Center Section - Bulkheads

I don't have many pictures that justify the amount of time I spent working on the plane today.  The next step I had to accomplish was adding the front 904 bulkhead onto the aft 904 bulkhead so the front row of holes of the bottom skin could be final drilled to the bottom bulkhead flange.  This was a simple task, but I spent gobs of time getting the spacer blocks as close to the right size as possible.  The blocks are just temporary, but they hold the fore and aft bulkheads the right distance apart so the wing spars can slide in tightly down the road.  Too tight and getting the wings on will be a bear.  Too loose and....well we don't want the wing spars to fit too loosely!  I had already made a couple of blocks a while back that were really close to the right width, but slightly big.  I started to lightly sand the surface to close in on the right width.  Easier said than done when you're talking thousandths of an inch.  Van's says make it 1.438" wide to match the thickness of the spar.  What I found to be the problem was that if I got the blocks really close to that number, as soon as I put them into the spar and clamped them down, they compressed a little bit.  I think after a lot of trial and error (and pieces of paper) I got it all close enough.  The spar has 10 bolts that will snug everything together, so I'm actually more worried about it all being too tight than too loose.

One of the last steps before the tedious deburring, dimpling and countersinking begins is to drill the 904H side doublers in place.  These help tie the fore and aft bulkhead portions together.  The doublers have pre-punched holes, but there are no holes in the bulkhead (aside from 4 reference holes to line the doubler up).  I very nearly screwed up, because I didn't initially see that the doubler isn't quite symmetrical.  It's close enough not to notice until you put it on the bulkhead wrong and it looks slightly off center.  Thankfully I realized this before I drilled any holes.  All I had to do was flip it around, but I'm wondering how many people have gotten caught by this.

I got the left doubler finished and made it 90% through the right one before it was time to take the dogs for a walk.  That means tomorrow I'll probably start taking it all apart and figuring out what gets dimpled and countersunk.  I can go ahead and dimple and/or countersink everything but the ribs, since the skin is already primed and the 904 bulkhead doesn't get primed.  Unfortunately I'm almost out of primer and they are out of stock at the moment, so it could be a little while before I can prime and assemble.  I have plenty to do though - the tailcone bottom skin still needs to be riveted and I can start building the firewall since I finally have the backordered parts.