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-7 Electric Rudder Trim

N814P

N814P

Member
Has anyone put electric rudder trim in a -7? I found numerous posts about electric rudder time in a -10 but not in a -7. I wanted to make sure it would all fit, and it made sense to install it prior to buttoning up the rudder.

Yeah, I know the -7 is a sport airplane, designed to be flown with the feeling of the wind in the feet, but I will do a lot of long flights and I would rather not fly lobsided :)

So, has anyone done it?
 
It will fit, and I think it's a worth while addition. My 6A does not have any offset built into it's vertical stab like some newer models have. I have a fixed metal trim tab on the rudder than can be re-bent if needed. For higher cruise speeds, I've got it to where the ball stays in the center. But if I fly at slower fuel saving speeds, then I'd really like a servo operated tab back there. I prefer sliding my toes under the pedals for long distance travel, rather than keeping the ball centered by constant pressure.

L.Adamson --- RV6A (flying)
 
Yes, I have one on my RV-7A, and I had put one on my first 10, and have done one on the second 10. It is very nice for long descents, and for keeping the ball centered with the autopilot enganged while on long cross country flights. I would encourage you to do it. We've put some pictures and measurements on Tim Olson's website. Here's the link:

http://myrv10.com/tips/mods/RudderTrim/index.html

Vic
 
Not Necessary

Ball is centered with 140 to 180 knots IAS on my -7, which covers most cross-country flights. However, rudder trim is needed outside of this speed range.


Bill
RV-7 N151WP
Lee's Summit, MO
 
Thanks!

Thanks everyone. I have decided to do it as close to the way the electric elevator trim is set up. I did see the Skunkworks spring version, but decided to keep it in the rudder.

I saw how this guy used a cut-out section of the rudder vs. adding the piano hinge on the end - I like how it looks. It kept the lines of the rudder the same. I need to check out a built -7 first to make sure there is no chance the horn and rod sticking out gets too close to the elevator with full deflection. I would rather keep it at the bottom of the rudder if I can.

I haven't done the greatest job keeping photos of every little step of the build thus far, but I will highly document this mod. I wish I hadn't riveted the stiffeners in the rudder, but I will work around that.

Thanks for the input!
 
Vic...

Do you have any pix, measurements of the install on your 7A?...Or did I overlook them on the website?
 
Measurements

OK, here they are for the 7A:

4" x 4" servo cover placed 18" up from the bottom of the rudder skin, and back 9" from the trailing edge (these measurements are to the center of the cover). I used a 9 1/2" piece of piano hinge for the actual tab.

Use one of the cable fairing covers from Avey tools to cover the pushrod exit.

Hope this helps.

Vic
 
Electric rudder trim in my RV-6

Yes, it is very doable, here are a couple of pix of mine. It is great for a x-country airplane because it allows for long, powered descents where you would normally have to hold in some left rudder. I think it looks neat, it's a great conversation starter at shows, and it avoids the unsightly fixed tab.

IMG_0585.jpg


IMG_0587.jpg
 
jarvis said:
Which servo did you use for your trim tabs?
Click to expand...

Jarvis, keep in mind that I first flew in 2002 and back then I used a MAC -4A servo with a travel of .7". I think the equivalent today is the Ray Allen T2-7a. Also, back then he had a "travel reducer" for this servo that further limited travel to .5". So, the smallest servo possible with the least travel.

Basically, I copied the elevator trim engineering as you can see, but the geometry is different, thus the offset. Bending the stiffener spar was the biggest challenge due to the precise dimensions required. I have some drawings that I can send as PDF files, if you are interested.
 
Very Nice Pat!

It looks like when you cut the rudder skin, you left tabs to bend over to cover the holes on top and bottom, correct? Basically, you did it the same way Vans did the elevator trim tab. Very clean - great job!
 
N814P said:
It looks like when you cut the rudder skin, you left tabs to bend over to cover the holes on top and bottom, correct? Basically, you did it the same way Vans did the elevator trim tab. Very clean - great job!
Click to expand...

Yes, that is correct. Thanks! I have really been pleased with its operation for the past 7 years, no problems at all. If you're really lazy, you can trim out the right rudder required for climb!
 
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