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RV-7 N8ZG
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Bulkheads

The tailcone is built around six bulkheads. 

F-705 serves as the rear wing spar attach point.  It also anchors the seatbelts and supports the seat backs.

Cut the F-705B stiffener to length and draw vertical and horizontal centerlines.  Use the pre-punched holes in the F-705A bottom channel to position the doubler and clamp it in place.  I drilled the center hole and the two holes just inboard of the F-605C doublers and used clecos to help hold it in place. 

Make F-605C.  HEY - PAY ATTENTION and save yourself $20 and a week waiting on parts.

Here's what I did. 
Study the prints and lay out the F-605C rear spar attach doubler accordingly.  For example, draw a centerline, measure from the indicated bend points, lop it off with the hacksaw and clean it up.

Here's what I should have done. 
Study the drawings, mark accordingly, and clamp it to the F-705 assembly.
Cut it down AFTER drilling the stinking holes.

Draw the lay-out lines on the F-605C doublers, but DO NOT MAKE ANY OF THE CUTS YET.  Measure and clamp the F-605C rear spar attach doublers to the F-705A & F-705B.   Back-drill the parts using the pre-punched holes in F-705A.  I made the taper-cuts before drilling F-605C.  The inboard-most holes were too close to the ends on both doublers and I had to order more parts and do it over.  Adjust the lay-out lines for edge distance, if necessary and then make the taper cuts and de-burr the holes and edges.

Make the F-705M spacer blocks from the short stub of bar stock.  I clamped the little chunks between two wood blocks to file the 1/64" shoulder.  Clamp the spacers in place and back-drill for AN3 bolts. 

Cleco F-705B and F-605C to F-705A.  Clamp the seat belt anchors to the assembly and back-drill to 3/16" for AN3 bolts.  Disregard the rivet positions, but be careful to allow enough clearance between the hole and the flange for the bolt head.  After the first pair walked around under the drill, I started using two clamps and more pressure to keep things in place while I drilled the steel.

Bolt the right anchor to F-705 and clamp the left anchor in position.  I used a bolt thru the shackle attachment hole and a stack of washers to position the loose ends, then used a piece of scrap to position the base.  Clamp it tightly.  Back-drill, disassemble and de-burr.  Repeat for the remaining three pairs.

While I was waiting for replacements for the parts that I screwed up, I started on the F-705C top channel.  Trim the 0.063x1/2 strips to length and de-burr.  Mark and drill the first hole in each strip.  Cleco and clamp the strips to the top channel and back-drill the remaining holes.  Take it apart and de-burr the holes. 

Cut the 0.040x2 strip to length for the F-705K plates and de-burr the edges.  I used my little Harbor-Freight bench bender to make the 4-degree bends - not perfect, but acceptable.

Measure, mark and drill the index holes shown on the prints.  Cleco and clamp the plates and spacers to the top channel and back-drill F-705K.  Countersink F-705K for AN426AD3 rivets.  Make the F-705J angles and drill the top channel to match.  be sure to allow for the 1/8" gap indicated on the prints.  I missed this little gem and had to make adjustments.  Rather than cut new angles, I shifted the parts to the correct position and carefully reamed the holes out to #20 for -5 rivets.  Take it all apart and de-burr.

With all the F-705 parts fitted and the the holes reamed, I scuffed with ScotchBrite, cleaned with denatured alcohol and primed with VariPrime.

Make note of the holes that need to be left open and rivet the doublers to the F-705D side pieces.  Rivet the F-705L spacers and F-705K plates to the F-705C top channel.  Rivet the F-705J angles to the top channel. 

Cleco the side pieces to the top and bottom channels.  The tip-up and slider versions have different requirements here.  Tip-up builders will leave many of the rivets out so that parts related to the latching mechanism may be riveted later.  Those building slider canopies may bang away, leaving only two rivets out on each side. 

Cleco the F-705B stiffener bar to the F-705A lower channel and set the outboard rivets (under where the doubler joggle will be).  The prints seem to call for AN470 universal rivets, but I was concerned about the clearance between the the rivet head and the F-605C doublers, so I countersunk these holes and used AN426AD4 rivets.  Cleco the F-605C rear spar doublers to the lower channel assembly. 

Rivet the rear spar doublers to the lower channel.  Be sure to leave the holes for the seat ribs open.

F-706 supports the elevator pushrod bellcrank and serves as the aft limit of the baggage compartment.

Nothing I tried would get all the wrinkles out of the curved bulkheads.  A few notes to some folks who are ahead of me in the build process confirmed that this is normal - quit fretting and press on.  So I clecoed the three parts that form the bulkhead together and started fitting the bellcrank ribs. 

The bellcrank ribs are formed with a single bent flange.  You need to cut and match-drill a length of angle for the un-bent side of each rib.

After fitting the angles to the ribs, cleco the whole mess together and ream the holes that mate the ribs to the bulkhead. 

F-707 supports the aft end of the F-728B bellcrank support rib and the rudder cable runs.  It looks like I neglected to get any pictures of F-707.  You're not missing much.  It looks just like F-708 (below) but a little bigger.  Cleco the centers together and ream the holes.  Take it apart and de-burr.

F-708 is a smaller version of F-707.  F-709 is a half-moon shaped bulkhead and closes the fuselage just in front of the HS attach point.  F-710 supports the aft deck.  F-711 supports the HS attach bars and the forward end of the tailspring mount.  F-712 supports the aft end of the tail spring mount, closes the aft end of the fuselage and secures the lower end of the VS spar.

To properly support the aft deck, F-710 needs a piece of angle across the top to provide a little rigidity.  Measure per the plans, lop it off and file it to fit across the bulkhead web.  Clamp the angle in place and match-drill the rivet holes.  After priming, rivet the angle to the bulkhead.

F-711 is made using two very similar parts riveted back-to-back.  Cleco the two halves together and ream the holes.  Next, lay-out and cut the F-711C bars from the provided stock.  Shave the outside corners off the upper ends and clamp the bars to the bulkhead.  Use the holes in the bulkhead to match-drill the bars.  If you're putting the tailwheel in front, you can trim the bars down to save a little weight.  If your tailwheel will be in back where it belongs, leave the bars to add strength to the tailspring mount points.

Firewall

Center Section