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Old 04-25-2024, 07:12 AM
bobdros bobdros is offline
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Default Epoxy fillet advice needed

I'm having trouble with the Apogge video technque of using expoxy putty for my Aerotech Initiator. I think I made the putty "snake" to fat to cover the edge of the fin and the body tube. I rolled it out and tried to spread it but it turned into a fat, globby mess. I need advice on how to make a nice concave fillet.


What advice can someone give on fixing this mess?

For another fin, how can I make a nice concave putty fillet with the epoxy putty?

(I had tried just using liquid expoxy on the other fin. That didn't work out too well either.)
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Old 04-25-2024, 07:49 AM
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astronwolf astronwolf is offline
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Don't use epoxy putty. Use a liquid epoxy. Rather than try to describe the process, I'll refer you to some resources:

https://youtu.be/mC-arswl4S4?si=U2RFrDH9PpnK9j3h

https://www.rocketryforum.com/threa...fillets.182031/

Edited to add - I just use 30-min epoxy and transfer it to the fin root with my mixing stick. Depends on the size of your model. You can pour it in too. Then I use a gloved finger or a popsicle stick to smooth out the fillet.

I just saw one of Tim van Milligan's videos. In it he mixes up his epoxy on plastic, folds it up so he can apply it to the model like he's a cake decorator, then promptly spooges too much epoxy all over his rocket. It's like a 30-min video and we only get to the spooging at 27-min. Weird. Don't over-complicate your rocket building.
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Old 04-25-2024, 08:32 AM
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Same here, but I don?t even wear gloves when I smooth it out.
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Old 04-25-2024, 08:47 AM
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I use gloves.
Eventually one will develop a contact allergy to the hardener used in Epoxy.
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Old 04-25-2024, 09:06 AM
bobdros bobdros is offline
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I liked the links Astronwolf posted. I had tried Tim Van Milligan's techniques with a bag with the liquid expoxy but I didn't do it correctly. I bought liquid expoxy from Apogee and will give it another try with tape and applicator sticks or popsicle sticks.

The Initiator has a kind of molded fillet on the fin. Am I wrong to try and add an expoxy fillet?

(And what should do I about the mess I created with the putty?)
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Old 04-25-2024, 09:38 AM
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Quote:
Originally Posted by bobdros
I had tried Tim Van Milligan's techniques with a bag with the liquid expoxy but I didn't do it correctly.

It's not you. His technique is just stupid. Rocketry is supposed to be fun.


Quote:
Originally Posted by bobdros
The Initiator has a kind of molded fillet on the fin. Am I wrong to try and add an expoxy fillet?

(And what should do I about the mess I created with the putty?)

IMHO, adding epoxy to Initiator fins is unnecessary. I've not built and flown an Initiator, but I have built and flown an Arreaux which is in the same family. Flown on one of those 135 N-s G80s no problem. Doesn't need fillets.

Maybe the guy who designed the rocket (Bob Sanford) will comment. He's the expert.

As for the mess you made, you can start sanding.
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Old 04-25-2024, 06:47 PM
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A nice aspect of the 'epoxy clay' is if you don't like how it's coming out, you can simply scrape it all off before it hardens, then mix up a new batch and try again.
If you let it harden, it's going to be a (expletive deleted) to remove.

I've had pretty good luck with dipping my finger in some denatured alcohol when smoothing the epoxy clay - it softens the stuff a bit and makes it easier to form.

However, for epoxy fillets, I use 15 minute epoxy, put a small bit of masking tape at the ends to keep if from 'leaving', and then let gravity do the smoothing. Works rather well so long as you are patient. The edges where you had the tape can be a little rough, but a little carving with a sharp hobby knife and some putty will clean that up.
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Old 04-28-2024, 07:37 AM
PaulK PaulK is offline
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Quote:
Originally Posted by bobdros
The Initiator has a kind of molded fillet on the fin. Am I wrong to try and add an expoxy fillet?
Yes. Not needed for strength or looks. Those fins will not ever come off with medium CA.
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Old 04-28-2024, 07:42 AM
PaulK PaulK is offline
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Quote:
Originally Posted by bobdros
(And what should do I about the mess I created with the putty?)
I use a dremel with carving bits to remove hardened fillets. Works well, and is fast. A little bit of filling is necessary when done. The relatively new 3AH Cordless Dremel tools are great for jobs like this, no cord to get in the way, and a surprisingly long runtime.
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Old 04-28-2024, 12:14 PM
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I use 15 or 30 min epoxy for fillets on any rocket using above D power.
I just use a 1/8" dowel to apply it sparingly and let it flow on its own.
Very easy.

Epoxy Putty pretty much sucks for ANYTHING.
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