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Old Sep 12, 2010, 09:20 PM
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Joined Sep 2010
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Motor mounted off center?

Hi all, this is my first post here. Just received an Airfield 800mm P-40 for my birthday and am having setup issues.

I've watched a good amount of videos, so I understand things like trim and adjustment, etc. Those are all set proper and the receiver is binded, things are generally great.

BUT, the plane pulls HARD to the right at mid to full throttle. I couldn't get the thing to take off properly, but I am a newbie, so there could be several problems there. But without even touching the ailerons and the rudder set as straight as possible, the plane pulls to the right as I ramp up the throttle just rolling around in the parking lot. I went to the grass and tried to hand launch it. The plane pretty much dived down and to the right.

I found a level section of grass to try a rolling take off. It would lift, but then dive straight to the right and into the ground. Trying to roll, basically.

Now keep in mind, before flight I set all the servos to zero and adjusted the linkages, the whole nine yards. It's as straight as possible with no trim. Also, the CG is set per the included instructions, which from what I've seen online is rather nose heavy. (The CG is at the leading edge of the cockpit pretty much.) I've also seen the occasional CG problems with these planes on here, but those were usually the Airfieed 800mm P-51's.

Anyhow, all that being said, I discovered how to take out the motor and it's clear that the thing is mounted WAY off center. If you're looking dead on from the front, it's low and far to the right. Pushing all that air to the left side of the plane and not the other might be causing my rolling issue, but I wanted to check in here and see how much tolerance was allowed before it's considered unfit to fly.

I did take a picture, but can't seem to find that darn camera cable. I'll post it later if I find it.

But anyhow, any ideas from the above information? Would an off center motor cause this much rolling or is it too nose heavy as well?
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Old Sep 12, 2010, 09:43 PM
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Brandon Ms.
Joined Feb 2009
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It's supposed to be down and to the right. How much may be an issue. Almost all of the planes I have require rudder imput while getting up to speed on take off. If you give it alot of throttle in a hurry it will pull hard. Try to ease into the throttle and hold down elevator until the plane picks up some speed. As far as what it does upon lift off, it sounds like a tip stall to me. Try to get up some more speed before going airborne and then climb out gradually. Pulling to much elevator can cause what I think you are describing to happen. Sounds like a great birhtday present. Oh and until you get used to the plane, nose heavy beats tail heavey every time.
Good luck, hope this helped,
Patrick
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Old Sep 12, 2010, 10:06 PM
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Patrick,

Thanks for the tips. I'm joining up with an autonomous vehicle team at UTA this semester where I'm taking Aerospace engineering (hence the username). The team builds an RC plane and programs it for autonomous flight. The head guy has done lots and lots of RC building in his time. I think I'll get him to look at it and maybe meet up with me next weekend so he can give it a run and see how it flies.

So why exactly are the engines mounted this way? Here's a shot of the motor mount.

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Old Sep 12, 2010, 10:40 PM
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United States, OK, Norman
Joined Mar 2010
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RC motors and engines are mounted with a thrust angle to help counter the effects of P factor, torque etc... Since they aren't mounted square, the mount must be moved to ensure where the prop exits the cowl is also centered.
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Old Sep 13, 2010, 07:27 PM
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Hmmmm, well, I destroyed that plane!

I looked online to see if the airframe was available before I went out and flew the thing again. I knew where it was and knew I'd be 40 bucks in the hole if I had to replace it. I took it out to the same field and after little luck with rolling take offs in the grass, I took it to the high grass and did some hand launching.

I managed to get some air a few times, but inevitably, I'd loop it and not be able to pull back up. Well, one time, the thing got away from me and went over a fence to a nearby football field and nosedived hardcore into the hard, flat ground. Engine mount is WAY off center now and the whole body got bowed. The front insert where the main wing is attached fell apart, so that's all loose as well. Pretty much a destroyed air frame.

SO, before I order another P-40 and transfer the electronics, can anyone recommend a good beginner airframe to put these electronics in?
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Old Sep 13, 2010, 08:05 PM
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Quote:
Originally Posted by JohnnyEngineer View Post
SO, before I order another P-40 and transfer the electronics, can anyone recommend a good beginner airframe to put these electronics in?
I can't recommend anything that would fit the electronics you got with that plane... I will give you some pointers though you may not want to hear them... but they are what I think you need to know as a newbie.

First and formost... do not get a warbird again, they are not trainers. If you get another plane that is too advanced for your current skills, it will likely only discourage you from learning instead of help. Look for something with a high wing, that has a decent amount of dihedral ( isn't straight ).

Talk to the "head guy" you mentioned earlier for some plane recommendations to train on... I suspect he will say the same thing if he has the experience you think he has. If he isn't available... go to a hobby shop that specializes in RC, they are usually happy to assist people to make certain they get the right things they need also.

Don't train by yourself... either get help from an experienced pilot or get some RC similator software if your computer is up to the task of running it.
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Old Sep 13, 2010, 08:18 PM
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I'm now looking at some ARF trainers now that I have a TX and RX. I imagine the next time around, I'll have somebody with me to give it a proper shakedown before I take the controls again.

Thanks, all.
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Old Sep 14, 2010, 12:18 PM
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Some quick good news, I got after the plane and was able to save everything except the fuselage, so instead of 40 bucks, it will only be 20 bucks to rebuild it.

Still looking at ARF trainers, though.
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Old Sep 14, 2010, 03:32 PM
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Originally Posted by JohnnyEngineer View Post
I'm now looking at some ARF trainers now that I have a TX and RX. I imagine the next time around, I'll have somebody with me to give it a proper shakedown before I take the controls again.

Thanks, all.
That is good to hear, just don't get impatient with yourself and you'll not have any problems to speak of...

It's also cool that you can get the other one fixed for around $20 so you can have it waiting in the wings for when you are ready to tackle a warbird...
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