The rudder build starts by taking rudder’s parts and cutting them into separate pieces, putting a radius on some edges, and lots of deburring. When the ribs are hydroformed at the factory, there can be a very slight curve on the webs of the ribs due to the forming. There is a process in which you use fluting pliers to put small indentations into the flanges which straightens the webs.
Next, there is a tab that needs to be removed from the rudder skins as well as other preparation. The rudder has a small piece of lead that acts as a counterbalance which needs to be prepared. Its mounting holes are countersunk and the countersink rib needs to be dimpled to accept AN509 screws.
The rudder skeleton and skins are primed with AKZO. There is about 1/2" strip on the trailing edge of the rudder which is taped off to prevent priming in this area. That area will later attach to an angled wedge which is permanently bonded with ProSeal and double flush set rivets. Areas with ProSeal don’t get primed as the proseal was designed to bond to raw metal and primer would actually weaken the bond.
After the rudder skeleton is completed, I worked on assembling the tip and bottom ribs, as well as the skin stiffners and shear clips.
Next, the trailing edge wedge is trimmed and prepared with countersunk holes. There is also some drilling of course. The trailing edge of the skins is dressed up with a very minor break with puts on a slight edge. That is done to ensure the skins lay nice and flat after the rivets are set.
The holes in the skins of the rudder are dimpled, as well as the internal skeleton.
The rudder stiffners are back riveted to the skins and the shear clips are also riveted.
I spoke with Kevin at Van’s support and he agreed that using ProSeal on the trailing edge rather than the 3M tape is a better way to go. The trouble is, it’s more expensive, messier, and takes more time. Oh well, it’s a small price to pay for a better end product.
We worked on prosealing the trailing edge and riveting the skins to the skeleton and stiffeners.
Next, the countersink was installed. Kevin said bedding the countersink in a thin layer of epoxy flox is a good way to make sure it never loosens or vibrates, so I put it together that way. There are three rivet holes on the top of the rudder near the trailing edge that plans call for using pop rivets. This is due to the extremely tight space which makes it impossible to use backriveting techniques and normal solid flush rivets. There is nothing wrong with the pop rivets here, except for aesthetics since the rivets won’t match the rest of the skin. Kevin mentioned some advanced techniques which would allow the rudder to have flush rivets in this area. While I’m not setting of on this build for the purpose of competing with showplanes, I do want to go the extra mile, take my time, and do the best job I can. In order to set these with flush rivets, it takes some creativity. I had a machine shop produce a special bucking bar which would fit in this tight area, as well as designed some 3d printed TPU parts to place on the rivets during bucking. The purpose of the TPU parts is to ensure the skin and rib flanges are forced together very tightly when being back riveted.
Kevin said there is no guarantee that when riveting, the process of riveting will also push the parts together tightly. Sometimes it does, othertimes it won’t. The advantage of these TPU parts is that it forces the parts together. When the rivet gun strikes the rivet and TPU, the TPU in turn presses the parts together. This method ensures that the head of the rivet is truly flush and won’t catch your fingernail. This isn’t really a new idea. Others cut a small piece of hose to place over the rivet which does the same thing. I just like the 3D printed way because it gives me the ability to make it very precisely. I plan on making a separate post about the metal and 3D printed I made so this makes more sense.
7-12: Write about trailing edge and angle