Best glue for SANDING?

if you know ahead of time you are going to do a lot of post gluing sanding, do some work better than others?

for most wood joints yellow glue works well since you will not be needing to sand great quantities of glue at any given moment, if you mean for something like filets, that is another fettle of kish. most glues have thermo-plastic properties(they tend to soften when heated and they don't conduct heat well so the surface will heat up fast when sanded). glues that sand well tend to be somewhat brittle.
Rex

Most if not all wood/cardboard or wood to wood joints work best with either white or Yellow carpenters glues. If using the double glue joint method there is generally very little build up so not a lot of sanding of these joints is required.
Fillets I almost always use 5 or 30minute epoxy as I can control the radii of the fillets and thereby reduce the need for excess sanding. Although I do sand all fillets to a feathered edge transition between fillet and fin and fillet and body tube. Both 5 and 30 minute Devcon epoxies maintain a good degree of flexibility after curing that have proven over the decades to keep butt jointed fins in place regardless of age.

Adhesives Like CA and most Urethane (gorilla) Glues become quite brittle shortly after curing. while they sand OK their strength is greatly reduced with age. CA should never be used as the sole adhesive in any model that is intended for more the 3 flights. I do use CA in construction of Competition models but these models are never intended to last more the a single flying season.

BABAR said:

if you know ahead of time you are going to do a lot of post gluing sanding, do some work better than others?

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If you're asking "which glue sands easiest?", then I'd have to go with CA followed by epoxy, then polyU, then the yellow/white glues. CA typically soaks in and hardens the substrate material. Typically, less is used in a joint (I don't think I've ever heard of fillets with it). On the other hand, alephatic resin glues never cure as hard, stay somewhat plastic after cure, and are somewhat "gummy" when sanded (these same features help create a tough glue joint...).

sooner.boomer said:

If you're asking "which glue sands easiest?", then I'd have to go with CA followed by epoxy, then polyU, then the yellow/white glues. CA typically soaks in and hardens the substrate material. Typically, less is used in a joint (I don't think I've ever heard of fillets with it). On the other hand, alephatic resin glues never cure as hard, stay somewhat plastic after cure, and are somewhat "gummy" when sanded (these same features help create a tough glue joint...).

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CA can be used to make internal fillets. In general the Loctite "Gel" CA will sand well and if you are building a Aerotech kit you don't need anything but CA.

Sanding CA drives me nuts, although I may be using a different type than others. BSI is also terrible though with quite a different feeling.

Wood glue sands great, and so can West depending on the filler.

The key to sanding CA is to sand as soon as possible after it sets. It will.continue to cure for an hour or so. I have use it as a filler on plastic models many times but it don't use it for rockets much. Even when it is still green, it is so much harder than balsa and paper that makes getting an even surface much more.of a challenge.

I like JB Weld for it's sand-ability. I use it to fill some things, and then sand smooth outdoors while wearing a respirator.

Finally, a glue thread where everyone agrees. :wink:

It really depends on what you are gluing as to the sanding qualities of adhesives. As do most of the answers on this forum concerning practically any subject which is evidenced by the plethora of answers given here. And all are likely correct depending on the application.

My contribution is that a big honking glob of glue is going to be harder to sand than glue applied sparingly to the parts it is to join. Also if the glue is harder than the materials it is joining it is going to be difficult to get a smooth surface without a ridge even with a sanding block.

My only exception to the answers in this thread is that CA joints tend to weaken after time. Not necessarily. I have R/C airplanes that are over twenty years old that are assembled with nothing but CA including the motor mounts and they are still together after dozens or maybe even hundreds of flights. I do concede that CA does give a rather brittle joint and probably is not suitable to surface mounting fins on a model rocket that is going to be flown a lot. For carbon fiber and fiberglass though CA is my go to adhesive.