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V. Stab & Rudder Question...

mkmuch

mkmuch

Active Member
Series of Questions...

The Set up - I am contemplating the rudder trim modification for the -10 now that I am nearing the end of my vert stab assembly. I have some questions about the various mods I see on several builder sites, thought I's just ask the team (that's you guys).

#1. What portion of the vert stab offers the most effectiveness to the aircraft? The bottom where it's longer, middle way up and medium length, or at the top where it's the smallest? Guess I am driving towards - is it the surface area of the vert, the position in the airstream, both or non of the above that offers the most efficiency?

#2. based on the answer to Q1 - is the answer the same for the rudder?

#3. Based on the answer to Q2 - Where is the optimal place to put an electric rudder trim section?

#4. For those that have done it (I have seen 2 methods - piano hinge hanging off the rudder about middle way up - and section the actual rudder control surface and incorporate the trim device into the rudder again about mid way up) is it just coincidence that you placed the rudder trim control surface mid way up or is there a method to it - see questions #1 & #2?

#5. Based on the variations of rudder trim solutions is there a formula for control surface area you want to achieve - i.e. the piano hinge clearly has less surface area than the sectioned in control surface?

#6. How about moment change for the rudder control surface? the servo and trim tab in the rudder have added extra weight to that control surface above what the counter weight was anticipating - does that manifest itself negatively in flight? Do you anticipate early hinge failure? Have you modified / beefed up the hinges to accommodate this change?

#7. How much drag do you anticipate this device with the control arm out in the airstream having on the overall performance of the aircraft - a couple of knots of speed?

#8. Has anyone spent anytime trying to engineer a piper Archer, Arrow, Cherokee type manual rudder trim knob into the plane? I am not intimate with the control type in the Piper so may not be compatible? The thought would be to turn the entire rudder into a self-trimming surface by manually or electrically moving the main rudder cables or pedals as is the case with the piper - thus eliminating the need for a trim tab all together?

#9. Am I over thinking the impacts of this - wait - Don't answer that one - already figured it out!

Sorry for the long post - just pondering and had to write it all down.
:rolleyes:
 
Why go to all the trouble fo fitting a mechanical or servo driven tab in the rudder?

The answer is at ML Skunkworks. https://www.mlskunkworks.com/

They have really nice rudder pedal extensions (well worth it) giving you better rudder control withoutout applying brake at the same time which can be a problem!

They now have a Rudder trim with bigger springs for the RV-10

DB:cool:
 
RV10inOz said:
Why go to all the trouble fo fitting a mechanical or servo driven tab in the rudder?

The answer is at ML Skunkworks. https://www.mlskunkworks.com/

They have really nice rudder pedal extensions (well worth it) giving you better rudder control withoutout applying brake at the same time which can be a problem!

They now have a Rudder trim with bigger springs for the RV-10
Click to expand...

Personally, I'm not a fan of bias springs for trim control. With servo operated (or fixed) trim tabs, all the pressure is taken off the linkages, cables, and push/pull tubes. I'm using the original Van's piano hinge trim tab, that's servo operated in my 6A aileron, and I'd do the same for my rudder if it was a 10. I know many that do.

L.Adamson --- RV6A
 
Thanks for the link - It appears to be similar in concept to the piper system. I am not sure how keen I'd be on the location - (knee killer) especially the **** raiser type knob they show - ouch!

That's closer to what I was thinking.

Still looking for any thoughts on the 7 other questions - like to understand the theory...
 
L.Adamson said:
Personally, I'm not a fan of bias springs for trim control. With servo operated (or fixed) trim tabs, all the pressure is taken off the linkages, cables, and push/pull tubes. I'm using the original Van's piano hinge trim tab, that's servo operated in my 6A aileron, and I'd do the same for my rudder if it was a 10. I know many that do.

L.Adamson --- RV6A
Click to expand...

Curious - why not? I know you mentioned pressure, it would seem that's no more than your feet would exert?

How does the piper system work? Since it's located in the center of the aircraft is it mechanical (gear drive of sorts?) or the spring type? That seems nearly fool proof?
 
you beat me to it!

The cables etc are meant to take peak loads, not just a constant lesser load so I am not sure that really hold much validity. But hey....why not use a servo!

As for the knob, you can mount it anywhere out of the way. I will make our flush with the bottom of the panel, and the knob delivered is not as thin and razor looking! :eek: The one I have is 7mm thick and not an injury worry. 7mm is over a 1/4" for you folk over there! :D

DB:cool:
 
No thoughts?

Was hoping for some feedback about the aerodynamic characteristics?

General thoughts about rudder trim placement?

:confused:
 
I went with the Piano hinge method and the tab is placed about half way up the rudder. I chose that location for a couple of reasons.

1) The theory was to reduce any chances of twisting the rudder.

2) The more important reason for the location is that it's not blanked by the fuselage in that location. I didn't want to get too low, because that area is blanked. I wanted the tab in the clean air.

Finally, the servo does change the balance of the rudder. But depending on where you mount it, it's effect can be minimized. Place the servo as far forward (closest to the hinges) as you possibly can. This reduces the leverage (Arm) of the servo and therefore reducing it's effect on the control surface balance.

Even a plans built rudder is out of balance. Vans just has you pop a lead weight in the front of it and go on. They could still use a nearly a couple of more pounds if you really wanted a perfectly balanced rudder. Vans doesn't seem to think rudder balance is all that critical of an issue. I'll probably add a 1/2 pound or so to the front just to off set the addition of the servo. But I haven't don't that yet.

I wouldn't lose too much sleep over it though. If you over think it too much, it'll take you forever to build. Just ask me how I know. :D
 
By the way, if I had it to do over again, I'd just build the rudder to plans and keep the project moving along.

Once I had a flying RV-10, then I'd spend the $150 for rudder parts and spend rainy days tinkering with the perfect rudder trim system to replace the flying one.

In the end, you'll end up with a better rudder trim, a project that keeps moving, and you'll have better skills to put together something nice and clean.

If this happens to be the first airplane you've built, my experience in tackling rudder trim before I even completed riveting my second piece says this just isn't the right time to try and build something elegant or perfect. I just didn't have all the skills I could have had if I had waited until later.

And waiting doesn't cost much more than $150 either.

If I was building another rudder, that's exactly what I would do. In fact, I'm still planning on building another rudder when this one starts flying. I plan on building the perfect rudder to replace the current one.
 
I added the rudder hinge tab while building my rudder (just finished it last week). The only thing I found that you had to do a different way was riveting the trailing edge. I could not follow the plans directly because I had this hinge in the middle of my rudder, but my rudder came out strait as an arrow anyway. I did not find it that hard to do the work needed however it was scarry cutting a big hole in the side of my pretty skin. If I were to do it differently I might see about putting spacers between the skin and the trim tab. This would center the weight more in the rudder and allow for the pushrod to exit the rudder at a better angle.
 
mkmuch said:
Series of Questions...

The Set up - I am contemplating the rudder trim modification for the -10 now that I am nearing the end of my vert stab assembly. I have some questions about the various mods I see on several builder sites, thought I's just ask the team (that's you guys).

#1. What portion of the vert stab offers the most effectiveness to the aircraft? The bottom where it's longer, middle way up and medium length, or at the top where it's the smallest? Guess I am driving towards - is it the surface area of the vert, the position in the airstream, both or non of the above that offers the most efficiency?

#2. based on the answer to Q1 - is the answer the same for the rudder?

#3. Based on the answer to Q2 - Where is the optimal place to put an electric rudder trim section?

#4. For those that have done it (I have seen 2 methods - piano hinge hanging off the rudder about middle way up - and section the actual rudder control surface and incorporate the trim device into the rudder again about mid way up) is it just coincidence that you placed the rudder trim control surface mid way up or is there a method to it - see questions #1 & #2?

#5. Based on the variations of rudder trim solutions is there a formula for control surface area you want to achieve - i.e. the piano hinge clearly has less surface area than the sectioned in control surface?

#6. How about moment change for the rudder control surface? the servo and trim tab in the rudder have added extra weight to that control surface above what the counter weight was anticipating - does that manifest itself negatively in flight? Do you anticipate early hinge failure? Have you modified / beefed up the hinges to accommodate this change?

#7. How much drag do you anticipate this device with the control arm out in the airstream having on the overall performance of the aircraft - a couple of knots of speed?

#8. Has anyone spent anytime trying to engineer a piper Archer, Arrow, Cherokee type manual rudder trim knob into the plane? I am not intimate with the control type in the Piper so may not be compatible? The thought would be to turn the entire rudder into a self-trimming surface by manually or electrically moving the main rudder cables or pedals as is the case with the piper - thus eliminating the need for a trim tab all together?

#9. Am I over thinking the impacts of this - wait - Don't answer that one - already figured it out!

Sorry for the long post - just pondering and had to write it all down.
:rolleyes:
Click to expand...

Ok munch,

You need to contact Alex Domince here at Eagles Nest. I know I spelled his name wrong but , any way he can set you up with excellent rudder tab kit, you have to install while your building the rudder thou. If the rudder is already completed don't bother, you have to use the spring or get a yaw damper. Send me a pm and i will give you his contact number. Good luck
 
To the left side on the main page is a list of links---------Alex is listed under "transition training"
 
Thanks for the links

I will continue the research on my aerodynamic / control surface effectiveness as well...

Building the mod is not really the challenge - easy enough - The engineer in me was trying to understand the mod, design characteristics, and considerations.

One other question was - why didn't VANS offer this in the kit or at least as an option? Seems kinda silly to leave off any plane but especially the -10?

Guess that's rhetorical - no need to answer...

M.
 
mkmuch said:
One other question was - why didn't VANS offer this in the kit or at least as an option? Seems kinda silly to leave off any plane but especially the -10?

M.
Click to expand...


Yeah I was wondering the same thing. We are going with a yaw damper. And if there is a problem we will probaly(sp) fit a tab in the last 6" of the rudder.
 
I havn't made my trim yet but I had a couple of things that I was considering about rudder trim.
Having the rudder trim low in the rudder is better for a couple of reasons. The effect of the trim tab will be greater near the bottom of the rudder because it is farther away from the hinge point (arm), and the wiring will not have to go up through the rudder. I would also put the servo as far forward and on the same side as the hinge of the tab with the connecting rod going out to the opposite side to the tab horn . The idea here is that the servo acts as far away from the hinge of the tab as possible to get more resolution out of the travel of the servo and that the connecting rod exits the skin at a greater angle. I would also put the tab horn on the bottom of the tab as opposed to the middle to give clean airflow to the tab.

I hope that this makes sense.

Nick
 
One more thing that I forgot to mention. Someone earlier said that they were worried about twisting the rudder. The rudder control cables act on the bottom of the rudder and if the trim was high up the ridder, there would be a twisting moment. The Rudder does more work near the bottom because it is larger there.
 
mkmuch said:
One other question was - why didn't VANS offer this in the kit or at least as an option? Seems kinda silly to leave off any plane but especially the -10?

Guess that's rhetorical - no need to answer...
Click to expand...
No, not rhetorical. The Van's response is to use a simple ground adjustable "fixed" rudder trim. Simple, effective and it works.

I'm amazed at all the effort people are putting into rudder trim that will be minimally used during a normal flight. I guess if you are really lazy and do not want to hold right rudder in a climb, you may use rudder trim a bit more, but for cruise mode, a fixed trim tab is all you need.
 
One reason that I would like to put rudder trim on my RV-10 is that I like to build things and I like gadgets. I like a good excuse to build something from scratch. Adding gadgets and trim that I don't necessarily "need" is one of the reasons that I am building in the first place. I am one of those "builder-flyers" (equally enjoying building as I do flying) ... the building / designing is half the fun!
 
Nictech said:
One reason that I would like to put rudder trim on my RV-10 is that I like to build things and I like gadgets. I like a good excuse to build something from scratch. Adding gadgets and trim that I don't necessarily "need" is one of the reasons that I am building in the first place. I am one of those "builder-flyers" (equally enjoying building as I do flying) ... the building / designing is half the fun!
Click to expand...

Besides, my stick has a coolie hat already in it, and I dont want to waste a couple of contacts:D
 
Last edited:
Nictech said:
One reason that I would like to put rudder trim on my RV-10 is that I like to build things and I like gadgets. I like a good excuse to build something from scratch. Adding gadgets and trim that I don't necessarily "need" is one of the reasons that I am building in the first place. I am one of those "builder-flyers" (equally enjoying building as I do flying) ... the building / designing is half the fun!
Click to expand...

Save your energy. By the time you get to the fuselage of the RV-10, there will be so many opportunities for modifications, upgrades, additions and gadgets, you will wonder why you wasted all that time thinking about rudder trim. Plus, you will be so frustrated with all the fiberglass you have to work with, you will be looking for other (non fiberglass) tasks to accomplish:D. The nice thing about rudder trim is that it is easy to add AFTER you are flying.
 
I don't get it. I don't have that much time in the ten but why can't the pilot push on the pedal in the climb and push on the other pedal on the descent? Isn't that just as much work as moving the trim tab? I fly a Citation that has rudder trim (mostly for an engine out) that I never use, I use the pedals on climb out then I turn on the yaw damper for passenger comfort.
 
I guess I should be asking if I should be thinking about the installing rudder trim myself. I am done with the rudder.

Do the pilots that installed this use it? Is there that much trim needed at take-off, descent in the 10? I couldn't tell with the little time I spent in it.
 
Rudder Trim

I installed rudder trim after my rudder was done. I now have 60+ hours in the airplane and am glad I have it. One of the mods I would definitely do again.
 
Mine is electric. It is from a now defunct company called Aerotrim. I would go with the Ray Allen servo and hardware used by Vic Syracuse, Tim Olson, and others if I were doing it again.
I have the control on my Infinity grip pinkie finger switch. Here is a photo during the installation.

 
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