RCU Forums - View Single Post - I need help locating CG on straight flying wing
Old 01-31-2004, 02:47 AM
  #8  
BMatthews
 
BMatthews's Avatar
 
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,425
Likes: 0
Received 22 Likes on 19 Posts
Default RE: I need help locating CG on straight flying wing

For the diamond you'll need to use the proper MAC to determine the CG. But on your diamond that's easy because it's actually just 1/2 the root chord located at 1/2 the way out the span of one wing. So if it's an 18 inch root chord and 18 inch span the MAC will be the 9 inch chord point 1/2 the way out the one wing. Taking 20% of that as your balance point puts it at 1.8 inches back at the MAC. Or 4.5 + 1.8 = 6.3 back at the root or fuselage. This will mean that you have 20% of the area in front of the balance point and 80% behind it just as it should be.

Sorry Paul but this one isn't that automatic. 25% back along the leading edge diagonal is only 25% of the first half of the wing or 9 inches. That would only put the balance back to the 2.25 inch mark at the root and make it totally too nose heavy.

I do agree with Paul's idea to separate the elevator and ailerons in this case. The sweep forward angle of the trailing edge means that only 1/2 the surface of the elevons would be doing what they are supposed to be doing anyway unlike with a plank style wing.