mk1spitfire

have any of you fellow speed freaks expereinced this with noticeable trails at tips.

Would like to know at what speed and climatic conditions or mods to the tips this is or could be achieved

Gregor32

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I havent heard about the tip vortices, but i did read about this type of thing a while back and i think it was in the jets forum, there was talk about the fog seen over wings during hi g manouvers it was in florida i think and it was a large heavy jet flying in very humid conditions. you could try asking over there. Greg

daven

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I haven't seen it, but I have flown through it many times. Use to think it was dumb thumbs when others claimed "bad air", but fly through it a few times and you will become a believer. Normally only see it over 160 mph, but have felt it at 130.  Nearly all control is lost and your plane can go in before you knew what happened.

Typically happens if you are slightly behind someone coming around either pylons #3 or #1. Took a couple of smashed planes to learn how to first, try to avoid it, and 2nd if you can get on the sticks quick enough to save it.

tIANci

Daven ... actually there is a simple cure for that all. Fly no more than 125 mph. Heheheheee ...

Mike Connor

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I would think that actually seeing visible moisture caused my wing tip vortices from a model would be rare. It is rare on full size aircraft. It is more likely you would feel it, as Daven pointed out. In full scale we were never concerned about it from a safety point of view unless the other aircraft was much larger then us. However, being right behind someone with a high speed pylon racer in a tight turn could give you a surprise bump from wake turbulence.

Mike Connor

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No, the cure is stay in front.

daven

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I usually feel it while lapping people, yeah thats it

mk1spitfire

I heard birds fly in a V. The trailing birds benefit from the vortices of the bird in front, helping them fly easier

BUT I've never seen a bird produce vortices trails, not even a super sonic periquin falcon

hotrodblazer

I have seen trails from the wings on top fuel dragsters in humid conditions, real cool looking!

mk1spitfire

yer like f1 cars wings.

tIANci

I hear from the local grapevine that you experience that many times in a race till you get so frustrated as you always lap them all a few times in each race. ROFL!

z06kal

You're talking about vapor trails off the wing tip vortecies.  I think you need substantial wing area to make this happen.  I doubt you would see a model do it...

HighPlains

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It depends on humidity and temperature, conditions that are conducive to creating fog.  I've seen it happen behind a car antenna at rather slow speed.

As far as the bad air often found in pylon turns, it is worse with higher wing loadings and high g turns.  The trailing airplane has the air disrupted over one side and it stalls.  The resulting snap roll usually puts the airplane into the ground.  To prevent it, the trailing airplane has to fly inside the lead airplanes path to avoid.

The problem is most dangerous on calm days, as the vortex energy will stay on the course for enough time, you can hit your own wake on the next lap.  Even sport airplanes can run into their own vortex on calm days.  People often think it is a radio glitch.

HornetFitter

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www.rcuniverse.com/gallery/galleryItem.cfm
Kinda like this?

MJD

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Don't know the actual numbers, but as I understand it you need moisture and a lot of dynamic pressure under the wing. Under marginal conditions AFAIK they will appear at the tips only, increase the numbers and it moves along the wing to just about anywhere the high pressure air is exiting behind the surface and expanding rapidly. So my guess is that it is a function of wing loading and atmospheric conditions, and due to the wing loading of typical R/C models achieving this under high G manouevers is still not typical. As someone observed, it was in Florida with a large heavy jet, which it seems moved the pointers up both scales to the "possible" zone.

MJD

mk1spitfire

here some wiki on it

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

and induced drag causes

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

HornetFitter

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Depending on the airfoil, the phenomenon can be visibly noted at speeds of less than 100 kts, if the alpha (angle of attack) is great enough and the humidity is high enough. In the pictre I posted above, this was a mach .92 topside pass in 85f, high humidity and the jet was pulling about 2-3g. When the flaps are down, there is an extremely low pressure zone on the top side of the flap/flaperon, which bleeds and the airflow from the high pressure area underneath rolls outboard where it creates a vortex which can usually be seen as wingtip vorticies and vapour.

tIANci

But fluid dynamics on a real plane and a small plane is not the same. Just like the Reynolds numbers ... however, it would be cool to see it happen on a RCplane!

MJD

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"

?? - I kind of thought it was the same, except for the specific differences due to low Reynold's numbers, mostly the difficulties maintaining laminar flow and whatever inefficiencies that result. But I am pretty sure the primary reason this must be rarely or ever seen on models is that we simply don't work with anywhere near the same kinds of wing loading and the resulting levels of pressure differential and dynamic pressure - otherwise I would have to think we'd need to start looking at aluminum wing skins and way better internal structures and whatever other voodoo would be manatory to keep the wings from disintegrating.

HornetFitter - thanks for the first hand explanation!

MJD

combatpigg

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I've noticed vapor trails at the wing tips of several commercial flights I've taken.......or was it just smoke billowing out of the hydraulic system?

MJD

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You open your eyes?

tIANci

Pigman ... did you not rush to get the extinguisher?

MJD ... the votices are seen because air is compressed and there is moisture so we see it. Maybe on our planes the vortices are too small to be seen, we should watch closely with binoculars! Hahahaahaa ...