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Old 03-10-2018, 10:12 AM
luke strawwalker's Avatar
luke strawwalker luke strawwalker is offline
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Join Date: Dec 2007
Location: Needville and Shiner, TX
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Quote:
Originally Posted by astronwolf
Toss out the weird separating glue, and buy yourself a small bottle of Titebond II. Problem solved.


Titebond 2 is a yellow wood glue, which will shrink and cause the "coke bottle effect" on body tubes when installing motor mounts. I've had that problem myself and switched to white glue to actually glue the centering rings to the body tube, but I DO use yellow glue to install the centering rings to the MOTOR tube of the motor mount, because yellow glue has greater heat resistance and retains its strength better than white glue-- so obviously when the motor burns the heat has to work it's way out from the source (burning propellant) though the paper casing, through the tiny air gap between the motor casing and the motor tube of the motor mount, and into the paper motor tube, then through the glue joint to the centering rings. The paper motor cases are an excellent insulator of heat, but the laws of thermodynamics wants to bring the system into equilibrium, so heat travels from the intensely hot burning propellant into the motor casing, and slowly and steadily makes it's way out from there. Once the ejection charge goes off, who cares, basically, but I don't want a glue joint in that close a proximity to the motor casing (and therefore the first to see heat from the motor casing itself) to possibly weaken right as the ejection charge is about to go off... hence why I choose to use yellow glue for that joint, and I've never had a problem because of it (and to be fair, I'm sure many thousands or millions of rockets have been built with white glue in that joint, and not had a problem either, BUT I like the extra insurance. And before anybody says it, "Well, then why not just 1 hour epoxy or something REALLY strong that's basically insensitive to the amount of heat we're talking about", NO thank you-- that's overkill IMHO and not necessary and not worth the extra hassle and aggravation and trouble of mixing and dealing with epoxy.)

Elmers has reformulated their white glue in recent years, and most folks seem to complain or at least comment that it is NOWHERE NEAR AS GOOD as it's been in years past. It's basically a lot more like their 'school glue' which is designed to be perfectly safe for the "glue eaters" in schools, and basically just hold their dinky school projects together long enough for it to get home and maybe live on the refrigerator for a month or so before it gets tossed in the trash or consigned to the attic to rot. IOW it's not a serious "modelers glue" anymore.

If I were you, I'd seek out a better brand of white glue. I think that Titebond makes one, if not Aileene's Tacky Glue is a good one, among others. If you're like me you don't want to waste the Elmer's you still have on hand-- what I'd do is take the cap off, run a bamboo skewer or a metal rod down in there (coat hangar, old launch rod half, etc) and stir it up thoroughly. I wouldn't use the clear liquid nor would I pour it off-- it's obviously part of the glue formulation and if it's separated out, using it isn't going to hold most likely since it's no longer part of the formulation, and pouring it off will only tend to change the formulation and probably make it thicker and thicker to the point it's "snot"...

One thing I do that seems to keep (most) glues fresher, particularly white and yellow glues, is I store them TIP DOWN in a box with all my glues and adhesives... that way the glue doesn't "dry out" in the tip or turn to thick gooey snot that clogs up the tip the next time I need to use it, and if it separates it separates toward the bottom of the bottle (which is stored on top) so the glue itself is down in/around the tip. Any "skin" that forms in the bottle will be near the bottom as well.

Later and hope this helps! OL J R
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