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Stubby Fat Plane hates right turns!!

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Old 09-28-2012, 06:43 AM
  #26
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Default RE: Stubby Fat Plane hates right turns!!

Thanks for all the helpful suggestions! If I go the "rudder increase route" I will definately use the temporary cardstock method! Some questions regarding the "Volume of Fuselage aft of the CG" issue. I'm trying to mentally develope an image of what might be at play. For instance, on a sailplane, lotsa wing, more than this of course, but some with just a stick for aft fuselage....really no volume at all. Is this effect different on a stubby short coupled type? Or is this an issue of there is a lot forward, so aft should be similar on this particular shape? And what is the moment or effect? Is this important because of airflow from the propwash striking these surfaces, or a balance issue involving percieved weight? Trying to wrap my brain around all the angles....lol.

ZZ.

PS. The plan (as it stands currently) is to employ a Master Airscrew 10x5 3blade prop to see if it makes any difference. Then, try some rudder increases as was suggested here.

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Old 09-28-2012, 10:15 AM
  #27
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Default RE: Stubby Fat Plane hates right turns!!

Let me start by saying that I'm a lifelong free-flighter and my R/C experience has been with rudder/elevator models only. Looking at your side view photo it appears that the fuselage is about neutral as far as side area, but the flat cowl and the rudder (It seems quite small for such a short coupled model) appear to be about the same area, throw in the flat wheels and it appears that you have more side area up front. My free flight mind says this will be a difficult situation. My gut instincts say more rudder/fin area. By the way, thin flat wheels also make very effective control surfaces if they are at all mis-aligned! The ailerons due to the short wing and their distance above the centerline would seem to limit their effectiveness in rolling the aircraft.

Just my free-flight perspective. Good luck with the project.

John
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Old 09-28-2012, 12:38 PM
  #28
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Default RE: Stubby Fat Plane hates right turns!!

Thanks John. You free flighters do have to be quite precise don't you? That can be helpful. I've changed the wheels out to more fat ones (almost 3 times as thick as the old ones), and moved them closer into the fuselage. Hopefully that will reduce the control surface effect you mentioned they could have. You are dead on with the ailerons being pretty innefective. They will pitch the plane (somewhat) however. I've installed a 3 blade prop and am waiting for another test hop to see what this might do. If however this is innefective, the larger rudder is next on the list.

ZZ.
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Old 09-28-2012, 12:58 PM
  #29
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Default RE: Stubby Fat Plane hates right turns!!

Have you flown this without the pilot? The wake from his turned head may be the issue. I would agree the rudder could be bigger, but IMOit is not so small. I would use a fla bottom wing. If you need this to look cartoonish then just leave it undercambered outboard of the struts and flat inboard.
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Old 09-28-2012, 03:20 PM
  #30
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Default RE: Stubby Fat Plane hates right turns!!

Ailerons do not turn an airplane. The rudder does. The rudder can be big medicine!
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Old 09-28-2012, 08:09 PM
  #31
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Default RE: Stubby Fat Plane hates right turns!!

Yes, pilot has no effect as he has been removed during testing. Undercambered airfoil is mandatory....part of the design parameters for build simplicity, and I like the slow floaty characteristics it imparts on the flight dynamics. I've had her aloft about six times, every time producing further refinement in handling and control. This turn thing is the last real barrier to overcome. Got the three blade prop installed today....perhaps soon a test run will prove:

1. whether I chose correctly and this 3 blader will have enough umph to get her off the ground.

and 2. If it solves the left torque issue that resisits the right turn.

ZZ.
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Old 09-29-2012, 07:37 AM
  #32
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Default RE: Stubby Fat Plane hates right turns!!

SUCCESS!! Conducted taxi tests with the new 3 blade master airscrew 10x5. Power seemed adequate, so I said, "what the hey" and gave her the gun. That three blader spun up into a whistling whine that sounded like a WWII corsair, and sped out on the nicest taxi and lift off you ever saw. I climbed gently to 3 mistakes high (turning lef the whole time...lol) and then once all seemed well trimmed, hit right rudder, she began to turn, I then added in a smidge of aileron to help and over she went...a touch more slowly than the left turn, but she went! What a sight. So I'm pretty stoked[8D]. I need to get a three blade spinner, adjust tweak some control throws a tad more for further refinement, but it seems overall, that she is over the final barrier. Granted, this design is unusual and will take certain considerations from the pilot to understand its nature before flying, but she seems calmed down enough to make that manageable now. One example, I've learned that due to the right thrust in the engine which counters the torque from the prop which is very strong due to the short wing plan, when landing you reduce throttle when the field is to the left of the machine, it turns itself onto final when the engine spools down and that right thrust disappears! So you kill throttle, she swings left, and you then line her up with 1/3 throttle, and landing is pretty standard after that. Just one of the small oddities of the design.

ZZ.
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Old 09-29-2012, 11:14 AM
  #33
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Default RE: Stubby Fat Plane hates right turns!!

Congratulations on getting the problem worked out. That is a very cool plane!
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Old 09-29-2012, 08:44 PM
  #34
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Default RE: Stubby Fat Plane hates right turns!!

Many thanks. I'll have to get some video shot now...always more to do. Then think about drawing up plans. geeeeesh

ZZ.

PS, that is of course if anybody thinks they would really want to build one....which I'm questioning. It is pretty strange after all.
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Old 09-29-2012, 10:03 PM
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Default RE: Stubby Fat Plane hates right turns!!

Coke or Pepsi?
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