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  #1  
Old 01-28-2021, 09:51 AM
Jeff1smith Jeff1smith is offline
 
Join Date: Mar 2020
Location: Port Angeles
Posts: 21
Default Rudder trim

Tired of resting right leg on rudder. Installed some foam to rest right calf, but need to fix the issue. I have a IO 200hp 360 and three blade prop.
Any ideas of how much of a wedge; height, width and thickness that has worked for you as a starting point?
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  #2  
Old 01-28-2021, 12:35 PM
skyking902001's Avatar
skyking902001 skyking902001 is offline
 
Join Date: Oct 2009
Location: Gunter, TX
Posts: 324
Default Wedge

Jeff, get a wedge--Cleveland Tools has plastic ones (about 4" long) or you can probably find a wedge from model airplane store. Tape it to the rudder--go fly. Probably be too much, so cut off 1/4" or so and fly again. Repeat until you find the correct length. Then paint and attach with double sided tape. Worked for me. YMMV.
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  #3  
Old 01-29-2021, 05:52 AM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 1,329
Default What I did

Same as Steve..used a model aircraft trailing edge piece (I had some laying around from R/C projects) Mine was about 1/4 thick and 1 1/2 wide stock. I put a guestimate wedge on with double sided tape and flew it with intent on zero ball at cruise. Only took 2 tries to get proper length. You will still have a right rudder push on climb, and screaming descents have a slight left rudder hold, but cruise is "feet on the floor" coordinated. I sealed and painted my balsa wedge and installed with proseal permanently. Light ,cheap,easy. If I was building again, I would but an electric tab on it like Pat hatch did on his -6.
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  #4  
Old 01-29-2021, 07:22 AM
Jpm757 Jpm757 is offline
 
Join Date: May 2013
Location: Sherman, CT
Posts: 894
Default

Quote:
Originally Posted by DARV8 View Post
Until you can find a permanent solution you can use a bungee cord on the opposite rudder pedal to relieve/or counter the tension from having to constantly push on the right pedal.

You can find adjustable bungees at any Home Depot for next to nothing and you can adjust it in flight it's not difficult for most. You can also remove it when not needed.
I used rudder pedal return springs on my -6 and -7. You can compensate for an out of trim rudder by adjusting the spring tension. The springs also keep tension on the cables when on the ground.
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  #5  
Old 01-29-2021, 07:36 AM
YvesCH YvesCH is offline
 
Join Date: Feb 2015
Location: Basel, Switzerland
Posts: 221
Default

Quote:
Originally Posted by fixnflyguy View Post
Same as Steve..used a model aircraft trailing edge piece (I had some laying around from R/C projects) Mine was about 1/4 thick and 1 1/2 wide stock. I put a guestimate wedge on with double sided tape and flew it with intent on zero ball at cruise. Only took 2 tries to get proper length. You will still have a right rudder push on climb, and screaming descents have a slight left rudder hold, but cruise is "feet on the floor" coordinated. I sealed and painted my balsa wedge and installed with proseal permanently. Light ,cheap,easy. If I was building again, I would but an electric tab on it like Pat hatch did on his -6.
I`ve also used a balsawood trailing wedge 1/4 thick, 1,5 wide and about 4" long... attached with douple sided tape and some aluminum speed tape.
It worked perfectly.. Now i just have to make a nice permanent one...
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  #6  
Old 01-29-2021, 01:53 PM
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RV7A Flyer RV7A Flyer is offline
 
Join Date: Jul 2013
Location: US
Posts: 2,374
Default

I don't need a trim tab/wedge, but I've always wondered (and had a few debates with buddies who do)...

Which dimensions work best? Short and wide, long and narrow? For a given amount of trim needed, you have 3 variables: length, width, angle. Right? So is there an "ideal" solution?

Just wondering out loud, as I'm a systems engineer, not an aerodynamicist.
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  #7  
Old 01-29-2021, 01:59 PM
abwaldal@gmail.com abwaldal@gmail.com is offline
 
Join Date: Jan 2017
Location: Battle Ground WA
Posts: 144
Default

A roll of tape and a bunch on wedges and go fly. It will be very obvious as to the correct wedge once flying. Long, short fat, skinny, all your choices.
Hey make it pink so it stands out that you are all trimmed up.
My RV-6A has a 2 1/2" tall x 1/4" out rolled edge aluminum wedge sort of thing.
I don't care how they look. I won't fly with out it
Art
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  #8  
Old 02-18-2021, 11:38 PM
Jeff1smith Jeff1smith is offline
 
Join Date: Mar 2020
Location: Port Angeles
Posts: 21
Default Rudder trim part deux

Got some balsa wood and made a wedge. Prior to flying I found a rudder trim for he Rv12 at the Vans store for all of $7. I called tech support and they said it would work on the 8. Figured that it would look nicer than a block of wood.
From what I gather, others have put on the tab and then just gone flying.
The A&P here says it needs to be balanced now. Itís going into the paint shop where all the flight controls will be balanced . Anyone see any problem with flying it without balance prior to paint?
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  #9  
Old 02-19-2021, 10:37 AM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 512
Default Cracks

When attaching a wedge to the trailing edge, consider the loads imparted to the skin.

> Does the wedge sit in the "field" between two rivets/stiffeners?
> Does it sit across one rivet/stiffener end?
> Can it span two or more rivet/stiffener ends?

I don't know the right answer here -- I just know that when I installed a wedge on the 2+ piece rudder (New RV-7, RV-9 et al.) I ended up with a crack at one of the T.E. rivets. The wedge applied additional force/bending moment/vibration that caused a crack to form at the nearest stress concentration point...
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2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
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