Vortex generators

[Rynoth]

Graeme, per the plans, the outermost wing rib is in the exact same orientation/angle of incidence as the root ribs. No twist or washout. The wing should be a flat rectangle hershey bar. The only reason there is even dihedral to the wings is because the bottom spar is shorter than the top spar, with reinforcement added to angled bottom edge where it passes through the spar tunnel.

[Sonex1517]

I cannot speak to the design aspect. I can address what we found when we built our wings.

We used a laser to ensure the wing was being built straight. It shot right down the clecoes on the wing skin without any twist. And that was at the leading edge, the trailing edge, and above the spar.

I’m sure others have a better answer.

(Edited to add - see? Ryan had a better answer!)

[GraemeSmith]

Robbie,

I believe you! I think your VG's are probably doing something along the lines of what you think they are doing for you. :-)

Attached a test flight report of flying my Sonex wing with and without VG's. I have to stress that this is a VERY limited data set but that I got some measurable trends that are probably worth further exploration if people want to explore VG's further.

And some of the video:

Sonex 1153 VG Tests.pdf

VG Test Flight Report

(527.11 KiB) Downloaded 671 times

Popcorn anyone?

[Rynoth]

Graeme, I love it! Great video and awesome write-up. I feel like pointing out that KIAS, unless painstakingly calibrated, it's going to vary from aircraft to aircraft. There's no way I'd see under 30 KIAS in my plane before being in a deep stall. However since you are using the same setup for your various tests it doesn't really matter for your comparisons. I just know that even with VG's I won't be seeing 18kts on the indicator and still be flying =D

[GraemeSmith]

Ryan - yep the calibration error is there and I think I alluded to trying to keep everything else the same to get some kind of a comparison.

Interestingly though - on still air days when I can use the GPS speed to compare to the ASI - it's not out THAT much. At 20 KIAS the plane is probably doing about 22 K Ground Speed at Sea Level. It's just that she is mushing downhill at 500fpm! In a stable(ish) attitude. She ain't flying. But she is controllable.

[WesRagle]

That was great Graeme!

Thanks,

Wes

[Sonex1517]

Very cool Graeme!

I will point out your VG’s are significantly larger than the ones I installed.

Please pass the popcorn.

[GraemeSmith]

Please pass the popcorn.

You want 'butter' with that?

[Sonex1517]

Lots of butter and some salt, please. This could get interesting!

Watching the video, it was interesting seeing the tufts break fairly evenly back at the inboard section of the wing. I’m not smart enough to know why. I’m sure someone can explain it.

Your video was also sent to me just as I finished watching it by a friend who is building an RV, so whatever tags you put on it worked!

[Carlos Trigo]

What is your opinion on using VG’s in a XENOS wing, for soaring?