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Old Feb 02, 2015, 06:35 PM
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I'm breaking-in helis.
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Greenland, Qaasuitsup
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tail travel limit!!

hey guys, i read somewhere that you don't want to set the tail travel limit too much, because it may stall tailblades with too much pitch and may be less effective.....

do you go to almost mechanical limit on the travel?(as far as it can go) or do you still have room left on the ends??

also, how does it impact if you fly with lower rpm's...?

let's hear it, i'm ready to be educated!
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Old Feb 02, 2015, 11:38 PM
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I set it so that it doesn't bind with the edges for both my Agile 5.5 and Goblin 500, for the Chase 360 the throw is so extreme i had to limit it to about half of it so that I could keep it under control.
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Old Feb 03, 2015, 12:00 AM
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Depends on the heli. Some I've needed to set it so I've got every fraction of a millimeter possible, a hair width from binding (The Trex). Others such as the 7HV the manual says to set it only traveling part way and i can still get the tail blades barking easily, so no need for more.
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Old Feb 03, 2015, 02:19 AM
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My experience with Align 500 and 550 is that I set it as close to the ends as I can. Never had an issue in flybarred or fbl form.
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Old Feb 03, 2015, 03:14 AM
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An easy question to answer in that you will probably know when you stall the tail blades.
And a difficult one to answer. The airflow is changing depending on how you fly. Peoples helicopters are different. So the maximum one can get away with, can be to much for someone else. How deep into the stall you can get away with also depends on those same things.
When you stall the blades you can get lots of noise. The drag goes way up, and the tail rotors lift drops quickly. Some high powered setups can overcome the increased drag to a point. If you go beyond that point you may lose control of the tail.
The rule of thumb is that around a max of + - 25 degree's is usually safe.
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Old Feb 03, 2015, 07:04 AM
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Quote:
Originally Posted by JetPlaneFlyer View Post
Depends on the heli. Some I've needed to set it so I've got every fraction of a millimeter possible, a hair width from binding (The Trex). Others such as the 7HV the manual says to set it only traveling part way and i can still get the tail blades barking easily, so no need for more.
I've always set mine to just avoid binding and getting the vbar happy. I've been happy enough to leave this to the gyro, although what you say does indeed have theoretical merit - if you're not using the whole tailshaft, why not get more resolution for the gyro?

I myself don't know how much of the tailshaft the vbar _atually_ uses on my helis, but I've not had any tail problems, so I'm likely to continue the way I am.
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Old Feb 03, 2015, 08:09 AM
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Quote:
Originally Posted by spykez View Post
if you're not using the whole tailshaft, why not get more resolution for the gyro?
I always get full resolution from the gyro. I do that by adjusting what hole I use on the servo arm so that the travel on the servo (as set in the FBL controller) is in the optimum range.

No point in always using every bit of travel that's mechanically available if all the last bit of travel is doing is stalling the blades.
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Old Feb 03, 2015, 10:29 AM
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o i see. well, i read somewhere that with lower rpm, blades stall quicker, so I figured since i'm flying with lower rpm, i need to limit my throws. But i don't have any blow-outs. I did when i was flying 860 headspeed using 3s, but that's another story and not very relevant i guess.

reason i'm asking is i have plenty more room for more pitch maybe i need to experiment again, but little reluctant because it works fine as it is now....25 degrees?? i read somewhere airfoil is good for 12 degrees...
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Old Feb 03, 2015, 11:50 AM
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Airfoils vary, 12 degree's is low, some are dropping by 8 degree's. Many can make 15 to 18, compared to the air flow into it. The Inflow can change things, however its hard to predict. So depends on how much risk your willing to take. If you are into less risk keep the max pitch under 18.
https://www.faa.gov/regulations_poli...a/hfh_ch02.pdf
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Old Feb 03, 2015, 12:07 PM
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aah, i see. well, if all works, then no need to adjust i guess...

i'm experimenting too much. need to fly more Boi i tell ya, there's a lot going on with the wings
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Old Feb 03, 2015, 01:03 PM
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just gotta mess with it!
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When you think of everything that's going on, it's amazing that single rotor helis fly as well as they do!

I noticed that my Forza can go up to about 42 degrees against torque, and about 39 with. Using that much will surely cause blade stall, so I may try reducing my tail limits. I normally set them just a few points off the mechanical limit to prevent the tail servo stalling. It's funny, tho, you'd think heli designers would make the tail rotor just long enough to be able to give the required pitch range in the tail rotor.
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Old Feb 04, 2015, 01:32 AM
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Can you guys explain what you mean by stalling the tail rotor?
When I hear stall,I think of the blades slowing or stopping and that just isn't possible unless it slows or stops the main rotor...90 degrees of pitch on the tail could never have any real effect on speed so you're obviously talking about something else.

As for pitch...I set mine up with everything it can get and then two clicks more.
Most tail gyros will take care of the rest.

I set my radio ATVs to 60% to get my 250 degrees per second piro rate.
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Old Feb 04, 2015, 01:36 AM
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For helis, it means the rotor blades are no longer able to produce any lift at that given RPM, which causes weird behaviours such as sudden uncontrolled banking or pitching (just an example not limited to) - in the case of the main rotor.
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Old Feb 04, 2015, 08:01 AM
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just gotta mess with it!
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Make it happen!

If a car engine stalls, it stops. With an airfoil, such as a wing or rotor blade, that's not what's meant. When the angle of the airfoil to the relative airflow gets to a critical point, the air will break away from the airfoil instead of flowing smoothly around it. Drag rises, and lift reduces.

There is a way to experience this quite safely. In HH mode, a heli will often spool up with the tail all the way over to one side or the other. As it spools up, the gyro will reduce pitch in the tail rotor when it starts to generate enough force to turn the heli.

If you have enough tail rotor pitch - that is, too much pitch - the tail rotor can be stalled. You will hear an odd "mushy" sound from the tail, and the heli will take longer to get up to full rpm. At some point, even tho stalled, the tail generates enough force to turn the heli and the gyro reduces tail pitch. The mushy sound goes away, and the rotors speed up more rapidly.

Of course you can avoid all this by centring the tail rotor before spooling up, but it's an easy way to see if you have too much tail pitch.

And friends, I know this story is true - because I can make it happen every time with my Forza if I set the tail limits to the full 42 degrees of pitch!
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Old Feb 04, 2015, 08:45 AM
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I max mine out in both direction so they don't bind . The real trick is to set a head speed and not get drift in rate before going into HH MODE
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