PHENOLIC AIRFRAMES
Phenolic tubing is a resin impregnated, spiral wrapped, and heat cured tube. It is much stronger than cardboard tubing, with almost 5x the compression strength.  It is also a very good base for rockets that will require the strengthening of fiberglass, Kevlar, carbon fiber, or similar materials. For this reason, we recommend phenolic as the appropriate tubing for rockets that are 6.0, 7.5, or 11.4" in diameter, or rockets that will require strengthening for the rigors of transonic or supersonic flight. We also recommend phenolic for transonic or supersonic flights in kits of 1.1" through 2.5" diameter, as phenolic can withstand those flights without strengthening in most instances. PML Phenolic tubing is very heat resistant and is highly recommended for motor mount tubes and minimum diameter applications.

When to use Phenolic Tube:
For all motor mounts and minimum diameter boosters.
For any rocket 1.1" through 2.5" diameter regardless of speed.
For any rocket 3.0" through 11.4" that will not exceed 0.85 mach.
For any rocket requiring extensive fiberglass, Kevlar, or carbon fiber reinforcing