C of G bi-plane

[Bravedan 106]

Is revising CG Calc OK??

 

BALANCING A BIPLANE

 

Usual Start point 25% - 23% MAC, but what is the MAC................

 

The MAC is the chord that represents the wings as a whole about which lift, drag and pitching moment forces act.

 

The MAC for a constant-chord, straight-wing biplane with no wing stagger is the chord of the top wing, since they are the same.

 

The MAC for a biplane with staggered wings (as Mini-Panic) is simply the combination of the top wings chord and the horizontal stagger distance.

 

To find the start CG, measure 25 percent of the MAC back from the top wings leading edge.

 

To find the MAC for a biplane with a swept top wing and a straight bottom wing (like an Ultimate), once you have determined the MAC as above, measure 25 percent of the MAC back from the leading edge and mark it on both top wing panels.

Connect the two points with a line, and then balance the biplane along this line.

 

Tune from this to your liking/after dive test, etc.

[arun 0]

Digitised version of the excellent article in RCM&E last month about biplane aerodynamics. Including two methods for calculating CoG.

 

http://bit.ly/Jota6D