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Storch turning HARD left

#1
Hi everyone,

I just completed my Storch and took it out for a maiden attempt on Thanksgiving day. This is the biggest plane I have maidened, and it is my first 4 channel that does not include a gyro stabilizer. I have expo dialed in at 30% and dual rate is at 70%. I built it with flaps, and all control surfaces are functioning normally.

I am having pretty serious problems right now. I tried to take it off the grass, and it kept wanting to turn hard left. I chalked this up to the grass being too deep for a smooth roll out, and had my girlfriend give me a hand launch. The plane banked incredibly hard left and nosed into the ground. Luckily with a little hot glue I got her back in action again quickly.

I thought that perhaps I just needed some right rudder trim. I added in quite a bit, enough that at about 40% throttle it taxis straight now. However, as I add in more power, that left turning tendency comes back really strongly, and I have to add major right rudder to keep it tracking at all. I didn't try a takeoff again, as I just wasn't feeling comfortable keeping this thing straight.

I am relatively new to the whole RC thing, and I'd definitely heard of adverse yaw from motor torque, and I am not sure if this is just my first experience with it and it is way more intense than I expected, or if something else is wrong.

I built the plane with the Power Pack C set up, and I got the 9x6 props. Am I just not used to the torque of the motor, or is something else going on? I know my control surfaces are correct and functioning normally. I haven't been moving fast enough for ailerons to be the problem I don't think. My tail appears to maybe have a very slight twist with the left side of the horizontal stabilizer being higher than the right, could this be my issue? Could it be that I just need more rudder trim? Any advice and/or guidance would be much appreciated, I'd love to get this new plane off the ground!!
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#2
Firstly ensure that the tail is properly aligned with the fuselage centre line. Seccondly do an internet search into "P" factor.

In basic terms "P" Factor is caused by the spiralling ariflow from the propeller pushing the vertical stabilizer sideways and therby inducing a left turn or a roll on take off.

Solutions. They can be numerous and varied but the first one to consider is the thrust line of the motor itself. to stop the plane trying to swing hard left on taxi or takeoff then increase the amount of right thrust of the motor. This can be achieved by adding some packing behind the motor mount screws on the side to which it turns.

Secondly fit a SF, (Slow Fly), propeller and try your taxiing again.

Finally hold the rudder against the turn and apply just enough power to get the plane rolling. Try to keep the plane straight and slowly increase the power to build up ground speed. When the plane is rolling across the ground at what is far higher than your normal take off speed apply up elevator gently and get ready to apply aileron roll control. If the plane is basically straight the plane should lift off gently and straight. Do NOT apply more throttle until you have gained a bit of height, (20ft), and then slowly push the throttle to maximum to see what effects the throttle setting has during flight. Be prepared to reduce throttle quickly if the plane suddenly becomes too hard to control. Land with minimal throttle or dead stick.

Re-adjust the planes thrust line and control surface deflections if required. The above is based on the steps I use in test flying my builds including any experimental craft I build.

Add more side thrust and try again!
 
Last edited:

localfiend

I like 3D printers...
Mentor
#3
Motor torque and adverse yaw are two different things. If your motor is straight, landing gear is straight, and control surfaces are correct all you'you've got to worry about is a little motor torque.

Unless your tail is way out of wack, a little bit of unevenness won't hurt you.

I wouldn't use trim to adjust for torque on takeoff. Rudder needs to be fed in manually as it will need more the faster your motor spins until you build up enough airspeed to make it unnecessary.

http://www.flitetest.com/articles/beginner-series-launching-and-landing

http://www.flitetest.com/articles/first-flight-quick-tips
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#4
Just an explanatory note as to the recommendation for a SF prop.

All lift generating surfaces, (wings and propellers), generate tip vortices. With a SF prop the pressure differential between the front and rear surfaces is far lower and therefore any tip vortex will be less severe and have a lesser effect in generating 'P' factor.
 
#5
My Storch, when fitted with the SF 10x4.5 (?) pops up in 4-5 feet, even in grass. I also have a tail wheel fitted, and so my initial wing angle is less than standard. The tail wheel lifts the tail more than the stock design. I did have roll issues initially because I built my landing gear wrong and the wing wasn't remotely level. So, I just cut the gear, soldered in an extension and called it a "field repair in time of war." Looks odd (like all field repairs), but works well.

Note: that's a 9x6 or so APC in the photo, not the slow-fly I ended up using.

Mike
 

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Capt_Beavis

Posted a thousand or more times
#6
What prop and motor are you using? The three storches I have seen all need a fairly significant amount of right aileron dialed in to fly level.
 
#7
Hi Hayduke27. It sounds like you did not try to fly the plane yet, right? Only low/mid/high power taxi? And the plane turns left immediately when you add the throttle, and you never allowed it to gain some speed? That might be just an effect of prop torque pushing left wheel into the ground harder and thus creating more drag on the left side when the tail surfaces are still not effective enough to counteract this tendency.

I'm flying my Storch with the relatively low power setup, and I do see the same thing: the plane starts to turn left immediately after applying full throttle. But I can make it go straight simply by applying FULL right rudder together with the throttle. The "turning left effect" disappears in the moment the plane lifts off, which means in less than 2 seconds; and that's the moment when I have to return the rudder to neutral position.

I think you should give it another try; and this time follow this simple rule of thumb: when on the ground, use the same amount of right rudder as you are using throttle. It should help, or at least get you close enough to the point when you can actually control the situation.

Good luck, and have fun!
 
#8
Hi Hayduke27. It sounds like you did not try to fly the plane yet, right? Only low/mid/high power taxi? And the plane turns left immediately when you add the throttle, and you never allowed it to gain some speed? That might be just an effect of prop torque pushing left wheel into the ground harder and thus creating more drag on the left side when the tail surfaces are still not effective enough to counteract this tendency.

I'm flying my Storch with the relatively low power setup, and I do see the same thing: the plane starts to turn left immediately after applying full throttle. But I can make it go straight simply by applying FULL right rudder together with the throttle. The "turning left effect" disappears in the moment the plane lifts off, which means in less than 2 seconds; and that's the moment when I have to return the rudder to neutral position.

I think you should give it another try; and this time follow this simple rule of thumb: when on the ground, use the same amount of right rudder as you are using throttle. It should help, or at least get you close enough to the point when you can actually control the situation.

Good luck, and have fun!
 
#9
Capt_Beavis: I'm using the Emaxx GT2215/09 motor (power pack C) with the 9x6 prop. It was the stronger set up. Even though I am still a bit of a noob, I live at 8,000 ft and wanted the more powerful set up for the thin air. I'm not sure if it was necessary, but I did it anyway :p

As I mentioned, I also have the flaps set up, but so far I have not engaged them for any of this testing.

Bayboos: I have not flown it yet. I tried an assisted hand launch (I wasn't giving it any rudder during that launch, I hadn't thought this through yet), and as mentioned above the plane made a hard left turn into the ground. I have done slow, fast, and medium taxiing. Last time I tried, I had a significant amount of right rudder trim, which allowed both slow and medium taxiing without too much right rudder. However, as suggested in the comments, I'm rethinking that right rudder trim. I think I'll work on some manual rudder for the taxiing today. Even with the above trim set up, I still had to add right rudder when I went up to higher power. Doing this, I got the tail of the ground and managed to keep the plane tracking for about 40-50ft. I didn't try a take off, however.

Thanks everybody for the advice. I suspected this was more a case of my lack of skill than a plane malfunction. I took my time with the plane, and it came out quite nicely (built from the speed build kit exactly following Josh's instructions from the video), so I do think it should be capable of flight. I'm going to head back over to the park and burn a couple of batteries practicing my rudder work. If I get confident enough to pull it off of the ground for a short flight, we'll see how she flies as well. I'll post an update later.
 
#10
Hey guys!

I just thought I'd drop a quick update in here, and I wanted to say THANK YOU to all of you, as you got me off the ground today :)

It turns out that everything I was experiencing was indeed engine torque. I practiced taxiing around, then went out into the grass for a takeoff. My first takeoff I didn't let off the right rudder early enough, and as I pulled it off the ground (a little bit too much up elevator) I kind of stalled/rolled right and into the ground. A quick repair and I had the bird back out again. This time after a couple of false starts (still working on that right rudder for takeoff!) I gently eased her into the air and made a couple of laps around the park. I still have some trim work to do, and I will admit that the flight ended in a crash due in part to a slight tendency to roll right (this is due to me needing to double check my linkage stoppers and set my trim a bit better). I have her fixed again, and I may even see if I can't redeem myself this evening!

The Storch is flying!! Thanks again for your help folks!



P.S.- Having the wing attached with rubber bands has saved my plane more than once now! Having that extra give as I pile in for a nice cartwheel has resulted in far less damage than a permanently attached wing would have sustained! Just an observation.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#11
Congratulations your perseverance has won through.

A little outboard Leading edge reinforcement with skewers or CF rod can really save the wings when impacting the ground. Don't ask me how I know but experience was a major contributor.:black_eyed:

Now this one is flying start working on a new one to keep in pristine condition for those crowded flying field days:rolleyes:.
 
#12
Congratulations!

You are absolutely right about the rubber bands - that's mostly why we keep using them even when we are flying planes that may benefit from more rigid wing mount (e.g. due to high speeds, high g etc.).

Hai-Lee is also right: it's very probable that the very first Storch will take a lot of beating while you learn how to fly it. It will be repairable most of the time (and flyable after the repair as well), but the flight characteristics (and performance, and aesthetics) will gradually degrade after each of those R.U.D.E. (Rapid Unexpected Disassembly Event) events. It's a good idea to start planning the build of your second Storch relatively soon; this way you will avoid the period of no-Storch-iness when the time comes to retire the current one. Trust me, I know this from both sides. My first one (SB kit) lasted around a year, and I already had the second one ready before the first one became unflyable. The second one lasted just a couple of months - it was eaten (literally) by very hungry and very aggressive 3D plane; it took me another two months to build new fuselage and fix the wing.

Good luck, and Have Fun!
 

Capt_Beavis

Posted a thousand or more times
#13
I am glad to hear you are flying! A 9x6 is a little on the aggressive side and may be adding to the torque tendency. A 9x4.5 may be a little more gentle.