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  #11  
Old 01-30-2021, 06:00 PM
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I used to put good sized fillets on centering rings when I was young and dumb. I stopped putting so much glue in and ended up with minimal shrinkage that a good thick coat of primer and a little sanding will take care of lickety split. If it's a little much for primer coverage, a little F'n'F or Bondo will take care of it. We're already filling seams anyway, right? (not you, GH)
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  #12  
Old 01-31-2021, 03:15 PM
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Quote:
Originally Posted by scigs30
So far I have used this new Aliphatic Resin glue from Titebond on one rocket, some furniture, a Guillows model and some test pieces. So far this glue is great, performs like Titebond original except it dries a lot faster. Best part, it dries clear and strong. I did some test pieces where I first sealed the balsa with Brodak balsa sealer, then glued it to another piece of sealed balsa. I added a small glue fillet and let it dry. The balsa broke apart before and the glue joint did not give. Also did a test on a bare body tube with sealed balsa with fillets, could not break the glue joint. So far this glue is working great. My next test will be on a large vintage RC balsa plane and maybe the Orbital Transporter. On the OT I will seal all the balsa first this time and then assemble, much easier than last time of building the rocket then applying the sealer. I will keep you updated on my glue trials.


Have you ever used Titebond Moulding and Trim Glue (TMTG), which they changed the name on to call it "Titebond Moulding Wood Glue" or something to that effect. It was really great stuff. I used it SOLELY for fillets-- made "instant fillets" that were perfect every time, no sanding required. No voids or pits either so long as you didn't make them HUGE fillets (but if you're doing those you should do them in steps anyway) and it dried clear, smoothed with a damp finger to make perfect fillets that WOULDN'T RUN.

For joining fins to tubes, I use the classic GH Stine "Double glue joint" method. I always thought it was nonsense TIL I TRIED IT and found out that it's *THE* best balsa-to-body tube joining method you can use... Apply a THIN layer of glue to the roughed-up tube line where the fin will go, and another THIN layer of glue to the fin root edge, and set them aside to dry (I put them root side up in an old egg carton that I make a cut across the egg cups after turning it upside down, which makes dandy "fin clamps" for holding the fins while the glue dries. Allow the glue to dry, which doesn't take long since the wood and paper tube take up the moisture from the glue quickly and wick it in, then apply another THIN layer of yellow wood glue to the fin root edge over the first coat, CAREFULLY position the fin where it will go over the tube, and then lower it into place... it will "lock" in place VERY QUICKLY so make sure everything is where you want it to be before you put the fin to the tube... hold it maybe 10 seconds or so and it will be LOCKED PERMANENTLY in place-- *almost* as fast as CA, but about 100X the joint strength once it's dry. No need for jigs or other stuff-- once the fin is "stuck fast" it's gonna hold whatever alignment you put into it. Allow to dry, then fillet with the TMTG.

As for strength?? I've had a rocket go awry during flight and impact the ground flat parallel to the ground, with one fin taking the brunt of the impact... the glue joint did not turn loose until nearly HALF of the fin which was PAPERED FOR STRENGTH AND FINISH had disintegrated upon contact, and when the fin finally DID come off, it WASN'T because the glue joint let go-- it was because the paper tube delaminated, and the outer layer of the tube wall came off with the glue joint intact along with the fin... I cut it away from the remains of the fin, shaved it and sanded it down, and glued it back to the tube, cut a new fin, sanded the airfoil in, and papered it, and then used a double glue joint to reattach the new fin to the tube, let it dry, and filleted it with TMTG, and then did a touch-up paint job-- good as new never knew it was damaged! Any time your glue joint strength EXCEEDS the strength of the materials it's bonding, there is NO NEED of any STRONGER glue joint, since that will NOT be where the failure occurs!!!

I'd be interested in hearing about the properties and qualities of this new glue... if it's like TMTG it should be some pretty good stuff!

Later! OL J R

PS... I did some threads about all this stuff showing lots of pictures and "how to" around here in several places... I know I covered papering fins in the "Dr. Zooch Vanguard Eagle" build thread complete with pictures and weight breakdowns... and the TMTG filleting in the "Dr. Zooch Delta-IV Heavy Orion" beta build thread IIRC... among others...
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Last edited by luke strawwalker : 01-31-2021 at 03:34 PM. Reason: left something out...
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  #13  
Old 01-31-2021, 03:23 PM
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Quote:
Originally Posted by Earl
Does this new version tend to shrink as much as the ‘old’ Titebond? I used Titebond quite a bit in my building, but not for gluing engine mounts into body tubes, as it shrinks too much when it dries and can ‘pull’ dimples into body tube outer surface where the glue dried around the mount/body tube interface. So, I always use epoxy for those applications.

Earl


Yeah, the dreaded "coke bottle effect"... had that happen myself. Better to use white glue for motor mounts, or if they're a tight fitting mount (or long contact area like the "stage coupler" type mounts in smaller diameter rockets) epoxy is DEFINITELY the way to go on those, since epoxy cures via chemical reaction rather than "drying" (evaporating a solvent, in this case water) to cure. Also no risk of the joint "locking up" halfway installed in the rocket like with white or wood glue, particularly on large surface-area joints like the stage-coupler type motor rings...

Later! OL J R
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  #14  
Old 01-31-2021, 03:31 PM
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Quote:
Originally Posted by Don Altschwager
I have been using these. Not sure if there is any real difference other than the color (one is greyish, the other white). Both dry without running. Can glue together a rocket and fillet the fins very quickly.


Yep the gray bottle is the good stuff... moulding and trim wood glue. no run no drip. Haven't tried the white version in the blue bottle yet, haven't seen it. Have to give that a shot.

What I like is, NO NEED to sand fillets with the stuff-- you just apply, smooth it out with a damp finger, and PRESTO it's DONE-- dries smooth and slick and exactly where (and HOW) you put it (the shape you put it in). PLUS, you can do ALL the fillets at one time; NO NEED to do them on two adjoining fins at a time and then laying the rocket horizontal to keep the stuff from running or dripping... Just "easy peasy" fillets that are strong and work well every time.

It doesn't shrink MUCH but if you put on a 1/4 inch thick fillet in one go it probably will open up a pit or void or a dimple you might not be happy with. It dries fast, though so if you're putting on a THICK ROUNDED FILLET like that (over say 1/8 inch deep) then you'll probably be happiest doing a first application small fillet, letting that dry, then a second fillet over that to get the final size/shape you want, without dimples, voids, or pits.

Later! OL J R
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