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Old Jan 27, 2015, 09:04 PM
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United States, OK, Oklahoma City
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Wing Rock

What causes wing rock when doing high-alpha maneuvers such as a harrier? We were discussing this today at the field. Prop size and the plane not being balanced laterally were the top two choices but no one knew for sure. So I mentioned I would post this question on RCG. I am hoping someone will give a good explanation and offer up suggestions for solving this problem. Thanks!!
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Last edited by mm2icbm; Jan 27, 2015 at 09:05 PM. Reason: wording error
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Old Jan 27, 2015, 09:11 PM
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United States, OK, Oklahoma City
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Sorry guys, I found a good explanation here: http://www.rcgroups.com/forums/showthread.php?t=209036

Will close this thread now.

It has been pointed out to me the above link is quite old (10+ years) and therefore, I decided to re-open this thread. I am looking forward to hearing your thoughts and suggestions regarding this topic.
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Last edited by mm2icbm; Jan 27, 2015 at 09:29 PM. Reason: re-opened thread.
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Old Jan 27, 2015, 10:33 PM
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central PA.
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wing rock is typically the momentary attachment and detachment of airflow to each wing. a few things set this off, like the interaction of the spiral slip stream from the prop interacting with the fuselage and flight surfaces, wingtip vortexes, and simply pilot input (being a little nervous on the rudder for example being a common cause).

planes noted for having noticeable wing rock, will rock the wings even when the pilot input is otherwise fine... pilot will have to chase it. then the scale of course goes all the way to planes that are so steady in harrier that they will also help fight wing rock against pilot error.

it's not uncommon that planes that have no wing rock can get a few people saying that it does, and typically indicates that they're a little nervous on rudder or ailerons. If this is the case, increasing expo can be a big help for some.

Airframe design can also help alleviate the issue by either promoting airflow over the wing or helping the departure for a cleaner stall (airfoil shape, etc), improving roll dampening (wingspan/area, SFG's), wing plan form, yaw stability (larger fin area above and below the fuselage), etc etc. There's a bunch of tricks to try out to help.

A quick way to see aerodynamic differences is to roll the plane on its back for inverted harrier... much more stable with the fin and rudder acting as a keel in cleaner airflow. many videos of planes with bad wing rock will get around it by having all the harrier maneuvers be inverted... and really terrible planes may skip regular harriers all together and fly rolling harriers (which look fantastic, but don't tell you much about airframe stability in 3D flight). If looking to purchase a new 3D plane, watch videos looking for upright harrier specifically.

that would be my spiel on wing rock
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Old Jan 28, 2015, 06:44 AM
Julian T
Fleet, UK
Joined Jun 2005
566 Posts
All of the above plus Mike Parson's comment re spoilerons in the referred thread will cure most airframes subject to excessive wing rock. The spoilerons effectively add washout which makes the wing less prone to stalling even at high alpha. Put it on a switchable mix and play with rates till it cures the rock. Having said all that, I don't know how they have done it, but a lot of modern airframes (I mainly have experience with the EXP range) exhibit little or no wing rock anyway, at least on calmer days. This is both with and without SFGs so it's not that. Blustery and turbulent days tend to induce the rock more for obvious reasons and then spoilerons come into their own.

Julian
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Old Jan 28, 2015, 09:53 AM
Team Hitec
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United States, CA, Alpine
Joined Oct 2007
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You will commonly find sweeping back LE's and curved wingtips to wing rock moreso than that of a straight wing and sharp edges (Edge 540's tend to be very stable in harriers, whereas Yak's tend to not be).
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Old Jan 28, 2015, 03:14 PM
Registered User
United States, OH, Massillon
Joined Apr 2011
10 Posts
Wing rock is dutch roll. for snaps and spins a plane with poor directional stability(how well does it stay staight no yaw) feels crisper in those manuevers. We need yaw stability (how well does it return to straight flight) to stop the snap or spin. That all combines into what we call wing rock. The tail is wagging back and forth and angle of attack causes the leading wing to rise. Usually I start with a couple of square inches of packing tape in front of the vertical fin to the top of the fuselage. This works well on yaks and also makes the plane more stable in a hover. An sbach for example does not respond well to that and needs wing help. A leading edge cuff (think mig15) a 1/2 inch tall along with a similar sized aileron tip plate works miracles on those.
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Old Jan 28, 2015, 05:20 PM
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United Kingdom
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In my experience, the biggest cause of wing rock when flying high alpha is a badly designed plane. When I first started flying RC I wanted to learn to land a plane by reducing the throttle at hight, pulling the nose up and dropping smoothly down to land tail first. I tried a number of different planes with no succes because of uncontrolable wing rock. I thought it was my lack of ability. I then purchased a 51 AJ Slick and after a few flights I was able to do it. I then got an EF 60 Edge and EF 60 Laser and again, no wing rock. Also my AJ Aircraft 56 Laser does it very easily and smoothly. It wasn't my lack of ability, but the planes lack of ability. Therefor, my advice to cure wing rock is to fly a well designed plane.
Hope this helps.
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Old Jan 29, 2015, 06:38 PM
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Great advice from everyone and I thank you for that. The plane is an EF 78" Extra set-up for electric. The plane does elevators all day long but harder that you know what to do a harrier. I'll recommend setting it up with some spoilerons as well as doing some inverted harriers, as suggested and see what happens. I'll report back once we get some decent weather here and have some time at the field.
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Old Jan 29, 2015, 07:15 PM
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Quote:
Originally Posted by mm2icbm View Post
Great advice from everyone and I thank you for that. The plane is an EF 78" Extra set-up for electric. The plane does elevators all day long but harder that you know what to do a harrier. I'll recommend setting it up with some spoilerons as well as doing some inverted harriers, as suggested and see what happens. I'll report back once we get some decent weather here and have some time at the field.
also try a little more expo on rudder... always worth trying.
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Old Jan 29, 2015, 09:46 PM
This is NOT a TOY?
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United States, GA, Atlanta
Joined Jul 2011
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Quote:
Originally Posted by mm2icbm View Post
Great advice from everyone and I thank you for that. The plane is an EF 78" Extra set-up for electric. The plane does elevators all day long but harder that you know what to do a harrier. I'll recommend setting it up with some spoilerons as well as doing some inverted harriers, as suggested and see what happens. I'll report back once we get some decent weather here and have some time at the field.
Ok wow, haven't read much of this with regard to that plane. That's one of the sweetest model Extra's out there.
I can tell you mine have never exhibited excessive rock, unless I was the one causing it.

Just a couple other thoughts:
Setup a harrier rate. 40-45-degrees elevator when it's pegged.
Make sure your expo 'knee' isn't right where your elevator is sitting around the harrier sweet spot. (I had this once. Played with throw/expo to move the knee)
Make sure cg is neutral to 3/4" or so ahead of neutral. Not excessively tail heavy.
Try the SFG's if you're not already. I know they seem to help me.
Vary the angle of attack you're trying to hold. Not too shallow.
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Old Jan 29, 2015, 10:37 PM
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theKM's Avatar
central PA.
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Originally Posted by C_Watkins View Post
Ok wow, haven't read much of this with regard to that plane. That's one of the sweetest model Extra's out there.
I can tell you mine have never exhibited excessive rock, unless I was the one causing it.

Just a couple other thoughts:
Setup a harrier rate. 40-45-degrees elevator when it's pegged.
Make sure your expo 'knee' isn't right where your elevator is sitting around the harrier sweet spot. (I had this once. Played with throw/expo to move the knee)
Make sure cg is neutral to 3/4" or so ahead of neutral. Not excessively tail heavy.
Try the SFG's if you're not already. I know they seem to help me.
Vary the angle of attack you're trying to hold. Not too shallow.
to me this just expresses the variance of setup and pilot. example that stood out to me a while back, was someone moving from the 3dhs 103 Extra to something else saying it had wing rock, when it's about the sweetest 3ding plane I've ever flown. I don't know that I could even simulate wing rock with it.

Airframe is what it is, setup does tweak things, but pilot is squarely in the picture of causes...
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Old Jan 29, 2015, 11:06 PM
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United States, WA, Battle Ground
Joined Sep 2009
428 Posts
I think it is all about the design if you get a good model it will not have much wing rock.
I always hear team pilots say you just need to fly at a steeper angle to prevent wing rock.
If the model is close to hovering of course it will not have wing rock.
What is desirable is a model that will transition from shallow to hovering without out any wing rock at all angles.
Make sure your lateral balance and CG are correct.
Here is another discussion on wing rock and the use of gyros.

http://www.rcgroups.com/forums/showt...68864&page=236

Information pages 236 to 241.
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Old Jan 30, 2015, 03:51 PM
Julian T
Fleet, UK
Joined Jun 2005
566 Posts
Quote:
Originally Posted by C_Watkins View Post
Ok wow, haven't read much of this with regard to that plane. That's one of the sweetest model Extra's out there.
I can tell you mine have never exhibited excessive rock, unless I was the one causing it.

Just a couple other thoughts:
Setup a harrier rate. 40-45-degrees elevator when it's pegged.
Make sure your expo 'knee' isn't right where your elevator is sitting around the harrier sweet spot. (I had this once. Played with throw/expo to move the knee)
Make sure cg is neutral to 3/4" or so ahead of neutral. Not excessively tail heavy.
Try the SFG's if you're not already. I know they seem to help me.
Vary the angle of attack you're trying to hold. Not too shallow.
Yep, if you are getting rock on this plane something is wrong. It really is a peach and I have never had wing rock on it, with or without SFGs. If all else fails I would check the wing incidences - I can't think of much else that could cause rock on this model, unless you regularly fly in very turbulent conditions. In that case any model will rock and you have to compensate with spoilerons.

Just my experience - ymmv.
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Old Jan 30, 2015, 07:10 PM
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Thanks again to everyone for taking the time to answer and especially for your suggestions. I agree with everyone's comments regarding the EF 78" Extra being a sweet flying plane. Had one before moving up to the 91" and never had an issue with wing rock either. That is what is baffling.

Weather here is expected to be less than ideal until the middle of next week, so it may be awhile before we can try some of the suggestions given. But we will take them, one at a time, and see if the problem can be narrowed down or better yet, completely eliminated.

Thanks again!!
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