Back in the 50s and 60s we didn't have epoxy. All we had was Ambroids and white wood glue. Gluing a firewall in could be challenging. Wood glue was always water soluble and glow fuel would eventually dissolve it. So you would have to glue the plywood to the balsa with wood glue and wait for it to dry well, then coat the exposed area with several coats of Ambroids and again wait for it to dry.

You could buy Ambroids in the quart can and it could be thinned with acetone. Several coats of thinned Ambroids you could completly fuel proof the engine compartment.

Then 5 min epoxy came along. You can thin it with acetone also. I could build a complete Ugly Stick in less than a week and be flying it that weekend.

Now we have CA and I love to hear people try to pronounce the name. That's why we call it CA and not Cyanoacrylate. A couple of years after the thin CA appeared the thick CA appeared. Thin CA will not adhere plywood very well but the thick will. I still use Epoxy for firewalls and landing gear mounts.

Whenever you are having a hard time with CA kicking off, sprinkle a little Arm & Hammer baking soda over the wet CA. It will cook off very quickly. It will also strenghten the joint.

Frank