Rudder Trim Tab

[jmvolpp]

In order to give my right leg a break, I'd like to install a trim tab on my '46 BC12D. Am I correct in assuming the shape of the tab and the mounting holes are the same as in earlier models, namely the '40 or '41, which I plan to copy? And that the holes in the rudder are probably already predrilled?

MV

[3Dreaming]

Re: Rudder Trim Tab

Most of these airplanes came from the factory without trim tabs on the rudder. I doubt you will have any holes unless a trim tab had been installed at some other time. Unless the airplane has damage that has been repaired it is most likely out of rig. With adjusting the rigging and using the rudder return springs you should be able to get it to fly hands off in smooth air. Tom

[VictorBravo]

Re: Rudder Trim Tab

Play with the rudder pedal springs BEFORE you drill holes in your rudder, IMHO !!!

[jmvolpp]

Re: Rudder Trim Tab

Thanks for the rigging tips. I'll look into that before any holes are drilled!

I do notice, however, that the Univair BC12D service manual depicts a rudder with trim tab (B-410) after S/N 6403 (mine is 10105). Having seen fixed tabs on numerous other light aircraft types, I just thought it was logical to have one anyway.

MV

[alwaysoar]

Re: Rudder Trim Tab

Forrest told me a long time ago that they came from the factory with rudder trim tabs installed, that there are holes already drilled. He sent me a template in an email attachment, and I made a trim tab from that. I poked around with something sharp and easily found the holes and attached the tab. The holes matched exactly the position of the holes in the template. He said something to the effect that because of manufacturing irregularities, no two planes were exactly alike and therefore needed trim tabs.

[mulwyk]

Re: Rudder Trim Tab

I've dug up this old thread so I could document the rudder trim tab on my BC12-D.
The tab I got with my project is apparently original, I only had to clean and paint it. It is mounted on the second rib up from the bottom of the rudder. It is overall 3 1/2" X 6 1/2" and the distance between the top and bottom holes is 6 1/8". The center hole is 1 1/8" forward from a line drawn between the other two holes.

The aft two inches of the trim tab is bent at an angle of 25 degrees. I don't know if that angle was set at the factory or by some previous owner.

[Hank Jarrett]

Re: Rudder Trim Tab

Looks exactly like the one on my 45 (different from the 41)
Hank

[dewhitaker]

Re: Rudder Trim Tab

Concerning the angle of the deflection on the trim tab: This is established by flying in calm air in level cruise flight. Very carefully bend tab so it flys straight with feet flat on floor. It may take several attempts to get it to your liking, just remember to fly at the same cruise RPM setting each time you make an adjustment.

Our '41 looks like this.

[n6346m]

Re: Rudder Trim Tab

In order to give my right leg a break, I'd like to install a trim tab on my '46 BC12D. Am I correct in assuming the shape of the tab and the mounting holes are the same as in earlier models, namely the '40 or '41, which I plan to copy? And that the holes in the rudder are probably already predrilled?

MV

You can try what I did with my L2. Although the parts book shows a rudder trim tab, mine didn't have one when I bough it. The airplane was a little out of rudder trim so after I made sure the rudder pedal return springs were the same, I simply took one link out of one side of the taiwheel chain and added it to the other side. The tailwheel makes a perfect rudder trim tab without going through all the trouble of actually making a tab and installing it on the rudder. It now flies perfectly trimmed hands and feet off all day long with no noticeable ground handling difference due to the minute adjustmen of the tailwheel spring chain (Scott 3200). One of the nice features of having a tandem seated airplane with interconnected wing tanks is that it's really easy to perfectly tweak them to fly hands off even when you add a passenger, it still flies the same.
Even if you do add a trim tab, be sure that it isn't fighting an out of rig tailwheel.

[Ron Greene]

Re: Rudder Trim Tab

All,

Here is B-410 the L-2 and BC-12D trim tab.

[mikeg]

Re: Rudder Trim Tab

In order to give my right leg a break, I'd like to install a trim tab on my '46 BC12D. Am I correct in assuming the shape of the tab and the mounting holes are the same as in earlier models, namely the '40 or '41, which I plan to copy? And that the holes in the rudder are probably already predrilled?

MV

Once upon a time I took a properly formed paddle, similar to a blade paddle, and "tweaked" my fin (ala Tri-Pacer) and got rid of my trim tab. It was covered with razorback and left out in the sun, the wrinkles disappeared. BTW-little goes a long way.
Mike
NC27451
NC29804