When a lot of amateur remote controlled aircraft builders get into a project, they don’t want to stop until the airplane is complete. The excitement of transforming a kit of balsa wood into a flying machine motivates us into working all hours of the night (if our wives would let us). It becomes somewhat annoying when the point in a project comes where there’s nothing left to do except let the glue dry.

Many first time builders have damaged a work-in-progress by attempting to work on a piece that hasn’t completely cured; nothing is as frustrating as re-doing a masterfully crafted wing because it began to reshape itself while you were doing a touch-up with sandpaper or trying to attach it to a spar.

A thought then pops into the builder’s head: “What if I use an epoxy with a shorter cure time?” Faster curing does mean you can get back to work sooner, but will the bonds hold up once the airplane is out flying?

I’m comparing two products from the same manufacturer: Devcon’s 2-ton clear epoxy and its 5-minute epoxy. All the posted information comes directly from their Technical Data Sheets for each product.

The 2-ton epoxy gives a longer working time: 8-12 minutes instead of a shorter 3-6 minutes with the 5 minute product. Functional cure (enough to actually move the part) is 2 hours with the 2-ton, and only 45 minutes to an hour for the 5-minute epoxy. At this point, you are trading off faster cure time for less time to set the piece correctly.

Looking further into the data, it appears that the 2-ton epoxy will be fully cured in 12 hours, which is exactly the same as the 5-minute epoxy, so no advantage there. For a fully cured piece, the strength differences are somewhat significant in some situations, but probably not for most remote-controlled airplane applications. The 2-ton has a shear strength of 2250psi, while the 5-minute’s is 1900psi. Since you’ll be using light wood, the bond is likely stronger than the actual parts being bonded together in either case.

The main result: If you can work accurately at a high speed, the 5-minute epoxy should work just fine if you want to speed up the building process. Most of us need a little extra time to ensure each piece is set correctly, and the 2-ton, with a longer working time, is a better option for checking and re-checking the part.