Start Here
The Builder
The Shop

RV-7 N8ZG
Empennage
   Horizontal Stab
   Vertical Stab
   Rudder
   Elevators
   Fiberglass
Wings
   Spars
   Ribs
   Wing Skins
   Fuel Tanks
   Ailerons
   Flaps
Fuselage
   Firewall
   Center Section
   Bulkheads
Cowling
Engine
Paint

Tools

Links

Center Section

The center section is rather important - it holds the wings on.  It's a massive assembly that needs careful attention to detail.  The drawings are rather busy and at first glance, the center section seems complex.  After a little study it's not so complicated, but I still checked and rechecked before wielding the drill.

The first step is to identify and enlarge all the holes that were pre-punched for snap bushings.  Two holes near the center of each half need to be located and pilot-drilled.  Here's another one of those points that makes me ask WTF-O.  Every other hole in the center section assembly is pre-punched - the location seems rather important.  Why were these not piloted?  Two holes in each half need to reamed out for bolts.

You can use the control column mounts as-supplied, or trim them down to save a few ounces.  I put tape over the bearings to keep the chips and shavings out.  After cleaning, more tape, trimmed to fit the bearing to keep the primer out.

Cut the spar web stiffeners from 0.063x3/4x3/4 angle stock.  Mark center lines, then clamp them in place to back-drill the mounting holes.  File or grind the ends if necessary to provide a little clearance between the angle and the spar bar.  Drill the holes for nutplates and prep for priming.

Fit and match-drill the cover support ribs to the forward face of the center section.  ream the holes in the forward flanges for nutplates and prep for priming.

Bolt the left and right control column mounts to the aft face of the center section and assemble the stick mounts. 

The manual says to clamp the spacer blocks in place and back-drill for the really long rivets that hold them in place before while the wings are off.  Wouldn't bolts work better?  I used short bolts and washers on both sides to prevent unnecessary scratches.  The nuts should be good and snug to keep the blocks from slipping around while you drill the holes.  After drilling, remove the blocks and countersink the inside face for the rivets that hold them to the center section.   

Ream and countersink the holes for the nutplates on the spar flanges. 

Then install the nutplates.

I rough-cut the spacer tubes a little longer than the 1-7/8" specified.  Then chucked the tubes in my cordless drill and buffed them down to spec with the ScotchBrite wheel.

I made wing-spar spacer blocks from some scraps of cabinet plywood.  Using the plywood blocks and the spacer-tubes, I assembled all the parts with bolts and clecos to check the fit and alignment.

Cleco the side pieces to their respective for and aft halves and rivet them in place.  I tried standing the parts on the table and banging free-hand, but the parts bounced around too much.  Back-riveting worked very well and was much easier.

That's about all that can be done until the assembly is installed in the fuselage.  Using the spacer tubes and plywood shims, I bolted the parts together and set it on the shelf for later.