Discussion High speed roll

[hpapilot]

That airplane is rediculously fast and has huge ailerons, I'm not entirely surprised you're seeing blowback with those servos. While torque doesn't actually change with servo arm length, the force that the servo can impart at the end of that arm does. How much throw are you mechanically set up to get? Make sure to shorten your arm so you can use about 130% end points to achieve the max throw you actually want to use.

[pryor808]

	Quote: Originally Posted by JackRC
	ya, my hariier left roll is faster or more predictable than right roll. That I believe is causing by the torque. could you tell me more about this blowback from the aileron servos? Thanks! Jack

Jack,

What size airframe are you flying?

[racelikustolit3k]

	Quote: Originally Posted by JackRC
	ahh, that make perfectly sense Vic!! Now think about it, whenever I start rolling first and then increase the throttle gradually then it roll faster and faster. However if I go full throttle first then start rolling then it slow like an egg roll because my servos don't seem to have the power to overcome the high velocity wind. btw, my plane is 3DHS 72" Extra 330SC with DLE30 , plenty of power for a lightweight setup. Full throttle is scary fast most of the time, probably need a better servo to keep up with it.

.

[pryor808]

Thanks Jessie,

Now that I see that Jack is flying a 25% airframe, there is no reason for him to get aileron high speed blowback if he is using HQ servos over 160 oz-in of torque especially, on the ailerons. No matter the throw factor. I see your using A123's and, 7985's. Do me a favor and, power up your servos and, apply pressure with your hand to your control surfaces. You may have a week (defective) servo somewhere.

[JackRC]

	Quote: Originally Posted by hpapilot
	That airplane is rediculously fast and has huge ailerons, I'm not entirely surprised you're seeing blowback with those servos. While torque doesn't actually change with servo arm length, the force that the servo can impart at the end of that arm does. How much throw are you mechanically set up to get? Make sure to shorten your arm so you can use about 130% end points to achieve the max throw you actually want to use.

I still have a lot of travel to play with on the aieron so I will shorten the arm and see what's up.
I pretty sure you are correct because all the symptoms pointing to blowback.

[JackRC]

	Quote: Originally Posted by pryor808
	Thanks Jessie, Now that I see that Jack is flying a 25% airframe, there is no reason for him to get aileron high speed blowback if he is using HQ servos over 160 oz-in of torque especially, on the ailerons. No matter the throw factor. I see your using A123's and, 7985's. Do me a favor and, power up your servos and, apply pressure with your hand to your control surfaces. You may have a week (defective) servo somewhere.

ok, I tried again today with high speed pass and start rolling, The roll rate was slow at the beginning but gradually picking up. So I am 90% sure it's the blowback from the wind pressure at full speed, The servo just don't have enough "initial force" to withstand the wind pressure.

My solution for now will be: "don't fly that fast and low when rolling", after today's 15 mins high speed test run, I got complains from people at the field saying I am reckless... hmn.. wait till I got a 103 Extra

[racelikustolit3k]

	Quote: Originally Posted by JackRC
	ok, I tried again today with high speed pass and start rolling, The roll rate was slow at the beginning but gradually picking up. So I am 90% sure it's the blowback from the wind pressure at full speed, The servo just don't have enough "initial force" to withstand the wind pressure. My solution for now will be: "don't fly that fast and low when rolling", after today's 15 mins high speed test run, I got complains from people at the field saying I am reckless... hmn.. I think they got really scared..

take a look at this calculator and start figuring it out.. http://mnbigbirds.com/Servo%20Torque%20Caculator.htm

if your plane is truely that fast any servo is going to blowback with 40+ degrees of throw

you may also majorly stress the aileron by flexing it.. been there done that..

start by lowering your rate of throw and run the plane full tilt boogie down the F/L and gradually add more throw until your content with the RR.. you may have way to much throw for what your trying to accomplish..

[Jaybird]

Wonder if you have too much throw on those giant ailerons and it's acting as an air brake at high speed ? I know foamys will do that but never messed with it on the bigger planes. It would be easy to back off a few degrees and give it a shot.

[JackRC]

	Quote: Originally Posted by racelikustolit3k
	take a look at this calculator and start figuring it out.. http://mnbigbirds.com/Servo%20Torque%20Caculator.htm if your plane is truely that fast any servo is going to blowback with 40+ degrees of throw you may also majorly stress the aileron by flexing it.. been there done that.. start by lowering your rate of throw and run the plane full tilt boogie down the F/L and gradually add more throw until your content with the RR.. you may have way to much throw for what your trying to accomplish..

cool, thanks a lot for the input!
ya, I have 35~40 degree right now, and I think that giant control surface double as a air brake at full throttle

[racelikustolit3k]

yep thats the jist of what I said.. my EF yak did that.. pulled the throw down and it still rolls like a monster

[Jaybird]

	Quote: Originally Posted by racelikustolit3k
	yep thats the jist of what I said.. my EF yak did that.. pulled the throw down and it still rolls like a monster

LOL. You posted while I was typing.

[Sukhoikid]

I gotta say the OMP Yak 33% is probably the fastest rolling plane I have seen. I have yet to see a plane roll faster than that plane!

[racelikustolit3k]

da 120 powered Carf 2.6m extra 260.. I love it

[William Storzuk]

I love mine too!!!!!!!

[JackRC]

	Quote: Originally Posted by racelikustolit3k
	da 120 powered Carf 2.6m extra 260.. I love it

I just look it up and it only weight 24.25- 27.5 lbs dry with full balsa wood. wow.
Will definitely put it into my wishlist.