apkp777

apkp777

Well Known Member
Has anyone installed some sort of adjustable link between the rudder pedal and rudder cable that can be ground adjusted giving you rudder trim? Something sort of like a small turnbuckle looking dohicky that you can turn by hand (knurled). The link that you are supposed to fabricate from 4130, the "length dependent on the rudder pedal position" seems kind of hokey. I think it would be a great place to put a rudder trim device. If I had a lathe I would fabricate them and sell them. I don't, and am not buying one, so someone who has a lathe, there you go. I'll buy one when your done.
 
Unless there is some tension on the cable there would be no rudder trim, just a fancy turn buckle to adjust the length of the link or position of the peddle. Am I missing something in your design idea? How about an adjustable bungie cord pulling on the peddle?
 
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You have to install one on both sides. "give a little, take a little" Simple but sufficient, I think.
 
apkp777 said:
You have to install one on both sides. "give a little, take a little" Simple but sufficient, I think.
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There will be no tension on the cable to manipulate the rudder. The rudder flies in the neutral position unless there is tension / pressure on one of the pedals. You could have the cables at different lengths, but that is not going to have an "input" to the rudder. Once you have rudder trim established (ball centered) on a -9 (a fixed trim tab on the rudder) there is usually no need for further adjustment.
 
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Hmmm, your right. Seems like my design might have to get really complicated. I haven't played with the pedals much, so I think I missed something in my thinking. You would have to have a Neutral (aft) stop installed on the pedals. I don't think I want to go there. Although you could make that work, just not as simple. Plus I think there may be an issue with cable tension on the RV's. Looks like it has to be pretty slack, because there are no pulleys for the corners. (whole lotta chafin goin on).

Anyhow, just some thoughts. It just would be nice to have trim without installing a tab. Those suck for sure.
 
All this comes to mind because I am connecting my cables (pedals to rudder) today! Yahooo! Flight control continuity. That is a huge milestone for me. I'll be sitting in it make plane noises in no time.
 
apkp777 said:
Anyhow, just some thoughts. It just would be nice to have trim without installing a tab. Those suck for sure.
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JMHO. When I see an RV with a rudder trim tab I see a builder / owner that has his plane dialed in, and a plane efficient for flying, not a building or airplane flaw. RV's are very fast and light. It does not take much for them to need to be trimmed for cruise flight. I guess it's all in perspective on how you look at things.

Congrats on the build progress. We need pictures!
 
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It Doesn't Work Like That

apkp777 said:
Has anyone installed some sort of adjustable link between the rudder pedal and rudder cable that can be ground adjusted giving you rudder trim? Something sort of like a small turnbuckle looking dohicky that you can turn by hand (knurled). The link that you are supposed to fabricate from 4130, the "length dependent on the rudder pedal position" seems kind of hokey. I think it would be a great place to put a rudder trim device. If I had a lathe I would fabricate them and sell them. I don't, and am not buying one, so someone who has a lathe, there you go. I'll buy one when your done.
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You'll need to sit in one with the rudder and pedals connected and have a play to see how they work :)

Some folks have added springs from the pedals but they need to react against some fixed structure. They won't do anything in the cable loop - apart from make it feel spongy.

Jim Sharkey
 
Jim- I don't think I would want a spring. It sounds like the tab can be pretty effective. I know from Cessnas, there are hard to "dial in". I am sure with some trial I can make a tab work.
 
jsharkey said:
You'll need to sit in one with the rudder and pedals connected and have a play to see how they work :)

Some folks have added springs from the pedals but they need to react against some fixed structure. They won't do anything in the cable loop - apart from make it feel spongy.

Jim Sharkey
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Van's has bungie cord type aileron trim kits for many 2 seaters that are very simple and work well. I wonder if we applied the same technique to the rudder peddle it might work. Attach a pulley to the firewall, bungie attachs to the peddle through the pulley and is adjusted by a turn crank. With the center tunnel in the -10 it would be all hidden except the handle.

Tony may have just sparked a good idea!

Hmmmmm. Gotta love experimentals.
 
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apkp777 said:
Anyhow, just some thoughts. It just would be nice to have trim without installing a tab. Those suck for sure.
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RV facts...........

RV's such as my 6A have a vertical stab with no offset. The 9 has an offset built in. I have a tab, and could care less. The 9 may not need one.

However, there is already a tensioning system for rudders on the market. It uses a small wheel and springs. Some pilots like it, some don't. There are a few other cable locking methods too. You can probably find these with a search. Personally I'm not a fan of bias springs for aileron or rudder. I have electric aileron trim that's hinged in the aileron and prefer it. Although my 6's rudder tab keeps the ball centered most of the time for cruise, I'd still prefer a hinged electric tab built into the rudder. A lot of the new RV10's have them.

L.Adamson --- RV6A
 
Larry- You might be on to something. I will give that a thought.

I had a Cherokee and I loved the rudder trim. I'll bet with the kind of innovation in the minds of us RV folk, we can come up with something.
 
LAdamson - I will look into the electric option.

What about just a cable lock that you install under the armrest. With like a 20 or so pound break away tension?
 
rudder trim

Is this what you are looking for? http://www.mlblueskunk.com/Rudder_Trim_System.html
I'm doing a very slow build RV7 and wanted to avoid the rudder wedges often found on really well built RV's. I haven't flown with this but have installed it on my plane and was impressed with the quality and I think it stands a good chance of working as advertised.
 
Loren said:
Is this what you are looking for? http://www.mlblueskunk.com/Rudder_Trim_System.html
I'm doing a very slow build RV7 and wanted to avoid the rudder wedges often found on really well built RV's. I haven't flown with this but have installed it on my plane and was impressed with the quality and I think it stands a good chance of working as advertised.
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That's the one I'm thinking of.

Perhaps I'm weird. I view airplanes as a bunch of movable surfaces and rivets. An added tab, wedge, or servo rod poking out just doesn't seem to bother me. But then I always enjoy looking at the mechanical complexity of an airliners wing, as the thumb screws seperate the flaps with all the hidden motors, hydraulics, wiring, etc..... to now be seen on landing. :)

L.Adamson ---- RV6A
 
I have the Van's spring trim for my ailerons and it works well. However with fuel and pilot balanced I don't need it and can fly feet and hands off at cruise in calm air.

I do have to use it when I add flaps for landing. I assumed that I had the flaps rigged unevenly but I can't measure any difference with a digital level. Perhaps there is something more fundamental with asymmetric prop wash acting differently on each flap when extended. Or perhaps I just need to tweak them a little - but I don't want to affect the current flaps retracted trim. Also I don't have the gear fairings or wheel pants fitted yet so I'm not ready for final rigging yet.

I'm a big believer in simple and light.

Jim Sharkey
RV6 - Phase 1
 
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jsharkey said:
I have the Van's spring trim for my ailerons and it works well. However with fuel and pilot balanced I don't need it and can fly feet and hands off at cruise in calm air.

I do have to use it when I add flaps for landing. I assumed that I had the flaps rigged unevenly but I can't measure any difference with a digital level. Perhaps there is something more fundamental with asymmetric prop wash acting differently on each flap when extended. Or perhaps I just need to tweak them a little - but I don't want to affect the current flaps retracted trim. Also I don't have the gear fairings or wheel pants fitted yet so I'm not ready for final rigging yet.

I'm a big believer in simple and light.

RV6 - Phase 1
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I do re-trim ailerons when ever I feel like it's slightly out. My 6A has no roll changes when applying flaps.

I use to believe that simple and light was they way to go, even if I didn't adhere to it. But it turns out that my 6A is really fast, light on the controls with a good feel..........................and isn't a light weight by any means. So bring on the constant speed prop and other goodies! :D

Heck.............I can only go a few miles before the airspeed is in the yellow zone as it is! :)

L.Adamson --- RV6A
 
The best laid schemes o' Mice an' Men,

L.Adamson said:
I use to believe that simple and light was they way to go, even if I didn't adhere to it. But it turns out that my 6A is really fast, light on the controls with a good feel..........................and isn't a light weight by any means. So bring on the constant speed prop and other goodies! :D
L.Adamson --- RV6A
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....Gang aft agley,

From To a Mouse
by Robert Burns
 
Like this?

IMG_1265_1.JPG


IMG_1266.JPG


The opposite side has a fixed spring. The spring tails are attached with 1/8 cable clamps (not the cushion clamps shown).
Vern

Flight testing is pending before I make the kit available. It is designed to augment a fixed tab, not replace it. This will allow trim adjustments based on speed or attitude.
 
Just wait until you are flying before installing any rudder trim system or tab.

My -9 flew ball centered with the small engine, no tab required. What I don't know is how it will fly with the new engine. I suspect it will not change any in cruise but climb is going to take a lot MORE of right rudder.
 
Bill - that's good advice. I will wait. Seems like there is a good solution that can be installed easily in a completed plane.
 
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