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Rudder Trailing Edge Trim Tab

iwannarv

Well Known Member
I am coming up on the step of riveting my rudder trailing edge. I am planning ahead and would like to add a trim tab for future adjustment. Question I have is how large of tab, and what relative location? Asking so I know which rivets I may need to leave open for now to add the tab later in the build.

What have others done?

PS...... I also plan to use the Aerosport spring bias system but was told I may need to use in conjunction with a tab/wedge (would prefer a tab).
 
Why?

Why would you need a tab and the spring bias system?

With the spring bias system, you are moving the ENTIRE rudder to a new center point. The tab/wedge would serve no purpose.

The tab is also adding more complexity to the system. The spring bias is, in comparison, very simple.

I originally looked at doing a tab but settled on the Aerosport system...
 
You got bad gouge --it's usually one or the other, not both. I have the Aerosport system spring system and it works well. Those that go with the fixed tab tend to epoxy on a wood or plastic wedge in place vs riveting on a metal tab. If you go that route, wait until you are flying then tape different sized wedges on until you find the right size for your plane. Then you can permanently attach it. A third but more complex option would be to install a servo rudder trim system driving a rudder trim tab (overkill IMO, but others will disagree).

FWIW, I flew for almost two years without anything at all. I found that all I needed to to do was rest my right foot on the right rudder pedal in cruise to keep the ball centered, but that started to get old on long X/C flights so I opted for the spring system and haven't looked back.
 
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Thanks.... A riveted metal tab was what I was referring to, not a cut out servo controlled tab as part of the rudder. Will move on and stick with the spring bias only.
 
I have both the Aerosport bias spring system and a fixed tab. I flew with just the Aerosport system for a while but found myself having to crank in a lot of right rudderbias all the time. I subsequently added a fixed tab to the trailing edge of the rudder up high (out of propwash?). It has made use of the Aerosport system more symmetrical, if that makes sense. I think many 10s need a right rudder bias in most flight modes. I would wait until flying...easy to drill out a few rivets and add a rudder tab when/if needed.
 
I have both the Aerosport bias spring system and a fixed tab. I flew with just the Aerosport system for a while but found myself having to crank in a lot of right rudderbias all the time. I subsequently added a fixed tab to the trailing edge of the rudder up high (out of propwash?). It has made use of the Aerosport system more symmetrical, if that makes sense. I think many 10s need a right rudder bias in most flight modes. I would wait until flying...easy to drill out a few rivets and add a rudder tab when/if needed.

I agree this is what I was told previously, with the need to have both, possibly. Will wait till flight.
 
Uh...

I would be curious to hear the reasoning behind having both.

From an aerodynamic standpoint, it doesn't make any sense. The fixed tab is used to create a new center point for the rudder by moving the rudder.

The spring bias system creates a new center point by moving the rudder.

If you need to add a tab to gain more rudder authority, then you probably have insufficient tension on the trim springs.

If you are using the tab to reduce rudder authority, then you are defeating the purpose of the rudder bias system.

So what would be the reasoning behind having both?

This is for the sake of discussion only. Each of us is building a custom machine and is free to do and try whatever they so desire.
 
a further thought

I was all settled on the AeroSport spring bias system until I heard about the yaw damper option being included in AFS/Dynon offerings. Fuselage now fitted with yaw damper servo mounting hardware as I plan to go that route.

Hoping that a small fixed tab is all I might ever need to add to the yaw damper setup, even knowing the servo isn't meant to supply constant trim bias - but I believe it can contribute some.

Any reports from the field on going this route?
 
YD

Don't know if you are going Garmin but they reference this topic in the manual.

As you stated, the YD can contribute, but is not meant to be a trim tab...
 
My -10 has an electric trim tab and I have to adjust it several times on any given flight depending on the speed. So in climb, with 25 squared, I'll have it trimmed differently than in cruise, and that will be different that approach and landing. Yes I still use the rudders on T/O and in the pattern, but only for short periods. I can't imagine a trim "tab" being very useful with the wide speed range of a -10.

-Marc
 
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I cna't imagine a trim "tab" being very useful with the wide speed range of a -10.

-Marc

You have to pick a specific flight regime, typically the one where you spend the most time. For most RVer's that have gone this route, it's cruise.
 
I used a Ray Allen servo and a short piece of hinge to fab my rudder trim tab. I found it to be an invaluable item for trimming the aircraft out. The servo was mounted to the access panel to the left of the rod fairing. Its not clearly visible in the photo.
39603230092_360f14f790_c.jpg
[/url]DSC01477 by David C, on Flickr[/IMG]
 
If you add a servo inside the rudder, you may be changing its flutter speed. I have no rudder trim on my RV8. The need for trim and in which direction change with speed and whether you are in climb or descent. In cruise, mine requires light right rudder pressure. Without it, I'm a half ball out. I've found no difference in speed ball centered or a half ball out.
 
?Everyone loves what they decided to do.?
Usually this quote is applied to avionics, but it applies here too.
Build the plane, fly it, then decide on rudder trim.
For the record, I went with a fixed wedge, ball centered in my typical cruise. Other cruise configurations might require a very slight rudder input - so small that once applied, friction holds it! Climb, I need to hold some right rudder, for sure. I have no intention of adding rudder trim. OTOH, adding aileron trim is on my wish list.
 
Why have both

I have used the spring system for a year or so and will be adding some kind of aerodynamic balance like a tab or wedge. The reason is that I would prefer to have the rudder trim always in the ballpark without the airplane constantly pulling right on the taxiway. So I'll have an aerodynamic balance to do the bulk of the trim and use the springs to fine tune for existing conditions.
 
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