Wing tip stalls

mat Redsell wrote:

Common knowlege about Glider wing designs says that a high taper ratio will
lead to Wing tip stalls.

However in our flights and research we have found that a straight or forward
swept flying wing will not stall a wing tip despite the very narrow chord
( renolds numbers of 325,000) and lack of washout at the tip. I can attempt
a stall in the Pioneer IId by bringing the stick slowly all the way back
giving a CL of about 1.5 at 32 mph. We do have some separation at the root
but there is no sudden wing tip stall despite no washout at the tips. The
glider itself will not stall.

The "modern" gliders don't have problems with tip stalls under the same
straight ahead stalls, either. They might have some washout, but may
instead use different airfoils at the root and tip. Winglets can also be
used to prevent tip stalling, and many gliders now have swept back
leading edges that probably reduce the tip stall likelihood. Taper ratio
isn't a very useful predictor for this problem, and it is barely
mentioned in Fundamentals of Sailplane Design.

Turning stalls are the ones you need to study, because almost every
glider can have a tip stall during a turn.


In the gliders I also fly with tails, Grob 103 and 102 there is also a
reluctance to not stall a wing tip but that is perhaps due to the washout at
the tips.

Does the wing tip stall suddenly in some of the high performance ships that
may not have the amount of washout that the lower performing ships? What
gliders if any do stall a wing tip easily?

I don't think this is a problem in the "modern" high performance glider.
The ones I've flown are generally quite benign in stalls, both straight
ahead and turning.

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Eric Greenwell
Washington State
USA