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V dihedral vs polyhedral wing

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V dihedral vs polyhedral wing

Old 09-17-2011, 09:19 AM
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Default V dihedral vs polyhedral wing

I am wondering which is more efficient on a RES glider? In a turn which has more turning effect, and stability. Thanks
Old 09-17-2011, 12:41 PM
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Default RE: V dihedral vs polyhedral wing

Polyhedral is more efficient because the tips have more lever to bank the plane, while the roots loose less lifting capability.
Old 10-05-2011, 06:48 AM
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Default RE: V dihedral vs polyhedral wing

poly is better starting the turn

V is better in the turn
Old 10-05-2011, 03:17 PM
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Default RE: V dihedral vs polyhedral wing

With polyhedral you can get away with slightly less overall dihedral because it puts the most effective angle out at the tips where the leverage is greater.

Technically the flatter inner panels are also giving up less of their effective lift as well. But with the slight extra drag from the airflow around the dihedral break it comes out as a wash.

Overall I prefer polyhedral for the snappier turn response which makes the model more controllable. You can achieve the same response with V dihedral but the angles needed to match the effectiveness of polyhedral leaves the model looking like a gliding pigeon...
Old 10-07-2011, 07:17 PM
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Default RE: V dihedral vs polyhedral wing

Polyhedral will be quick to turn. Irecently completed and have many flights now with a Great Planes Spirit. A true polyhedral wing. They are easy to turn and they find their own way to level out both left / right and up / down. At any point in time, given you have enough altitude, you can let go completely the controls and it will find it's own way to return to straight and level flight. However, they lose a little bit of glide ratio, as opposed to dihedral.
Old 10-09-2011, 09:33 PM
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Default RE: V dihedral vs polyhedral wing

In reality the difference in flight characteristics and wing efficiency of well designed V-dihedral vs. polyhedral wings is (very) small.
Nearly identical flight performance of wings can be achieved by calculating the Equivalent Dihedral angle between V-dihedral and polyhedral wings.
Wings of the same wing area and aspect ratio that have the same Equivalent Dihedral Angle (even though one wing is V-Dihedral and the other is Polyhedral) should have, to first order, equal roll characteristics.
(In the real world, other factors do come into play like the mass or weight of each wing and particularly the mass of the outer tip panels - for excellent roll performance it is highly desirable to have very light tips as this minimizes angular inertia - but if both the V-dihedral and Polyhedral wing have about the same weight and have the same Equivalent Dihedral angle, they should have about the same roll characteristics).

A fine reference that will allow you to design both V-dihedral and polyhedral wings with equivalent roll characteristics (equivalent roll moment) is the following:

Calculation of Equivalent Dihedral Angle
by Blaine K. Beron-Rawdon

EDA is a major factor in roll response, roll rate and spiral stability.
-RJS (Best wishes)

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