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applying epoxy? syringe?

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rocketsonly

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How do you all apply epoxy to make those 'perfect' fillets? I've been using a popsicle stick for quite awhile now and have found it very messy. Do you all think a disposable syringe would work? I bet I could get my science teacher to find some.

Any comments or suggestions would be greatly appreciated!
 

DynaSoar

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Originally posted by rocketsonly
How do you all apply epoxy to make those 'perfect' fillets? I've been using a popsicle stick for quite awhile now and have found it very messy. Do you all think a disposable syringe would work? I bet I could get my science teacher to find some.

Any comments or suggestions would be greatly appreciated!
I just use 1/8" by 1' bamboo skewers to stir and apply. I dribble it into the space, and draw the skewer through it to even it out. Since it's already "wetted" it draws the epoxy out without changing the width of what's been laid down. Occasionally I'll have to fix a goof by drawing the end of a popsicle stick across the top, or wipe a bit up with paper towel, but that's all.
 

wwattles

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If you're trying to reach into deep crevices (such as internal fillets) there are a couple methods. One is to run it down a large straw into the desired location. Another is to use a syringe applicator.

I found a specialty syringe epoxy at my local auto parts store that uses a "mixing syringe" that mixes the 2 parts together as it comes out of the tubes, and squirts it wherever you need it. Overall depth you could go into is somewhat limited (about 6 inches or so), but that long syringe/nozzle combo is nice because it saves you from having to mix it by hand and then dip it into your desired location.

WW
 

Missileman

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I have recently discovered the joys of microballoons.
Not only does it make epoxy fillets much lighter but fairly easy to sand, PLUS if I mix the right consistancy I can do all my fillets at the same time.
I spread it out and shape it with popsicle sticks on small to midsize rockets and I use the edge of a plastic spoon on larger models.
 

BKROSNEY

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For external (i.e. fin root chord) fillets, Jason's approach is very similar to my own, a couple of points I've learned....

If the epoxy has just the right viscosity, when you pull away the masking tape borders it will flow to an almost perfect flushness with the fin and BT face. I've done this with NO NEED TO SAND. I'm still amazed on how good those fillets came out!

Too thick and you have a ridge after removing the tape and you need to smooth the fillet with something. I use a gloved finger dipped in isopropyl (sp?) .. rubbing... alcohol.

Too thin and it will run.

I've found that NHP 30 min. EPOXY is almost the perfect viscosity mixed as is. With something like West Systems where you have to add some filler, I've come closer, but never as good. Maybe just need more practice ;-)

The downside is that because the epoxy WILL flow somewhat (this is what you want), the fin root chord must be level so that it doesn't flow off the aft or forward ends. Also you rely on the correct positioning of fins to create a "valley" between the BT and the fin face. With 4x fins (90 degrees from each other, 8 fillets) I can do 2 at a time. So, it does take several apply glue and wait to set sequences.

... Bill
 
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