Every time I see this thread.... I think of Don Ho. (may he rest in peace)

Now you will have that song in your head for the rest of the day.

Yeah, same here, but I had been able to keep the song out of my head until now. Curse you!!

How about heating? These are the two ways of reducing viscosity and improve penetration...

I think you will find that this kicks your epoxy much faster then you would want. It is hard enough some times avoiding premature kicking on large batches as it is. I don't understand why you think it won't saturate enough all by itself. WEST stands for wood epoxy saturation technique. They designed their material expressly for that purpose. Other brands do it quite well also.

[stone]

Unless you are building new hulls, polyester is never acceptable. Even then it is only 'good enough'.

I completely disagree.

[stone]

For the record, I am using epoxy. I will pre-wet the next batch of balsa with a thinned mix before I apply the cloth and report back here.

You will thin the epoxy with a solvent? I know of no brand of epoxy that was formulated to be thinned. I see no good coming of this.

You can actually thin epoxy with acetone but you may be changing some of its characteristics(for better or worse).This is usually done right before you wet out as the acetone evaporates pretty quickly.

Im surprised you are having trouble wetting out 6 oz cloth. What brand are you using? I have recently tried the epoxy from J Greer in San Diego and Composites one in Florida both were alot easier than laminating with West but still a pain to wet out compared to Polyester or Vinylester resin.
http://www.shopmaninc.com/epoxy.html
http://www.jgreer.com/index.htm

[Oscar]

It's wetting out just fine, the bubbles show up about 15 minutes later.....

[bcooke]

I completely disagree.

And do you have a reason for this opinion? Knowing that you don't agree alone doesn't add much to the discussion.

The reason for my opinion is widely publicized on this site dozens of times and I really don't think it needs to be reiterated. I, or many others here, can explain it if it still isn't clear.

You can actually thin epoxy with acetone

I am curious as to where this fact comes from. To my knowledge, most epoxy mfg's do not approve of thinning their product. I don't have the advanced education in chemistry to argue with them.

[Figment]

For the record, I am using epoxy. I will pre-wet the next batch of balsa with a thinned mix before I apply the cloth and report back here.

You will thin the epoxy with a solvent? I know of no brand of epoxy that was formulated to be thinned. I see no good coming of this.

I've thinned epoxy with alcohol. I think (maybe?) that System Three talks about this in their Epoxy Book, or whatever they call their epoxy-for-dummies manual.
Yes, it does alter the cured properties. The cured resin is flexible and rubbery, but still has excellent adhesion. Very much a rubber cement on steriods.

Back on Oscar's topic: I think the posts above regarding falling temperatures are dead on.

Maaaakes me hap-py... Maaakes me feel fiiiiiiine!

[preserved_killick]

This is something I've come across:

Thinning WEST SYSTEM epoxy, by Brian Knight

Through knowledge gained from our comprehensive test programs and from 30 years of practical experience, we have learned that epoxy formulation is a balancing act. When one characteristic is altered—e.g. changing handling attributes by adding a volatile solvent—other characteristics like moisture resistance and strength are also changed. Our chemists formulate a well balanced, versatile epoxy that provides excellent structural strength and moisture resistance. If you elect to modify it, you become an epoxy formulator and need to understand the effects of your changes. Armed with the information in this article, you can decide if thinning epoxy is worth the tradeoff in performance.

See:

http://www.westsystem.com/ss/thinning-w ... tem-epoxy/

-Jeff

[stone]

I completely disagree.

And do you have a reason for this opinion? Knowing that you don't agree alone doesn't add much to the discussion.
My own almost 45 year old boat. Out of everything I have done the hull has remained untouched except for painting .

The reason for my opinion is widely publicized on this site dozens of times and I really don't think it needs to be reiterated. I, or many others here, can explain it if it still isn't clear.

No need to. I respect your opinion, but I still dont agree with your statement.

You can actually thin epoxy with acetone

I am curious as to where this fact comes from. To my knowledge, most epoxy mfg's do not approve of thinning their product. I don't have the advanced education in chemistry to argue with them.

Nor do I . Give them a call.

[mitiempo]

Based on my reading and using WEST system on and off for almost 20 years thinning is not recommended for this brand. However MAS epoxies are designed to be thinned with alcohol as shown in the videos on their website - the owner of MAS is doing the thinning so the first coat penetrates the wood before overlaying with straight epoxy and then varnish. I believe 10% alcohol was recommended. Having said this, 6oz cloth should not need thinned epoxy in my opinion, and I and many others (Tim) have wet out much heavier cloth or biax without thinning. If you first wet out the surface to be overlaid before applying cloth it should go well.
Brian
ps - MAS epoxies, which I have never used, apparently have no amine blush and therefore don't need to be scrubbed for recoat if past green stage.

[Hirilondë]

However MAS epoxies are designed to be thinned with alcohol as shown in the videos on their website - the owner of MAS is doing the thinning so the first coat penetrates the wood before overlaying with straight epoxy and then varnish.

Yeah, I'm not sure what designed to be thinned means. My guess is that the manufacturer is saying it will still be good enough. If you change the chemical you are changing the reaction. When you consider that all of the so called problems of using epoxy can be dealt with by using good techniques I see no reason to thin. People can do what they like, I will never dilute/thin because there is no good reason to that anyone has shown me to do so, and good enough isn't good enough for me when I know I can have the best.

[mitiempo]

I have never thinned epoxy and probably never will. But MAS epoxies are different than other epoxies as far as I can tell as they are I believe the only ones without amine blush. Their formulation must be different to accomplish this. Their website is full of how-to instruction and a lot of videos and well worth perusing if only to see how they do things. One of the interesting topics is repairing molded non skid - the video for this is on their main page. They make it look damn easy! Recoring is another topic of course. The video showing thinned epoxy is here - #2 http://www.masepoxies.com//Videos/Clear ... _Wood.html
I'm not advocating this - just throwing it out there.
Brian

[Tim]

But MAS epoxies are different than other epoxies as far as I can tell as they are I believe the only ones without amine blush.

Actually, many epoxies are blushless. There are a lot more epoxy brands than the big three or four with which most boaters are familiar.

However, note that formulating epoxy that does not form amine blush during the curing process means that other characteristics of the epoxy change as well. One always gives one thing away to gain another.

Every brand of epoxy on the market is some form of compromise between the various desirable and undesirable characteristics. One is not necessarily better than the next, but the characteristics of one product versus another may well better suit your intended use in any individual situation. So be aware of how mix ratios, blush formation, cure time, and other factors might affect the actual performance of any epoxy.

[Tim]

One of the interesting topics is repairing molded non skid - the video for this is on their main page.

Ship-Shape TV?

That was all I needed to see of that video to tell me its worth. ;<)