8/30/2006
I can't say drilling the holes for the aft spar is one of the more fun things about building an RV8. I spent almost 4 hours lining everything up and a few stressful minutes doing the drilling.
I started by leveling the plane (now it is a plane, not just a fuselage since the wings are attached). I propped the tail on a small table with some wooden spacers until the top longerons were level. I am not sure if it is necessary but I also leveled the plane spanwise by bleeding a little air out of the left tire (my garage slopes a little).
I dropped plumb lines down the trailing edge of the wing rather than down the front since the wheels interfere with then line on the ground in the next step. I put washers where the plumb bobs touched the ground and then shined a laser between the two outer washers. Then I measured the distance between each wing tip and the outside back corner of each wing. I made changes to the positioning of the rear spars and clamped them back into place. I iterated through this process many times over about a 2 hour period until the trailing edge of the both wings were in alignment and the distances to the rear of the fuselage were the same.
It would have been a lot faster to have used 4 plumb bobs rather than one but this would have cost me $21 to buy the other three.
I then set the angle of incidence. I made the gauge below from some angle clamped together. Both wings were close to dead on without me having to do anything. I tweaked the left wing just slightly to get 0.0 on the SmartLevel. Again this operation took a while due to the checking and double checking of everything.
Then I marked 5/8" from each edge. I had to estimate where the bottom edge of the wing side of the spar was since the bottom fuselage skin blocks the view. This formed a rectangular area where it is safe to drill and meet Van's restriction that the hole center needs to be 5/8" or more away from and edge. I placed a mark in the center of the rectangle, drilled an 1/8" hole and put in a #30 cleco. I did this for both wings.
Then I went back, droped plumb lines, re-measured everything and verified than nothing had shifted. I then enlarged the holes to 1/4" and then again to 5/16". I then temporarily installed the bolts.
Whew! I am glad this is over with. No major screw ups but I will check again tomorrow to make sure. One minor screw up is that the rear spar tongues sticking out of the fuselage are upside down. The slightly tapered side is on top rather than on the bottom. This wasn't an issue in being able to maintain 5/8" from the top edge but I may have to trip a very slight amount off the bottom so that the skin will sit flush.
