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General control line discussion => Open Forum => Topic started by: Peter Anglberger on September 17, 2014, 07:42:45 PM
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I am considering installing vortex generators on one of my Yatsenko Classics. I read PJ's comprehensive 2011 post found via the search function. One thing that is not entirely clear is the exact position chordwise. Should the tabs be centred on the high point or should the rear be coincident with the high point, or some other specific distance forward of the high point. I'm sure PJ will reply to this, but I would also be interested in locations tried by other users of vortex generators.
Regards,
Peter
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There is no aerodynamic significance to the "high point". I don't know where to tell you to put them, though. It's probably a function of the wing upon which you are putting them. Here's a picture of where I put mine and a picture of VGs on Dan Hune's Yatsenko Shark.
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"I found the best location was just near the Highpoint, which is further back than the initial 10% back that I was recommended"
http://stunthanger.com/smf/index.php/topic,23110.0.html
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A while back I did a google search for the v/g and found that on real planes it's important where they go.
http://www.stolspeed.com/installing-vortex-generators
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We discussed this at the Paducah contest and came to this conclusion: Ink them on with your rapidograph pen, high point or low point maters not.
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We discussed this at the Paducah contest and came to this conclusion: Ink them on with your rapidograph pen, high point or low point maters not.
Designed to intimidate more than anything else?
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We discussed this at the Paducah contest and came to this conclusion: Ink them on with your rapidograph pen, high point or low point maters not.
I would caution against the "everybody is stupid but us" approach. Paul and David are pretty convinced they are doing something useful, and they are not particularly prone to deluding themselves. I have seen many things that couldn't possibly work - like turbulators made from flying lines we got out of the garbage can - have remarkable effects. Like the difference between making it through the pattern, and not making it.
I don't have an vortex generators myself but I would certainly not dismiss it out of hand. I came in 4th, David won and Paul was 3rd.
Brett
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If they work on the wing, would they work on the stab?
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I did a little experiment with VG's and here are my findings:
https://www.youtube.com/watch?v=py1JwDponho (https://www.youtube.com/watch?v=py1JwDponho)
I just ordered two sets of VG's and will have them on my next years planes...
-Chris Rud
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I came in 4th, David won and Paul was 3rd.
Brett
And how many times did that happen before they started using them? Doug was 2nd with no gaybulators.
Derek
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My personal experience with them was that they improved the tracking and corner significantly on a Whitely Shoestring that was a little too heavy.
The airplane flew fairly well and was reasonably easy to get through a pattern with no real problems. It was well trimmed as blessed by RJ W., Bart K., and Me...We all agreed that it flew a little "heavy", but was basically an "honest airplane".
I obtained some of Howards VG's and installed them on the Shoestring...Voila...different airplane!
The heavy feel was gone and the corner was much improved. All that flew it agreed. In fact it was the first airplane to appear here in Tucson with VG's and as a result of this success they began to "bloom" on a lot of other stunters here with very "mixed" results.
When I first put them on the Shoestring and sent a photo to Howard He very kindly informed me that I had installed them in a configuration that was angled in oppisition to normal practice (I think this was Howards nice way of saying I was stupid and put them on the wrong way!) LL~
So after about 20 flights I changed them to what was supposed to be the conventional pattern and surprise, surprise...they didn't seem to work nearly as well! So I put them back on "Wrong" and they worked again...Go figure!
So my opinion at this point is that they work but better on some airplanes than others, and how they are installed does make a difference, but I haven't a clue as to why or how that should be on different wings.
Incidentally they were installed on the Stab also and remain there.
The biggest problem I had with them is keeping them on the airplane!!! When they fall off, the flight characteristics of the airplane are noticeably different! In fact it caused hingeing on the airplane when they came off the top of outboard wing and stayed on the inboard!!!
There's certainly nothing "scientific" about this post but it did simply raise a lot of questions for me!
I'm not at all sure I will use them on my New Shoestring as it's going to be significantly lighter and a litte larger than the one described above. My opinion is simply that they do something and I'm not sure what!! LL~ LL~ LL~ LL~
The configuration shown in the photos is the way they work best..."the wrong way".
Randy Cuberly
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And how many times did that happen before they started using them? Doug was 2nd with no gaybulators.
Derek
LOL thats funny.
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I confess that I hadn't seen Chris's video until now. Good job, Chris. You went to a lot of effort to do a good experiment.
I can't see much difference in the video on insides, which you'd think is where it would matter. Either the tufts are stiff or there's not much separation. It might be interesting to put the camera back farther and look at the flow on the flaps. Use the smallest, most flexible tufts you can see. One trick is to use fluorescent tufts in UV light.
Chris's VGs are on backwards, but if there's no separation, it doesn't matter.
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The biggest problem I had with them is keeping them on the airplane!!! When they fall off, the flight characteristics of the airplane are noticeably different! In fact it caused hingeing on the airplane when they came off the top of outboard wing and stayed on the inboard!!!
You wax your airplanes or something? Elmer's rubber cement applied with a Starbucks stirring stick should work OK. UHU Twist & Glue holds the VGs on a little better than rubber cement, and it dries faster. VGs still come off when you want them to. They leave some glue on the surface, but it’s easily removed (from catalyzed polyurethane clearcoat) with isopropyl alcohol. I don't know how it would affect a dope finish. I got my UHU in Poland. Amazon has it here, but I don't know if it's the same stuff.
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And how many times did that happen before they started using them? Doug was 2nd with no gaybulators.
Says the guy who couldn't make the Nats finals without VGs.
You can pay me now,
Or you can pay me later,
But you can't win at stunt
With no vortex generator.
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Hi Howard,
Waxed, Yes but cleaned with Isopropol Alcohol. It is a doped surface...Old technology, like me!
I've used several different brands of rubber cement to no avail. Haven't tried the UHU stuff. I'll look for some.
Thanks,
Randy Cuberly
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Says the guy who couldn't make the Nats finals without VGs.
You can pay me now,
Or you can pay me later,
But you can't win at stunt
With no vortex generator.
I think my top 5 qualifications outnumber yours, with or without VGs....
I cant blame the judges for being a little sleepy on those first couple flights of the day can I? Stuff happens...
Derek
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"I can't see much difference in the video on insides, which you'd think is where it would matter. "
Howard .... check the triangles again .... with and without the VG's ..... there is a blast of separation about half way out the span without the vg's.
Chris's plane is fairly light and has a super thick airfoil (probably not too prone to stalling)...... think what it might look like with one of my battleships.
Frank
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And how many times did that happen before they started using them? Doug was 2nd with no gaybulators.
So, they're SO good that even though they are doing something pointless or counter-productive, they can easily overcome it with magically special skills? More to the point, you see absolutely no connection between long-term willingness to reject dogma and objectively evaluate a large number of alternatives, and long-term domination of the event?
Actually, they *do* have special skills, the most important special skill being able to change to something that works better, even if what they have is pretty good already.
Brett
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I think my top 5 qualifications outnumber yours, with or without VGs....
You whupped me back when
I was without 'em
Now it's reversed
Til you cease to doubt 'em.
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So, they're SO good that even though they are doing something pointless or counter-productive, they can easily overcome it with magically special skills? More to the point, you see absolutely no connection between long-term willingness to reject dogma and objectively evaluate a large number of alternatives, and long-term domination of the event?
Actually, they *do* have special skills, the most important special skill being able to change to something that works better, even if what they have is pretty good already.
Brett
I do see the connection, Dave and Paul are two of the best at building, trimming, and flying control line airplanes and if something is working for them they should use it. That does not mean that I will be gluing those little turds all over my planes. I think the only reason people use them is to annoy me, kind of like electric motors.
Derek
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You whupped me back when
I was without 'em
Now it's reversed
Til you cease to doubt 'em.
Howard is on a roll!!
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....snip.... I think the only reason people use them is to annoy me, kind of like electric motors.
Derek
Haha! That is funny. :) :)
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They do work. You can see them all over real planes, military, commercial, and personal.
After reading about these things for many years it is evident they do something and what it is they do is proven out as well. There are many illustrations and wind tunnel tests pics and videos as well showing what these things do and how.
They show the most improvement on a flying aircraft when it is put in a situation where it is approaching its stall speed. These allow for a slower speed before it stalls, due attached boundary because of the type of airflow caused by the devices. That is it. That is what they do. They are very helpful on small aircraft during final approach. Giving the pilot more control in a vulnerable situation. BUT since the VGs are affecting the boundary layer at all times the second improvement is that the air is more consistent across the wing at all times creating more over all control.
For stunt planes we see a slow down our speed during maneuvers and the VG will help with tracking as it helps the air stick to the wing better when the airspeed has slowed. You will note the second square or triangle is easier and tracks as well as the first one. Or you may notice better tracking to keep your maneuvers right on top of each other. I feel this is due to the consistency of the air passing over the wing as it is "cleaned" while passing across the VGs.
It would be most interesting if we could see Chris's plane in the air going slower where a hard corner actually stalls the wing. Then with the VGs at the same lap time and see if the stall is lessened or gone.
It is also noted that Chip Hyde posted on his FB page pics of one of his pattern plane with VGs on it and stated he got this from the CLPA guys and his plane flew like it was on rails like never before.
I have also noticed many of the RC planes for sale now have them as well. Many of the little foam planes have them molded into the foam.
Here is what I found back in 2011 when I tested them. Other people report the same or near same results.
http://stunthanger.com/smf/index.php/topic,23110.msg222103.html#msg222103
Why dont I have them on my most recent plane? No time to test before the big show. So I forged ahead as normal. It worked out pretty good...but not good enough... :)
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I think the only reason people use them is to annoy me, kind of like electric motors.
Worse yet, those people have Corian countertops.
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. I think the only reason people use them is to annoy me, kind of like electric motors.
Derek
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Dang, you finally figured it out! :(
Now I will have to remove them from my planes and replace them with turbulator strips. You can't possibly complain about those!
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I think the only reason people use them is to annoy me, kind of like electric motors.
That *is* actually a pretty good reason.
Brett
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Worse yet, those people have Corian countertops.
Good lord man! Why would you have such a thing?
Derek
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. I think the only reason people use them is to annoy me, kind of like electric motors.
Derek
Dang, you finally figured it out! :(
Now I will have to remove them from my planes and replace them with turbulator strips. You can't possibly complain about those!
Turbulator strips? HB~>
In all fairness, at least yours match your plane. Howard could at least print yellow and orange VGs for his own planes. Don't get me started on Dave, I bet he will have them going down the side of the fuse and around the spinner and on the wheel pants by the next Nats. Hey, at least he is giving Howard pierogi money.
I will come back next year with my VG free machine and kick all your butts. 8)
Derek
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Could you use VGs in lieu of an area tab on the outboard flap of some hypothetical plane?
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Worse yet, those people have Corian countertops.
Derek is right on that one. When I come in from a long day of stampeding mastodons off a cliff, just to feed my family, I want it cooked in the dirt over a buffalo-dung flame, no synthetic materials for me. Probably poisonous, anyway.
I mean, Ryan Seacrest probably has Corian countertops - 'nuff said!
Brett
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The NASA engineer who I talked to and he watched Chris Ruds video "Chuckled and said pretty much useless" But I knew that. Flame away
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The NASA engineer who I talked to and he watched Chris Ruds video "Chuckled and said pretty much useless" But I knew that. Flame away
I worked at Cape Kennedy in the 1970's and knew a lot of NASA Engineers... I was an assistant to the Chief propulsion engineer for NASA...Some of those guys were briliant...and some of them were as dumb as posts... LL~ LL~ LL~
I doubt that any real aerodynamicist worth his salt would call them useless. If they are why do you see so many on full scale aircraft...Is it only because they want the extra weight?
Did this NASA Engineer fly Stunt? Missile aerodynamics is a little different...things change a little around Mach 7 or so...besides aerodynamics don't make a lot of difference in space! %^@ %^@ n~
Randy C. LL~ LL~ LL~
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The NASA engineer who I talked to and he watched Chris Ruds video "Chuckled and said pretty much useless" But I knew that. Flame away
I guess the guys who built this plane aren't up to speed on the facts for and against VGs...
In this application there is some significance as to where they are placed.
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These guys are a clueless too.
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Oh yeah, don't forget these guys too..
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So, we have proven the airline engineers are out to lunch on the aerodynamic capabilities of those teeny tiny little fins placed on the wings of their aircraft in very specific places. I mean the NASA guy said they are worthless right? Or maybe he just meant they were worthless on Chris's model. But wait, isn't the air going over Chris's wing the same air that goes over the wing of an airliner? I am not sure. But if it is the effect would be the same. Must be different air. It has to be.
Look at this, their engineer are lost too...
The under belly of a Lola chassis has VGs on it to get the air traveling under the car to stay attached to the car in the negative pressure areas so when it passes through the rear tunnels the desired effect is achieved. These guys must be kidding themselves that there is actually anything at all happening, even though they have 100s of millions of dollars in their programs and time in the wind tunnels....
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Whoa what is this? It is the front end under belly of an LMP2 (LeMans Prototype 2) Nissan. Another team of crack pot engineers thought it would be helpful to put these little do dads on their car all in the name of speed. What are they trying to do here? Keep the air stuck to the car as it goes UNDER the car. They are trying to get the best possible grip in all situations by using these things to create an active boundary layer. What a waste of their time.
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They work on real aircraft. Exact quote "we don't fly in scale air" But I knew that.
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I don't see any VGs here but this is a funny pic. ;D ;D ;D
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Hey, cut Sparky some slack here.
I'm sure he has put in hundreds of flights on his planes testing them out. That's how he knows!
Otherwise it would be foolish to make procolmations like he did without real facts and data. Right?
Sparky said it so it HAS to be true!
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They work on real aircraft. Exact quote "we don't fly in scale air" But I knew that.
Can you please elaborate so we know what you are talking about? These one liners dont say much. Maybe you are just S?P
Do our wings not stall the exact same way an airliner's wing would stall, or the exact same way an aerobatic full sized aircraft would stall?
Why on earth would stunt plane wings not be beholden to physics?
Please explain..
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They work on real aircraft. Exact quote "we don't fly in scale air" But I knew that.
They work on cars and those things aren't even flying......
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If it makes you feel like it does something by all means do it. Oh and by the way I bet they are bigger than a 1/16-1/8 tall
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If it makes you feel like it does something by all means do it. Oh and by the way I bet they are bigger than a 1/16-1/8 tall
Wait a minute. You mentioned scale, look at that first pic I posted with the VGs place toward the front of wing ahead of the moveable surface behind. If you scaled that wing down to our size their VG would be but tiny bumps hardly noticable. PJ discussed this at length years ago. In scale ours, and the ones you find on many aerobatic RC aircraft now, are actually larger. But hey it doesn't really matter right? Their air must be different than our air.
You made it sound like you have hard evidence they don't work and those who think so are fools..... Care to elaborate or is it just more one liners with not much to offer.
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Care to elaborate
No. I'm not going to debate this. Just keep doing it. When Brett Buck has concrete evidence they work and they are on his airplane I might think about it.
Yes Brett I put that much faith in what you say "sometimes". LL~
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Doug,
You posted a number of pictures of heavy planes with relatively small wings and high wing loadings. I am sure that VGs do help these types of planes, however, if you build a 700 sq. inch plane at 63 oz. you will realize that VGs are not needed.
Derek
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As I see it , everyone is trying to come up with some new innovation and the last true innovation in stunt was the NOBLER.
I think it was Palmer who did differential flaps, how good did that work? If it worked good why aren't we using them? To Paul you could put a engine on a toilet seat and win so VG's are a moot point.
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As I see it , everyone is trying to come up with some new innovation and the last true innovation in stunt was the NOBLER.
I think it was Palmer who did differential flaps, how good did that work? If it worked good why aren't we using them? To Paul you could put a engine on a toilet seat and win so VG's are a moot point.
Differential flaps didn't work well, so nobody uses them.
The last very significant innovation in stunt was electric feedback control (2010?). Prior to that, and going back in time,
electric/lithium polymer batteries (early 2000s),
tuned pipe and/or low pitch props (86)
the low-aspect ratio tail (early 80's),
increased tail moment (sorry howard) and associated aft CG (78/9),
increased tail volume (71-72). That takes us back to the early 70's.
BTW, since you are an expert on the history of stunt, what innovation did the Nobler introduce? Because it's almost certainly not what you think, and it's almost certainly something you would be arguing against vehemently if some did it now. To save you some time, it wasn't coupled flaps and it wasn't the 4-2 break/slow flying.
Brett
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Doug,
You posted a number of pictures of heavy planes with relatively small wings and high wing loadings. I am sure that VGs do help these types of planes, however, if you build a 700 sq. inch plane at 63 oz. you will realize that VGs are not needed.
Derek
Like "others", you miss the point entirely. They are not there to make a porker fly. They are there to make things more consistent.
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Differential flaps didn't work well, so nobody uses them.
The last very significant innovation in stunt was electric feedback control (2010?). Prior to that, and going back in time,
electric/lithium polymer batteries (early 2000s),
tuned pipe and/or low pitch props (86)
the low-aspect ratio tail (early 80's),
increased tail moment (sorry howard) and associated aft CG (78/9),
increased tail volume (71-72). That takes us back to the early 70's.
BTW, since you are an expert on the history of stunt, what innovation did the Nobler introduce? Because it's almost certainly not what you think, and it's almost certainly something you would be arguing against vehemently if some did it now. To save you some time, it wasn't coupled flaps and it wasn't the 4-2 break/slow flying.
Brett
Yep your right I know nothing as always
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what innovation did the Nobler introduce?
That's an easy one.
You could have an ugly plane that can fly well.
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Like "others", you miss the point entirely. They are not there to make a porker fly. They are there to make things more consistent.
Isn't one of the side effects making a porker fly better? I have heard enough people describe what the VGs do so I do not doubt that they are doing something. I think you miss the point, to me, they are ugly. I am not convinced that they do "enough" for me to be willing to screw up the finish on my plane. Maybe if I could figure out a good way to make them part of the finish I would feel differently.
Also, I have found that my inconsistencies have less to do with the design of my planes or the way it flies and more to do with the fact that I fly about 30 flights a year and 20 of those are on the L-pad.
Derek
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Derek,
You find them on light weight planes as well.
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Derek,
You find them on light weight planes as well.
Well damn.
Derek
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Not sure how much flak I'll get for this .... but didn't people think that if you sailed off into the ocean you would fall off as the world was flat ? and didn't people think that the planet earth was in the center and everything else revolved around it ? and didn't doctors think it was a foolish idea to wash their hands before touching another patient ? -- so it very much exists a possibility that until proven false VG's really do work from even a small amount to large amount ?
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I think you miss the point, to me, they are ugly. I am not convinced that they do "enough" for me to be willing to screw up the finish on my plane.
In development at Jive Combat Team Laboratories as we speak are VGs with integral LEDs. The printed circuit array on the wing surface should fit in nicely with the Matrix paint scheme.
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I'm going to give it a try. In Ozark fashion I've found a cheap substitute for those high tech jobs. (Sorry Howard). I'm taking this clear acetal corner protector -4 feet for two bucks- and trimming down to spec. It's about .040x5/8"x5/8". This has adhesive strips on as purchased but will be removed. It's clear so wouldn't make the birds at the flying field think they are bugs and attack.
Dave
Counterfeits *. The invisible vortex generator!
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In development at Jive Combat Team Laboratories as we speak are VGs with integral LEDs. The printed circuit array on the wing surface should fit in nicely with the Matrix paint scheme.
The Matrix needs RT"s (VGs) that have the Magnetic Pulse Generators tied into the circuits array , and able to get direct power from Li-Po source
Randy
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Derek,
You find them on light weight planes as well.
Doug all this is apples and oranges so far as comparing, they are not there to do the same thing, and NONE of the full scale planes you show, or any others, are doing what the models are doing. I have , in my experience seen VGs and trips work well with heavy planes, not so well , or not at all on light planes, This comes from testing them, and talking with other who have, plus first hand accounts seeing the difference when applied to OPPs ( Other peps planes). For example I saw a plane, in terrible damp conditions, in Summer stalling/falling out of maneuvers, adding trips to the wing and stab worked wonders, The same exact time, other light stuntships were NOT affected by the poor conditions.
I think this comes down to individuals planes and circumstances.
Randy
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The Matrix needs RT"s (VGs) that have the Magnetic Pulse Generators tied into the circuits array , and able to get direct power from Li-Po source
They will come with "available" (as they say in the car ads) Magnetic Pulse Generators. The LiPo can be attached directly to Derek's fuel tank and can be charged in the airplane with a cheap no-balance charger for our additional enjoyment.
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I'm going to give it a try. In Ozark fashion I've found a cheap substitute for those high tech jobs. (Sorry Howard). I'm taking this clear acetal corner protector -4 feet for two bucks- and trimming down to spec. It's about .040x5/8"x5/8". This has adhesive strips on as purchased but will be removed. It's clear so wouldn't make the birds at the flying field think they are bugs and attack.
Beware of imitations! 3D-printed Rush VGs have cambered airfoils, so they are annoyingly right- or left-handed, and have little nubbins on the side for the laser-cut alignment templates to sit on. They are also gluten-free and are made without synthetic growth hormones.
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In development at Jive Combat Team Laboratories as we speak are VGs with integral LEDs. The printed circuit array on the wing surface should fit in nicely with the Matrix paint scheme.
Now that is something I would buy.
I was so close to putting LED lights in the pipe tunnel of the Matrix, I had them with me at that Nats. I thought being the only plane in the 180 building with a green glow from beneath was just a little too much. Maybe I will put them in the Cutlass for next year. The battery weighs about .75 oz and the lights don't weigh much at all. I did a test and it did look really cool.
Derek
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If they work on the wing, would they work on the stab?
PW and David use them on stabs. I've had them on and off the stab of last year's airplane a couple of times. I couldn't tell any effect.
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Doug all this is apples and oranges so far as comparing, they are not there to do the same thing, and NONE of the full scale planes you show, or any others, are doing what the models are doing. I have , in my experience seen VGs and trips work well with heavy planes, not so well , or not at all on light planes, This comes from testing them, and talking with other who have, plus first hand accounts seeing the difference when applied to OPPs ( Other peps planes). For example I saw a plane, in terrible damp conditions, in Summer stalling/falling out of maneuvers, adding trips to the wing and stab worked wonders, The same exact time, other light stuntships were NOT affected by the poor conditions.
I think this comes down to individuals planes and circumstances.
Randy
If you can create an active boundary across a surface which the air is flowing you will have more control than the surface with a less active boundary layer. But hey, if you don't think so, then so be it.
If the VG is on there and the surface is moving it is creating a vortex. That is what they do. Helping your situation or not, well that would have to do with application and the desired effect.
I for one absolutely hate taped hinge lines. I have only one plane where I could tell a difference in how the plane performed between taped and non taped hinge lines. (I have not tested my latest plane due to time constraints.) But I am not going to sit here and say taped hinge lines don't work. The most certainly do work. They keep air from traveling through the hinge gap. That's what they do. Do they make the plane fly better? Sure for some but not for me and some others I know who have tried it. So I don't use it. But the taped lines still do their job. If you sealed the hinge lines on a 777 (I have no idea how you would do that, one hell of a roll of tape!!) it would do the same thing. Keep air from traveling through the gap. VGs create a vortex. Doesn't really matter what they are on. That's what they do.
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If you sealed the hinge lines on a 777 (I have no idea how you would do that, one hell of a roll of tape!!) it would do the same thing. Keep air from traveling through the gap.
Not what you'd want to do in that case.
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Not what you'd want to do in that case.
Right! ;D
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Alright, I'll put a cat among the pigeons... S?P
What about turbulator tape on the wings the same as Igor's?
Which is better, VGs or the tape?
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I have tested them too and had positive results. My testing and evaluation of others applications as well doesn't count?
As far as comparing planes it is not apples and oranges. If you can create an active boundary across a surface which the air is flowing you will have more control than the surface with a less active boundary layer. But hey, if you don't think so, then so be it.
If the VG is on there and the surface is moving it is creating a vortex. That is what they do. Helping your situation or not, well that would have to do with application and the desired effect.
I for one absolutely hate taped hinge lines. I have only one plane where I could tell a difference in how the plane performed between taped and non taped hinge lines. (I have not tested my latest plane due to time constraints.) But I am not going to sit here and say taped hinge lines don't work. The most certainly do work. They keep air from traveling through the hinge gap. That's what they do. Do they make the plane fly better? Sure for some but not for me and some others I know who have tried it. So I don't use it. But the taped lines still do their job. If you sealed the hinge lines on a 777 (I have no idea how you would do that, one hell of a roll of tape!!) it would do the same thing. Keep air from traveling through the gap. VGs create a vortex. Doesn't really matter what they are on. That's what they do.
To start with NO where did I say your testing didn't matter
NO where did I say they do NOT work so stop putting words here I never said.
And YES they are doing different things, just because they make a Vortex means little if it is NOt helping you, means a LOT if it is, go read what i said, from what i have seen they help heavy planes much much more than light ones, they may help your plane and NOt others.
What it boils down to is they may help some planes, that does NOT mean they help ALL planes, They may NOT help some planes, and that does NOT mean they don't help others.
And you are in the minority on seal hinge lines, they **Almost** always help stuntships. Go to show , some things are NOt 100% across the board in what works in stunt.
Randy
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Alright, I'll put a cat among the pigeons... S?P
What about turbulator tape on the wings the same as Igor's?
Which is better, VGs or the tape?
No one knows... for sure
Randy
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Beware of imitations! 3D-printed Rush VGs have cambered airfoils, so they are annoyingly right- or left-handed, and have little nubbins on the side for the laser-cut alignment templates to sit on. They are also gluten-free and are made without synthetic growth hormones.
UUUhhhhhh Howard, Why do they work better if they're on BACKWARDS!
Understand I'm not complaining...They work for me!
I do agree with some that say they tend to work better on heavy airplanes than light ones (checked on OPP's). I don't have any light airplanes anymore.
I think they simply aren't as likely to be needed in a semi-stalled condition on light airplanes..but I'm just a dumb old mechanic...and never got around to Aerodynamics and all those funny smokey graphs you guys use so much.
LL~ LL~ LL~
Randy C.
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Alright, I'll put a cat among the pigeons... S?P
What about turbulator tape on the wings the same as Igor's?
Which is better, VGs or the tape?
Which is better, aluminum or peaches? They do different things. VGs make vortices to bring high-speed air down next to the surface. I don't know what Igor has in mind with his tape, but "turbulators" or trip strips trip the boundary layer from laminar flow to turbulent flow. Here's a piece on that: http://stunthanger.com/smf/index.php/topic,30917.0.html . Note Peter Germann's observation about zigzag tape at 10% chord.
Now that you mention it, the tape would be much easier to embed wiring in for the bling that you so appreciate.
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I am simply saying the VG creates a vortex. Will it help all planes ALL planes perform better? That's for each one to decide on their own.
I know I am in the minority on taped lines. I hear it touted all the time. I am certain without a doubt they work, stop the air bleed, in ALL cases. Does it improve the planes performance. That's for the each one to decide on their own. Only once for me. Why that is I don't know. Maybe I just can't tell. But as I said before I will always try it so I am certain I have explored the possible options to give me any kind of an edge on the circle.
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I read your first post several times before I responded. It read to me like you were saying I was out in looney land and had no clue what I was talking about. I am simply saying the VG creates a vortex. Will it help all planes ALL planes perform better? That's for each one to decide on their own.
I know I am in the minority on taped lines. I hear it touted all the time. I am certain without a doubt they work, stop the air bleed, in ALL cases. Does it improve the planes performance. That's for the each one to decide on their own. Only once for me. Why that is I don't know. Maybe I just can't tell. But as I said before I will always try it so I am certain I have explored the possible options to give me any kind of an edge on the circle.
I am a believer inn looking under all the rocks, you never know what you will find, and I agree, and stated as much, each person has to find out if it works for their program, taping/sealing hingelines is pretty much, one of the most universal things that helps most, hardly any ones gaps are smaller than air molecules , so sealing hingelines does what Paul says RTs (radical turbulators) do for his ships... makes them more consistent... But fact is they do NOT work the same on all stuntships.
I saw a very good stuntship improved greatly by installing trips on the wing and stab, this is a plane that had no problems at all in most conditions, I have also seen tape stop a stuntship from stalling and falling out of maneuvers like a rock !
I also hate putting tape on my flaps.. but do it anyway, and I have very tight gaps. As you say.. do what you need and explore it all.
Randy
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If they work on the wing, would they work on the stab?
Most Stab./ Elev's. on the Stunters I've seen are flat surfaces. (non-airfoil)
They generate a pressure differential at the hinge line rather than "lift" like an airfoil.
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If they work on the wing, would they work on the stab?
PW and David use them on stabs. I've had them on and off the stab of last year's airplane a couple of times. I couldn't tell any effect.
See above.
ps- My counter tops are Formica from 1981. My sink? Well, that's Harvest Gold. <=
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"quote from: Howard Rush on September 19, 2014, 02:33:36 PM
Worse yet, those people have Corian countertops.
Good lord man! Why would you have such a thing?
Derek "
LOL even worse than that, some times it seems like some stunters wings were made from Corian !! ;D ;D ;D
Randy
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Have any of the carrier guys experimented with VGs yet? I would be interested to know if it would significantly effect their slow speed flight.
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Have any of the carrier guys experimented with VGs yet? I would be interested to know if it would significantly effect their slow speed flight.
I don't think the local guys has.. But I'm sure it'll be beneficial to some degree after seeing how it improved one of my plane's landing glide.
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Have any of the carrier guys experimented with VGs yet? I would be interested to know if it would significantly effect their slow speed flight.
Slow speed flight for competitive CL Carrier planes is done at such a high angle of attack (typically 60 degrees) that it's highly unlikely there is any real airflow over the top of the wing. The airplane simply flies in a totally stalled attitude and the prop keeps it airborne by modulating the throttle. Hence, VG's would do nothing but add a small amount of weight to the airplane. <= <=
Randy Cuberly
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Slow speed flight for competitive CL Carrier planes is done at such a high angle of attack (typically 60 degrees) that it's highly unlikely there is any real airflow over the top of the wing. The airplane simply flies in a totally stalled attitude and the prop keeps it airborne by modulating the throttle. Hence, VG's would do nothing but add a small amount of weight to the airplane. <= <=
Randy Cuberly
Hence the Hover vs. Slow flight debate.
Carrier across the pond is still 45 vs. our 60 degree AoA.
They might work better on their models.
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To answer the question my fellow OZ ark asked..
I found anything forward of the highpoint was less effective compared to on or up to 1 " back from the high point. I run mine 1cm back from the thickest part of the wing @ my CG, My theory is they work best at the CG.
The direction they sit in relation to the airflow or the forward LE sweep I found didn't make any noticable difference.
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Now onto the "debate"
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Its fair to say that Vortex Generators work. I've done more testing of these things than I care to remember, and more elite racing event are starting to employ some form of drag control. Remember those racing suits the swimmers were wearing to break multiple world records that are now banned ? They were dimpled like a shark skin. Formula 1, Red Bull Air Racing, golf - it doesnt matter - they are looking into ways to CONTROL AIRFLOW.
To say you're not looking into some form of boundary layer control simply means your not looking at every angle and seeking every advantage out there to make your planes fly at a 100% optimum level. ( Which is fine, its no different to practice if your having 50 flights a year or 500 - it reflects your commitment to getting better )
It seems to me, there are some that use them, some that don't - I've had a few conversations with Igor Burger about this exact technology ( why he does or does not use them) and he doesnt use them exactly, however DOES use Zig Zag tape located along close to the highpoint. Now I also know that the height of a Vortex Generator in our scale would work out to be close to 1/64th - So Im sure the ZigZag tape is working along similar principles to the VG's . I don't believe they are ( the Zig Zag tape ) simply disturbing the airflow, I think they are creating the same effect but in a more subtle way. How do I know this ? I've done back to back testing on both systems. My point isnt to say I think the VG's are better .. or Worse. My testing indicated to ME that the deployment of VG's had a more pronounced noticable effect on more segments of the pattern than the Zig Zag Tape. Now Igor is a true master and revolutionary thinker and dual World Champion - So his practice is also acceptable, just for me personally I found something that worked differently.
The point of my VG program was to develop them to be as subtle as possible - on my planes they are almost hidden. I also tried hard to develop them to a minimal setup that still gave 95% improvement compared to having them ALL OVER the plane.
I found NO IMPROVEMENT in running them on the stab - When I talk to those who ARE running them on the stab the consensus is "minimal improvement" almost to the point of subjective improvements. Which for me isnt enough, I need concrete ( lost 1/2 oz of tip weight ) obvious.
I never shouted out that I thought they were required to make Top 5.. and the fact that Paul Walker or Dave Fitzgerald or Doug Moon or any other "name" flier are using them... isnt relevant. What IS relevant is these are clinical minds and methodical approaches to flying Stunt and they win for a REASON. VG's are not the reason but they are a byproduct of that reason - commitment to improvement.
Its pretty simple really : There is NO ONE RIGHT WAY. Electrics / Pipes / Igor Timers or PA 75's - Whatever I need to build which will help ME put the model in the right places more times than the other guy is what I want.
Derek : I was on your circle at the Nats and felt I put up some DAMN good flights and you eclipsed me by 20 something points, which was an impressive display. You build light and straight and in general are a Top flier and worthy of a Nats crown. Your views are respected by many, I certainly respect ( and agree with) some of your views and stances on many of the topics you advocate. However It would be nice if you TESTED them on your own plane with your OWN flying style and then made a judgement call on their effectiveness for your program.
Sparky : " When Brett Buck has concrete evidence they work and they are on his airplane I might think about it "
That's an indication of many MANY things ... however I will just leave you with a small snipette of basic personality psychology 101.
Conformity = A change in behavior or belief as a result of real or imagined group pressure.
2. Types of conformity
A. Compliance. Publicly acting in accord with social pressure while privately disagreeing. This term best describes the behavior of a person who is motivated to gain reward or avoid punishment. On the level of compliance, many experimenters see little difference between animals and humans, because all organisms respond to rewards and punishments.
B. Identification. As with compliance, we do not behave in a particular way because such behavior is intrinsically satisfying. Rather, we adopt a particular behavior because it puts us in a satisfying relationship to the person or persons with whom we are identifying. We do come to believe in the opinions and values we adopt, though not very strongly. We want to be like some particular person.
EX: Want to be just like your father.
C. Internalization (or acceptance). Both acting and believing in accord with social pressure. This is the most permanent, deeply rooted response to social influence. Internalization is motivated by a desire to be right. If the person who provides the influence is perceived to be trustworthy and of good judgment, we accept the belief he or she advocates and we integrate it into our belief system.
There are COUNTLESS articles on the psychological aspects of conformity... and how that differs from being a free thinker and innovator.
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To PJ If they make you feel good do it. I will spell it out for you it was a joke. I would not glue rat droppings on my plane EVER. If and it's a big IF I was to use them I would build and finish them on the wing.
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Derek : I was on your circle at the Nats and felt I put up some DAMN good flights and you eclipsed me by 20 something points, which was an impressive display. You build light and straight and in general are a Top flier and worthy of a Nats crown. Your views are respected by many, I certainly respect ( and agree with) some of your views and stances on many of the topics you advocate. However It would be nice if you TESTED them on your own plane with your OWN flying style and then made a judgement call on their effectiveness for your program.
But PJ,
That would mean that I would actually have to go out and practice. LL~
All kidding aside, I still have the VGs that you were kind enough to send me. I do want to test them and if they work well enough for me to keep them on my plane I will be happy to eat crow. (it would not be the first time and certainly won't be the last). With the limited time I have had over the past few years it is difficult for me to find time to do anything stunt related (other than a few contest a year that I never miss). I do look forward to trying them out and then I will give my honest opinion.
I got Masters tickets this year for the first day of practice. I have two extra if you and Rhiannon would like to come. It would be a long trip for one day in Augusta. Maybe I can just send you a hat?
Derek
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VG tests this morning.
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VG tests this morning.
It is confirmed that they will not prevent a crash I guess. Either that, or they are way more harmful to a finish than I thought.
Sorry to make fun Dave; what happened?
Derek
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...
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Derek I got out early in good air to test them out. The plus is I do think they make tracking the rounds a touch smoother and easier. The airplane flew away at the top of the vertical eight which it doesn't normally do even though I got the needle a touch fast. Not sure the cause. The BIG change was when the engine cut. The glide speed and distance cut in half the normal. I couldn't get over a rut on the field the hay truck left a few weeks ago. I've done this routinely with this plane until this morning. It just ran out of steam. When the gear came out it dropped onto the VGs, which caught and peeled the sheeting like a banana.
Dave
As an afterthought..these create a certain amount of drag (obviously) and it might simply be that drag keeping the airplane from accelerating down the backsides of the rounds that give the sense of more control.
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Derek I got out early in good air to test them out. The plus is I do think they make tracking the rounds a touch smoother and easier. The airplane flew away at the top of the vertical eight which it doesn't normally do even though I got the needle a touch fast. Not sure the cause. The BIG change was when the engine cut. The glide speed and distance cut in half the normal. I couldn't get over a rut on the field the hay truck left a few weeks ago. I've done this routinely with this plane until this morning. It just ran out of steam. When the gear came out it dropped onto the VGs, which caught and peeled the sheeting like a banana.
Dave
As an afterthought..these create a certain amount of drag (obviously) and it might simply be that drag keeping the airplane from accelerating down the backsides of the rounds that give the sense of more control.
Orestes told me one time that one of the reasons the Sharks fly like they do is because of all the drag. The cheek and chin cowls, thick rudder, very thick wing and stab all added to this. He said that they were thinking about adding more drag on future designs. The Yak 54 is probably an example of that thinking.
Derek
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Looks like the angle of the VGs is pretty steep. You might try 15 to 20 degrees. If the VGs were working, you would have gotten a better lift/drag ratio, hence better glide angle, as Joe did.
I don't notice any change in L/D on my dogs with VGs.
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Might be Howard. I set them at 30 which is pretty serious plowing.
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Derek : Dang.. I might just have to run it past Rhiannon and see if we can sweek out another trip ! Id rather see you NOT run VG's any advantage I have over you I need to keep !
Robert ; " To PJ If they make you feel good do it. I will spell it out for you it was a joke " Sure, I knew it was a joke - most of your stuff is.
The vgs on the crashed test plane show here also look a bit far forward - closer to 10 % - Ive found this to increase drag to much - solution in the past was to run 8" pitch - however moving them back fixes this issue 25 - 30 %
Incidently I wanted to get some better data on the VG's drag co-efficient so when the electrics started to run them - I checked with the guy who is running both VG's and Electric in combination and found out there was no additional battery usage and only a 0.05 lap time change.
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Robert had the right idea, if you are going to use them, about building them into the model. That "T" base just durties the air movement over the airfoil. IMHO.
Renders them less efficent because of this. IMHO.
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Today must have been a bad day to be flying. My Dreadnought got torn up in a takeoff accident this morning. Regrettably, VGs cannot be implicated in the crash.
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One of the most notable things on my Shoestring with Howards VG's was a definite improvement in the glide.
Befor ethe VG's were installed it was an airplane that wone had to be very careful about trying to extend the glide on. Attempts to do this ususlly ended in a stall and flop onto the wheels from about 6-8 inches above the pavement.
With the VG's installed the glide could be played to make landings easier and ground contact much smoother at a distintly slower speed.
I played with this a lot because this had always been a slightly difficult airplane to land smoothly. After the VG's were installed it is a piece of cake!
I used only two set of VG's on each wing and really noticed no increased drag or lap time changes.
The Shoestring is a smalish airplane at 620 sq inches and 64 oz. PA65, Pipe.
Randy Cuberly
PS: Sorry about your poor Broken Airplane Dave! Get it fixed, and fill in that dam hole!
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Steve sorry about your bad luck. First day of fall I guess. Hope you can get it back together.
Randy maybe placement of the VGs played a part. I had three sets on each wing panel and a set on each stab surface. They were turned pretty hard to the airflow. I do know they felt decent in the air rounding bottoms of loops and eights. I also found it nearly impossible to get any milage from whipping it after the engine cut. I'm really convinced much of the benefit of these is about adding drag to control speed in certain spots. If that's the case I'd rather dirty up the fuselage or something to achieve that end. I even hooked my shirt on one of these carrying the machine which could have torn something loose at a bad moment. I don't think they are about adding lift-a few more square inches, more flaps, more wing thickness or lighter weight would all achieve that for you. I don't think they are magic. I just think it's about drag. But that's just this man's thought.
The airplane is actually several years old now and was doing the duty to keep the miles off my best .76 ships for next year. This does finish off the last of my .61 size Desperados. The bigger ones are better.
The hole? Well I would but I'll only have the field a few more weeks. I need a dump truck load at the new field....
Dave
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Robert ; " To PJ If they make you feel good do it. I will spell it out for you it was a joke " Sure, I knew it was a joke - most of your stuff is.
Better make sure those VG's can hold fuel. So who was the joke on? I got a great idea why don't you build a website and turn it into the best in the world and I will come there and bash you?
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...........what innovation did the Nobler introduce?
Brett
Since this thread has turned all warm and fuzzy could I please get an answer to the above before it gets locked?
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Since this thread has turned all warm and fuzzy could I please get an answer to the above before it gets locked?
Aft side area. But what do I know everything I do is a joke. So well designed its copied to this day.
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I got a great idea why don't you build a website and turn it into the best in the world and I will come there and bash you?
Bashing you? No that wasn't bashing you, but disrespecting opinions and idea's ranks low on my list of qualities I admire..
Sure thing - Ive got a better idea, why dont you build a take apart plane travel 1/2 way across the world - Qualify for Top 20 Finals and bash me there ?
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Aft side area. But what do I know everything I do is a joke. So well designed its copied to this day.
Thankyou.
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I got a great idea why don't you build a website and turn it into the best in the world and I will come there and bash you?
Bashing you? No that wasn't bashing you, but disrespecting opinions and idea's ranks low on my list of qualities I admire..
Sure thing - Ive got a better idea, why dont you build a take apart plane travel 1/2 way across the world - Qualify for Top 20 Finals and bash me there ?
Exact quote from a NASA engineer they are the wrong shape and in the wrong place to do much good at low speeds. As far as coming there not a chance. You said everything I do is a Joke. You wouldn't call that bashing?
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Going back to Dave's experiences, I'm wondering if it wasn't simply a case of too much angle on them? If you think of them as like a tiny wing, then an appropriate angle of attack will give you low pressure on one side, high pressure on the other, and a resulting vortex round the tip. But too much AoA , they stall, and the system breaks down - you don't get the pressure differential you're trying to create, and just end with an aerodynamic mess and a bunch of drag. So stalled VGs wouldn't give any benefit to the boundary layer (and would bugger it right up instead), and would certainly hurt the glide by virtue of the additional drag. Any chance you could try them again with less angle, Dave?
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Exact quote from a NASA engineer they are the wrong shape and in the wrong place to do much good at low speeds.
It doesn't really matter who said they are wrong ... - They work : FACT :) and Countless Open Nats #1 trophies are sitting in the rooms of guys who agree enough to sprinkle them on their setups.
On another point of order - I don't see many people using Fibrous refractory composite insulation on their stunt planes - perhaps ask him if he thinks that's of any use for us.
" You said everything I do is a Joke. You wouldn't call that bashing? "
If we are exact quoting.. that's not what I said..
" Sure, I knew it was a joke - most of your stuff is. "
Most isn't everything.
It was not a personal attack or a bashing - it was simply a double entendre , said with intent ,reflective of the initial pretext statement of being "a Joke" - perhaps my sense of humor runs a different axis.
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Exact quote from a NASA engineer they are the wrong shape and in the wrong place to do much good at low speeds.
Does he (or she) speak from having flown stunt with VGs, from having experimented with stunt airfoils at our Reynolds number in a wind tunnel, or from an analysis of the boundary layer physics? Let's see the data.
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...Countless Open Nats #1 trophies are sitting in the rooms of guys who agree enough to sprinkle them on their setups.
Come on, PJ, you should be able to count that high. It's only 20 or so.
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Exact quote from a NASA engineer they are the wrong shape and in the wrong place to do much good at low speeds.
Oo. Come to think of if, maybe that's me you're quoting. I did spend time at NASA Langley. I don't think I said they're the wrong shape, but I did figure that PJ's were in the wrong place until I tried them there. I don't think I would have said "low speeds": I would have related it to Reynolds number, but I don't know how their effect would vary with Reynolds number except for maybe how big to make them. I do agree that the configurations I've tried experimentally don't do much good. I think that for my airplane the VG arrangement I have now does a little good.
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Going back to Dave's experiences, I'm wondering if it wasn't simply a case of too much angle on them? If you think of them as like a tiny wing, then an appropriate angle of attack will give you low pressure on one side, high pressure on the other, and a resulting vortex round the tip. But too much AoA , they stall, and the system breaks down - you don't get the pressure differential you're trying to create, and just end with an aerodynamic mess and a bunch of drag. So stalled VGs wouldn't give any benefit to the boundary layer (and would bugger it right up instead), and would certainly hurt the glide by virtue of the additional drag. Any chance you could try them again with less angle, Dave?
Steve I sure might at some time down the road a little. I'm not going to fix that airplane-it's borderline too heavy as is and my flying season is rapidly winding down here due to weather . I'm trying some new fuel tanks in my best airplanes now while I can. I really have too many pots stirring already to do much now. Trying new things is good and I will. If my theory is right about the VGs it's still a good thing used in the right way.
Dave
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If you guys wish to use them DO IT. I will not be taking a aeronautical intercourse and a rolling piece of pastry anytime soon. But one piece of advice get off my back.
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If you guys wish to use them DO IT. I will not be taking a aeronautical intercourse and a rolling piece of pastry anytime soon. But one piece of advice get off my back.
Yeah, but I knew that!
OK, take your ball and go home so no one else can play!
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I have not shut this thread down have I? No I am just telling everyone I have had it. Kind of like when the dog growls at you. I had had more patience than Leonard would have had.
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Hmmmm. Late to the debate. I've gotta try to keep up better.
I grew up working at the Renton, Washington airport where my father had an FBO/Cessna dealership. I was privileged to see a number of historic airplanes as that was where Boeing built and flew the maiden flights of a number of iconic airliners. I watched the maiden flights of the original 707 and 727, both very memorable events. Of interest with respect to this thread is the following.
You pretty much all know the 727 had three engines. One on each side of the aft fuselage and a third exhausting at the tail end of the fuselage. The outboards had direct airflow into them in the conventional manner. The middle engine, however, had the intake of the engine itself somewhere just aft of the last row of coach passengers. Boeing had to figure out a way to get large amounts of air into a cleverly contrived "S" duct that had it's intake on the top of the fuselage just forward of the vertical stabilizer. The intake was connected to the front of the engine by ducting in the shape of an "S" through which huge masses of air had to flow smoothly to sate the hungry middle engine. A convoluted but clever solution, right!
On the maiden voyage the crew spooled up all three engines at the south end of the one mile long runway heading toward the far end that abutted Lake Washington. Once the engines were up to thrust they released the brakes and the first 727 flight was about to begin. It raced down the runway, got to Vr (rotation speed), the nose was raised to the appropriate angle for lift off...and a big BOOM! was heard fractionally after flames shot from the exhaust of the middle engine AND out the intake...shooting halfway up toward the nose of the airplane. Too late to reject the takeoff they lowered the nose slightly in anticipation of losing the engine but the (what turned to be compressor stage stalls) ceased as the body angle was reduced.
Evaluation post flight determined that at required rotation angles the flow of air through "S" duct separated and the engine made it's displeasure very obvious.
The solution? You guessed it. Vortex generators were located strategically within the "S" duct (most likely at the "inner radius" of each of the "S" curves but I'm not certain of the exact location) to maintain laminar flow (that might not be the right technical term...but the bottom line was to prevent reduction of flow through the duct) back to the engine which, henceforth on hundreds and hundreds of 727s and 727 variants, operated without the rotation stalls thanks to the VGs.
A curious side note. Compressor stalls much earlier in the takeoff roll did become a known problem on the 727 and a technique was developed to prevent them. It would occur just at the start of the takeoff rolls as the engines were accelerating on runways experiencing strong cross winds. The crosswise flow at the intake once again interrupted laminar flow and the engine would bark it's displeasure. As the airplane accelerated and the relative airflow was more direct the stalls would cease and normal operation returned. The technique for such conditions consisted of slightly delaying takeoff thrust on the center engine until forward motion was established and the thrust lever was then more gradually positioned to take off thrust.
I've no idea whether any thought was given to redistribute additional VGs within the duct to deal with this situation. It might have been that there were simply to many variables given varying angles and amounts of cross wind conditions to predict anything like an ideal "one size fits all" location.
Ted
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Thanks for that one, Ted. All through the 1980s I was a frequent "back of the bus" flyer on literally dozens (perhaps hundreds) of 727s (100s and 200s) in connection with business travel for Hughes Aircraft Co.
Now that you've mentioned it, I seem to recall that on takeoff quite often the center engine didn't fully kick-in until near V1 or Vr (though perhaps that's my faulty memory).
At any rate, my thanks to Boeing engineers and the "G/GUF" (guys/gals up front) for the many hours of safe flying. The ol' 727 was quite a machine.
As to compressor stalls, the only time I experienced that was aboard a DC-9-32 out of Melbourne, FL just prior to cruising alt. Still climbing, when suddenly there was this alarming "Bang!" (I was seated near the rear). Certainly does get one's attention! There was no communication from the flight deck. "Just another day at the office?"
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I watched the maiden flights of the original 707 and 727, both very memorable events.
H^^ Now that really is something.
Our F-111s had a bunch of VGs in the inlet ducts, for the same reason. I'm aware of at least one incident involving one of our ground crew and a young lady, where the VGs would've caused a certain amount of discomfort and inconvenience... Probably outside the bounds of this discussion, though!
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<snip>
The solution? You guessed it. Vortex generators were located strategically within the "S" duct (most likely at the "inner radius" of each of the "S" curves but I'm not certain of the exact location) to maintain laminar flow (that might not be the right technical term...but the bottom line was to prevent reduction of flow through the duct) back to the engine which, henceforth on hundreds and hundreds of 727s and 727 variants, operated without the rotation stalls thanks to the VGs.<snip>
Ted
Ted, et all,
I have over 19 years overhauling all versions of the Boeing 727 with two different Airlines. What Eastern called the "S duct", American called the "Worm duct", same-same.
Yes, they had VG's installed along the inner radius of each bend. I have scars to prove it! The early -100 series had an oval intake that was changed to a conventional round intake when the stretch (-200 series) versions came out. Also there are VG's installed forward of the split rudder hinge line because the intake for #2 is wider than the verticle fin.
I remember Eastern got rid of their "Shortys" in the early 80's (I was at MIA). A couple showed up as FedEx Freighters at our overhaul line at American (TUL) in the late 90's. It was like seeing an old friend. We also overhauled converted Pan Am and Braniff 727's (FedEx).
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If you sealed the hinge lines on a 777 (I have no idea how you would do that, one hell of a roll of tape!!) it would do the same thing. Keep air from traveling through the gap. VGs create a vortex. Doesn't really matter what they are on. That's what they do.
Boeing 777's use flexible silicone gap seals reinforced with a mesh. They're sealed.
So are the ailerons and rudder. Flaps are sealed in the UP position.
Agree with your point. But on full scale they are used for boundry layer control and to control stall progression at high AoA's.
On some aircraft you'll notice them installed fwd. of the airlerons only.
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And the new Enya venturi inserts have vortex tabs in them also for yet another entirely related reason. ;D
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Boeing 777's use flexible silicone gap seals reinforced with a mesh. They're sealed.
So are the ailerons and rudder. Flaps are sealed in the UP position.
Agree with your point. But on full scale they are used for boundry layer control and to control stall progression at high AoA's.
On some aircraft you'll notice them installed fwd. of the airlerons only.
Doug,
My memory may be incorrect on the following but IIRC early Boeing jets utilized "balance panels" between some movable and fixed surfaces (stabs and elevators maybe?)...sort of triple hinged affairs that utilized the pressure differential between the high and low pressure surfaces to reduce control input forces necessary to deflect the control surface. As an added bonus they served as gap seals...although I suspect that it was more likely the desire to seal the gap provided the impetus to design them so as to do the "balance" part of their roles. I sort of remember that early Boeings used control tabs for reducing input forces...looked like trim tabs but were driven by the pilots wheel inputs to aerodynamically drive the much larger ailerons in the desired direction.
Does any of that sound at all familiar????
Slotted flaps are, of course, unsealed when extended in order to do their job properly redirecting airflow over the multiple surfaces that are deployed.
Ted
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...although I suspect that it was more likely the desire to seal the gap provided the impetus to design them so as to do the "balance" part of their roles.
No, the balance was needed because you didn't eat your Wheaties.
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Doug,
My memory may be incorrect on the following but IIRC early Boeing jets utilized "balance panels" between some movable and fixed surfaces (stabs and elevators maybe?)...sort of triple hinged affairs that utilized the pressure differential between the high and low pressure surfaces to reduce control input forces necessary to deflect the control surface. As an added bonus they served as gap seals...although I suspect that it was more likely the desire to seal the gap provided the impetus to design them so as to do the "balance" part of their roles. I sort of remember that early Boeings used control tabs for reducing input forces...looked like trim tabs but were driven by the pilots wheel inputs to aerodynamically drive the much larger ailerons in the desired direction.
Does any of that sound at all familiar????
Slotted flaps are, of course, unsealed when extended in order to do their job properly redirecting airflow over the multiple surfaces that are deployed.
Ted
Not sure on the 707's, but yes on the 727's. The balance panels had a habit of collecting snow and ice. I remember bird nests being a problem on our USAF KC-135's, so I'm thinkin' they had them also.
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There is no reason to wonder if the vg’s work or not. Chris’ video of the wing with tufts going through maneuvers both with and without vg’s shows that the vg’s have a real measurable effect. The video goes pretty fast even at the slow motion rate and you have to look close. The maneuver to look at is the entry into the triangle. There is a definite stalled area of the wing with no vg’s and it is just barely disturbed when the vg’s are in place.
The stalled area is the middle section of the rear third of the wing and flap. Apparently close to the fuselage the prop wash is enough extra velocity to prevent stall. The very tip area of the wing is influenced by the tip vortex and is also less affected. But, the center rearward portion of the wing clearly has significant flow separation on the entrance to the triangle ……. for this plane anyway.
This was a fairly light weight plane with a nice thick airfoil, probably not tending to stall very much. I think that the average plane with a bit thinner airfoil and a bit “porkier” may be seeing this partial stall on more of the harder square corners. This “slight stall” is probably what pilots refer to as “inconsistent pullouts”. The fix of the vg’s is to remove the inconsistencies. A picture is worth a thousand words.
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Hi Frank,
That is a very interesting observation, and obviously there is separation present without the VG's.
I did notice one thing of intrest however (at least to me).
The tip of the Stab and elevator are also visible in both photos and in the one with no VG's there is still significant up elevator deflection, wheras in the photo with the VG's the elevator appears to have returned to approximately neutral. I would think that this means that the turn was completed at the point of no elevator deflection, but not yet completed in the photo without the VG's, since the elevator is still deflected.
It might be possible that the stall on the wing occurred because the turn was more abrupt and driven harder by more elevator deflection.
Also, it may be just a trick of the angle of the photo, but there doesn't appear to be much flap deflection in the one that still has elevator deflection.
Is it possible to capture both photos with the same approximate elevator deflection.
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The tip of the Stab and elevator are also visible in both photos and in the one with no VG's there is still significant up elevator deflection, wheras in the photo with the VG's the elevator appears to have returned to approximately neutral. I would think that this means that the turn was completed at the point of no elevator deflection, but not yet completed in the photo without the VG's, since the elevator is still deflected.
Hi Randy
I think its the other way around ..... the deflected elevator is with no vg's ..... the neutral elevator is with vg's .....
actually the video WITH vg's doesn't have any real disturbance ... so I just selected one of the frames
I've included one with the vg's and the elevator matching the frame without vg's.
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Frank, how did putting them just ahead of the flaps work?
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The tip of the Stab and elevator are also visible in both photos and in the one with no VG's there is still significant up elevator deflection, wheras in the photo with the VG's the elevator appears to have returned to approximately neutral. I would think that this means that the turn was completed at the point of no elevator deflection, but not yet completed in the photo without the VG's, since the elevator is still deflected.
Hi Randy
I think its the other way around ..... the deflected elevator is with no vg's ..... the neutral elevator is with vg's .....
actually the video WITH vg's doesn't have any real disturbance ... so I just selected one of the frames
I've included one with the vg's and the elevator matching the frame without vg's.
Uhhhh......NO....The deflected elevator in your photos is with VGs...
My conjecture, and I admit it's strictly conjecture, is that the indication might be that the triangle corner with no VG's could have been stalled by pulling harder and faster on the corner to make it tighter and thereby induce the stall.
However I do understand your point that it is simply a frame out of a video and the frames did not match in time. They do seem to match closely in relative angles, so I came to the conclusion that the corner may have been softer on the one with VG's.
Also there appears to be a significant disturbance in the covering aft of the high point in that same area. I'm not at all sure if that could influence what is showing. It appears to be more "dimpled" in the one with VG's. It seems to be torn and taped, and the tape is deflecting more in the one with VG's
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The tip of the Stab and elevator are also visible in both photos and in the one with no VG's there is still significant up elevator deflection, wheras in the photo with the VG's the elevator appears to have returned to approximately neutral. I would think that this means that the turn was completed at the point of no elevator deflection, but not yet completed in the photo without the VG's, since the elevator is still deflected.
Hi Randy
I think its the other way around ..... the deflected elevator is with no vg's ..... the neutral elevator is with vg's .....
actually the video WITH vg's doesn't have any real disturbance ... so I just selected one of the frames
I've included one with the vg's and the elevator matching the frame without vg's.
The pictures are impressive but I think it could be something as simple as Chris' inconsistencies from one flight to another, where the amount of control input is concerned. OR it might be directly related to the VGs, this one would be hard to prove. It is obvious in the pictures that the VGs are cleaning up the air over the wings. I love the taste of crow.
Derek
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Randy
Old people shouldn't post after 9pm .... sorry 'bout that .... but the point is that ... WITH VG's I couldn't find a frame with obvious separation.
Howard
I flew one plane with vg's right before the flaps, trying to get the vortices to help hold the flow on the flaps ..... once again it was a subtle effect ... nothing jumped out.
I can tell you though that a control surface deflection greater than 15 degrees, the flow over the flap or elevator is pretty much separated. The little turning vanes I had on some planes back through the years did help...... not so much on the flaps as they did on the tail surfaces.
Probably one of the best solutions recently is Igor's "blended airfoil/flap" intersection . I should note also that Al Rabe did the same thing with his airfoil shapes some years back.
Derek
I think that these little "mini stalls" probably occur more often than we are aware. A little extra handle in the corner might cause these "inconsistencies" that make the plane be just a little off of where we expected it to be. Maybe also wind conditions might effect the flow just enough to change the angle of attack just enough to push the wing into a separated flow.
From Chris' video, I do think that we see that the area of concern is the mid wing area and that vg placement in that range of the span would probably be the most benificial.
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All,
I put this test on hold because my daughter was about to be born. This winter I intend to build a profile ship that I can mount a camera on different locations. The current plane doesn't allow very many camera positions. I would invite anyone to "request an experiment" and I will do my best to test it. I would love to know what people want to know NOW so I can finish the design of the test ship with the experiments in mind.
Thanks,
Chris
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Probably one of the best solutions recently is Igor's "blended airfoil/flap" intersection . I should note also that Al Rabe did the same thing with his airfoil shapes some years back.
Didn't Claus Maikis back in the 80's feature something like that with his 'knuckle jointed' flap hinges also?