Center Bay & More

1/6/2008

After I was happy with the initial rigging: All the wings were set in stone on all axis. Trammeling to the tail post gave me a 1/8 difference on the uppers, and 0 difference on the lowers (pure luck of course). Upper wing incidence at several stations were crack on 0.0 on the digital level, and numerous plumb lines were within 3/32 of their opposites at worse. So at that point, I took a deep breath and finally did what I had been waiting to do for months...I drilled and bolted the center wing cabane spar plates. Here is my fool proof way of doing this:

- 2 cabane plates, one drilled 1/64 undersize on all the 1/4 spar holes, and the other with no holes for the 1/4 holes.

- bolted the two cabane plates to the cabanes. Slipped the spar down between the plates

- used a mini level sat on both plates either side the spar. When set in position, clamped up.

- Using a drill block, I drilled through the spar until i felt the blank steel plate on the other side, then applied a little pressure to ensure I marked the plate (a counter bore drill would have been better I reckon).

- removed the marked blank plate and drilled out on the drill press. Then refitted.

- played with my adjustable reamers until I sneaked up to what I wanted for the 1/4 AN bolts.

The lower right wing incidence at the root [brackets] was 0.1, and 0.2 on the left wing. I have to adjust both rear lower wing brackets anyways due to the 'ears' being slightly narrow on the right wing, and one hole being skewed slightly on the left wing (this is a pre built fuselage). So when I mess around with those brackets, I will strife for 0.0 just for grins.

Center Bow

I was scratching my head thinking up of a way to conceal the rear cabane nuts behind the hand-hold, yet still have future access. I decided to recess a face plate with the router and a side/face cutter (see pic). Not in the pic, but I drilled several small lightening holes in the rear of the plate. The large inner ears in the pic are from an old balsa block, the 'outer' ears are 3/16 ply. The contour/curve on these ears is a transition from the center bay ply to the hand grip. A nice idea is to foam/glass the center bow area, but I am terrible at glassing, so I'll be going the fabric covering route. I will post a finished pic to my blog when the bow is finally attached, which I cannot fit until the auxilary tank and top ply is complete (in process).

I-struts

I am trying to utilize old I-struts to save a bit of money...streamline tubing is $40/foot! My second hand ones of course don't fit :0| I have cut off the upper box sections, and I am hoping the streamline tubing will be long enough when I weld the new box section up there - welding causes steel to shrink, so I may well be 1/8+ short. I am trying to avoid shimming with washers...I once saw a lovely Pitts with SEVEN washers at the rear attach point. They are scrap anyways, so I may as well tinker with them...one never knows 'til one tries.

Flying/Landing Wires

The wires (second hand) were stripped of all terminals, to check if they all were indeed the correct length: I marked on each end thread with nail polish where the terminal fitting could screw up to until the witness hole was obstructed, thus confirming enough thread is in the terminal fitting. Thankfully they all fitted fine with plenty of room left for final tensioning. I will be sending the terminal assemblies away for silver ('white') plating.