Match Drilling AFT Fuse - Plumb??

So I have seen on some builder sites where they get the fuse all plumb before match drilling anything on the aft fuse...

But in the Orndorff video all he does is move the centerline marked on the j-stringers into view through the pre-punched holes, and drills.

So which is acceptable?

danielhv said:

But in the Orndorff video all he does is move the centerline marked on the j-stringers into view through the pre-punched holes, and drills.

Click to expand...

Can't think of a reason that it wouldn't work just fine in that application just as everywhere else that technique is used...

it's all prepunched, line it up with clecos, verify it with level/plumb

and then one day, adjust your trim as needed, i don't really get people getting all fancy with lasers and a bunch of other things, though I'm guilty of having tried it- just build the darn thing is my opinion

There can be a little bit of twist with just the side and bottom skins clecoed to the rear fuselage bulkheads. I draped the rear top skins over the bulkheads and clecoed them in while I match drilled all of the bottom and side skins in the rear fuselage. Putting the top skins on completely eliminates any ability to twist. I did the same thing when leveling and drilling the aft deck. The match hole punched parts are spot on and make it impossible to build any appreciable twist into the fuselage.

any other thoughts? I'll be doing this tomorrow, so I'd like a little more backup here!!

Plumb

Just did this on my RV-9A aft fuselage today. Manual recommends plumb bobs so I did, but prepunched fuselage is pretty much dead on. The manual says lay aft fuselage on three sawhorses, so if bottom skin is horizontal that means bulkheads are sloped aft. The difficulty I had was making the longitudinal centerline on the lower aft skin so that the plumb bob (hanging from the bulkhead tooling hole) point had a reference. Much easier if you draw this centerline on the lower aft skin with a Sharpie before clecoing bulkheads to it. Helps to weight fuselage with shot bags after bulkheads and side skins are added so it doesn't move around.

I didn't expect it to be out of plumb because it's prepunched, but it doesn't hurt to check.

danielhv said:

any other thoughts? I'll be doing this tomorrow, so I'd like a little more backup here!!

Click to expand...

IIRC, all I did was follow the instructions as written...came out virtually perfect. Pre-punched kits, hard to mess up.

The only adjustment necessary later was when I put the wings on to drill the aft spar, and then the empennage to match them to the wings, the HS needed one very thin shim underneath to make it align perfectly to the wings. Traced this difference to the aft bulkhead with the two attach bars running vertically to bolt to the empennage...since it was constructed much earlier, the aft deck goes on top of the angle aluminum running crosswise, and it was off on one side by < 1/64th of an inch...precisely the amount needed to shim. Caused a misalignment of 0.1 degrees. If it were me, I'd change the order of construction slightly to install that cross-piece later, but it all worked out just fine.

Just follow the instructions, and shim if necessary later.