Testing VG'S under the leading edge.

[TJay 1041]

[ChrisBolkan 130]

That's interesting. I read that years ago and was interested in experimenting with it but never did. As I see it, there should be no difference at high angles of attack and slower flight like on landing. VGs on top would affect that.

It seems that any beneficial difference would be at the fastest possible cruise speed when the air is (maybe) stalled out under the leading edge of the wing due to the under camber. Is it really stalled out? I don't know. But if it were stalling it would be at the highest cruise shallowest angle of attack, and closer to the tips of the wings where washout is greatest, right?

So IF the air is stalling under the outer portion of the wing at your maximum cruise speed when angle of attack is least, then the VG's should make that air stick better to the wing, reduce drag and increase your top speed potentially, right?

I don't know. Just thinking out loud. It might be that IF this is true and it WILL work, that the engines we are running don't have enough power to actually get the angle of attack flat enough to get the air to stall out under the portion of wing with the shallowest angle of attack, which would actually be the steepest angle of attack under the wing, right?

Maybe a dive could test the theory if engine power alone won't? But how would you actually measure and improvement in cruise speed or wing efficiency at high speed? 

I'm way out of my league here, but it is sure fun to think about!

Chris

[1avidflyer 1983]

Just looking at and thinking about this some more.  I wonder what a  video would have looked like with yarn in place, but not having the VGs there. How much does the twist in the wing effect what's happening?  I don't know, but like you say Chris, I'm out of my league, but it's fun to think about..  JImChuk

[TJay 1041]

Not sure If Ill do anymore testing on this subject. Kind of an erie feeling doing this stuff but I had to find out what Harry Riblett was talking about and Now I some what understand it.

[1avidflyer 1983]

For sure not asking you to do something dangerous, but it would be interesting to see the whole bottom of the wing with yarn and no VGs.  JImChuk

[TJay 1041]

The yarn that broke off by the lift strut was facing forward most of the time ha. With that method you could really pinpoint where to clean these airplanes up.

[SuberAvid 617]

Great test, thanks TJay.  I had tried them on the underside of my original HH wings several years ago and and could tell no difference in performance slow or fast, but never put yarn on the wing.  That was interesting to see.