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Old May 20, 2012, 07:46 AM
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United States, IL, Belvidere
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Question
YB-22 Jet Torque Roll

Hoping that the wisdom out here can help me. Got a YB-22 Park model and it's a ton of fun except for the excessive torque roll to the left at about 3/4 to full throttle. Am using 1300 3cell, DS6i, 7x5 prop. I did program about 40% expo in it. With the 7x5 prop the torque roll is insane and after a few tries I don't dare run it much beyond half throttle. I added a couple of finishing nail in the right wing as the manual suggests but no change. I went to a 6x4 prop and it was a little better but still I cannot give it enough right stick (turn) to counteract the roll. Anybody out here have any ideas? Figured I would post it here also as the the Yard Bird forum seems pretty dead. Thanks in advance!
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Old May 21, 2012, 03:44 AM
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United States, CO, Westminster
Joined Jul 2011
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My 50mm edf F35 i converted to a pusher had alot of torque and rolled to the left. I had my trim set so much to the right it was a 1in or more diffrence.
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Old May 21, 2012, 07:14 AM
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United States, IL, Belvidere
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That must have been hard to control during normal flight & that's my concern. I thought about trimming it much more but I figured that during normal flight I would constantly need to give if left stick all the time making it not so much fun to fly.
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Old May 21, 2012, 11:46 AM
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United States, FL, Sebring
Joined Feb 2006
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Quote:
Originally Posted by HiTekCub1 View Post
Hoping that the wisdom out here can help me. Got a YB-22 Park model and it's a ton of fun except for the excessive torque roll to the left at about 3/4 to full throttle. Am using 1300 3cell, DS6i, 7x5 prop. I did program about 40% expo in it. With the 7x5 prop the torque roll is insane and after a few tries I don't dare run it much beyond half throttle. I added a couple of finishing nail in the right wing as the manual suggests but no change. I went to a 6x4 prop and it was a little better but still I cannot give it enough right stick (turn) to counteract the roll. Anybody out here have any ideas? Figured I would post it here also as the the Yard Bird forum seems pretty dead. Thanks in advance!
What motor are you running? You might need to change the approach. Most of my pusher Jets run a high kv motor with small props. one setup that I happen to like is a 3000 KV outrunner, apc 4.4x4.1.... the smaller props don't contribute as much to torque roll like big props do.
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Old May 21, 2012, 12:05 PM
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United States, IL, Belvidere
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I'll have to find out for you but thanks for the reply. I did measure the wattage & it was 301 at full throttle. Drew 31 amps with the 7x5 & 19.8 with the 6x4
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Old May 21, 2012, 12:08 PM
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To help you best, please post the length, wignspan and weight of the model as well.
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Old May 21, 2012, 12:17 PM
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L-34-1/2" Wingspan 24" / 17oz weight
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Old May 21, 2012, 12:28 PM
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United States, FL, Sebring
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Wingspan 24"
uh oh, I see a problem right there. Generally speaking, a prop size of 1/3 the wingspan is on the ragged edge of the maximum recommended prop size. On jets like this, you will definately see a reduction of torque roll by dropping that prop down a few inches in diameter. As long as your speed controller and motor is rated for the voltage, you drop a couple inches on prop diameter and add an extra cell in the lipo to spin the motor faster.

I generally prefer prop jets to have a prop size that is more like 18-20% of the wingspan and spin it really fast. Tricky thing is that each jet design responds a little different so you end up having to play with the prop size a little bit. I tended to keep a whole selection of test props and ultimately ordered a few of whatever prop gets selected for a particular build.
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Old May 21, 2012, 12:39 PM
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Ok, The manual call for a 7x5 which is with the motor they suggest. I went to a 6x4 which is what the local hobby shop suggests. And Yardbird suggests a motor that's 26 watts less. So you think maybe I should go smaller. Any suggestions on size to try? I've got more info from you than I've had in a week & I really thank you for it!!! I'm just surprised It would even fly with a smaller prop!!
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Old May 21, 2012, 12:48 PM
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Originally Posted by Joe 1320 View Post
uh oh, I see a problem right there. Generally speaking, a prop size of 1/3 the wingspan is on the ragged edge of the maximum recommended prop size. On jets like this, you will definately see a reduction of torque roll by dropping that prop down a few inches in diameter. As long as your speed controller and motor is rated for the voltage, you drop a couple inches on prop diameter and add an extra cell in the lipo to spin the motor faster.

I generally prefer prop jets to have a prop size that is more like 18-20% of the wingspan and spin it really fast. Tricky thing is that each jet design responds a little different so you end up having to play with the prop size a little bit. I tended to keep a whole selection of test props and ultimately ordered a few of whatever prop gets selected for a particular build.
You have been a wealth of information and I thank you very much. This gives me renewed hope to overcome the problem. I'm gonna get to the hobby store hopefully today & get a stock of different size props!!!
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Old May 21, 2012, 12:55 PM
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United States, FL, Sebring
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Quote:
Originally Posted by HiTekCub1 View Post
Ok, The manual call for a 7x5 which is with the motor they suggest. I went to a 6x4 which is what the local hobby shop suggests. And Yardbird suggests a motor that's 26 watts less. So you think maybe I should go smaller. Any suggestions on size to try? I've got more info from you than I've had in a week & I really thank you for it!!! I'm just surprised It would even fly with a smaller prop!!
well, here's the deal. It's all about leverage. You could spin an 8" prop if the motor spools slow and the plane is a slow flyer. The more power you put into a prop, the more leverage the prop has against the air.....AND the more leverage the prop has against the airframe (Torque induced counter roll) The bigger the prop, the greater the leverage in both directions.

here's the skinny on props. The diameter contributed the most to the amount of thrust. The pitch of the blades gives airspeed. It doesn't matter what size prop, the faster you spin it.... the greater the thrust and speed. what modelers try to do is pick a motor and prop that gives good enough performance with the lowest amps draw. the smaller the prop, the faster you have to spin it in order to keep up with a larger prop.

prop jets need higher pitch speeds in order to get the jet like speeds. that generally means steep pitch (like a 7x6 vs. 7x3 ) or you have to spin the prop faster. (step down to a 5x5 and spin it 25% faster.) it would be hard to narrow down the prop without knowing what motor you have.
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Old May 21, 2012, 01:02 PM
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United States, IL, Belvidere
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Originally Posted by Joe 1320 View Post
well, here's the deal. It's all about leverage. You could spin an 8" prop if the motor spools slow and the plane is a slow flyer. The more power you put into a prop, the more leverage the prop has against the air.....AND the more leverage the prop has against the airframe (Torque induced counter roll) The bigger the prop, the greater the leverage in both directions.

here's the skinny on props. The diameter contributed the most to the amount of thrust. The pitch of the blades gives airspeed. It doesn't matter what size prop, the faster you spin it.... the greater the thrust and speed. what modelers try to do is pick a motor and prop that gives good enough performance with the lowest amps draw. the smaller the prop, the faster you have to spin it in order to keep up with a larger prop.

prop jets need higher pitch speeds in order to get the jet like speeds. that generally means steep pitch (like a 7x6 vs. 7x3 ) or you have to spin the prop faster. (step down to a 5x5 and spin it 25% faster.) it would be hard to narrow down the prop without knowing what motor you have.
Well I have solid direction now and can work with that. I've heard about every idea in the book so far but until now none of it has made much sense.
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Old May 21, 2012, 01:22 PM
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Well I have solid direction now and can work with that. I've heard about every idea in the book so far but until now none of it has made much sense.
Great. You see, the part that makes it difficult for jets is that in regular prop planes, the air coming off prop is flowing over the surface of the aircraft and your flight controls can take advantage of that. In a pusher jet, that's not happening and the flight surfaces don't work until you get some airspeed. Hand launches can be a nightmare if the plane's not tuned properly.

little by little, you'll get up to speed so to speak. just glad to help.
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Old May 23, 2012, 06:48 AM
it wasn't me flying that plane
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United States, NC, Wilmington
Joined Mar 2011
704 Posts
Fixed my torque problems by installing stronger servos on the tailerons..also be sure your linkages are not flexing as this will not allow you to correct no matter the equipment..try JR mn48's..that should give you the power to counter any roll..
I have been through this with upgrading power systems..
I really think will fix your problems...
Take care......chris
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Old May 23, 2012, 07:17 AM
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United States, IL, Belvidere
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That's a consideration I've not given! The servos are JR but I am going to look those over. One thing I did notice is the Yardbird SU-40 is nowhere near as reinforced as the Yardbird F-15. I can actually watch the foam flex at the wooden motor mount area. I don't see that in the F-15. So while I did seem to almost eliminate the problem with a 5x5 prop I keep getting told that the motor/plane combo (2200kv) should support the 6x4. I know someone with the F-15 & it seems to be much more rigid. Joe 1320 suggested the smaller prop and it did work & work well based on his experiences. But if I can modify the plane to make it more rigid I'll attempt that also. Thanks Chris!!
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