Conrod

Hi Guys
The Lanier Dominator plan shows a rear CG of 2.75inch,can you go back further and has anyone done so,if so how far?
Geoff

DMyer

My Feedback: (2)

You can move the CG as far back as you feel comfortable... however... a good rule of thumb is 3/16" of elevator travel for a full on pylon one turn. Adjust the balance until it is so and you will be on the road to a hacing a good pylon racer.

Dan

Ed Smith

I build my own Quickies. Dimensionaly they are not that much different from all of the rest. My C.G. is set at 3" from the L.E.

Ed S

SSAN

Just like Ed, I design and build my own quickie. I've played with CG quite a bit and found some interesting thing about CG affect for different airfoils as well as distance area from the tail moment. Although, your airfoil may vary and you might have to stay with the 28-30% rule of thumb to start with, and then move up from there depend on your liking.

The rule of thumb works for most airfoil. However, my latest modified NACA 66-012 quickie wing defy all rules and I can go even further back, up to 3 3/8 inch aft from the LE and still have the plane fly smoothly without hunting issue. This is unusual, but it has been good so far. Go figure?

luv to race

My Feedback: (1)

Sam? 3 3/8" Your a better flyer than most of these guys. Travis, Freeman Jr., Marcus Blanchard(National Champion)... none of those guys fly that airfoil that far back ... 3" at the most, 2 3/4 for some. What's your secret, maybe we could find some more speed and finally break that 1:03 mark in Q500.

RB

DMyer

My Feedback: (2)

I flew a 66-012 last year at between 2 7/8 - 3 1/4... mostly at 3 1/8. I am convinced it flew best at 2 7/8 - 3" and plan to set my 428 planes at that CG this year. What was the "Modified" part of the 66-012?

bl10

From my experience the N-66-12 airfoil gets very pitch sensitive if the CG is pushed back any further than about 3 inches. Most that I know are somewhere between 2 ¾ and 3 inches from the leading edge. A longer tail moment or larger stab will permit the CG a little further back but not much. I got a look as Sam’s modified N-66-12 at the Winterfest. I noticed the High Point was moved way back, probably to 60% or so. I no longer think a rear CG is all its cracked up to be if the trade off is stability, which it is. Look at the current Q40 faired hair boy, Burce DeChastle’s Pole Cat. Most fly the thing so nose heavy it needs high rate elevator just to glide level. I figured it should glide with about the same trim as when flying. When I moved the CG back far enough to even get close is was virtually un-flyable. The moral of the story is put the CG where the kit says to start with and be very careful when moving it back.


Barry

SSAN

Randy,

Yes. 3 3/8' aft is what I fly with now for testing, but I haven't got the plane dial in so I don't know what it will do. However, I raced another model with CG at 3 5/16" and it turns awesome. It comes around like a slingshot from pylon 3 going to pylon 1, and that's with a heavy plane, weight 3 lb. 14oz. (beefed up glass wing for R&D purpose). Although, the best CG I prefer so far is 3 3/16" to 3 1/4" max for 3 lb. 8oz plane. This can only be done using the correct tail moment from TE of wing to LE of V-tail. Otherwise, you got one snap happy baby (trust me, I've been there!).

No secret at all. The only think I do is pushed the envelope to see where the limit is, and so far its been positive. Trial and error I guess, but I based my original design from a proven model you fly.

PJ_TankPilot

Most Q-500 aircraft look alike but they don’t fly alike.
CG is like a lot of other variables, the ‘best’ CG is what works for your flying style.

Take some lead tape to the practice course and try different CG locations. You will notice the difference and can choose the one that suites you. CG also affects take off and landing so pay attention during the entire flight.

Personally, I can get around the poles faster on the nose heavy side.

SSAN

Barry,

I agree with you in term of pitch sensitive, but only if the design doesn't have the correct tail moment to the CG or one use CG way off manufacturer recommendation. Otherwise it is workable, like a place for everything and everything in its place. It's all relevant.

I tested one model with a 13 1/2" tail moment from wing TE to V-tail LE at 3" aft and it was fine, but when I moved CG further back, it was a snappy baby. I wasn't happy and wanted more stability so I built new models and made changes where I needed most. From there, I just keep on testing with new models and change one thing at a time to see what the effect or benefits are. So far, all I can say is it works and I've been flying all my quickies with CG further back than 3 3/16" for the reason of higher speed coming of pylon 3.

As for the aifroil being way back, that has nothing to do with stability, but mainly for overall top speed. I've tried 5 different airfoils configuration and three of them are quite positive, but I won't stop there until I find that magic number/wing. So on and so forth...

Like the old saying goes... " If you're not moving forward, you're going backward! ". So pushing to the limit and constant testing to improve is always my goal.