Tuesday, July 3, 2012

Jumping Ahead To The Anti-Servo Tabs

In an effort to have more parts to prime, decided it best to jump ahead in the plans and begin working on the anti-servo tabs. Because Van’s designed the RV-12 to use a stabilator (which means the horizontal stabilizer and elevator are one unit or essentially a flying tail), the anti-servo tabs are used for trim control or another way of saying it … pitch adjustment. There is a left and right servo tab and they will be attached to the stabilator (which is not assembled yet) .

The anti-servo skins come with metal tabs at each end that are cut off per the plans. (I’m guessing the tabs were used to hold the position of the material during CNC machining). After using a pair of tin snips to cut the tabs off, a file is used to remove any excess material until the edge is smooth.
The remnants of the tabs that were cut off will be filed down to make a smooth edge.

The ribs used in both the left and right anti-servo tabs are all the same. Because some ribs are faced inboard and others outboard, the holes nearest the trailing edge (thinnest) need to be matched drilled. The reason for this step is because Van’s offset the holes at the narrow end of the skins so the rivets there won’t interfere with one another. To make the ribs universal, Van’s has two small pilot holes drilled at the narrow end of the ribs on both sides. This allows the ribs to be installed either facing inboard or outboard in either the left or right servo tab … once installed, the appropriate pilot hole gets drilled out.
 The offset in the rivet holes at the narrow end of the skin can be seen along with the two pilot holes in the rib.

If the above photo is enlarged, one can clearly see the two pilot holes at the narrow end of the ribs along with the offset of the holes drilled into the skin.
                                                  Match drilling the trailing edge holes on the anti-servo tabs.

The two control horns were the next items that required a little TLC. After separating the left and right control horns from each other, the five rivet holes in each that will attach them to the anti-servo tab needed  to be countersunk.
                                 Fortunately the countersink cage was still set correctly from the last time
                                 it was used so countersinking all the holes was quick and easy.
                                       Countersunk control horns … looking closely, you can see how a rivet
                                      sets flush in the front center hole of the control horn on the right .