kstick

I am finishing up a Midwest Citabria kit. The instructions call for the CG to be 4- 5/16 inch behind the leading edge of the wing. My calculations show this is 36% of the mean chord(which I measured as 12 inches). This is further back percentage wise than even called for by my other planes such as the Venus II and Aeroworks 61 sized Edge.

Is this a viable starting point for the first flight or should I follow my instincts and start at about 3-5/8" which would be 30%? I welcome all view points, but will give most weight to those who have experience with this particular plane.

As a note to those considering building this kit. It's probably not the best kit for a beginning builder (I have previously built 6 or so kits and still found it challenging).

tailskid

My Feedback: (34)

Start with 4" for the first flights....then move back as desired....

johndou

I finished my Midwest Citabria earlier this year but haven't had much of an opportunity to fly. It's only got a few flights on it now - (3 or 4) - It's got a Magnum 91 under the cowl and Sullivan flying wires on the tail, it weighed in at 8 lbs. 5 ozs. The CG came in right at 4 5/16" with the batteries right at the CG, so I left it there. It flies slightly nose heavy. I plan to move the CG forward to something around 4" - 4 1/8"

The only modifications that I made in the build was to build the wing flat with a washout. The Citabria was my first kit after returning to the hobby after 20+/- years away. I agree that it's not an easy kit to build but if you take your time, which is the point behind building a kit, it builds pretty straight forward with no major issues. Plus the fuselage requires little to no jig building and almost snaps together straight and true.

johndou

Chock it up to having other things on my mind ... I won't be moving me CG forward on a plane that already seems to fly slightly nose heavy ...

I'd suggest starting out with the CG as recommended by the designer and move it if you feel the need after a couple of flights.

iflyfisher

kstick, I have one of these with a fair number of flights on it. I was having some trimming issues so I moved the cg a bit forward of the point recommended in the plans, and it absolutely killed my roll rate. If you are going to start with the cg forward, make sure you have a little altitude when you try that first roll as you might be surprised on how long it will take to rotate. I did a quick check, and my cg is now between 4 1/2" and 4 3/4" inches back. I like a little snappier performance, and still don't find it squirrelly at all. I'd go with the recommended rate of 4 5/16". You may find yourself moving it a bit back from there.

It is a fun flying airplane. Not a point and shoot plane, but it will do pretty much what you ask of it. Mine still gets regular stick time.

Ken

kstick

Thank you to all who responded. You may have helped me avoid an error. I'll go with the cg recommendation of Midwest.

As point of information I ran the dimensions I measured through an online cg calculator. I shows the neutral point being at 5.75"(where static margin = 0). The recommended cg has a static margin of 12% which is a good value. My first thought of cg at 30% of chord has a static margin of 18% which is probably too stable to be very responsive.

Anyway, thanks again. Just goes to show that rules of thumb can sometimes lead one astray.