Thread: Ventus 3
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Old December 27th 15, 09:56 AM posted to rec.aviation.soaring
J. Nieuwenhuize
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Default Ventus 3

Op vrijdag 25 december 2015 02:38:04 UTC+1 schreef :
On Thursday, December 24, 2015 at 4:56:27 PM UTC-5, Jonathan St. Cloud wrote:
One aerodynamicist explained that it is a benefit in climb but has a penalty in cruise. It does look cool though. Word on the street it is a three year wait for a new Ventus


I spoke at length with Tilo at the factory this year regarding the new V3.. He had put together a crack team, with many aerodynamicists outside the direct employment of SH to design a wing whose purpose is for less time thermalling and more time in level flight. I doubt that they would purposely design such a wing that pays more of a penality in straight flight. Tilo specifically mentioned that newer models of optimal lift theory/design account for a three dimensional model that dictates the need for dihedral for straight flight optimization of lift. His words, not mine. The wing is amazing when seen in person. Photographs do not do it justice.



If we go back to theory, the perfect wing is a double super-ellipse (Lamé curve):
http://en.wikipedia.org/wiki/Superellipse

Both the top view and the dihedral of the wing should have the shape of a super-ellipse for lowest induced drag for a given bending moment (structural weight) and wetted area (profile drag at high speeds). Both the A350 and the Dreamliner are very close to this ideal:
wallpaperswide.com/download/boeing_787_dreamliner-wallpaper-1920x1200.jpg

Another plus compared to a wing without dihedral and winglets is that the interference drag between the winglet and the wing is much reduced since it's proportional to the radius of the fillet and how sharp the break is.

Such a gradually curved wing is impossible to build because all the control surfaces would have a bend in them. The wing with sections progressively canted more and more (polyhedral) is a good compromise.

It also helps with flutter apparantly. The Vortex shedding frequency of the various sections make the critical flutter speed for such a wing higher, allowing either a higher VNE, or a less stiff and thus lighter wing structure.