Would it not make more sense to just wait for the results instead of panning it?
THEY CLAIM a 30% reduction in induced drag. Unless the baseline design they're comparing to is really awful, there simply isn't 30% worth of improvement there to be made, not without making substantial increases in wing span.
A wing makes lift by grabbing chunks of air and shoving them down. Assuming you're using the air the wing grabs reasonably efficiently to begin with (i.e.: a spanwise lift distribution that's reasonably close to elliptical), the only way to make a substantial improvement in induced drag for a given amount of lift is to grab a bigger chunk of air. To get a 30% reduction in induced drag, you would need to increase the effective span by approximately 20%. It's simple physics. Do you really believe that they can grab a chunk of air that's 20% bigger in diameter by making wingtips that look like curly fries? In addition, that wingtip has a hole with all the flow distortions associated with that, two inside corners at the inboard end of the hole that also disturb the flow over the upper surface of the wing in that region, and that little vane creates additional inside corners with more interference drag, and a whole bunch more whetted area, all of which eats away some of whatever induced drag benefits it might have. In addition, they add mass at what's one of the worst possible places to add mass, degrading the dynamic stability and handling and probably needing a bigger tail to compensate. As far as the tips being removable for test, unless they have conventional tips to replace them, they're testing a reduced span conventional layout against an increased-span winglet design. Not exactly a valid comparison.
There are folks out there trying to tell us that if we install their little piece of modified window screen in our car's carburetor, it will get 30% better gas mileage. Those claims are also obviously bogus, even a rudimentary knowledge of physics will tell you that.
If the folks promoting these new wingtips had claimed a few percent instead of 30%, it might be more believable. In any case, they have claimed an unbelievable (and I chose that word very carefully) improvement, and they need to substantiate it.
The easiest way to make a 30% improvement in induced drag is to make a 30% reduction in weight for a given span. That's very do-able, and entirely in keeping with the laws of physics.
Don Stackhouse @ DJ Aerotech [EMAIL PROTECTED] http://www.djaerotech.com
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