decalage -- lots of interesting stuff

Decalage refers to the angle between a plane's main wings and the elevator, or the two pairs of wings on a biplane.  There's a great discussion in the RCG UMX Radian thread.  I'm capturing it here coz... well you know how searching on RCG is.  Post numbers are 3431, 3434, 3435, and 3442. Big Thanks to Phil Alvarez and turboparker for sleuthing these out of the thread.

My Summary:

• Porpoising is caused by bad decalage.
• Don't try to solve by changing CG.
• Small foamies can incur twists due to their light construction.

Standard decalage test:

• Perform a power-off vertical dive from high altitude (neutralize elevator).
• A. Model continues straight down: No change needed. 
• B. Model pulls to canopy: Increase stab incidence with respect to the wing.
• C. Model pulls to belly: Reduce stab incidence with respect to the wing.

And the words of the masters: