Hall Vortex generators

13 posts in this topic

Posted

I just noticed that Hall,  the makers of the disk style ultralight airspeed indicators also sell VG kits.

These VG's appear to be larger than VG's I have had experience with and are much easier to line up when installing.

Hall also has a 30 day money back policy.

Years ago I tried Micro Aero VG's on my Model 2 Kitfox (undercambered wing) and returned them since I did not notice much if any reduced stall speeds or improved aileron or elevator authority.

A while back Joey noted better elevator effectiveness with STOL speed VG's on the bottom of his horizontal stab.

Has there been VG discussion on this forum in the past?

Any reports on how the Hall VG's have worked on Avid or Fox undercambered wings?

How about Model 4 Kitfox semi symmetrical wings?

Thanks

Herman

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Posted

Herman,

 

Please let us know your experience with them when you try them.  There has been some discussions on the VG's and several are running them as I am.  I have the Land Shorter VG's on my wings and under the HS; they did not reallyy lower the stall much but they did add aeleron authority and elevator authority so I like them and thought they were worth it.  I just ordered a set of STOL Speed VG's and plan to try them on the underside of the wing to see if they will add some speed to my undercamber wing; plus I added the ones to the underside of the tips at mid chord last weekend but have not flown it yet.  I want to try them before I add the ones to the underside of the wing so I can determine the change from each.

 

Randy

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Posted

Thanks Randy for responding.

I asked the same question in TeamKitfox and was directed to some past threads.

Seems like the impressions varied from no difference to some difference in stall speed.

Almost all felt the control authority improved with VG's.

I feel my Model 2 control authority is fine so I will probably not try VG's.

I will be interested in your results since my Kitfox cruises quite slow and burns a lot of fuel with it's under cambered wing and 582.

Herman

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Posted

Very interested in the outcome of under wing VG tests.

Chris

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Posted

I just installed a full set of VG's that I made to the top of my under cambered wing. I extended them across the top of the skylight as well. I forgot to count them but there is a bunch installed now. I ended up making 24 more to finish the job. I did the math and knew how many I needed but I used the 24 before to install under the tips and horizontal stabilizer.

 

I should be able to fly tomorrow morning and see what results I get out of these. The next step will be to make fairings for the fuel caps. I'll write up a different thread for that one after reading about what they may help with.

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Posted

I extended them across the top of the skylight as well.

Ok, help me out here. Why is this a good idea?

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Posted

Any time you can get the boundary layer thicker (thicker is good) it helps overall to reduce pressure drag. With the wider cockpit that the Pursang has I can't help but wonder if there disrupted airflow, which would reduced effectiveness of the tail group or at least very cause very turbulent air. Thus installing them over the top of the skylight may help increase the boundary layer, reduce the pressure drag and allow better and hopefully less disrupted air flow to the rudder and elevator....at least that's my theory.

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Posted

Makes sense. With a bit wider cabin on the Avid+, now I'm curious too. In any event, I thought John raised the H.S. and elevator on the plane, presumably to keep it in clean air or prevent it from getting blanked? Now I need go look for a pic to see how much higher yours is vs. an Avid Mk-IV. Next time you let the owner fly with you, maybe put some tufts back there and see what it looks like?

I also wonder what difference, if any, the flat vertical and rudder would make under the circumstances. Some who have flown Avids with flat tail feathers and Kitfoxes with speedster tail mods comment the Avid tail hunts for center more. My KF3 was all flat and my KF4 has the airfoiled H.S. and elevator, but not the airfoiled vertical. I couldn't tell any difference but was thinking of air foiling everything on my Avid+ tail.

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Posted

John actually dropped the HS down. His reason was that it would be out of the turbulent air of the flaperons and wings down lower. I'm guessing it's about 6" from what I can tell looking at pictures. The elevator is fairly effective, that's never been any issue to me at all. I'm sure it could be bigger so that it would trim out for slower speeds on final and what not. I run out of trim right at about 75 to 80 MPH depending on how I'm loaded.

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Posted (edited)

Doug,

     I think the airfoiled vertical and rudder would probably perform better - from what I have read, the flat horizontal is just about as efficient at Avid speeds as the airfoiled, and the choice is mainly based on looks???

     Looks like John lowered the horizontal to about where the Kitfox has it?

EDMO

Edited by Ed In Missouri

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Posted

THanks for the above info- may have some more please? LOL

Im just starting to fly the HH I bought and was rather surprised at its stall speed. I always thought Avid/KF would be lower. While it’s is pretty much right where the plans say it should be I would like better handling at the lower speeds. It is the HH wing with the flat HS and rudder. Would I gain that much by installing both wing and tail?

appreciate the information amd help

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Posted

If you type Vortex Generators into the search bar you will get back a few days worth of reading on the subject. Lots of different configurations and tests have been conducted. I have a detailed write up with before and after data on here someplace. 

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Posted

That’s how I got to this point...I’ve been reading most of the day. Quite a bit of knowledge on this site

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