Eliminating torque roll

twistair

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Today we tested a simpliest antitorque addon on a Calidus stabilizer to see if it works.
First flight shows how a gyroplane without this addon reacts when rotor is unloaded and engine rpm are high. At each attempt one can see apparent roll to the right.
Second flight made half an hour later shows that there is next to none tendency to roll right when this addon is installed.
Main thing is that this addon costs less than $1. It takes half an hour to make it and to install it. It is a pair of simpliest Gurney flaps made of 20"x1.25" aluminium strip 0.5 mm thick each. Bend the strip so it makes 20x10mm angle bent to 90 degrees. Wider side is installed with double-side scotch to the stab' trailing edge so that it pitches left stab down and right stab up.
Video shows the difference in torque roll tendency with and without these flaps.

[video=youtube;1WXbi-ZWWQw]https://www.youtube.com/watch?v=1WXbi-ZWWQw[/video]

Fly safe!
 
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C. Beaty

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Gurney flaps are a very simple and clever way of producing differential lift effect in the horizontal stabilizer.

I’m surprised that the Calidus horizontal stabilizer catches enough of the propeller slipstream to be as effective as it appears.

It would be interesting to see the numbers when main wheels are placed on scales, tail tied to tree and throttle is run up and down.

Be careful when unloading the rotor.
 

twistair

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C. Beaty;n1118281 said:
I’m surprised that the Calidus horizontal stabilizer catches enough of the propeller slipstream to be as effective as it appears.

It would be interesting to see the numbers when main wheels are placed on scales, tail tied to tree and throttle is run up and down.

Be careful when unloading the rotor.
I also doubt that Calidus stab works well where it is placed. It is 50 mm only above prop disk lower point. I plan to rise stabs 250-300 mm higher. And yes, I understand that quantitive test with scales is necessary to make this job more precise. Will try to find them.

As for unloading rotor - I understand all the risk and try to enter these tests with very small steps. German rotor is much more sluggish than, say, DragonWings so it gives more time space for such experiments. In fact I started to palp torque roll after Dubai MTOsport crash and I use to show students how it looks alike
when one enters it.

AirCommandPilot;n1118282 said:
do you have a picture of the flaps installed?
I forgot photos at the airfield today, will post tomorrow.
 

swilliams

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Thanks for posting the video was interesting to watch.

Sincerely SWilliams
 

swilliams

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Thanks for posting the video was very interesting to watch.

Sincerely SWilliams
 

eddie

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great testing,does the flaps slow overall cruise speed,if so how much ?




Best Regards,
 

twistair

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Photos show temporary flaps fabricated of 0.5 mm thick alu sheet just for testing. Looks like 0.8 mm thick would be more practical.
 

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twistair

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eddie;n1118288 said:
great testing,does the flaps slow overall cruise speed,if so how much ?
We couldn't notice any changes in cruise or max speeds which isn't surprising at all since G-flaps add very little drag if any. They mostly virtually just curve an existing airfoil.
 

twistair

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AirCommandPilot;n1118318 said:
Does this also work while on the take-off run?
It's known that Rotax-powered pusher tends to roll right at full throttle while on take-off roll. With G-flaps installed I'd said this right roll is roughly twice weaker. This is for a tandem with two on board. I still need to check all the things solo. I also plan to try G-flaps for the rudder to decrease yaw effect caused by engine rpm changes.
 

Doug Riley

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The fastest portion of the prop slipstream is located at about 2/3 of the prop's radius from the center of the slipstream. The exact location of this "fastest" portion varies with such factors as the design of the prop itself and the ratio of slipstream speed to freestream speed.

The slipstream moves about (up, down and sideways) in response to changes in the fuselage's angle of attack. For example, the rotational axis of the slipstream will swing to one side during a slip.

During the gentle "pushover" maneuver shown in the videos, the fuselage is more nose-down (relative to the freestream) than usual. Therefore, the slipstream will point "downhill" (toward the tail tube and the HS) more than normal. Hence, the HS (with its G-flaps) will be more immersed during a pushover than it is in level cruising flight. This is fortunate, and probably accounts for the fact that the many Magni clones all appear to be PPO-resistant (or proof?) despite the typically low placement of their H-stabs and high thrustlines.

A HTL gyro whose H-stab is not normally immersed in the prop slipstream (because the H-stab is too low), but BECOMES immersed when the nose drops will exhibit telltale behavior. When power is abruptly increased, the nose will dip a bit, but will not continue to drop beyond a certain angle. OTOH, a gyro with a low thrustline and centered H-stab, such as the Dominator, will not drop its nose at all when power is increased; in fact, the nose will rise.
 

twistair

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Yesterday we made a primary (well, a very primitive) test to see propwash airspeed distribution for a Calidus. Simple testbench allowed to place pitot to certain nodes which made 20x20 cm cells. 350 kmh airspeed gauge was used and we measured airspeed at 4000 engine rpm. Airspeeds measured at each yellow lines intersection. Below are some pictures. Last picture show results where white empty circles show boundary area where no airspeed move was detected. Light green circles show area where gauge arrow just twitched. Dark green circles - gauge arrow twitched more but no numerical speed could be read. Numerical speeds are in kmh.
If I understand correctly this picture shows that horizontal stab isn't affected by a propwash at all and the upper one quarter or even one third of vertical fin and rudder doesn't work also.
I'm curious how this changes in flight.
 

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Vance

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Great work Alex!

Thank you for sharing what you have found.
 

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twistair;n1119772 said:
Yesterday we made a primary (well, a very primitive) test to see propwash airspeed distribution for a Calidus. Simple testbench allowed to place pitot to certain nodes which made 20x20 cm cells. 350 kmh airspeed gauge was used and we measured airspeed at 4000 engine rpm. Airspeeds measured at each yellow lines intersection. Below are some pictures. Last picture show results where white empty circles show boundary area where no airspeed move was detected. Light green circles show area where gauge arrow just twitched. Dark green circles - gauge arrow twitched more but no numerical speed could be read. Numerical speeds are in kmh.
If I understand correctly this picture shows that horizontal stab isn't affected by a propwash at all and the upper one quarter or even one third of vertical fin and rudder doesn't work also.
I'm curious how this changes in flight.
Wow very impressive, thank you so much for sharing your testing and findings.
We love these types of test !!!
U-ROCK!
 

loftus

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twistair;n1119772 said:
Yesterday we made a primary (well, a very primitive) test to see propwash airspeed distribution for a Calidus. Simple testbench allowed to place pitot to certain nodes which made 20x20 cm cells. 350 kmh airspeed gauge was used and we measured airspeed at 4000 engine rpm. Airspeeds measured at each yellow lines intersection. Below are some pictures. Last picture show results where white empty circles show boundary area where no airspeed move was detected. Light green circles show area where gauge arrow just twitched. Dark green circles - gauge arrow twitched more but no numerical speed could be read. Numerical speeds are in kmh.
If I understand correctly this picture shows that horizontal stab isn't affected by a propwash at all and the upper one quarter or even one third of vertical fin and rudder doesn't work also.
I'm curious how this changes in flight.
Just a guess, but airflow over the areas where no airflow is detected during static testing would be more or less equivalent to airspeed while in flight, and the more central areas where prop wash is detected may be less affected by airspeed in flight due to shielding by the engine etc. The net result being less difference in airflow than the static testing indicates. This might account for the effect of the flaps in flight, despite being out of the prop wash. I'd be interested to hear Abid's thoughts on this and the effect of having the tail further back as he has done in the AR-1.
 

Resasi

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Alex it was most interesting finding this thread, and I guess Abid has either used or experimented with Gurney flaps as I have seen him comment on them.

I was looking at a Gurney on one horizontal stab as being a possible means of self regulating counteraction to the extra torque I am expecting with the 100 hp on the single seat Explorer presently being built. IE the more power, the greater the slipstream the greater the effect, so finding this was very fortuitous.

While searching I did find a video of rotors using flaps. Too complex for gyros no doubt but interesting to see them in use.
 
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Doug Riley

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Dar: Seeing is believing.

Can you show us what anti-torque device(s) you are using? There appears still to be some torque roll, even with the device(s) installed.

Have you tried correlating these flight tests with static ground tests using scales under the main wheels?

You're tickling the dragon's tail any time you do intentional pushover maneuvers in a gyro. Careful is the word.
 
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