Vortex generators on Dragon Wings

[gyroav8r]

I am going to be trying some sort of Dimple Tape or zig zag tape on my 23 Dragon Wings that I will be hand-starting on my ultra-light gyro. As anyone familiar with Dragon Wings knows, they are great blades with an efficient airfoil but they are very difficult to #@**&>! hand start!!
I am planning to place the tape on the inboard half to two thirds of the blades, the area responsible for the driving auto-rotational force on the blades.
Has anyone tried this? If so, any success and what turbulator medium did you use?
I know there are blades out there that will easily hand-start but they are too heavy. My 23 Dragon Wings weigh 43 lbs and I am currently right at 254 lbs.

[gyroav8r]

Here is a link to some work VG experimenting on a glider wing.

http://ecomodder.com/forum/showthrea...rs-1209-4.html

[Resasi]

I'm a newbie, not well versed in Rotor aerodynamics, but my instinct would be to steer well clear of this. I would be concerned in the potential in flight effect of partial tape separation on one of the blades.

Most aircraft using vortex generation would probably not be so flight critical in the case of such loss.

Very interested in any comment and feedback this thread generates. (No pun intended I assure you.)

[gyroav8r]

Thanks for the input. In the airforce, we used blade tape to protect thehelicopter rotors which often came off during flight in rain with quite a lot of stick shake but nothing dangerous. In this attempt, I will only be taping the inboard sections.
All testing will be done in ground effect - trust me!!

[gyromike]

Roy,

Are you going to try to "map" the airflow over the rotor blades, like the link above?
It would be interesting to see just where along the blade span the airflow seperates before applying the tape, and again after.

[getut]

I would be VERY interested in hearing from the experts on this to confirm or deny my understanding of things.. hopefully with an explanation.

But my understanding is that the driving and driven regions of the blade as they are depicted in most rotorcraft manuals are more conceptual than fact and are necessary more from the standpoint of needing a quantification of driving and driven ratio to work with math calculations. Again, in my understanding the whole length of the airfoil actually participates in being both driving and driven but in a different ratio depending on where you are in the span of the blade.

In other words.... for the forces acting on and produced by the blade... you don't get a magical, sudden and abrupt switch from driving to driven at a certain point in the airfoil. Both forces occur for the whole length of the blade.

[Resasi]

Roy interesting to hear of the use of leading edge tape on helicopter rotors, we certainly used it on exec jets.

Are you aware of any application of such tape to rotors, or are you leading the way.

Certainly seems an interesting field to move into.

A gradual creep down the blade with the tape during testing might well establish a maximum efficiency point for a particular regime. In your case hand starting.

[dinoa]

If my understanding is correct. Dimple and zig-zag tapes are used on laminar flow airfoils to delay the onset of turbulent, or even worse, separated air flow. They are thin because they aim to trip the laminar boundary layer a little further downstream at an obvious point and then to slightly turbulent flow. They are usually located no further forward than say 70% chord. They would have no influence on delaying stall. Also the small join line where the solid extrusuion is bonded to the aluminum sheet on DW and other blades is probably enough to trip any laminar flow beyond that point not mention the waviness of the aluminum skin further aft.

Stall prevention aids such as vortex generators are much thicker and aim to energize a thick turbulent boundary layer to prevent it from seperating at high angles of attack. They are usually located forward of the maximum thickness of the airfoil.

Dino

[kolibri282]

There was a pretty thorough discussion of the quastion here:
http://www.rotaryforum.com/forum/sho...ht=dimple+tape

You might want to read the thesis mentioned in answer #26

Cheers,

Juergen

[gyroav8r]

From my Airforce studies on rotorcraft aerodymics, rusty as they may be now, the autorotational vector on the rotor blade is most tilted forward at the root with the vector becoming more vertical further towards the tip until it actually starts tilting rearward at the tip. Typically approx the last third to quarter of the blade is supplying most of the lift and most of the rotor drag.
The dimple tape is used effectively on props at the point of greatest camber so no reason it wont help energise the boundary layer on a gyro blade.
It does not have to be a laminar flow airfoil to work. See the links below.

No harm in trying.

http://www.dimpletape.com/
http://www.wingsandwheels.com/page29.htm

http://ecomodder.com/forum/showthrea...rs-1209-4.html

[kolibri282]

A boundary layer can not be energized by a passive device. Any turbulence dissipates energy from the boundary layer. A beneficial effect will only be seen in very limited regions of Reynolds number if the turbulent layer inhibits flow separation. Since the flow speed varies along the blade radius it requires a very sopisticated CFD analysis to find a combination of parameters that will improve the flow over the airfoil and this will only be in a very limited region of the blade, if at all. Measuring this effect requires equipment that probably comes at 10 to 100 times the price of your gyro...;-)

[bpearson]

All of this experimentation stuff is good and should be encouraged.

[gyrojake]

Roy great Idea!! Just take into consideration a stall on the down wind blade.
Stall gaurds and votex generators always recieve air in one direction. This may cause high pressure on the trailing edge of the down wind blade.

Just a thought, or the beer or the weed!!!!

~~JAKE~~

[Friendly]

Originally Posted by gyroav8r

I am going to be trying some sort of Dimple Tape or zig zag tape on my 23 Dragon Wings that I will be hand-starting on my ultra-light gyro. As anyone familiar with Dragon Wings knows, they are great blades with an efficient airfoil but they are very difficult to #@**&>! hand start!!
I am planning to place the tape on the inboard half to two thirds of the blades, the area responsible for the driving auto-rotational force on the blades.
Has anyone tried this? If so, any success and what turbulator medium did you use?
I know there are blades out there that will easily hand-start but they are too heavy. My 23 Dragon Wings weigh 43 lbs and I am currently right at 254 lbs.

If the tape were to peel in flight wouldn't it change to airfoil shape drastically?

[RotoPlane]

I plan on trying vortex generators on the inboard 1/3 of my blades, just forward of the CP. They are the "T" type (1/4" h x 1" lg) and are positioned in pairs starting with 40* included angle and ending with 10* at the furthest out'bd pair. I want to see if they increase rotor rpm with the same loading….I believe they will and also will help to extend the retreating blade stall….. I can't see how "dimples" can do that….but until it is tried who knows….