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Old Dec 27, 2012, 10:21 PM
Pusher jets rule!
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Mesa, AZ
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Originally Posted by gatorb8 View Post
I'll have to take that back about no difference between 3S and 4S due to drag cause tonight I noticed the prop was on backwards!

back to the field tomarrow!
Don't feel bad, you're not the first (or the last) to do that.

Pat
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Old Dec 28, 2012, 07:02 AM
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Originally Posted by crxmanpat View Post
I personally would not even bother using digital servos in this plane. As it's a belly lander it will get it's share of hard landings and unexpected "arrivals" to the ground.

I use good ol cheap HXT900s in all of my full sized pusher jets. Work just fine, and only cost about $3 each.

Pat
Good point! inexpensive analog servos went in last night, prop corrected, endpoints corrected, test pilot ready to go!
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Last edited by gatorb8; Dec 28, 2012 at 07:11 AM.
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Old Dec 28, 2012, 02:02 PM
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much much better with prop on right!
Speed runs are into 10-15 mph wind
F22propright (3 min 26 sec)
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Old Dec 28, 2012, 04:33 PM
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Quote:
Originally Posted by crxmanpat View Post
Don't feel bad, you're not the first (or the last) to do that.

Pat
sure isnt!!
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Old Dec 28, 2012, 05:22 PM
Pusher jets rule!
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Mesa, AZ
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Nice job!

I have more fun flying mine in the wind.

Pat
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Old Jan 02, 2013, 05:26 PM
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My first one was in gusty10-15. And after I trimmed her out it flew great! Still having fun w these pushers!

Hey Pat it's been a while. Any new builds lately. Pics are always good.
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Old Jan 02, 2013, 05:33 PM
Pusher jets rule!
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Mesa, AZ
Joined Jan 2006
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Nothing new for now, still working on getting ready for the AMA Convention.

Pat
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Old Jan 03, 2013, 11:41 AM
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Wondering if anybody has any ideas for mods to these (excellent) single prop vectored thrust aircraft to reduce the torque reaction?

I have a whale of a time with my Mig-29 (from the other thread) but find that with Tailerons only, run out of right aileron when trying to go very very slow. I see that with a twin prop model with no torque reaction it is possible to slow to a hover......I can't see how you would be able to do that with a single prop?

I am doing a mod at the moment to put some angled vertical strakes on the upper and lower part of the fuselage with the aim of reducing the torque roll....see how it goes!
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Old Jan 03, 2013, 05:38 PM
Pusher jets rule!
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Mesa, AZ
Joined Jan 2006
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On these models, there is almost no torque factor. Failure to turn is typically caused by one of two things:

1. CG too far fore or aft.

2. Too little airflow over the control surface.

#1 can be solved by correcting the CG. #2 can be solved by adding power.

I have had mine in a high alpha near-hover, applied full right aileron, and it still tracks to the left. While I'm sure torque plays a small part in this, there's really not much you can do about it, except to make it a twin with counter-rotating props.

Pat
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Old Jan 03, 2013, 05:57 PM
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Hey what about loading it up with gyros? That would be interesting. Also I always go bigger when cutting out the tailerons.
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Old Jan 03, 2013, 06:53 PM
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Interesting. Aircraft is nicely trimmed straight and level at all power settings, slow down and I have to feed in more and more right stick. In fact, that is the limiting factor to how much I can slow up.

Got plenty of control throw and plenty of power - about 400w on a 6x4 and tailerons to drawing.

CRX, I wasn't sure why you say there is virtually no torque factor, but go on to describe the same flight characteristics that I am getting. Surely torque reaction is the only factor that could cause this isn't it, or maybe it's my understanding of the terminology.

I recently flew a VF F-15 that I put together for a friend and it does exactly the same.
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Old Jan 03, 2013, 08:51 PM
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Mine to. I'm sure at some point the small amount of torque will have some effect. it is floating on air.
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Old Jan 03, 2013, 09:47 PM
Pusher jets rule!
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Mesa, AZ
Joined Jan 2006
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The closer the prop is to the CG of the plane, the smaller the torque affect is. Just look at the difference between a mid mounted motor and a tail mounted. Or any plane with a very powerful motor on the nose.

I can launch my F-22 at full throttle, with a slight toss at 45, and it will fly straight away without any turn to the left. But I can't do that with any of my tail mounted pusher jets. Those I have to give a big shove and be ready for some right aileron until it gets up to speed.

I'm not saying there's no torque in mid mounted motor planes, but it is way less at slow speeds than others. Now, I once had an F-15 that would not turn right to save its life, even with some speed on, and even though it seemed well trimmed and balanced. If I tried to turn right it would kind of knife edge until I was forced to turn left. Moved the CG further forward and the issue completely disappeared.

Pat
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Old Jan 04, 2013, 05:13 PM
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That is interesting. I think I have a theory.

In any aircraft the torque reacted back through the airframe is equal to the amount of torque needed to drive the prop. So that won't change for any motor configuration.

However, for a mid-mounted motor there is the aft fuselage which is present (and isn't for a forward or rear mounted engine). The effect of this is to react the rotating component of the propwash (i.e. kill/disrupt the swirl effect) and if you think about it, the effect on the airframe opposes the effect of the motor torque. I can't imagine why the relationship with the C of G is a factor, but I am convinced that the flow straightening effect of the aft fuselage section must significantly reduce the reaction torque from the motor.

Sound feasible?
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Old Jan 09, 2013, 03:29 PM
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I made a simple 18" WS EPP profile version with a hextronik 3000kv. First flight had bad torque to the left on full power. Bench test showed the whole frame was twisting from motor torque. A depron stiffiner plate across the bottom took most of the torque out. Flys sweet now. Any chance your airframe is twisting?
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