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Old Nov 03, 2012, 01:51 PM
I don't like your altitude
Stupot46's Avatar
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Quote:
Originally Posted by HerkS View Post
This plank flew quite well with just the tip fins.
It did have the drag rudders at that time, but the directional stability was fine when no control inputs were being made. Deleting the central fin and rudder had almost no noticeable effect. Maybe I should make a few more test flights with it. The drag rudders have been removed and plain ailerons are installed at this time.

This model has no sweep, no taper and no twist.
Missed the one that answered my question!No toe in on these it would appear.
Thanks guys,got me a bit further down the road.
Regards Stuart.
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Old Nov 03, 2012, 02:27 PM
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Knoll53's Avatar
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Quote:
Originally Posted by HerkS View Post
This model has no sweep, no taper and no twist.
Now THAT'S a plank !

Maybe you should take the project name Plank 101?

Kent
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Old Nov 04, 2012, 07:15 AM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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My first go at a planform.One piece wing,with a fuselage.
Tip fins initially.
Any comments/advice would be appreciated.
Stuart
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Old Nov 04, 2012, 07:20 AM
I don't like your altitude
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Quote:
Originally Posted by Knoll53 View Post
Now THAT'S a plank !

Maybe you should take the project name Plank 101?

Kent
Nah,that ones Max Plan(c)k
Stuart
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Old Nov 11, 2012, 03:17 PM
Just call me crash for short
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United States, OH, The Plains
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Pitch-O-Plank (POP)

I've had this idea bouncing around for a while now and would like to get some outside thoughts on the subject. Below is a scaled down prototype of the idea. Should be fast to build and not much material gone if it doesn't work out. The plan is to move the entire tips of the wing (last 4" on a 16" half span) for pitchoron control.

I have no worries about roll as that is an easy given. Pitch control however might be an area of some debate?? Unless anyone has a real good reason that there is no way this would ever work, think I'll cut the parts in the next day or so as I am itching to give a real run with the new (just finished) CNC router.

If this does work out, I'd eventually like to scale it up to 2 -3 m and drop (or make optional) the motor. Airfoil is the Wortmann FX-66-H-120 12% - Thoughts?

Mark
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Old Nov 11, 2012, 04:53 PM
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I'll bet 10 quid that it DOES work ! By changing the AoA of the entire wing tip you'll be able to control pitch no problem. Use a plank airfoil and it will jump when you pull back on the stick, ESPECIALLY if the CG is pushed way back to 3% static margin.

If you are going to let the covering sag between the ribs, I'd suggest at thickened PW51. Very happy with the Plank 101.

Have you named this little bugger yet?

Kent
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Old Nov 11, 2012, 05:42 PM
Just call me crash for short
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Quote:
Originally Posted by Knoll53 View Post
I'll bet 10 quid that it DOES work ! By changing the AoA of the entire wing tip you'll be able to control pitch no problem. Use a plank airfoil and it will jump when you pull back on the stick, ESPECIALLY if the CG is pushed way back to 3% static margin.

If you are going to let the covering sag between the ribs, I'd suggest at thickened PW51. Very happy with the Plank 101.

Have you named this little bugger yet?

Kent
Thanks Kent. the FX-66-H is a plank airfoil, most notably used on the Charles Fauvel AV36 /48 and a few others (full scale at 15.9%) though that thick does not look good for the lower re numbers. I'm thinking it should work too, at least that is what my TLAR scenes is telling me anyway. So maybe I'll go ahead and crank out the Gcode tonight.... AFTER The Walking Dead

Name? Humm, maybe TWIP? (Twist WIng Plank). Or sense the wing was somewhat inspired by Paul Plecan's Manta, maybe call it Manta-Pitch? Maybe just The P-O-P, (Pitch-O-Plank). I'll have to give it some thought. Any suggestions?

Mark
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Last edited by Quick61; Nov 11, 2012 at 05:49 PM.
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Old Nov 11, 2012, 05:54 PM
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Can't believe that I missed the TITLE !

Pitch-O-Plank is brilliant. Other than that maybe something about the natural look.

You're giving my Samurdactyl a run the money.

Even if you put a thick airfoil in it, the covering sag will thin it down.

The Plank 101 only took 19 days to build, including the time waiting for parts to be cut. Beat that !

Kent
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Old Nov 11, 2012, 06:01 PM
Just call me crash for short
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Quote:
Originally Posted by Knoll53 View Post
Can't believe that I missed the TITLE !

Pitch-O-Plank is brilliant. Other than that maybe something about the natural look.

You're giving my Samurdactyl a run the money.

Even if you put a thick airfoil in it, the covering sag will thin it down.

The Plank 101 only took 19 days to build, including the time waiting for parts to be cut. Beat that !

Kent
Well, sense my waiting on "parts to be cut" will be a matter of minuets instead of days, I just might be able to. The one thing that could hold me up to getting it in the air would be if my LiPo I have planed for it will still take a charge. Haven't used it in a coons age and it was not the best when i last had it in the air so i might need to order another one. We'll see.

Mark
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Old Nov 11, 2012, 08:59 PM
internet gadfly
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Quote:
Originally Posted by Quick61 View Post

I have no worries about roll as that is an easy given. Pitch control however might be an area of some debate?? Unless anyone has a real good reason that there is no way this would ever work, think I'll cut the parts in the next day or so as I am itching to give a real run with the new (just finished) CNC router.
I don't see how rotating wing tips could affect pitch unless the aerodynamic center of the movable section is significantly forward or aft of the lateral axis that passes through the CG. Simply changing the angle of attack doesn't significantly change the airfoil pitching moment and, as I understand it, you have to change the airfoil pitching moment to affect pitch in a 'wing with no external surfaces or 1/4 chord sweep.

--Norm
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Old Nov 12, 2012, 12:33 AM
Just call me crash for short
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Quote:
Originally Posted by nmasters View Post
I don't see how rotating wing tips could affect pitch unless the aerodynamic center of the movable section is significantly forward or aft of the lateral axis that passes through the CG. Simply changing the angle of attack doesn't significantly change the airfoil pitching moment and, as I understand it, you have to change the airfoil pitching moment to affect pitch in a 'wing with no external surfaces or 1/4 chord sweep.

--Norm
Your counsel on these matters is to far and few in between Norm, I miss your insight. Well, the pivot point is at 25% on the root of the rotating chord, so it is more than likely close to the aerodynamic center of the pitching tip section. With that given, where would you put the axial for the tip section in percentage of chord? Would moving it forward to something like 10% be enough to "reasonably" affect pitch? Moving the axial forward would be far more preferable than aft, mechanically speaking. At this point it would be an easy thing to change as no parts are cut yet.

Mark
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Old Nov 12, 2012, 01:08 PM
internet gadfly
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So you're thinking of using the internal torque reaction of the servos to affect pitch? Interesting but I doubt there would be enough torque to get good pitch control. It seems to me that no matter where you put the axis the torque will be equal and opposite so the net pitching moment will be zero but I'm having a hard time visualizing what might happen with the axis significantly ahead of the 1/4 chord so it's not unlikely that I'm wrong. Yeah, that happens a lot, you just don't hear about it. So anyway I'm pretty sure that this would work if you put an anti-servo tab on the wing so if the floating tips don't work by themselves you could try that.

--Norm
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Old Nov 12, 2012, 01:32 PM
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So Mark, I'm not really familiar with these pitcheron type planes. How were you thinking of controlling the tip? With a pin in a slot?

Kent
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Old Nov 12, 2012, 02:25 PM
Just call me crash for short
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To answer the question of how I am thinking of moving the tips I'll just drop a few pics in to help along. The first is the fuse section that has the servos. The servo works a crank that is attached to a 3mm CF tube that acts as the axle. That tube rides inside the 5mm spar that doubles as the axle housing. The 5mm spar/axle housing ends at the separation point between the fixed part of the wing and the rotating tip as shown in the second X-ray pic. The 3mm axle continues on, attached to the rotating end section of the wing. 3rd pic is showing the tip in a rotated state. That clear a few things up?

Mark
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Old Nov 12, 2012, 02:38 PM
Just call me crash for short
Quick61's Avatar
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Joined Jan 2011
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Giving this a little more thought, if the tips are really going to struggle at the job of affecting pitch, they could be just left to the task of roll, (a job which I think we all believe they will work well at), and add in elevators back at the root, maybe 1/3 span each side?

Mark
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