VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-14
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 02-12-2020, 05:05 PM
Arablenz Arablenz is offline
 
Join Date: Dec 2014
Location: South Island ,New Zealand
Posts: 69
Default Rudder trim for taildragger

I am 15 hours into flight testing my RV 14 and it has been performing very nicely. As I am new to flying RV aircraft I am looking for some advice.
On climb out with full power I require right rudder but once level and at cruise power, no rudder Input required until above 130 knots .
I then require slight left rudder input .
I think I should install the Aerosport rudder trim system as a wedge on the rudder only helps for the one input , when it would be great to have trim for both climb and cruise.
When doing lateral stability testing it becomes very apparent at the different phases of flight.
Is this a sensible option or are there other thoughts?
Reply With Quote
  #2  
Old 02-12-2020, 06:05 PM
David Paule David Paule is online now
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,146
Default

Some people have installed rudder return springs that were cockpit adjustable for rudder trim. While this works, it'll probably take some experimentation to get right.

This shows part of such an installation on an RV-3. The lower arrow points to the rudder pedal, which is considerably different than yours. The upper arrow points to the pulley which turns the adjustment cable around so it goes back to a spring and the cockpit control.



As you can see, the cable is a very light one. The loads are low.

Dave
Reply With Quote
  #3  
Old 02-12-2020, 06:17 PM
KHeidorn KHeidorn is offline
 
Join Date: Nov 2013
Location: Heber City, UT
Posts: 108
Default

My RV-14 had the exact same issue. I added the adjustable rudder trim you are thinking about. I found that the springs weren't strong enough. I added a wedge to the rudder and found the combination of the wedge and the rudder trim worked very well.
__________________
Ken Heidorn,
Debur..Dimple..Rivet..Repeat...

"You're never too old to learn something stupid." - unknown
Reply With Quote
  #4  
Old 02-12-2020, 06:51 PM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,145
Default

Quote:
Originally Posted by KHeidorn View Post
My RV-14 had the exact same issue. I added the adjustable rudder trim you are thinking about. I found that the springs weren't strong enough. I added a wedge to the rudder and found the combination of the wedge and the rudder trim worked very well.
You can double or use stronger spring, especially for the RV14 that has a bigger rudder. But also it would be great if you can verify all your rigging, wheel pants or anything else that is effecting this, and see if there is anything that is causing it.
Mine is a 14A and the only time that I need to hold rudder is on climb, like most planes need it. Other than that, my feet are on the floor.
__________________
Mehrdad
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - Flying
Dues paid
Reply With Quote
  #5  
Old 02-13-2020, 05:46 AM
RV6-KPTW RV6-KPTW is offline
 
Join Date: Oct 2014
Location: Sebastian Fl X26
Posts: 63
Default

I added a wedge on the right side of the rudder to deal with the cruise trim issue and use my feet for other situations.
__________________
Dennis Callaghan (X26)
- RV14 sn:140193 - first flight 12/19/2019
- 2000+ hours on my RV6! Sold (so sad...)
- donation 12/30/2019 * 2
Reply With Quote
  #6  
Old 02-13-2020, 08:44 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 8,643
Default

The RV-14A and RV-14 prototypes have different rudder trim compensation as well (the 14A has a wedge adding a little bit of right rudder trim.... the 14 has a wedge adding a little bit of left rudder trim.

Why the difference? I can't say for sure, but I do know that fixed landing gear has a lot more influence on the aerodynamics of the airframe than a lot of people realize.

Keep in mind that the airflow around the fuselage is in a spiral because of the influence of the propeller rotation. Add to this the influence of gear legs (with wide leg fairings on them) positioned at different points relative to the C.G. (the yaw axis), and it is easy to see why the might be differences between the two airplanes.

As for rudder trim?
Most people add a fixed tab or wedge that trims for the condition that the airplane will spend the most time in (cruise flight). The rudder forces aren't very high and the additional amount of right rudder that would be needed, because of a left rudder tab having been added, is very small.

My suggestion would be to trim using a temporarily installed trim tab, for what ever cruise condition you will likely use the most. Fly for a while, and see how you like it.

A small balsa wood wedge (about 1.5 inches wide X 6 inches long X 1/8" max thickness would be a good starting point), attached with clear plastic packing tape works well (it is what we use for all of our flight testing).
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #7  
Old 02-13-2020, 11:35 AM
Arablenz Arablenz is offline
 
Join Date: Dec 2014
Location: South Island ,New Zealand
Posts: 69
Default

Thankyou all for your replies. It is good to know that others have the same need for rudder trim.
I have flown with my leg and pant fairings on and off and have eliminated them as having any effect on yaw.
I will do as Scott suggested and then see if I need the Aerosport trim as well or instead of the wedge.
Great support here.
Regards
Roger

Last edited by Arablenz : 02-13-2020 at 02:42 PM.
Reply With Quote
  #8  
Old 03-04-2020, 04:46 PM
Arablenz Arablenz is offline
 
Join Date: Dec 2014
Location: South Island ,New Zealand
Posts: 69
Default

Just updating that I did as Scott kindly suggested and plane flies beautifully hands and feet off in cruise now.
How does everyone that needs a trim tab attach theirs permanently to a painted surface?
I am thinking proseal or avery strong automotive double sided tape but wondering if I need to remove the paint for good adhesion.
Reply With Quote
  #9  
Old 03-04-2020, 04:59 PM
N941WR's Avatar
N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 12,675
Default

I did see a photo someplace of a trim tab attached through the rear position light/strobe.

It appeared to be a simple and elegant solution.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Reply With Quote
  #10  
Old 03-04-2020, 05:15 PM
RV8JD's Avatar
RV8JD RV8JD is offline
 
Join Date: Jan 2005
Posts: 665
Default

Quote:
Originally Posted by N941WR View Post
I did see a photo someplace of a trim tab attached through the rear position light/strobe.

It appeared to be a simple and elegant solution.
This is the trim tab attached through the rear position light/strobe on the rudder of my RV-8. It is set up for cruise and works well.



__________________
Carl N.
Arlington, WA (KAWO)
RV-8, 675 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B - Sold
Rolladen-Schneider LS1-f - No longer owned

Last edited by RV8JD : 03-04-2020 at 05:26 PM.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 07:25 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.