CG and Cambered Wing

[chiozza]

Does the CG change any when balancing a wing with and undercamber like the USA-32? Or is it still 30-25% of the MAC?

[Ollie]

The CG affects stability and trim. Decalage affects trim but not stability. Therefore, the CG should be adjusted for the desired stability. The camber of the airfoil affects the trim through its zero lift angle of attack. The decalage should be adjusted to balance the nose down pitching moment associated with a cambered airfoil. The more camber, the more negative the zero lift angle of attack and the stronger the nose down pitching moment. Therefore, the more decalage that is needed to trim the desired CG location and associated stability.

The decalage should be adjusted for the glide. The thrust line also affects pitch trim depending on its vertical location. After the CG is set for the desired stability, then the decalage should be set for the power off glide. Lastly, the thrust line should be adjusted to give minimum pitch change with throttle variation.

If you do not adjust the decalage for power off glide with sufficient stall margin then you have every right to fear dead stick landings. If you do adjust the decalage as recommended then dead stick landings are a piece of cake.

[Sail 'n Soar]

Originally posted by chiozza
Does the CG change any when balancing a wing with and undercamber like the USA-32? Or is it still 30-25% of the MAC?

No.

SnS

[Sail 'n Soar]

Does the CG change any when balancing a wing with and undercamber like the USA-32?

Oops, quoted too much. In ref to the above, No.