Vortex generators, slow the plane down?

[rogerh12]

Howdy All;

I was thinking about shortining my model 4 wings a bit, and installing vortex generators to bring the stall speed back down. I thought shorter wings would let the plane go faster in cruise. However, won't the vortex generators just add more drag again and even things out?

Any hard facts on this?

Thanks
Roger

[Newkid]

The two won't make up for each other. The shorter wing only goes 2-3 mph faster but raises the stall considerably. The VGs won't make up for not having the longer wing. The short wing will role a lot faster and give you a better ride in turbulence, and you will still probably be able to go everywhere you go now. I've never heard of VGs slowing a plane down on the top end. Everyone one has different opinions on what installing VGs did for their plane.

[catz631]

I have VG's on my plane but can't say they do much. Look cool though.

[jtpitkin06]

Catz,

The vortex generators in your photo look like they are mounted too far aft.

It is likely the air has already separated from the airfoil by the time it gets to the generators. Did anyone do flight testing of these VG in other positions before selling them to you. Or did they just "wing it" in the mounting instructions? There are several suppliers making generators for experimental airplanes who have never tested them on a Kitfox and market them as good "for any airplane".

I have a Cardinal RG and there are some STCs for VGs on them. All of them are mounted much further forward, and yes, they do slow the airplane down a bit in cruise. The owners who install VGs are looking for slower approach speeds and shorter landing distance for the airfields they fly in and out of. They are willing to give up some on the top end.

I suspect the same is true for the Kitfox.

We're still looking for that free lunch.

John Pitkin
Greenville, TX

[akflyer]

I have VG's on my plane but can't say they do much. Look cool though.

WAY too far aft and the spacing is effed up too..

[kitfoxnick]

Way to far back. I seem to remember 8% of wing cord. I love mine no decrease in top end. My stall speed wasn't drastically reduced maybe a knot or two. Totally different plane at slow speed.

[BigJohn]

I would agree that your's are way to far aft. I put VG's on my KF-5 and found significant improvement. 4-5mph on light loading and upto 9mph at full gross in lower stall speeds and significant improvement on handling.

Here a a couple of photo's on Mine. Also I noticed no change in Cruise Speed, However my Max Speed did loose approx 3mph, Not an issue and the benefit was worth all the effort.