Wings 42.5,Total 505.5 - Deburring spars and Match Drilling Supports

Tonight I managed to get the left rear spar deburred using my scotch brite wheel on the grinder. I had to place it in the middle of the garage to have enough room to feed one end of the spar through the wheel. I had just enough room, and the spar was light enough, to be able to do this on my own without any assistance from anyone else. It took about 3 passes on each long edge to get them smoothed out the way that I wanted. It also required some preparatory hand-filing of the small burs from the cutting process at the factory, similar to the burs on the thicker doubler and support brackets, but not quite as extreme. A small hobby flat file is all it took to knock those down.

Here is an attempt at a super closeup pic showing the unfinished spar edge to show the slightly raised bumps about every 3 inches along each edge of the spar:

Blue vinyl protective covering removed. It just gets in the way for this part of the build. You need to clamp the aileron support brackets to the web of the spar and match drill several rivet holes, and this bracket needs to be clamped tightly to the spar. If you leave the vinyl covering on both parts you are not getting a truly snug, tight fit of the parts, so I chose to remove all the covering. My hope is that by this weekend I will be priming everything anyway, so these metal parts won't stay bare for very long.

Here is the clamping setup I used to match drill the holes in the spar and the outboard aileron support bracket for the left wing. the support bracket is placed flush with the top and outer edges of the spar. Using the cleco clamps for this worked out real nice. Start with the top so that it snugs of the flanges of the bracket and the spar, and then secure the outer edges.

One note about setting up for drilling. Notice the stacked wood blocks I also stacked other blocks of wood along the remaining portion of the spar, but I dod not clamp any of them or the spar to the work bench. The idea was to place wood underneath the spar to prevent the burs from getting too bad. Well, once I started drilling, I got down to the last one or two holes, and had to get creative about positioning a piece of wood under the last hole in between the clecos, and suddenly the entire spar slipped off the table. and twanged as it hit the garage floor. Luckily there does not appear to be any damage to the spar, but this was a wake up call to me to follow the clamping rules I had established long ago, after experiencing similar problems.

SO I had my stupid moment for the night and decided to call it quits for the night. For all remaining drilling, I will be clamping the part to the table. I should ahve used my drill board, but unfortunately it is still sitting undeneath my Horizontal stab on the table, and I really need to get that hung up and out of the way again. Will probably resolve that this weekend if not before. It's just a pain to get it hung back up on the wall without dinging it up somehow.

The rear spar has Z channel flanges, similar to the trim tab spar. As such, the spar will sit nicely over the edge of the bench on top of a drill board, so don't do as I do - just do as I say and your project will come out looking very nice!

Here is the inboard aileron support bracket clamped into position. The odd looking large hole is the hole where the aileron pushrod exits the spar and attaches to the control horn for the aileron. This has to be cut out of the support bracket using a unibit and some other tools. The reason it is so odd looking is that this is the actual path that the rod will travel as it moves in and out when the bellcrank is actuated by the control stick inside the plane. The rod will travel slightly to the side as well as slightly up and down, which is why this clearance hole is shaped the way that it is.

I found this to be one of the more interesting things about this part of the build. I never really thought much about how this hole would need to be shaped to provide the necessary clearance for the the non-symmetrical movement of the pushrod as the control surface is moved through its entire range of motion. the rod does travel up and down and from side to side, as the shape of this hole indicates.

Next is a pic of the other side of this bracket to show how the flange butts up against the inside of the spar flange. The flange of the bracket is already pre-bent, so at least you don't have to worry about doing that. To position it you measure and draw a line for the outboard edge that is exactly 50 3/4 inches from the outboard edge of the spar. This ends up leaving about a 1/4 inch edge distance from the rivet holes around the perimeter of the bracket. There are additional holes for the gap seals for the aileron and the flaps that are also very close to the edges of the bracket, so proper placement of this part is somewhat critical or you may be faced with trimming the ends of the gap seals, and that may cause problems with riveting those later on.

And here is the root end of the spar with the doubler fork clecoed in place on the other side. this fork and the doubler that goes with it are the attach points for the rear of each wing to the fuselage. The final drilling of the bolt hole in these parts is absolutely critical to the flight characteristics of the airplane, since this hole determines the actual angle of incidence of the Wing. The angle of incidence is the angle that is formed between the chordl line of the wing and longitudinal axis of the airplane. I won't go into more detail than that, except to say that if you are a pilot, you already know what this is and why it is so critical. It literally determines how straight and true the airplane will fly through the air.

And finally a shot of where I positioned my scotch brite wheel to debur the edges of the spars. I only did the left one tonight, so I will work on the right spar tomorrow night. I still have lots of holes to match drill as well.