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  #1  
Old 08-19-2021, 02:32 PM
Rightfooted's Avatar
Rightfooted Rightfooted is offline
 
Join Date: Sep 2020
Location: Oro Valley, AZ
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Default Armless Build Question: Trim Options

Thank you all again for the help looking at the different RV models and starting the ideas rolling on how to modify them. I'm still working on the heavy hitters like flight control inputs, etc.

In the meantime, we have identified one area that will probably help me out a lot: trim.

Elevator trim is an obvious need and I've looked around the forums and seen a lot of posts about "the -10 doesn't need rudder trim." While that is true, having it onboard looks like something that will help me.

Can some of you experienced builders point me in the direction of a mechanical trim system that has electric inputs? I'm looking for something for both elevator and rudder trim.

I will need to be able to disable the electric inputs in the case of runaway trim but still use the trim with the electronics disabled.

It's a long story as to why (I'll post a video on my YouTube channel soon if you want all the details), but I wanted to get the ball rolling while it was fresh. Thank you all!
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  #2  
Old 08-19-2021, 02:52 PM
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Paddy Paddy is offline
 
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Location: Prosper, TX
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Default Trim

Jessica,
The -10 includes electric pitch and roll trim as standard. Some builders add rudder trim as well, or rely on a yaw damper that's part of the autopilot. For runaway trim protection, the VPX electronic circuit breaker system includes this feature as does one of the Garmin G3X modules if I remember correctly.
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  #3  
Old 08-19-2021, 03:05 PM
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Paddy Paddy is offline
 
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Default Trim 2

If you need to be able to operate the trim with the electric inputs disabled, that's going to be more of a challenge on the -10. Both pitch and roll control are solid push rod actuated, so not so easy to attach a mechanically operated tension cable like on a Cessna or a Cherokee. Pitch trim tabs are actuated by cables but they're push/pull type, so again not easy to work in a capstan or other mechanism. Rudder is much easier since it's a conventional tension cable arrangement. I have a spring bias rudder trim on my plane that operates via a servo but could easily have a mechanical input as well.
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  #4  
Old 08-19-2021, 05:57 PM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
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Default Trim

Setting up pitch and roll trim to be mechanical as well as electric would be problematic in the -10. Rudder trim would be fairly easy. I modified the aerosport rudder trim to be electric without a manual overide but it would not be difficult to accomplish.

Actually, now that I think about it, I take it all back. I think you could modify the aileron trim to use a gsa28 servo instead of the RAC servo then if you needed to disconnect it, you remove power. A spring bias system on the stick base may be a solution to manual control.

Pitch trim is a bit more complicated. It may be possible to use a telaflex cable in place of the rack servo drive. This could feasibly be coupled to servo like the gsa28 to move the cable when necessary but runs free when unpowered. It may be doable…
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  #5  
Old 08-19-2021, 06:39 PM
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Vern Vern is offline
 
Join Date: Jan 2005
Location: Peachtree City, Ga
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Exclamation Trim on RV-10

I’ve flown all RV models and find the 10 and 14 need much more attention to pitch trim , especially as flaps are lowered or raised. When I do checkouts on either I tell the students that elevator trim is the one thing that could kill you in either plane. A go around with full flaps can be very challenging.

In my opinion, a 9 would be much more suitable for you.

Perhaps you could get flights in both to see my point.
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  #6  
Old 08-19-2021, 08:46 PM
Norman CYYJ Norman CYYJ is offline
 
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Default

In order to make elevator trim mechanical and electric install two trim tabs. One being electric on say the port side and a mechanical trim tab on the starboard side.
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  #7  
Old 08-19-2021, 09:02 PM
BobTurner BobTurner is offline
 
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The -10 already has two trim tabs. I suppose you could re-route one cable to the front, and tie it into a trim wheel somehow. Not sure that just one tab has sufficient force for trim over all speeds, though.
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  #8  
Old 08-19-2021, 09:14 PM
rocketman1988 rocketman1988 is offline
 
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Default But…

But if you remove the RAC servo and attach a telaflex cable, you could run the telaflex cable forward to a manual trim wheel. That wheel could be driven by a stepper motor for electric trim. Remove power and now the trim wheel is manual with the stepper free wheeling…
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  #9  
Old 08-20-2021, 05:18 AM
PhatRV PhatRV is offline
 
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Default

Quote:
Originally Posted by Vern View Post
In my opinion, a 9 would be much more suitable for you.

Perhaps you could get flights in both to see my point.
I think the reason for the RV10 is the additional space for passengers which is one of the goals of her project. Her Ercoupe has only two seats and it is limiting her outreach mission.
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  #10  
Old 08-20-2021, 07:08 AM
leok leok is offline
 
Join Date: Apr 2013
Location: Clarkston, MI
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Default

Pitch trim on the 10 is very powerful, and used all of the time. Every speed and load change requires trim as well as flap deploy.
Last week I ran the trim all the way back (full up) at idle to see what speed would result. It gave 65 knots. To get 85 knots I had to come back almost 80% towards neutral. If I remember correctly, the tab movement geometry (correct me if I am wrong) moves both tabs for up and only one tab for down. Any manual over ride to the system as set up would likely move both tabs together both ways.
I can see two ways to get electric/manual trim; One is to replace the entire Vans system with a cable into the center console with a stepper motor/wheel combination. The other would be to modify the trim motor to manually slide fore/aft with a manual cable, there by moving the tabs.

My electric rudder trim, I use all of the time to center the ball. A combination of loading, power (climb/cruise) and the nose wheel pant position all seem to contribute to minor trimming on almost every flight. What I installed is not powerful and could be easily overcome or just 'lived with' if disabled. I see no reason to install a manual over ride. See this link for my solution;
http://www.mykitlog.com/users/displa...225089&row=190

One thing I wish I had done is to add the Yaw Damper servo to the Garmin auto pilot. I find the 10 wags it's tail in bumpy air. I have never had any front or rear seat passengers complain, but I notice it. A little less wagging in bumps would be worth the incremental cost in my view.

Aileron trim is used almost not at all in my flying to date. A little to balance the load, but rarely. I switch tanks to balance fuel load more often to balance the roll tendency than trim. It is a servo/spring system connected to the push rod in the wing. I have never tried to run the trim all the way to the stops to see how powerful the effect is, so not sure what a run away might be like. I suspect, like the pitch trim, the aileron trim servo could be mounted on a manual slider to provide over ride control. The servo is in the wing (either side depending on builder preference) so a cable routing might be a bit of fun.

As mentioned before the Vertical Power and the Garmin system will disable the trim motors power after, I believe, 2 seconds of constant run time to minimize a run away event. Even that would be a hand full on pitch. Both systems also have speed sensitive trim scheduling. Garmin has programable continuous scheduling while Vertical Power is a single speed/step function. In my view, the Garmin system is smoother to fly with

Good luck. Hope this helps.

Leo
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