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moocrew

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Alright did some searches found things. But I wanted to know if anything is new.

What do you guys use for fillets? on lpr
I tried elmers glue all but it shrinks like crazy and gets bubbles just as bad. Epoxy may be a bit over board. What about elmers fill n finish? does this stuff work well?

Gimmie some opinions..i wanna know what has and hasn't worked.

Thanks!

-matt
 

SecretSquirrel

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Originally posted by moocrew
What about elmers fill n finish? does this stuff work well?

Yes it does, apply it over your white or yellow glue fillets and sand it smooth. It gives a very nice appearance after painting.
 

moocrew

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what about cracks?
I tried some fill n finish on a fin both sides...and it cracked..real shallow crack but still cracked. Should I try to make the fillets smaller?.... what might have caused this?
 

SecretSquirrel

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Originally posted by moocrew
what about cracks?
I tried some fill n finish on a fin both sides...and it cracked..real shallow crack but still cracked. Should I try to make the fillets smaller?.... what might have caused this?
Hard to say without more info, I don't know how big you're trying to make the fillets. F'nF isn't structural, it's purely a finish material. I only apply a very thin layer over my glue fillets. It's so thin I often sand through the F'nF in spots.
 

flying_silverad

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For non-cracking FnF fillets, just sand fillet first, then coat with a drop or two of thin CA. I then take a latex coated finger (surgical glove...no I am not checking for any lower GI issues) and smooth the glue over the fillet. Makes em rock hard. Just make sure you do most of your sanding first.
 

limd21

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From a structural standpoint, I'd agree that epoxy is overkill for LPR fillets. That said, I still use them *all* the time. Not because I'm seeking strength, but because they're the fastest, easiest way to get a nice smooth fillet. Most times, they're smooth enough to be painted with no sanding.

Here's my method:
1) support the rocket so it's horizontal and that two fillets from adjacent fins are up (e.g. on a 3 fin rocket, one fin would be hanging straight down on a 4-fin model, the fins make a perfect "X" - each a 45deg)
2) mix a bit of 5-minute epoxy - just enough for the two joints that are now facing "up"
3) apply a small amount to each of the two joints. A little goes a long ways! Remember this is an LPR fillet, not caulk around your bathrooom tub.
4) with a finger (always covered in a vinyl/nitrile/latex glove), dip it into some alcohol to wet it and immediately smooth each joint, leaving just enough to form a nice, small, smooth fillet. It typically takes two or three passes with your finger to get it just right, so be sure to wipe excess epoxy off the your finger and freshly dip in in the alcohol before each smoothing pass.
5) You should have a glass-smooth fillet in each joint. In a few minutes, they will set enough so you can repeat for the remaining fillet "pairs" (remember, a pair are the two joints closest to each other on *adjacent* fins, not the two on the same fin!)

I've done this with 90-second (!) epoxy, too, which makes the process really fast, but I'd recommend practicing with the 5-minute stuff before using the ultra fast stuff - once it sets, if it's not "just right" the only way to clean or smooth it is with lots of sanding.

No sanding, fast, and (obviously) more-than-strong enough. The downside is needing to be extra careful because epoxy demands an extra measure of safety. Some may claim that epoxy is too heavy, but I contend that a good fillet is pretty small for most LPR and it can't be significantly different than a PVA (white/wood glue) fillet in terms of weight.
 

DynaSoar

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Originally posted by moocrew
What do you guys use for fillets? on lpr
I tried elmers glue all but it shrinks like crazy and gets bubbles just as bad.
Elmer's, both white and yellow, shrink a little bit. Sounds like you're using way too much, especially the bubbles.
 

Zack Lau

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I typically use thick CA to make quick and easy fillets.
I used a piece of piano wire to spread it out after applying
a drop or two from the bottle.

For really nice looking thick fillets, I use Red Devil one time
spackling for a very lightweight base, and apply Elmer's
FnF over it.
 

rbeckey

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I agree with limd21. I use a small epoxy fillet on LPR. If you don't use great gobs of it, weight is not an issue. I find it much harder to get good fillets with yellow glue. Epoxy gel is another product that you could try. It stays exactly where you put it and typically sets in five minutes. I usually apply the stuff and wait auntil it barely starts to set before smoothing with alcohol. Gel seems to remain somewhat flexible when cured. Some claim that brittleness is a failing of epoxy fillets.

When working with kids they get to use glue only. We just get the fillets as good as possible with thin layers. Generally their patience run out before optimal results are reached, so it requires a little guidance to keep them on the right track.
 

bcdlr

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One problem I have is that my fillets are always visible through the paint job. I've been using yellow glue and when I smooth it with my finger and get to the top there's always that "pull away mark" that shows up. It's hard to sand glue off the tube! It's hard to get yellow glue to look good (for me).
Would filler impart any strength to the joint?
I'm using that Micro Fill (NHP products). Got it at Hobby Lobby. So far I love it. Easy to use with just a drip or two of water to make it pastey. Dries QUICK. Sands great, just like the label says. I made little 'spreaders' out of cottage cheese container lid.
 

limd21

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Originally posted by bcdlr
One problem ... when I smooth it with my finger and get to the top there's always that "pull away mark" that shows up.
Have you tried smoothing towards the tail?

Fillers, generally, don't add strength, but that is of little concern in LPR.
 

Stymye

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for low power fillets

I like to run my finger across the fillet and curve it around the edge of the fin than I do it again in the opposite direction, makes a nice blend to the fillet, I use yellow glue ,sand, fill-n finish than sand smooth.

sometimes I will harden the fill n finish with thin cya.
 

moocrew

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well i do my fillets mainly for aesthetics.
and ive found that even thou FnF works well it even tends to crack and sometimes even break off after awhile. And believe me ive tried everything to get it to stick. so i may try my luck with some epoxy again. hopefully it works better this time than last.
thnx for all the ideas/sugg.
-matt
 

moocrew

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oh yeah before i forget..... what to you guys use to actually apply the epoxy onto the roc w/o getting it everywhere....i've tried popsicle sticks..but those get real messy.
any suggestions?
 

limd21

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Originally posted by moocrew
oh yeah before i forget..... what to you guys use to actually apply the epoxy onto the roc w/o getting it everywhere....i've tried popsicle sticks..but those get real messy.
any suggestions?
I subscribe to the philosophy that "a small fillet is a good fillet". So a little material goes a long way and epoxy doesn't shrink like white/wood glue. With that in mind, I use whatever small object is handy - toothpicks, a finishing nail, a coffee stirrer. A popsicle stick would definitely be too big for most LPR. To me, it's just right when I lay in just enough so that my smoothing passes pick up very little excess epoxy.
 

Stymye

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a plastic spoon works great, any excess glue curls into the spoon
you can also shape the spoon end for smaller fillets by sanding it
 

sveinbjorn

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Originally posted by moocrew
oh yeah before i forget..... what to you guys use to actually apply the epoxy onto the roc w/o getting it everywhere....i
What works best for me is just to mask off any area I don't want epoxy on. If the epoxy is thin enough to make good fillet, it's very hard to control drips and overruns. Oh yeah, don't forget to put newspaper down. My wife nearly brained me for getting epoxy on the counter. :eek: (I work in the house when the temp goes above 90)

HIH,
Ed
 

Justin

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Usually I do a couple of thin layers of Titebond glue for fillets. Titebond is far and away superior to Elmers. It dosen't shrink as much, it dries faster, and according to several professional carpenters I know it's much stronger (though they have stronger stuff for some uses). They come out pretty smooth if you are careful (I spread them towards the tail as some mentioned earlier). Catch the drops while it's still wet to avoid the "pulled look". Structural and nice to look at.

I do agree with limd21 also though. 5 min epoxy makes nice fillets you don't have to really sand if you get then on smooth. I don't have a problem with overkill. I'm not an extreme altitude guy, I don't mind a little extra weight to toughen up a bird..:D
 

DynaSoar

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Originally posted by moocrew
oh yeah before i forget..... what to you guys use to actually apply the epoxy onto the roc w/o getting it everywhere....i've tried popsicle sticks..but those get real messy.
any suggestions?
I always mix on a flat surface using a bamboo kebab skewer, and apoply iyt with the point end of that. I can lay down very small amount, or long thin trails, or I can gob on several gobs along the root and let it melt together and forma nice smooth fillet.
 

rbeckey

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Treat epoxy application like painting. Put tape where you don't want it to go. Get painter's tape and lay a strip down the fin and BT at the edge of your chosen fillet area. Ideally, after you apply the epoxy it should just barely touch the edge of the tape, with perhaps a few smears. BEFORE the epoxy sets significantly, pull up the tape. Any small ridges at the tape line should settle out if you pulled it off early enough. If not, wait until the epoxy barely starts to gel, then smooth everything out with a (gloved) finger dipped in alcohol.
 

stevecarr

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Yellow glue is not a one shot deal. I smooth it out with my finger. Let them dry [comletely]. Then go over with a second layer. Again removing excess with my finger.
This takes a little time but you can get super results if you let dry between coats.:D
 

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