What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Rudder Trim?

czechsix

Well Known Member
Is there any provision for rudder trim on the -14? I don't see any trim tab on the prototype. I've flown in half a dozen different RV's and every one of them including my -8A needed right rudder trim to center the ball in cruise. I don't mind stepping on the right pedal during climb phase, but it is annoying having to rest my foot on the pedal throughout the cruise phase. I considered offsetting the LE of the vertical stab when I built my -8A but didn't know how much it would need, and the thought of reworking the fiberglass intersection fairing was enough to discourage me, so I put it on straight per the plans and have never gotten around to fitting, installing, and painting a fixed trim tab. Was hoping that Vans would find a way to get the ball centered in cruise configuration on the -14 and maybe they've adjusted the engine offset or vertical stab alignment to accomplish this without needing a tab?

If all else fails a yaw damper servo would probably get the job done, but that's kind of the brute force solution...

Mark Navratil
Spring Hill, KS
RV-8A N2D
 
Simple rudder trim system

If one wants just neutral rudder at cruise, consider this simple system.
Mentally extend the rudder cables forward to the inside of the firewall.
Drill a small anchor hole in a structural element as is convenient as near that point as possible.
Drill a small hole through the same plate that the rudder cable attached to the rudder pedal.
Attach a bias spring between the anchor hole and the rudder pedal using a short loop of .041 safety wire. Repeat on other rudder pedal.
Rudder trim is adjusted by making small changes to the length of a safety wire loop.
Springs need to be long enough to allow full rudder travel.
Once you know which rudder pedal you must step on in cruise, you only need to attach one spring.
Remember to exercise all due caution regarding safety and reliability of flight controls.
This system is relatively simple, reliable, low weight, inexpensive, and creates no drag. It is easy to re-adjust when you add a new antenna or correct the alignment of the gear leg fairings. ...But the in-flight adjustable trim looks cool.

- Roger
 
Ken, have you taken that the RV-14 is aerobatic capable? I had planned to do the same as I did on the RV-10, love it, til Tim O. mentioned this fact. It might be fine but I opted out and will use Geoff's trim System.
 
Or This

If you are in the mood to roll your own.
Works very well using a Vans flap motor assembly.
Flap motor is controlled via a relay deck by left and right buttons on the stick.
A word of caution; This will not work with a trim servo.

IMG_1698.JPG
 
I think I will...

I did go ahead and add an access plate to the RV14 rudder, and will probably add the rudder trim. I'm not 100% positive on it yet, but the wire is there now, and I will probably even add the screw holes for the servo. I just find on long x/c flights it's very nice to have. I may not actually install the hinge and servo right away, but I will build everything else to be ready for it.
 
Rudder trim

All Piper Cherokee derived airplanes have adjustable bias springs for rudder trim. Works great for trim but the springs are much heavier than necessary.
 
I had not thought about the impact on the aerobatic capability. Maybe the aerosport product is the way to go.

not sure how much aerobatics I will do, but I don't want to screw up the plane for aerobatics.
 
When the vertical stabilizer is mounted on the fuselage it is mounted at a slight angle. I think this is to eliminate holding rudder in cruise.
 
What does this mean? This IS the trim servo, right? Are you saying that plugging it in place of another type of servo won't work? I'm curious why.

The servo in his picture is not a trim servo, it is the flap drive motor. Much longer arm throw and force. On a regular trim servo the arm throw is probably not enough to change the tension on his springs very much.
 
BlueSkunk

I put the M L Skunkworks rudder trim in my -6, it's an under panel mounted spring bias system. System works great and is nice on long climbs or descents. In practice I use it very rarely - I set it for cruise and there it stays. I would just use a rudder wedge if doing it again. It is a fine system though.

Here's link if you'd like to take a look: http://www.mlblueskunk.com/Rudder_Trim_System.php
 
Last edited:
My Rudder Trim

I've been asked offline a couple times for more info on the rudder trim I used, especially regarding where I mounted it. Here are some pics that should be fairly self explanatory. The hinge section is 11" long I believe. I got this trim idea from Vic Syracuse. He used it on his RV-10 and I copied it on mine and it worked real well, so I used it here. So far my ball isn't too far out of center on the -14 without fairings, but I still tweaked it a bit on my 2nd flight. For X/C I will definitely be happy to have it.
All it takes is a rocker switch in the panel, 2 wires to the tail, and a servo. I don't use an indicator, as the skid ball is your indicator. The wires go into the lower rudder fairing to connect, but exit the same hole as the tail beacon wires. I did purchase (because I couldn't make ones as nice) the rudder cable fairings from aircraft spruce and bought enough to cover my rudder cables, and this trim exit. They're cheap, and just prosealed on to the rudder and tail skins.

RV14_Rudder_Trim_01.jpg


RV14_Rudder_Trim_02.jpg


RV14_Rudder_Trim_03.jpg
 
I had the Skunkworks rudder trim installed on our last 6 and it worked great. My first 6 I made a wedge and attached it with VHB tape at the lower portion of the rudder. Here are my personal observations:
1. Fancy knob type trim-costly, took quite a while to install, maybe 2-3 hrs-Actually used one time in flight and I never touched it again for 5 years and 600 hrs.

2. Wedge made out of a piece of pine-cost $0.00-weight, next to nothing-install time, 30 seconds each for two tries while sizing-after takeoff, never needed to trim just as in the expensive rudder trim.

As always, it's a matter of personal choice. If we run into a trim necessity on the 14, I will opt for a wedge adhering to the KISS principal.
My 2cw.
 
I had the Skunkworks rudder trim installed on our last 6 and it worked great. My first 6 I made a wedge and attached it with VHB tape at the lower portion of the rudder. Here are my personal observations:
1. Fancy knob type trim-costly, took quite a while to install, maybe 2-3 hrs-Actually used one time in flight and I never touched it again for 5 years and 600 hrs.

2. Wedge made out of a piece of pine-cost $0.00-weight, next to nothing-install time, 30 seconds each for two tries while sizing-after takeoff, never needed to trim just as in the expensive rudder trim.

As always, it's a matter of personal choice. If we run into a trim necessity on the 14, I will opt for a wedge adhering to the KISS principal.
My 2cw.

Van's 14 has a little wedge on it, but not sure what it's made of, I think aluminum and not sure how it is adhered.
 
The short answer is no, I did not add extra mass. I don't think it's a bad idea to consider. When Vic first did the mod on the RV-10 he asked Van's about it. They had no concerns. Since that time, he and I and many folks put hundreds of hours on with no issue. The rudder on the -10 is not the same as the rudder on the -14. I didn't ask on the RV-14. I may be wrong, and probably should have. So do the mod at your own risk, use your best discretion, and I think a builder should consider calling Van's. If you call and find out they recommend more mass, I'd like to hear it, and would consider adding some. But I don't expect any issues at this point, myself.
 
Back
Top