Aeropoxy ES6209 GRRRR!!!

I wish it were possible to get more than two fillets poured in a day with this stuff. Actually, in my impatience it's difficult to get even that second fillet poured.

I waited three or four hours after pouring the first fillet and thought it set up enough that it wouldn't run and I was incorrect. So far most of the epoxy (internal fillet) has shifted from the fin to the motor mount. Hopefully, it won't shift too much more and I won't need to add more to the fin.

It's just maddening, but since I'm already committed to the fillet on the opposite side of the fin, all I can do is sit and wait.

Yep, I do one set per day.
There's always something else to do around here while it cures (not often rocket related, but that's life).

hball55 said:

I wish it were possible to get more than two fillets poured in a day with this stuff. Actually, in my impatience it's difficult to get even that second fillet poured.

I waited three or four hours after pouring the first fillet and thought it set up enough that it wouldn't run and I was incorrect. So far most of the epoxy (internal fillet) has shifted from the fin to the motor mount. Hopefully, it won't shift too much more and I won't need to add more to the fin.

It's just maddening, but since I'm already committed to the fillet on the opposite side of the fin, all I can do is sit and wait.

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It's not really something to pour.... you have to push it around.

CarVac said:

It's not really something to pour.... you have to push it around.

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We're talking about internal fillets in a 4" rocket, no room to push around . . . you have to count on gravity and a heat gun to thin the epoxy enough to run. Not too much heat gun either for even though heat speeds curing, I feel it weakens the overall bond if too much heat is applied.

Actually, I let it dribble off the tip of a tongue depressor and it actually rolls down the fillet path like a very slow volcanic flow. It's weird that as thick as the epoxy is, that two to three hours later gravity will still have its way with it.

I love the stuff but it is pretty slow to cure unless the temperature is above 70 degrees in my experience. Looks as though that may not be the problem for you. Like chuck said, one set a day!
-Ken

Other than building several together like an assembly line, you just gotta wait or switch to a faster cure.

I got sick of the slow cure stuff too. Would use it on a big or high performance rocket. Not the smaller stuff.

I leave the bottom bulkhead unglued so once the fin can assembly is installed, one can get in there with a dowel or an acid brush on a dowel. I'd add thickneers to the epoxy to make it thixotropic so it doesn't run. Bottom bulkhead gets glued in last.

Gerald

G_T said:

I leave the bottom bulkhead unglued so once the fin can assembly is installed, one can get in there with a dowel or an acid brush on a dowel. I'd add thickneers to the epoxy to make it thixotropic so it doesn't run. Bottom bulkhead gets glued in last.

Gerald

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Yes, my bottom centering ring is removed; has to be in order to pour internal fillets. I use milled glass fibers as a thickening agent, though I may need to try something else. These milled glass fibers, made by Shadow Composites, Inc. are pretty fine/powdery.

hball55 said:

Yes, my bottom centering ring is removed; has to be in order to pour internal fillets. I use milled glass fibers as a thickening agent, though I may need to try something else. These milled glass fibers, made by Shadow Composites, Inc. are pretty fine/powdery.

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A potential solution to your problem is to use fumed silica. Like Gerald says, this makes the epoxy thixotropic. This means it flows, but once it's in place, it doesn't run. West 406 (colloidal silica) is one brand. With thick epoxy, it doesn't take much to make it stay in place. But if you use too much, you won't be able to get it to flow into an internal fillet area. So, the amount added must be optimized, or better, use a method that doesn't rely on the epoxy having to flow into the joint.

Fumed silica also tends to clump. I use a popsicle stick to scrap the epoxy along the side of a plastic cup. Going back and forth eventually distributes the clumps. Fumed silica is very handy to have around.

Jim

Have you ever used milled glass? Does it actually enhance the structural characteristics of the epoxy fillet? Is colloidal silica just a thickening agent or does it add to the structural properties of the epoxy fillet? Thanks in advance for any answers and, of course, thanks for the recommendations.

hball55 said:

Have you ever used milled glass? Does it actually enhance the structural characteristics of the epoxy fillet? Is colloidal silica just a thickening agent or does it add to the structural properties of the epoxy fillet? Thanks in advance for any answers and, of course, thanks for the recommendations.

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I use lots of milled glass (and I hate working with it). Being a fiber, I would expect it to improve the tensile strength of the epoxy. But it doesn't really make the epoxy thicker (i.e., the epoxy is still runny, even if you use lots of milled glass). Colloidal silica is a thickener, but more than that, it makes epoxy thixotropic. This means you can easily form a fillet, for example, but then the epoxy stays in that form. Working with epoxy that is thick enough not to run can be difficult. This is why fumed silica is useful. Being a sphere, I wouldn't expect it to add much strength, but lots of folks and some suppliers say it does.

I often use both milled glass and fumed silica. I mix in the milled glass first and then the silica.

Jim

I use Aerosil - Cabosil, from US Composites, as a thickening agent with my aeropoxy and have obtained great results. I mask my fillets before applying, and once completed I remove the tape.

Smaug said:

I use Aerosil - Cabosil, from US Composites, as a thickening agent with my aeropoxy and have obtained great results. I mask my fillets before applying, and once completed I remove the tape.

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That's the stuff I just ordered off of Ebay.

Thanks everybody