The manual for this AT6 calls for 3.5 to 4 inches from the leading edge to the CG. This plane snaps on landings unless I burn it in. Since we have a short runway I built in flaps and barn door ailerons. That did not help. I have now stripped the wing and built in 3 degrees of washout. It is about ready to go and so I wanted to be sure about the correct CG.

Now I am confused! My calculations show the CG to be only 2.5 from the leading edge. So to be sure I drew the wing on graph paper and it also shows 2.5. This figure is 25 percent of the MAC. One panel of the wing is 29 inches span. The root rib is 10.5. And the tip rib is 7.5. There is a leading edge sweep of about 3 inches.

I would love to have somebody else calculate the MAC and CG to either agree or disagree with my calcs.

Thanks, Arno

Arno
Hi, I'm just about to build one myself (OZ version) and took very close note of your comments. From my experiences with two ARF's of late, "Scanner" " Air Speed 40" the recommended CG is back about an inch (2-2.5cm) of where it should be for (my opinion) of nice flying/landing qualities. Subsequently i was landing long, at Mach 2, in a sweat, and making battery, receiver, engine mounting forwards adjustments very quickly. The Scanner required lead!!
The book says 5-6cm at the wing tip. I can't vouch for your calculations but sounds logical. I will start mine at about 2.5-4cm at the tip and go from thier. Interested in how you go with it.
Luck to you
DLA

The answer to any CG location is as easy as 2 minutes with a yardstick. Take a look at the few measurements that www.geistware.com takes as input for their CG locator application. It takes only a minute or two to make the measurements (which are dead easy to do) and only a minute to plug them into the application.

http://www.geistware.com/rcmodeling/cg_super_calc.htm

Simple to do.
No real effort.
Absolute accuracy.
Not biased or sound byte BS.

Hi all,

I just tried to reply and screwed it up so you may find two replies. This one should be complete.

Ok here is an easy and nearly exact way to find the CG of most any wing.

Measure the root in this case 10.5 inches. Measure the last tip rib and here it is 7.5.

Add the root and tip measurements together and devide by 2. So we are looking for the rib that measures 9 inches (the MAC).

Find the 9 inch rib and measure from the liading edge back 25 percent (2.25 inches minimum CG). Then measure 30 percent (2.7 inches maximum CG).

Remember these measurements are on the 9 in rib. You can draw a straight line from 2.25 etc. to the fuse if you like and mark the CG there.

This works for me and is a safe starting CG. I start there and sometimes make small adjustments after the maiden flight.

I Hope this is helpful. There is actually a longer formula for finding the CG but the above puts you nearly as accurate.

Arno

One more note. When I wrote the original notes I may have failed to remember that my calcs would be at the 9 inch rib. I'm curious as to where on the wing they said you should make the measurement.

I have found a few kits in the past that gave CG measurements that were wrong. So since my first wrtie up I have researched a lot of information on wings. Especially since I love to scratch build.

Arno

Hi anyone heard DLA engines?they said their DLA56 is less 25g than DLE55.DLA112 is 50g lighter than DLE111?is that true?have anyone tried this engines?