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Increasing Fuse length and Cof G

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Increasing Fuse length and Cof G

Old 04-24-2016, 04:50 AM
  #51  
ron ward
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da Rock has it right.
although the balance point changes it s the influence that the tail moment has on the CG that is changing how the glider flies .the tail moment's effect on attitude work through the CG the pane's attitude is dependent on where the CG is, in relation to the center of lit created by the wing's airfoil. the CG isn't necessarily moving, the center of lift is moving in relation to the CG., so it affects the attitude the plane has in relation to the balance between lift and the influence that the tail surfaces have on steering the lift produced. that produces level flight. when that balance is equal, it produces level flight, if that balance is biased rearward or forward, lift overtakes steering and the planes attitude is upset, making it do loops,or dives. in either case the CG doesn't change, the distance between center of lift and CG is what changes. when that changes, it changes the influence the tail surfaces have on the plane's attitude in flight.
Old 04-25-2016, 04:28 AM
  #52  
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Default C/g goes with wing

Originally Posted by ron ward View Post
da Rock has it right.
although the balance point changes it s the influence that the tail moment has on the CG that is changing how the glider flies .the tail moment's effect on attitude work through the CG the pane's attitude is dependent on where the CG is, in relation to the center of lit created by the wing's airfoil. the CG isn't necessarily moving, the center of lift is moving in relation to the CG., so it affects the attitude the plane has in relation to the balance between lift and the influence that the tail surfaces have on steering the lift produced. that produces level flight. when that balance is equal, it produces level flight, if that balance is biased rearward or forward, lift overtakes steering and the planes attitude is upset, making it do loops,or dives. in either case the CG doesn't change, the distance between center of lift and CG is what changes. when that changes, it changes the influence the tail surfaces have on the plane's attitude in flight.
{ in either case the CG doesn't change}
GOT THAT PART RIGHT. C/G IS LOCATED" ON WING."


FLYING WING STILL HAS C/G ..
COME ON GUYS !!!

CAN FIND, C/G OF ANY PLANE, IN 3 MINUTES WITH RULER.
Old 04-26-2016, 03:54 AM
  #53  
da Rock
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Originally Posted by RAPPTOR View Post
{ in either case the CG doesn't change}
GOT THAT PART RIGHT. C/G IS LOCATED" ON WING."


FLYING WING STILL HAS C/G ..
COME ON GUYS !!!

CAN FIND, C/G OF ANY PLANE, IN 3 MINUTES WITH RULER.
Flying wings also have close to zero CG range. My 60size Corsair however has close to 2" of forward-aft safe range for it's CG, and thanks to that it has been possible to take off and land without nosing over and tearing the prop and cowl to pieces. None of the retracts that fit it, actually fit it properly. None of them would place the tire foot prints far enough forward and also retract those wheels into the wheel wells. So I ran the pitch stability formulas to see how far aft the balance point could be and shifted the CG as far back as safe. AND knowing the elevator efficiency would increase, the dual rates were setup for that. Gear design is as complex as CG location. The tire foot prints for conventional gear need to be angled 15-20 degrees forward of the MOST FORWARD CG location for safe ground handling. Also, the actual location of the CG has to be used, not it's balance point designation on the wing. Shifting a couple of servos far aft moved the CG over an inch behind the mfg's suggested CG. The plane is no longer a noseover about to happen.

As for flying wings having a CG, yup. They also have pitch stability that's controlled by something else they have, an elevator that's sized to suit the requirements. And the CG range is also figured out beforehand. It's so narrow the actively flying full scale ones were designed with that overriding thought. For example, the bomb load of the B1 was penciled in exactly on the spanwise CG so the CG wouldn't shift when those bombs were dropped. And that took some head scratching because the fuel tanks were in the way. They couldn't be placed very far from the CG Scl either. But before they started cutting the parts out, they very carefully worked out what size the tail volume would be. And then tested that in the wind tunnel. Tail volume is the size of the tail and how far aft of the CG it's going to be. How far aft or forward the volume is would be called tail moment. It's a lot easier to measure when there isn't a fuselage, btw.

Last edited by da Rock; 04-26-2016 at 07:34 AM.
Old 04-26-2016, 06:33 AM
  #54  
da Rock
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The CG affects and is affected by lots of other things. The air balance of my Corsair truly wasn't as important to begin with as it's ground balance. If you can't get it into the air, how it flies really doesn't matter, does it.



Where the CG is "on the wing" often isn't that important. The layout above came from R/C Model Aircraft Design, by Andy Lennon. It shows where the CG actually is, the one of many that is used to figure out where the foot print of the tires need to be for successful ground handling.

Notice the top blueprint refers to the "forward most" CG. The lower diagram shows the "aftmost CG". Notice also the CGs shown don't happen to be inside the wing at all. What is usually talked about in our ARF models assembly notes is actually a balance point. It's absolutely positively great info to have, but knowing the full range of safe CGs you get from running the formula twice gives you far more than twice as much info.

It takes very little "extra" time to measure both the wing and the tail. What you get actually fits the airplane the way it's laid out.

Being able to fix the Corsair's ground handling without going outside it's pitch stability envelope was one result of using the correct formulas. Knowing to adjust the elevator throws to make the maiden flight easier on the pilot was a really good extra.
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Last edited by da Rock; 04-26-2016 at 06:38 AM.
Old 04-26-2016, 06:37 AM
  #55  
Lone Star Charles
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Originally Posted by da Rock View Post
The tire foot prints for tricycle gear need to be angled 15-20 degrees forward of the MOST FORWARD CG location for safe ground handling.
I suspect that you mean conventional gear.

Cheers
Charles
Old 04-26-2016, 07:31 AM
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da Rock
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Originally Posted by Lone Star Charles View Post
I suspect that you mean conventional gear.

Cheers
Charles
it's cool that people actually read some of this stuff.... thanks
Old 04-26-2016, 12:59 PM
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ron ward
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i would hope he means conventional gear !.

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