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Tail Wagging RV-7

birddog486 said:
I've been spending a lot of time in the RV-7 this year and I've checked rigging, alignments and twist in all the control surfaces without any luck in finding whats causing this tail wagging.

It only takes a slight amount of turbulence to set it in motion. I can keep both feet pressed hard on the rudder or just let it float and neither will stop it. It doesn't make a difference being fast or slow but the stronger the turbulence the more aggressive the wagging.

Anyone have thoughts on this.

https://youtu.be/fgnwp1I3nfI
Click to expand...

WHERE ARE your feet.... If you have your feet on the floor many planes will yaw or Dutch roll.... Also if not on autopilot and loose in the stick the plane will move around in turbulence. It is NORMAL...

Two place RV's are short coupled... not too short but just right for overall performance and control desired (fast, sporty, XC plane). Personally the RV's ride turbulence well. I love the RV. It has a sold feel and very responsive to input. Also keep in mind you are going much faster than a typical single engine, fixed gear GA plane which affects how it flies and feels in bumps.

SUGGESTION in turbulence slow down a little bit, may make the difference in ride. OR change altitude, a few 1000's feet may make a big difference.

Put your FEET on the Pedals... Lightly and feel them. If you get good you can actually be a human Yaw Damper. I flew a Ted Smith TS61 (later Piper Aerostar). The people in the back appreciated how I dampened out turbulence and the yaw by making subtitle rudder inputs. Kind of like a tail dragger in technique, quick small corrections than neutral, little inputs timed to dampen. Takes some practice. JUST RESTING FEET ON PEDALS... Big help.

Second pointer. Don't fly in turbulence. ha ha

Most of all the jet airlines I flew had YAW DAMPERS..... Some business jets, Lear Jets come to mind, am Inop yaw damper was a no go item.
 
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You could try some Mylar gap seals from
Wings and wheels.com
to see what effect that has on your tail wag.

We used these Mylar gap seals on Bill Beaton’s Race 57, part of our quest for speed. Bill reported slightly stiffer control effort (ailerons&elevators) & nominal speed increase. Would be interesting what effect this treatment had with your condition.
Also, the recent thread on the Rotax RV9A showed a dorsal fin added to the vertical stabilizer, should be easy to tape on a temporary fin to see if that helps on your plane.
 
When I bought my 4 that was one of the 1st things I noticed coming from a 177A Cardinal to the RV4.

After a while I never even noticed it and my GF in the back also never said anything.

I think over time you probably won't notice it.

On my new RV9A, certainly none of that on it that's noticeable.

Tim
 
Rudder TE

Lots of comments from folks a lot smarter than me so far, but unless I missed it, have you checked the radius of the bend on the trailing edge of the rudder?

I can't remember which, but either Undersqueezed (too fat) or Oversqueezed (too thin) might cause the issue.

Smarter folks comment now, please! :eek:
 
Not smarter, just older.

The V tail Bonanza dance is directional/lateral coupling, maybe from the big dihedral effect of the V tail. From the pilot's view to the left, the wingtips will make make counter-clockwise donuts on the horizon in any turbulence.

If in the OP's case, there is any circular motion of the wingtips, as with the Bonanza, the wing-aileron details cannot be discarded as suspect. Wingtips Stock? I'm in long shot territory here. :)

Ron
 
To the OP:

Have you flown or ridden in another -7 to compare? They are all gonna get thrown around in turbulence. You even said yourself in your second post it flies hands off in smooth air.

Hard to tell much from the video
 
RV74ME said:
To the OP:

Have you flown or ridden in another -7 to compare? They are all gonna get thrown around in turbulence. You even said yourself in your second post it flies hands off in smooth air.

Hard to tell much from the video
Click to expand...

I agree. He may be chasing a problem that does not exist. I have never been in any RV-7 that does not wag the tail a bit in turbulence.
 
RV74ME said:
To the OP:

Have you flown or ridden in another -7 to compare? They are all gonna get thrown around in turbulence. You even said yourself in your second post it flies hands off in smooth air.

Hard to tell much from the video
Click to expand...

Yup, I've ridden in a couple. There's definitely something going on I just haven't been able to pinpoint it yet.

I'm hoping to get it side by side with another 7 soon and see what I can find. After checking everything again the bottom side of the ailerons are perfectly flat from trailing edge to the spar and from the spar forward is flat but from the spar forward it angles up slightly across the entire surface including the end ribs on both ailerons.

If that's causing it there must be enough drag created there in equal amounts In smooth air the effects cancel each other out but when rough air is encountered it starts the side to side motion. Just guessing:confused:

Anyone have a picture of a perfectly flat aileron from leading edge to trailing edge from there 7. I'm hoping to solve this before the snow flys.
 
This was already mentioned but no comment was made about the apparent “tab” sticking out on one side of the light?
 
750 hours?! Bravo, I have flown 1/10 of that this year and feel like I've been getting up a lot. 750 hours equates to over 1 month spent inside your flying airplane, just this year. Must be some kind of RV record.


birddog486 said:
Riveted trailing edge on the rudder and its been the last thing I've focused on before coming back here for ideas. Using a straight edge vertically on the trailing edge is almost perfectly straight and from the trailing edge forward its flat.

One thing I notice is a straight edge from the trailing edge of the rudder forward across the verticle stab reveals the trailing edge of the vertical stab is about 1/8" wider than the rudder on both sides.

I'm not sure if that's enough to cause turbulence across the rudder but I think its a possibility.

As far as the leg fairings and wheel pants go, there is no difference in the wagging with them either on or off.

I've flown 750 hrs this year in this plane and half of that has been without the fairing installed. Running at
45% power and 5 gph wasnt slow enough.
Click to expand...
 
birddog486 said:
That's a trim tab at the light. It's approx 1/4" wide and 1.5" tall
Click to expand...

I would remove the tab.
Fly and see if you have any movement to the right.

Still thinking you have a heavy wing.

Countering with that trim tab ???

Boomer
 
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