Stol Speed Vortex Generators

[BDA]

Spent ALL DAY installing VGs today.

Cool little doodads.

The glue stickum stuff is way cool. Very sticky, but no big deal to remove with a razor blade, peel glue off the reapply.

I will def order more.

[BDA]

So VGs in front of spoilers seem pointless...

[BDA]

Anyone put vgs on the bottom of the vertical??

[BDA]

The instructions for these VGs say to put them 4” in front of the elevator gap and rudder gap. I understand that this is to energize the air over the gap and hinge point to keep it attached to the tail surface.

But - if I have sealed the gap, the wouldnt the VGs be better on the leading edge??

I need to make a phone call to Australia.

[danerazz]

I think it is more the huge angle change at the joint, even with the gap seals you have a big angle you need energized air over that angle to remain attached behind it. The gap seals just keep it from slipping through the gap and energizing the “wrong” side of the surface.

At high aircraft AOA, the horizontal stabilizer has a very low (negative) AOA and the elevator is most likely in a position of high, or at least positive, AOA. You are trying to get that air to stay attached to the elevator at it’s relative AOA. Remember, tails produce lift primarily downward. You have to think of them as inverted wings.

[BDA]

Ok, I can see that... so why then dont we put VGs 4” in front of the flaps?

Does a slotted flap such as ours, not disturb the boundry layer with air through the slot from the bottom??

Or should there be VGs on the flaps themselves.

[Tralika]

If your really curious about Vortex Generators do a web search for "NASA Vortex Generators". Better have some time on your hands because you might be there a while.

[BDA]

Thanks John
There is a ton of info there, I have read a fair amount of it, but too much of it is based on faster wings at a much higher reynolds number than is relevant to us.

I am more interested in real world results on our airplanes by you guys.

[danerazz]

Ok, I can see that... so why then dont we put VGs 4” in front of the flaps?

Does a slotted flap such as ours, not disturb the boundry layer with air through the slot from the bottom??

Or should there be VGs on the flaps themselves.

“Why not” I can’t answer. The slots in slotted flaps are supposed to introduce high energy air from under the wing to over the flap, I do not know all of the intricacies of how well this airflow stays attached. I would think there could be a benefit of VGs on the flap itself, but there would likely be an interference issue when the flaps are retracted.

The metal strip flap gap seals that most seem to be putting on their standard Highlanders help direct this air from just blowing up through the gap to over the top surface of the flaps in a more laminar fashion.

You may not be able to put the VGs far enough forward to be effective AND be able to retract all the way. It would be fun to experiment with though.

I would like to reshape the trailing edge into a smooth “S” curve instead of the folded angles that come with the kit, perhaps put a radius piece in the inside corner at the top. I would like the bottom to have a more gradual approach into the slot as well.

[stede52]

The best type of VG to try on the flaps would be turbulator tape https://wingsandwheels.com/turbulator-dimple-tape.html, I was going to try it on my Highlander but sold it before I had the change. Gliders use this tape in lots of area of the plane