Started on August 11, 2009 - Build Time 29 hours
After looking for as many different ideas on adding rudder trim. I have chosen to use the method that both Robin Marks and Geoff Combs have used.
I am thinking of making just a few changes to there method and will try to give as best description of this as I go.
My first step is to mark out on the rudder where everything will go. I tried to get pretty close to the middle of two skin stiffeners. I picked the ones that the middle hinge cutout is.
The tab is 7" wide and 3 3/4" deep at and 2 3/8". The difference is to make the front side of the tab perpendicular to the leading edge of the rudder. I then marked out the access plate, locating it 3 1/8" from the leading edge of the tab.
The next step was to drill a starting hole for the access plate. I then clecoed and then match drilled all the outside holes with a #30 bit. I probably should have used a #40 but used the #30 by mistake. To match up all the rivets so they look the same, I will just use the 1097AD4-3 (also known as Oops Rivets). I then clecoed the access cover to the skin and marked where I need to cut out.
The cut out was made with a dremel and cutoff wheel. To make the cut straight, I laid a straight edge to where the cut needed to be and ran the dremel with a sanding wheel along it. The cut came out nice and straight. I also made the elongated hole for the push rod also with a dremel tool.
Everything was then deburred, dimpled then alodine and Akzo primer applied.
Tonight I started with cutting trim tab out of the rudder. I used once again a dremel with cut off wheel then finished the trim work with a file and a sand drum on the dremel. This was a bit nerve racking to do, but it worked out just about perfect.
I then made a U-shaped rib to fit between the 2 skin stiffeners that will give the skin some more strength. Also, the hinge for the trim tab will be also be riveted to it.
I then used a rivet spacing fan to mark out the holes on the trim tab and the hinge. Then did the same for the holes that protrude through the skin, the new u-brace, and the hinge attached to the rudder.
After getting this area for the hing cut out, It came to me that I should have flipped the hinge over so that it did not protrude out. It is only a very little bit and do not think it will make any performance issues so I just left it the way it was.
Then clecoed everything together to check the fit and looked pretty good except for some minor trimming. Like a bit of skin removal for the hing pivot area. Once that was done, I deburred all the edges and holes and dimpled.
I then moved on to the access plate, I dimpled all the holes and riveted on the nut plates (k1000-06) and then riveted the access plate frame to the rudder skin. Since the nut plates use #6 screws, I had do re-dimple the access cover and plate with a number 6 dimple die.
Today I Finished cleaning up all the holes. Had to dimple the holes for the piano hinge and the holes in trim tab. Removed the brace that runs vertically placed by the trim tab slot that the skin and hinge attache to so it could be deburred and trimmed just a bit.
Then it was time to manufacture a control horn. Just took an extra piece of aluminum and cut to the shape I was looking for. Then put in a bend 1" down so that it could be attached to the trim tab with a couple of rivets. If you look at the horn, you will notice that I had to cut a bit of it out to allow for travel on the forward side.
Once this was done, I riveted the brace in place. Since it would be impossible to try to run solid rivets into the trim tab, I ended up using stainless steel cs-4 pull rivets. I though about putting nut plates in the hinge so it could be screwed on but the holes on the ends of the hinge would not allow it.
My next step was to try and finish of the slot where the push rod goes through the skin. I used a fairing purchased from Aircraft Spruce. I put it in from the inside and then finished forming the outside with Super Fill. This worked out pretty good. Kind of nervous about how much travel I will get with such a small hole so may have to bore out a bit.
I also used Super Fill to go around the control horn on the trim tab to fill in all the gaps and cover the rivets. This needs a bit more sanding but turned out better than I expected. In addition to this, I filled inside of the trim tab also with Super Fill to make it stiffer.
Following are some pictures with this all done with the servo and control rod just in place for pictures. I am waiting for some Click Bond studs to mount the servo.
Finally received the Click Bond studs and got them installed. The servo is now temporarily installed and mounted with push rod.
I am having some issues with the push rod hitting the rudder outer skin when pushed and the flare when it is pulled. Trying to get some ideas on how to get more travel. Right not there is about 1/2 an inch but the servo has 7/8" of travel. Otherwise, it is finished and I am pretty satisfied with how everything turned out.