Christchurch and District Model Flying Club
 

Glues for depron and foam

by Mike Roach

I’m often asked which glues I use for depron and foam, and I think there are three options. But first, always sand off the lovely sheen from the depron you are glueing, or the joint will eventually fall apart. The same applies to covering with tissue or glasscloth—always sand off the sheen or you will be able to peel off all your hard work.

UHU Por. This is a foam-safe contact adhesive available from Channel 4. I spread a bead along one component, rub the two components together so that the glue is evenly spread on and between them, then set aside for the advised 20 minutes, then push the two components together for an immediate bond. There are no second chances, but there are strategies for ensuring that (say) the sheet side of a fuselage is neatly aligned with the formers.

Advantages—good bond, waterproof, flexible, quick. Ideal for internal joints.

Disadvantages—rubbery, can’t be sanded or painted. If you don’t wait the 20 minutes, the bond is poor and can be pulled apart. Fumes?

Foam-safe cyano. Just like medium cyano in aspect and use. The instructions say you must use appropriate kicker to activate the glue, but a rub of water/spit on one surface gives a good and almost immediate bond.

Advantages.—quick(20 sec) , good bond if all goes well.

Disadvantages—brittle bond, much harder than the foam, so difficult to sand. Does not fill gaps. Fumes?

Wood glue. I use Titebond (Ch 4) nowadays, but I expect Aliphatic resin and plain wood glue are as good. Always use a rubbed joint (see above). If you want to, dot the joint line with FS Cyano and press together with weights for at least 30 minutes (much longer without the cyano)

Advantages—a good bond, sands very easily and almost at the same rate as depron, so ideal for external joints. No fumes.

Disadvantages—takes a day or so to set completely because the depron is almost impermeable and the glue can’t dry out.

Having written this, I remembered epoxy. The 5-minute stuff is excellent for high-stress joints, but can’t be sanded and will add weight unless used sparingly. But my goodness, it’s quick!

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