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Old Sep 08, 2012, 09:25 AM
KillerCut is offline
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Discussion

Self stabilizing through vertical fins?


I like the parkzone stykers a lot, especially if built light. I just dont like that I cant fly perfectly straight for over 15 seconds without having to correct. How could I modify the vertical fins in order to give it some self stabilizing ability? Or its just not going to happen because the center of gravity between the top and bottom is too much towards the top of the plane?
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Old Sep 08, 2012, 12:47 PM
djacob7 is offline
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Zen in the art of foam
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I think that flat wings always need some correction. A slight dihedral will stabilize it. Or flared wing tips.
Old Sep 08, 2012, 01:43 PM
vincent123 is offline
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InceCreations
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Hi,

when the vertical fins are placed at the wing tips, they act as winglets, with 2 advantages:
1) more lift and less drag
2) when placed toe in, they will be self stabilizing

Vincent
Old Sep 08, 2012, 02:07 PM
KillerCut is offline
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flared wing tips? like winglets that are not vertical? 45degrees or so?

Toe in? so they form an upside down V ?

Like this (sorry I'm bad at art, lol)?
Old Sep 08, 2012, 10:33 PM
KillerCut is offline
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ohh I get what you mean by toe in, but that wont keep the plane level, that would just cause more drag....
Old Sep 09, 2012, 02:19 AM
vincent123 is offline
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InceCreations
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What kind of stability do you want? Yaw, pitch?
Creating stability, means accepting drag, when talking about fins.

Wingtips can be vertical, toe in is having an angle in flight direction of about 2-4degrees.
Drag is limited, but yaw stability increases a lot.

Pitch stability: is your cg correct, not too much backward?
Line of trust above or below the cg? Best is to have it in line with the cg.

Hopes this gives you ideas

Vincent
Old Sep 09, 2012, 01:44 PM
KillerCut is offline
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ROLL stability

http://www.grc.nasa.gov/WWW/k-12/airplane/roll.html

If it just had some roll stability, it would fly perfectly straight forever...
Last edited by KillerCut; Sep 09, 2012 at 02:08 PM.
Old Sep 10, 2012, 02:01 PM
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InceCreations
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Google "dutch roll": is that what you see?
Old Sep 10, 2012, 04:23 PM
KillerCut is offline
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no, well, only at very low speeds, like 5mph or less...

I only have problems with roll instability, it goes straight for 10-15 seconds and then starts leaning to one side or the other, and eventually it will drop the wing all the way and nose dive...
Old Sep 10, 2012, 04:45 PM
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Does it not start leaning until AFTER 10-15 seconds, or is it a constant thing you have to correct after opening the throttle? Almost sounds like torque. I have a similar situation with my Prodigy wing, and the effect is exaggerated when I run a larger prop, and that's further exaggerated the more I open the throttle.
Old Sep 10, 2012, 05:23 PM
KillerCut is offline
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Its the normal thing most planes do. If you set it straight and level then let go of the sticks, it will eventually lean to one side or the other. I have it trimmed out perfectly. It doesn't start to turn to one side in particular, just a gust of wind gets it to start to lean to one side and then it drops the wing slowly until its heading straight down nose first..

It could take 10-15 seconds, sometimes 2-5 seconds, depending on how windy it is. If there is zero wind, it could probably take 30+ seconds until it starts turning...

It would be nice if I can set it straight and level and watch my fpv monitor for a minute or 2 without having to correct...
Old Sep 10, 2012, 07:49 PM
ray foley is offline
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volare est vivere
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hi there from Toledo

Gyro stablization of the roll axis could help with that or maybe an FMA Pilot system or a way point GPS control system. Have fun researching.

ciao -rjf
Old Sep 10, 2012, 08:16 PM
KillerCut is offline
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I dont want to add weight, I was hoping to do it with fins or winglets...


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