SO I came up with the plan to use a piece of 3/16 inch piano wire that I had laying around. I use it for landing gear legs on RC models. The wire was long enough to extend beyond both edges of the trim tab. I set the trim tab in between two pieces of wood so that I could make a recess for the control horn on the bottom, and then I clamped the piano wire up against the trim tab spar web and the bottom trim tab skin. The wire gave me a bit of a radius from which the skin could bend around so that the bend would not be too sharp.
Once everything was clamped down I simply lifted the rear end of the trim tab, keeping the leading edge as flat on the boards as possible, and bent the leading edge of the bottom skin just enough to ensure that it would clear everything. Came out not the greatest but good enough for me.
The above pic kind of gives you the clue as to why you need to bend the bottom skin. Eventually it will come into contact with the bottom of the elevator and the rear spar. The only question is how much of a bend is needed? This is largely trial and error here and Van's offers absolutely no information about this whatsoever in the plans, except for the picture of the bend and a note that says to bend it.
I also drilled out and reset the two flush rivets holding the corner of the rear spar adn the E705 end rib. They did not set very flush the first time. I may have applied too much primer in the countersunk holes in the rear spar, or perhaps I did not countersink them enough, Once I drilled them out, I countersunk the holes a bit more and then reset two new rivets. The new ones turned out mucho better. You can just see the heads on the right side of the above pic, along the vertical spar web on the end of the spar.
If it bends too far down, the control horn of the trim tab will contact the bottom skin of the elevator, so you know that allowing the trim tab to rotate down that much is going to be too far. The reality is that Van's indicates that the range of motion for the trim tab is supposed to be 25 30 degrees. However, there are many posts on VAF that confirm that the actual range of the electric trim servo is well short of this mark both up and down. Apparently Van's has even provided clarification, as well as others that have completed their airplanes adn ahve been flying them for quite some time now, that you don't need that much travel for the normal operation of the aircraft. Using my digital level, I determined that my up travel is about 25 degrees, and the down travel is about 19-20 degrees.
This next pic shows the down travel allowed after the bend was completed at the point where the bottom skin contacts the rear spar. This is way more than 30 degrees.
Tonight I decided to install the trim servo, adjust the threaded rod for "level" trim, and then ran the servo through its range of motion to check for clearance of the rod and clevis assemblies with the elevator skin. I found it interesting that running it through its full up and full down range did not really cause much interference with the exit hole on the bottom of the elevator skin. I will still need to do some trimming but not very much. Others have had to trim away quite a bit of material to allow the free travel of the rod without digging into the elevator skin for some reason, but I am not seeing the need. The clearances are very small, but they are sufficient I think.
First pics are with trim tab full up, then full down, and then in level position. Remember that the elevator is turned upside down during all this, so up is down and down is up! I also show my magic trick for connecting the servo wires to the 9 volt battery and running the supplied switch to move the servo. Quite the balancing act....
BTW, the stop nuts on both ends of the clevis require a 1/4 inch wrench to secure and hold them in place while you screw the clevis in or out as needed to set the level position of the trim tab. This can also be fine tuned after you start flying if you determine that the original level position is giving you something other than true level trim of the elevator in flight.
Next pic shows that the rod is just barely contacting the elevator skin on the edge of the exit hole. Maybe 1/8 inch or 1/4 inch more clearance will be sufficient. Clevis on the control horn of the trim tab is very close to the elevator skin, but it still clears.
And now for the down pics
The above pic shows several things. Note how the push rod still favors the right side of the exit hole duw to the misalignment of the control horn with the center of the precut exit hole in the elevator skin. See my extensive previous posts about my concerns with this. Now that the trim tab is fitted and hinged to the elevator, and the trim servo is installed, I am satisfied that any stress on the trim tab servo is minimal. It was only offset about 3/32 inches anyway, and there seems to be enough "give" in the assembly to the point that this is not a concern. Also notice how the clevis on the control horn strongly favors one side of the horn. This is actually drawn in the plans from Van's, and shows the same installation picture with one side of the clevis placed firmly up against one side of the clevis, with a sizable gap appearing on the other side. I guess this is the way it is supposed to be.
And finally some pics of the trim tab servo all wired up with the switch and the position indicator that was supplie with the servo.
And finally back to level position....
Tomorrow I prep the leading edges for primer and then start the rolling process.....
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