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Electric Elevator Trim RV-4

Sully73

Active Member
I need to re-skin my left elevator and will install an electric trim servo. I plan to start from a flat sheet of aluminum instead of buying the piece from Vans (maybe not smart). I have seen photos that show the servo mounted to the skin of the elevator. That does not seem like the best way. I am planning to mount the servo to a base plate that is connected to the Elevator frame.

Am I crazy? Wouldn't that be more stable?

Also, Can someone direct me to drawings that show where this servo should be mounted. All I have are drawing that show the manual system.
Thanks
 
I just built new elevators for my -4 using 0.020 skins. Van's skins are expensive, so I can see the motivation for getting your own material. However, the pre-bent skin with the correct bend radius makes forming the trailing edge much easier. I'm sure either route is viable, especially if you have access to a press brake.

The trim servo is attached to the bottom skin via a doubler that is around 0.032 thick. It has 2 flanges so it is quite stiff. I riveted and pro-sealed it to the bottom skin and have no concerns about it. My current elevator with 0.016 skins and no pro-seal shows no signs of cracking around the servo mount after more than 1000 hours in service.

That being said, if I were starting over, I would use a thinner doubler and increase the flange height to I could tie it to the spar. It may have to be done with blind rivets depending upon the assembly sequence.

Good luck,

Dean
 
Electric elevator trim

I have a Ray Allen servo mounted inside my RV-4 that has worked well for years. About one year ago I finished a scratch- built Thatcher CX5 that is a tandem like my -4, so I copied the elevator trim set up in the Thatcher. Recently another CX5 builder contacted me about my installation. I sent him a number of photos that could help you.

If you are interested, I will send those same photos to you. I don’t know exactly how to display photos in this forum. Send me your email address to ([email protected]) and I’ll send photos immediately.

Jake Thiessen
Independence, OR

RV4 Fastback O-360, C/S N504Jt
Thatcher CX5 - Revmaster
 
What I did on my RV-4

I did mine pretty much as the electric trim kit sketch dictated. The MAC servo is mounted to the skin access plate and all goes in together. Easy and effective. I had already cut the elevator skin for the manual cable, so I did make some minor adjustments, but this photo may help.
 

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When i converted my old rv4 to electric trim i just mou ted the servo under the vertical stabilizer and ran a small cable to trim tab. Worked out great.
 
Cable info

When i converted my old rv4 to electric trim i just mou ted the servo under the vertical stabilizer and ran a small cable to trim tab. Worked out great.

I would be interested in knowing more about the cable used and the mounting of the servo.
 
Someone used to make a short cable to connect a rear deck mounted Ray Allen servo to the elevator trim tab horn. This helped keep weight off the elevator. If you install the trim motor in the elevator on a flying airplane, make sure you rebalance the left elevator (independent from the right elevator). This will require adding some weight to the left elevator counterbalance for flutter protection.
 
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