First blood! Flettner tab 1, me 0

I started on the anti-servo tab tonight. I promised to explain what an anti-servo tab is/does in the last posting, but I'm too tired to write it up. Wikipedia has a nice, concise explanation of it here.

Too lazy to click through? Well, ok. It's just as easy for me to copy and paste, but you'll miss out on the explanatory diagram:

A Servo tab (sometimes called a Flettner tab after its inventor Anton Flettner) is a small hinged device installed on an aircraft control surface to assist the movement of the control surface.

Servo tabs

Servo tabs move in the opposite direction of the control surface. The tab has a leverage advantage, being located closer to the trailing edge of the surface and thus can lever the control surface in the opposite direction. This has the effect of reducing the control force required by the pilot to move the controls.

In the case of some aircraft the servo tab is the only control that is connected to the pilot's stick or wheel. The pilot moves the wheel which moves the servo tab and then the servo tab, using its mechanical advantage, moves the elevator or aileron, which is otherwise free-floating.

Anti-servo tabs

An anti-servo tab works in the opposite way to a servo tab. It deploys in the same direction as the control surface, making the movement of the control surface more difficult and requires more force applied to the controls by the pilot. This may seem counter-productive, but it is commonly used on aircraft where the controls are too light or the aircraft requires additional stability in that axis of movement. The anti-servo tab serves to artificially increase stability and also make the controls heavier in feel to the pilot.

On some aircraft with all-flying stabilators (ed: like the RV-12) an anti-servo tab acts as a trimming device. In this use some manufacturers term it a "balance tab" or "anti-balance tab".

Simply for the pleasure of exercising my pomposity and fluffing up my street cred, I will hereafter refer to it as the Flettner tab.

The Flettner tab looked like it would be a one evening wonder, going from deburring to completion in a single work session. 'Twas not to be. There's nothing truly exotic about the construction of the Flettner tab (getting tired of that yet?) other than its size: it's the smallest thing I've worked on yet. You wouldn't think that would have any adverse effect on the difficulty, but it does. It makes it harder to deburr. Well, it was easy enough on the outside, but none of my fancy powered deburring tools would fit down inside. Ugh, deburring with hand tools! How utterly quaint! Naught to be done about it, though, as the deburring must be done.

Here's a nifty little tool that has various bits that can be installed for different deburring situations. This bit is used for edges:



You just position it to get the sharp edge of the tool right where it can do the most good and stroke it down the length of the edge:



What you don't want to do, though, is slip and run your thumb along the edge yet to be duburred:



Ouch! Sure points out why we deburr, doesn't it?

After getting a bandaid, the next step is to cleco the little bitty even-harder-to-deburr ribs into place. Should be easy, but Van's threw a little wrinkle at me:



See how the hole closest to the trailing edge is smaller than the rest? Do you wonder why? Well, so do I. Either through loss of blood or the fatigue of a brain-draining Monday at my paying job, I just didn't feel like trying to figure it out. It'll still be there tomorrow. For tonight, here's how far I got before quitting time:



Here's a thought I came up with later:

I think the holes in the skins are offset so the top skin will use a different hole in the rib than the bottom. In other words, the top skin will use the furthest aft hole, while the bottom skin will use the second furthest aft. That will keep the rivets from interfering with each other.

As far as having to drill them to #30 when the other holes already have that done, the holes are smaller because if both were large enough for the rivet, (i.e. #30) they'd be giving up a lot of strength since the distance between two #30 sized holes would be much smaller.