jimm

My Feedback: (1)

I read once that on planes with long noses that lift is generated with it. Planes like the F104 has a very far forward CG point, much farther forward than one would think it should be. Perhaps that is happening with this plane?

Jim

crossley51

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I attempted to fly the BB with 22cm cg with the same nose drop on takoff. As soon as I backed off on the 45 degree up elevator to maybe 15-25 degrees its nose dropped like it had full down elevator. The original designer in the RCM said that finding the CG is trial and error and he didn't have a reason why the FB BB CG is so far back from his original design. He also said he likes elevons over the FB model.

After looking at the profile of the BB and the way the nose drops when lowering the elevator It could be that angle of attack AOT is much higher than what appears for the wing alone. This would mean that the elevators should be set with say 15 degrees up to keep the nose AOT up and the lifting body working to raise the airplane nose and not pushing it down.

I'm not sure if my bird can be patched up. I may try again if it can be fixed. Next I may go to elevons and trim up elevator. I'll also move the CG to 22.5.

Let me know if your guys have any success. You may never hear out of me agian if the bird is junked. Good Luck

MattyC-130

My Feedback: (5)

10+ flights on the SR-71. I have one of these with GMS .47 and Sping Air retracts. Had to mount battery under engine mount to make CG approx. 23 CM back. Aircraft will sit fine on three gear on ground but if tip all the way back, nose up, it will sit on tail and mains.
I have about 40MM travel up and down on elevator vise 70MM as called for on directions. Using a 10x7 P Zinger wood prop. Flys beautifully and I can even aerobrake on landing rolls. Keep some power on on final and you will get some real nice nose high touchdowns.
Hope this helps,
Matty

crossley51

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MattyC,

Why did you pick a 23 CG? Did you try anyother CG? I'm glad to hear your report . I knew someone would figure it out.

MattyC-130

My Feedback: (5)

I read the previous posts and it sonded to me it was still nose heavy at 22 CM I also wanted the CG as close as possible to the retracts so it would rotate easily. My main retracts are mounted in the same spot as the fixed gear. I will try to post some pics in the next few days.
MATTY

crossley51

My Feedback: (1)

Matty, Thanks for the info. I'm going to patch it up and try the 23 cm again. The original designer said you will need a little up trim but not 15 degrees. He said it will fly a little nose high but not really noticeable. He also prefered elevons. Are you flying with a little up trim and elevons? I really like the plane and wished they would make it in a bigger version.

crossley51

My Feedback: (1)

It still seems nose heavy with a 23 cm CG. The plane rotated nicely with a little up elevator but nosed down as soon as I backed off a little on the up elevator. I tried moving back to 23.5 and ended up with a complete tail heavy takeoff and stall. If you have a flying BB I would like to talk to you. HELP.... 5053254590

combatpigg

My Feedback: (3)

I haven't heard anyone mention what their birds weigh RTF. The heavier the plane [should rephrase that to higher wing loading], the more critical the CG will be......all the way to the extreme of never finding a workable CG. The published plan that I looked at has the potential to end up a pretty heavy plane for its' size.

Miken96

OK...
I have been playing with this one for awhile... The plans seem to be VERY vauge. I tried the CD from the rear of the aircraft (Just like my Enforcer from Balsa USA) and that did npt seem right. Then I tried to measure from the leading edge (Stupid in theory, but the lack of REAL direction in the plans led me this way) and I still did not feel good. The nose was VERY light and during taxi tests, wouldn't stay on the ground. I have a OS 55AX engine with a 10X6 Pusher Prop. Meaasuring from the leading edge of the slot for the propeller, where is the OPTIMUM CG point located? I would perfer this measurement instead of hte leading edge if possible. Inches or Centimeters...... Whatever works best...

TIA