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Fixed rudder trim

Machsandy

Active Member
Please may I ask what most have done regarding RV10 rudder trimming?

Our aeroplane has flown in balance, feet off in the cruise, since we bought it over 6 years ago. It has a semicircular rubber seal, protected by tape on the left side of the rudder trailing edge.

I would have presumed that would apply left rudder due to coanda effect?

After recent work on spats and ailerons, we now need a steady right pressure on the rudder to maintain balanced flight.

If I am correct about coanda, should we remove the existing rubber seal as a starting point?

What, if anything, have others done?

I don’t want to fit an adjustable rudder trimmer, it is no inconvenience to apply some right pressure during the climb.
 
Fixed Rudder trim

My original question was maybe too involved?

Is the RV10 engine mount offset so that rudder trim is not required in the cruise?

Has anyone fabricated any form of fixed rudder trim correction on a RV10?
 
A lot of RV-10 builders fabricate an adjustable rudder trim and use a Ray Allen trim servo to adjust in flight. I used an 8" piece of hinge on the rudder trailing edge. I have seen another who fabricated a short piece of the trailing edge to be adjustable similiar to the elevator trim tab. I liked it on my last RV-10 for cross country flights. No need to keep foot pressure on the pedal when adjusted as needed. I am putting one on my RV-9A and will also put one on my second -10.
 
I’ve seen 3 different methods for rudder trim — fixed tab/wedge on the trailing edge, a servo driven trim tab, and a spring bias system attached to the rudder pedals. I personally have the Aerpsport spring bias system and it works great and is relatively easy to install on flying aircraft.
 
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Yes, the thrust line is offset but you still need a "squeeze" of rudder with power changes.

My feeling is that a rudder trim isn't necessary and is an unnecessary complication. I just have a fixed wedge on the rudder set for cruise power - works great.
 
Hello Paul

Yes that is the system we have had, with a wedge made of semicircular plastic faired with tape.

As I mentioned on the first post, as the wedge is on the left side of the rudder trailing edge, I wondered if coanda affect would cause that to apply left rudder correction?

Is your wedge on the left side and is it wedge shaped rather than curved?

Thanks

Sandy
 
Hello Paul

As I mentioned on the first post, as the wedge is on the left side of the rudder trailing edge, I wondered if coanda affect would cause that to apply left rudder correction?

Is your wedge on the left side and is it wedge shaped rather than curved?

Thanks

Sandy

I have a small (about 5? high, 1? wide) wedge on the left side of my rudder. The air stream pushes on the wedge, moving the rudder right, which moves the tail left, nose right - same as applying some right rudder. It corrected about a half ball width out of center (right), in cruise. Strangely enough, at the start of phase 1, with no wheel or gear leg fairings, the plane flew ball-centered. So the fairings are mis-aligned. But despite several re-measurings, I couldn?t find where, so I added the wedge. Mine?s foam covered with fiberglass, glued on near the trailing edge.
 
I have a small (about 5? high, 1? wide) wedge on the left side of my rudder.


What is the thickness of the wedge?
 
I?m thinking about adding a wedge. I have the Aerosport rudder trim which works great but since my wheel fairings were put on I need what I think is a lot of right rudder. Too late to modify wheel pants and I think I may be maxing out tension on spring and cable for right trim. I?ve been keeping my right foot on rudder pedal a little during cruise. I may have to readjust spring bracket and bias it a little for right trim at neutral length, not quite sure yet if that will help.
 
This is what is on our RV-10. It works perfect for cruise flight and saves the aesthetics of extra stuff on the sides of the rudder. Of course in climb additional rudder input is required (and a steep descent to keep the ball centered for that matter). The trim piece is aluminum sheet cut to the shape of the strobe/light housing with a small tab on on side. It is sandwiched between the light housing and the fairing. Not my idea but its friggin sweet!

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Mine required just a tiny bit of R rudder in cruise.
I cut a piece of sheet Al about 8" long x 3" wide, to parallel the angle of the rear of the rudder. Gently bent it in the middle, and attached with 3M double sided tape. It is bent very slightly to the left.

It has been in place for over 2 years with no issues.

I've got pics somewhere I'll see if I can dig them up....
 
Hello Paul

Yes that is the system we have had, with a wedge made of semicircular plastic faired with tape.

As I mentioned on the first post, as the wedge is on the left side of the rudder trailing edge, I wondered if coanda affect would cause that to apply left rudder correction?

Is your wedge on the left side and is it wedge shaped rather than curved?

Thanks

Sandy

Yes. I used a piece of trailing edge section fixed on with double-sided carpet tape. Left side (giving right rudder) about 8" long
 
This is what is on our RV-10. It works perfect for cruise flight and saves the aesthetics of extra stuff on the sides of the rudder. Of course in climb additional rudder input is required (and a steep descent to keep the ball centered for that matter). The trim piece is aluminum sheet cut to the shape of the strobe/light housing with a small tab on on side. It is sandwiched between the light housing and the fairing. Not my idea but its friggin sweet!


Didn’t see a photo come thru, can you send a picture?
 
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Would be happy to email a picture. Message me your email.

This is what is on our RV-10. It works perfect for cruise flight and saves the aesthetics of extra stuff on the sides of the rudder. Of course in climb additional rudder input is required (and a steep descent to keep the ball centered for that matter). The trim piece is aluminum sheet cut to the shape of the strobe/light housing with a small tab on on side. It is sandwiched between the light housing and the fairing. Not my idea but its friggin sweet!


Didn?t see a photo come thru, can you send a picture?
 
Candola effect

There are some cool videos on YouTube of the Candola effect.. guys throwing a basketball off a really tall dam.. but it's been my experience that a wedge on the left side of the rudder causes the surface to move to the right, as if right rudder is being held. I wonder if now after your fairings and spats (wheel pants here in 'merica ;) maybe you need a bigger or more deflected tab? Perhaps the wheel pants are causing the out of trim condition? Were the flaps re-rigged in the aileron work?
 
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Hello Tom

We didn?t knowingly change the flaps as part of the aileron work but we did remove them to gain access then replaced them.

We also worked on the spatpants. We had the compressed spacer issue where the stock aluminium spacers that hold the pant bracket had compressed making the pants loose. They had been loose since we bought the aeroplane 6 years ago, as they are now firm, this may be the cause of the change in aerodynamics?

We are going to replace the tape on the wedge and report back.

The other replies imply that the wedge, even although ours is curved, actually works as a conventional wedge rather than a coanda lifting surface?
 
After reading about the Dan Gurney Flap (wickerbill), I tried it on my RV4 rudder. Very powerful - you don't need much to make a big change.
 
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