P40 ground handling
 

My Zirolli P40 has terrible ground handling. On take off I steers hard left, not a drift, a turn left.
Gear is straight, both wheels roll free, engine thrust is good Flys like it is on rails , once you get it in the air, landing are straight
Engine is a 3w75 turning 6700, Mej 3 blade 22x10. Any suggestion would be helpful.

RE: P40 ground handling
 

Never flown a Ziroli P-40 but my Skyshark P-40 will pull hard left on takeoff. My buddy's Yellow P-40 does the same. I'm sure the 3 blade adds to the problem, the old P-factor at work. I find that a very slow throttle up on takeoff until the tail is up with a lot of right rudder is about the only way to stay straight down the runway. Some warbirds do seem to be worse than others.

Carl

RE: P40 ground handling
 

Have you tried more toe-in? I had a Shoestring that was just crazy on the ground till I got enough toe-in, but I remember I also changed prop brands too around the same time. Went from APC to a MAS. Either or both of those changes cured the ground handling craziness. Good luck. Jon

RE: P40 ground handling
 

Ran the engine to check tuning. Did notice the engine rpm came up very quick. Engine at full rpm with with transmitter stick at half throttle. Going to try adding expo to slow throttle. Never tried this before. No room to servo or add a longer arm without major rework

RE: P40 ground handling
 

Harley,
My Ziroli P-40 has slight toe-in. I ease up the throttle at take-off with no problems with tracking Add rudder as needed.
Happy Flying

RE: P40 ground handling
 

being gradual on the throttle is key, coupled with right rudder, full up elevator on initial portion of roll... Pin that tail down initially, otherwise the tailwheel will not be useful. Slowly release elevator as ground and airspeed build, rudder will be come more authoritative. Use rudder as necessary to maintain heading and continue to relax elevator to neutral position as tail lifts. Speed continues to build on the take off roll. Boom. You're flying. Of course this is an over simplification, and it all comes down to the quirks of your airframe and powerplant. You'll have to keep working at it until you master that specific airframe. SOunds like you've got it into the air in the past. Keep working at it and try to stay ahead of the plane! Anticipate the hard left and compensate before it happens.

I fly an Avenger and the gear are are VERY narrowly space. My Avenger will ground loop (like your P-40 does) in a heartbeat if I don't stay ahead of the plane and anticipate it's "quirks" before they actually happen.

Let's see some pictures!

Good luck.

RE: P40 ground handling
 

Thanks, as soon as the weather is good ill give it another try. Sounds like easy on the throttle is the key

RE: P40 ground handling
 

a few degrees of toe in helps, also a high speed, high torque rudder servo slaved to a gyro works wonders. I had one on my last P40 and had it coupled to the retract channel so that when retracts when up the gyro gain went to zero and vice versa.

RE: P40 ground handling
 

It sounds to me like it's acting like a real airplane! P-Factor and slipstream effect working here. All of the advice above is on the money. Slow acceleration, keep the tail down until the rudder becomes effective. My CMP P-40 will do the same thing if I just go to full power at the beginning of the takeoff roll. Dash

RE: P40 ground handling
 

<div>"<span style="background-color: rgb(251, 252, 255); font-family: Verdana, Arial; font-size: 12.800000190734863px;"> </span><span style="background-color: rgb(251, 252, 255); font-family: Verdana, Arial; font-size: 12.800000190734863px;">Engine at full rpm with with transmitter stick at half throttle. Going to try adding expo to slow throttle. Never tried this before."</span></div><div>
</div><font size="2">harley, don't know what Tx you have, but my Futaba has a throttle curve feature. If your Tx  has it, that feature probably works better than using expo on a throttle.</font><div>
</div><div>Brian</div>

RE: P40 ground handling
 

Plus 1 on the throttle curve suggestion. Also, a SLIGHT amount of toe-in helps a lot.

RE: P40 ground handling
 

If your rigging does not make right angles where the pushrod connects at the carb arm and servo arm, you will have what you describe.

Where the pushrod connects to the carb there should be a right angle from the pushrod with the carb arm when the carb is halfway open.
Where the pushrod connects to the servo, the servo arm should make a right angle with the pushrod.

RE: P40 ground handling
 

I have 2 ziroli P-40 so can share my 2 cents:
1) If there is cross wind coming at you, make sure you take off in direction of wind blowing toward the right fuselage or you will not stand a chance no matter how good your throttle management is. Right to left if you're facing the wind.
2) P-factor is bigger factor with bigger warbirds. Compensate for that with right and down engine thrust about 3-4 degrees. The P4- sits more noseup than some others so P-factor becomes more prominent until the tail is off the ground. Goal is to get your throttle up enough to get that tail off the ground asap. Tail off the ground will reduce P-factor and also allows rudder to be more effective. Common mistake is to give too much rudder at the start to anticipate that hard pull left, but once tail is in the air need to reduce rudder feed because of the 2 reasons above, or else you find the bird now heading to the right and end up swirling left to right like a drunk on the freeway!!!
3) Do not pull the elevator stick until you got straight tracking and solid airspeed. That 40 lbs P40 will tortoise if you take off too soon even if you got a big 85cc monster up front. I'm not going to tell you how I know :D
I do find that take offs with these 40 lbs beasts are trickier than landings sometimes.

RE: P40 ground handling
 

A little right rudder mixed in with the throttle. Just like the real ones..throttle goes up right foot goes in.

RE: P40 ground handling
 

The real one was a handful to handle on the ground. So why would you think that the model would be any easier? Lol.

RE: P40 ground handling
 

Gyro?

RE: P40 ground handling
 

I am certainly no expert, but wouldn't wind blowing "towards" the right side of the plane tend to push it further to the left?

RE: P40 ground handling
 

It would push the tail left and the nose right. Helping offset thrust.

RE: P40 ground handling
 

It will push on the large vertical stab in the back "pushing" the tail toward the left and somewhat keeping the typical left pull(nose to the left,tail to the right) in check. That's the outcome when you apply right rudder to compensate.....push the tail to the left.
  If the wind is blowing against the tail from the left it will push the tail to the right making the typical left nose pull even worse and harder to compensate with right rudder.

RE: P40 ground handling
 

As long as the main gear wheels are on the ground this is the "pivot point" for the fuselage. Since there is more side area behind the wheels than in front the wind pushes more on the tail. A wind from the right pushes the tail to the left and swings the nose of the plane to the right....essentially the same as adding right rudder.

As soon as the wheels leave the ground the wind pushes the entire plane to the left.

RE: P40 ground handling
 

That might help for takeoff but then you will have too much rudder offset in cruise. Better to do it like the full size plane and add right rudder trim for takeoff and then take the trim out for cruise.

RE: P40 ground handling
 

Well that should have been obvious ... http://www.rcuniverse.com/forum/js/f.../red_smile.gif

RE: P40 ground handling
 

Lots of things are obvious once you understand them....like gravity for instance.

RE: P40 ground handling
 

I've got a couple of 60-sized electric planes that behave exactly as stated above. "On take off I steers hard left, not a drift, a turn left." I feel like such an idiot when this happens especially if somebody's watching. I always hear somebody say: "What the heck was that?!?" It's a hard left turn just as the plane is becoming airborne. It always takes off but looks really stupid. I added some right thrust and a yaw gyro to one of the planes. If the wind will every stop blowing here I'll figure out if it worked. The yaw gyro wasn't helping much.

RE: P40 ground handling
 

P-40's ground handling, with both r/c models and full size, are tricky due to narrow gear and short coupling.
Use of right rudder and throttle management are key. If your throttle linkage is not set up correctly, it can give you fits on take off.
Here's how to set up throttle linkage;
Use a Servo arm where the "take off" or "ball link attach" point is about 5/8" from center of shaft. Purpose of that distance is to ensure that you'll be close to needing 100% ATV on both ends of the throttle channel, making the "clicks" of throttle less profound. You don't want big differences per click, and a longer arm will be too much. Shorter arm requires too much ATV diddling, and introduces mechanical expo which may not be in the "correct" direction.

On the Carb, use an arm with the ball link take off point at 3/4" from shaft center. This permits more rotation of the arm, and helps solve sensitivity issues mechanically at the carb. Walbro carbs are HORRIFICALLY non linear and overly sensitive...