Epoxy boiling? And hole repair question.

C

Cutty Sark

New member
Hey guys anyone run into this. Im working on filling some screw holes in the floor of my 16 angler, a couple had very minor water in the balsa so I cleared it out around the inside until I got to clean dry wood and am in the process of filling with west systems epoxy and 206 filler. On two of the holes (the largest ones) I filled and made sure there were no bubbles etc.. As it was curing it actually boiled and came bubbbling back up through the hole. I cleared what came up before it cured. But now there are bubbles in the epoxy plug. since I'm not going to put hard ware in these couple holes. I'll probably just redrill partway and reseal with epoxy without any thickener to seal nicely. But why am I getting this boil up?too large a batch? Wrong hardener? Im using the west systems pumps that measure for you.

Question 2

I had one spot that required me to take a 2" hole saw to clear out the core. Do I need to replace the core in that spot or can I just make a thickened epoxy plug. The west systems manual seems to allude that size is fine to just fill, but i don't want to make a hard spot that will cause cracking later . Any tips?

Sark
 
I am sure Dr. Bob will pipe in and give you all the reasons why your epoxy boiled...but the short story is to reduce the amount of hardener for such a small vessel...and let it slow harden.
 
Sark,

I've used the West Systems epoxy for over 20 years, taken their professional boat builders and repair class in Bay City twice and interviewed the Gougeon brothers for a magazine article and have never encountered boiling epoxy before or heard of it. It might not be a bad idea to give them a call.

Good luck,

Nick
"Valkyrie"
 
I suspect the "boiling" of the epoxy was too hot as it was curing. Epoxy harderner/curing agent is different than polyester. Polyester, you can change the amount of Methyl ethyl ketone peroxide (hardener) and make the mixture hotter (cures faster) or cooler (cures slower). For epoxy the ratio of hardener and resin are a set ratio. They vary from company to company and with the type of epoxy.

I keep three curing agents for epoxy on hand--one is the slow for warm weather, one is the extra slow for our very hot weather, and one is fast for cool weather. These also have different pot lifes. You can increase the working time by keeping the epoxy cool, and I avoid excess heat in either epoxy or polyester resins. For the most part curing agents for epoxy are amines--and accelorate the cross linking process. As there are many different epoxies, there are also many different curing agents. I happen to use West Systems, because it is what I have used for many years. When I was building boats, I purchased my epoxy directly from Shell, and the formulation was different.

The fast cure epoxyies are different formulations--not just more "hardener".

I am a bit puzzled by your use of the "206 filler" the 200 series products are hardners/curing agents, and the 206 is a slow cure with pot time of about 20 to 25 minutes at 72 degrees F. This is the usual curing agent I use. For filler, I use a combination of Cabosil (406 in the West system) and a microlite filler (410 in West system).

As for the "boiling" it might be too hot a mixture (too short a pot life). Too liquid a mixuture (for filling holes as you describe, I would suggest a peanut butter consistancy.) It might also result for incomplete mixing, bad batch of curing agent, comtamination of the epoxy, old epoxy resin or excess moisture in the substrait you are filling, combined with a high temp of the resin as it begins the curing process.

Nick, I would be interested in your thoughts about this, since you have taken courses. I have just used the stuff and read the literature.

As for 2" being an area you can fill alone: I would not worry about a "hard place on the bottom of the boat, but would probably layer in glass , not just pour in epoxy. I layer in glass if the hole is more than 1/2 " in diameter and open. If it is closed (under cut) I don't put in glass. But just a hunk of cured resin, is no where as good as glass. When you put in the glass, taper out the edges, and that will help to avoid hard places. The usual bevel is 12/1--but in this case, probably 4:1 would work fine. Any more than 2" I would fashion a plug of material--could be end grain balsa or could be a core material of foam etc. I am wondering if the 2" diameter place is where you found this "boiling"..
 
The "boiling" was probably moisture or trapped gasses venting out from the heat generated as the resin cured. As someone said, you can't use less hardener with epoxy; the proportions are fixed.

Couple choices: use slow hardener; or, start with resin that is cool. In any case, make sure all moisture is gone and that that area has cycled through a couple heat/cool periods, such as heat of the day followed by a cool night.

And, use the resin quickly after mixing. In larger batches, the heat of setting up will accelerate the cure if the epoxy is in the mixing pot, and it can get really hot!.
 
Sark here, this is an alternate account I started a ways back when I couldn't access mine.

Ok, I was typing pretty quick earlier so let me set some stuff straight. First off the filler was 406 not 206, and the hardener is 205 which I think is my problem, its a fast set. I got that because It's what I've used before and had good results previously(boat outside in driveway). I didn't take into account that my boat is in a heated( almost hot) warehouse space at my office. I think the warm air temps along with the amount of epoxy(mixed a large batch, 3 squirts from hardener and resin) is what caused it. I had the epoxy do the same thing in a plastic cup and kinda melt the cup so, it's not moisture in the hull or wood, besides the balsa is quite dry, I made sure of that. I did smaller batches and opened the bay door and that seemed to alleviate the problem, but everything I was filling was a smaller hole too. I 'm not sure if the epoxy was actually boiling, it did bubble up out of the holes and definitly got hot so, maybe even steamed a bit.... For the larger area I need to fill I'll make sure to get some extra slow set.

Sark
 
Well I spent the rest of the weekend filling holes and refinishing teak. The epoxy gave me no more trouble once I cooled the room down and made smaller batches, I also think the first batch or two wasn't thickened enough which contributed to the bubbling etc... I've redone pretty much everything that was screwed into the hull or transom, and am almost ready to do a bit of gelcoat repair, and re coat the cockpit floor. and she will then be ready for a shakedown cruise.

Sark
 
It is amazing how fast and how hot curing epoxy can burn. Once building a boat in the summer I learned how hot epoxy can become; I burned my hands when I went to pick up the cup! No injury but definitely a surprise.

I almost always do my epoxy work in the Spring before launch (cool temps) so I always use fast set hardener.
 
2 ounces of epoxy in a plug hole of foam core will go into thermal runaway - guaranteed...
The bubbles are not trapped water etc, they are epoxy 'steam' bubbles - actually MEK boiling...

When mixing epoxy in a small "dixie" cup, if I am going to use it slowly, I float the cup in an icewater bath...
Better yet is to pour it into a flat pan made from or lined with, aluminum foil, after mixing... The increased surface area allows the reaction heat to radiate instead of pushing the catalyst into runaway...
I have been known to pop the flat pan into the freezer for 15 minutes to get the freshly mixed epoxy nicely chilled to slow its thermal rise when I pour it into an insulated hole...

To fill a plug hole, mix only a partial volume, say 1/4, 1/3, or 1/2, then pour into the hole and wait... After the catalyst kicks off and the epoxy is now rubbery but still sticky on top (leaves goo on your finger when you touch it), then add another portion of freshly mixed epoxy and let it kick, etc... This limits the thermal rise as each portion is smaller and generates less total heat... And the new layer of epoxy will polymerize (bond) with the surface of the previous batch because the molecules on the sticky surface are still chemically reactive...

denny-o
 
I had something similar in a " little" project I had. I found if you just go with the slow hardener and mix little batches in larger surface area containers you will have better results for filling holes. I must admit mine never boiled it did however smoke a bit. It was learning curve to find what works.

Good luck!

Chris Bulovsky
 
The key is to use the proper hardener for the conditions. If you build boats you don't do it in 15 cc increments...If the proper hardner/curing agent is used. Consider that 75 foot boats are being built with one resin infusion. (some are epoxy and some are polyester)--you know that the temperature of that reaction is very carefully calculated. Yes, cooling the reagents does help, also the thickening agents also help delay the reaction.
 
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