Vortex Generators

[vk3auu]

Just found this page about VG's.

 

http://www.avweb.com/news/reviews/182564-1.html

 

Happy slow flying,

 

David

 

 

[Ultralights]

im not a fan of registering just to read 1 article.

 

 

[Bigglesworth]

Try Bugmenot and see if it is on there, I will check

 

 

[Bigglesworth]

Good old Bugmenot

 

try name:[email protected]

 

Password:password

 

that'll get you in

 

 

[Guest Fred Bear]

Or more food for thought at:

 

http://en.wikipedia.org/wiki/Vortex_generator

 

 

[Guest disperse]

ok so i read the article not throughly but what i get from it is PRO- decreases stall speed and low speed handling. CON- increases drag.

 

you all know im not a flyer yet. but if we have aircraft with a stall below 45kts so i dont see the point....unless STOL is of a priority ....but i can see the mechanic's of why it works

 

 

[Guest Fred Bear]

Aah, you learn every single day mate. PROS and CONS all over the place in aircraft. Remember, one aircraft will always do what another cannot. ;)

 

 

[poteroo]

Read recently a response to installing all these STOL or SPEED kits which said:

 

(1) Keep the engine tuned, the prop clean, and airframe rigged well

 

(2) Polish the aircraft

 

(3) Keep the weight down

 

(4) Balance the load so that it flies at neutral trim......and you save lots of $$$$

 

happy days,

 

 

[vk3auu]

Actually the drag penalty in most aircraft is virtually nil. The lower approach and landing speed is always a bonus because if you can reduce the touch down speed by 10 percent, you will reduce brake and tyre wear by 21 percent. Also, if you put then on the rudder, you get a bit more rudder authority at slow speeds which comes in handy during cross wind landings after you get all the wheels on the ground, particularly in a real aeroplane/taildrager.

 

David

 

 

[Guest Fred Bear]

particularly in a real aeroplane/taildrager.

Oh come on

 

 

[poteroo]

Man after my own heart !

 

If only we could return to the 'good old days' of a huge paddock with all-over operations - then taildraggers would still be as popular, and as easy to teach ab initio in.

 

happy days,

 

 

[Guest osprey5]

Interesting stuff!

 

So who's going to be first trying this on their Jabiru?

 

 

[Guest Fred Bear]

We have a young man at The Oaks who has the Jabiru SP with the vortex generators.

 

 

[Guest osprey5]

Well that's a surprise - so we don't need to get Savanah's to land on shorter strips - any idea what his t/o and landing distances are?

 

 

[Guest Fred Bear]

I will find out for you. Dave C might have an idea too but somewhat reduced. Makes other characteristics totally out of the ordinary too. Stall speed etc. As I said, will find out some more.

 

 

[vk3auu]

Now we have to convince Rod Stiff to put them on as standard. Then we would have a good aeroplane. Might cost a bit extra for the certification though. They would go well on the little rudders of the early models too. Also, if you put them on the wings, you need to put them on the underneath side of the elevator to get more authority at the lower landing speeds.

 

 

[Vev]

Hi … did any of you guys decide to fit VG’s to a Jab???

 

 

I spoke with a fellow in the US a couple of days ago that has fitted them to his SK and said that it made a huge difference to stall & manoeuvring speed including improved climb rates. He said that he has fitted them to both his wing as well as the underside of his tail so as to maintain elevator authority. He also said that his max speed has not really changed but may have dropped a 1 knot.

 

 

I have to say there seems little down side … keen to hear views?

 

 

Regards

 

Jack

 

 

[facthunter]

VG's

 

These have been around for a long time. They are used on the sides of the vertical stabiliser on the Boeing 727. I have seen an approved kit on a chieftain. The idea is to impart energy to the airflow close to the surface of the aerofoil and delay separation at high angles of attack and provide more lift at lower airspeeds, ie. make the wing work harder.

 

They should be affixed somewhere near the leading edge, at a location BEFORE the airflow gets turbulent. The underside of the horizontal stabiliser would be the place to apply them regarding tailplane effectiveness, (NOT the elevator). Tapes or gap seals fitted to control surfaces assists effectiveness also.

 

I would be surprised if there was much speed loss (if any) to most of the planes that we operate when these are fitted.. Nev.

 

 

[Yenn]

Have a look at Land Shorter! Home.

 

There is a bit of info and they supply the VG.s at what they claim is a good price. I was toying with the idea of trying them on the Corby. We extended the strip about 300m and I can still not land before the old threshold, because of the upslope and some small trees.

 

 

[vk3auu]

Actually the underside of the elevator is the place to put them for maximum effectiveness. On my CH701 I have them placed right at the bottom when the elevator is at full up deflection. On the wing, the best place seems to be to place them right at the highest point when the angle of attack is about 15 degrees, which is where most wings usually stall. The earlier Jabs with their little rudders could probably also benefit from fitting them to the sides of the rudder, again at the extreme outside when at 15 degrees deflection.

 

John Gilpin at Maleny is the bloke to get them from.

 

David

 

 

[Vev]

Thanks for the responses everyone…. Greatly appreciated.

 

 

I have been doing some reading on the net which mostly seems to concur with your feedback.

 

 

I also spoke to Joa (designer and owner of Land Short in the US) following Ian’s suggestion to take a look at the web site. He was stating the best placement is to have the centre of the VG's at about 10% of the cord, which is about 100mm in from the leading edge for the wing on my J160. He said that some wings work best at 8% and others at 12% but 10% is about right for most. However he said to be mindful that one takes into account if you have swept back or forward wings as the cord length will be different to the actual wing itself, which is not an issue for my Jab.

 

 

One the things I’m interested in is the potential to increase climb rate on my Jab 160, particularly of hot days. Most of the information seems to indicate that this is possible but I can’t seem to find a lot of documented support for this other than manufactures claims…. Any thoughts???

 

 

Cheers

 

Jack

 

 

[Walter Klatt]

Landshorter VGs

 

I use the Landshorter VGs on 2 of my airplanes. One is a Murphy Rebel amphib floatplane, and it has them at the 10 % chord position. Results were much better than expected. Stall was reduced by about 8 or 9 mph. This was at the recommended 10% chord position.

 

Then I put them on my 912 Chinook, also an amphib floatplane, and for some reason, did not get anywhere near the same results. First, I tried them at the 10% chord position, but stall only reduced by about 1 or 2 mph at best. Then Joa told me to try them further forward, and that helped a little. I ended up at the 7 % chord position, but still only about 2 or 3 mph stall improvement.

 

So it seems to depend a lot on the wing airfoil, I think. The Rebel has a modified 4415 wing, and not sure what the Chinook has, but it is thinner, and it is also a fabric wing vs the metal for the Rebel.

 

No change in cruise speeds or any other handling or stalls with either plane using the VGs. Water take-offs on the Rebel are now faster, but they do require more power and/or technique change, as the VGs produce more drag at low airspeed and a higher angle of attack. I think climb is better, but that is hard to prove.

 

Walter

 

 

[Vev]

Hi Walter… Many thanks for your input.

 

 

It sounds like you must have stuck the VG’s on with some sort of double sided tape to try out the optimum position? If this is the case, what did you use and did you loose any of them in the process?

 

 

Still keen to hear from someone with a Jab that has used VGs ???

 

 

Cheers

 

Jack

 

 

[djpacro]

Stall was reduced by about 8 or 9 mph

VG's can have a significant effect so I hope that some-one is looking at the effect on the design flight envelope eg http://www.recreationalflying.com/forum/general-discussion/18066-va-vso-vvvvvvvv.html

 

 

[geoffreywh]

I think that Aviation spruce have VG's for all types, Including Props! Apparently the first third of the prop gets to do some work. Very believable......If the dollar had not crashed then I would have tried some....I used VG's on A/2 Gliders since the early seventies I wouldn't build one without them!....