Fixed rudder trim

Machsandy · #1 12-13-2019, 06:24 AM

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.

Machsandy · #2 12-22-2019, 04:51 AM

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?

9GT · #3 12-22-2019, 05:00 AM

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.

Auburntsts · #4 12-22-2019, 06:21 AM

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.

paul330 · #5 12-22-2019, 08:35 AM

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.

Machsandy · #6 12-22-2019, 02:35 PM

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

BobTurner · #7 12-22-2019, 09:41 PM

Quote:

Originally Posted by Machsandy

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.

rvdave · #8 12-23-2019, 01:32 PM

I have a small (about 5? high, 1? wide) wedge on the left side of my rudder.

What is the thickness of the wedge?

BobTurner · #9 12-23-2019, 06:25 PM

Quote:

Originally Posted by rvdave

I have a small (about 5? high, 1? wide) wedge on the left side of my rudder.

What is the thickness of the wedge?

Okay, I went and measured. It?s bigger than I thought.
11? high, 2? wide, 1/2? thick at the aft end.

rvdave · #10 12-23-2019, 07:33 PM

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.