||To position and measure the bulkheads
I've put an extrusion on top and positioned the three builkheads at 90 degrees
with the extrusion. Then, I measured the distance between the bulkheads
so I can pre-drill the center holes on the rear top skin.
My middle bulkhead is installed a little bit forward (10 or 15mm)of the
plans specified position. This is because at the specified position, it
was deforming the fuselage, pushing it on both sides. I also installed a
0.064 shim to make that bulkhead a bit higher. In fact, that shim is
quite good as it attaches the bulkhead with the longeron with several more
rivets (2 in bulkhead flange, 3 in longeron).
||Da da dA da dA....You can keep your hat on....
I cut the skin a bit larger than needed and drilled the three center holes
to match the predrilled bulkheads. The difficulty is in holding
everything square... for the drilling phase.
||Talking about square
We can't see it, but the center bulkhead is fixed in position using straps
of aluminum (1/2" wide) clamped to the bulkhead, fore and aft and on both
sides. This is a fair starting point. The key is in fixing the
skin so nothing moves... I used duct tape liberally and I also clamped the
skin at the front end so the assembly does not move during the drilling phase.
To drill, I work from inside-out, as shown in the sequence manual.
||One side done
One side is pre-drilled. I taped the other side in preparation for
drilling. Only after it is taped and clamped at the front-end, did I
remove the clecoes on the left side. (notice that this is actually my
second attempt.... I did not do that step on my first attempt and trashed the
skin as a result).
As I did for the left side, I drilled from inside-out by working under the
for me, at least. Both sides are drilled to final size, except for the
front bulkhead which I leave with #40 clecoes. I will have to drill the
top middle skin with it later. To ensure that nothing moves when I do
that (the middle top skin), I installed a few (6) 3/32" flush solid
||The right side
As you can see, my skin is cut quite a bit oversize. This is something I
learned very early in the project. It is easier to cut oversize and trim
later after it is all drilled.
||Those B2 and B3... ouf!
To bend the B2 and B3 frames, I filled the 3/4" X 0.035" tubes
with sand and plugged the tubes at both ends. This way, we can work the
tube without undue risk of kinking it.
I used a variety of form blocs I had depending on the bending radius I
needed. This nose rib bloc was used for the more severe curves.
The layout have been drawn on computer so I have the required smooth
curve... but beware! The plans are not pefect! A lot of fitting
and rework are required when installing the tubes on the plane.
||B3 being positioned
I used the upper longeron forming template as a straight edge to position
the B3 tube. It is in perfect extension with the rear top skin.
However, I found it very difficult to have the contour follow the top rear
skin all around... eventually, I just tried a skin on and declare myself
||B2 with B3 (why not U2?)
The B2 tube required even more work than B3... I ended up installing
the skin to the side, rear bulkhead and B3 and then fit B2 in
||Stop working the tubes and go for it!
I was starting to feel that these tubes will never be perfect so I decided to
stop and just go ahead and drill. Well, this was a good idea and I am
very please with the fit.
I did a couple of things different from the plans... the rivet pitch on the
longeron, between B2 and B3 is 30 instead of the mandated 40mm. This
eliminates some bulking that so many people complain about. I also kept
a pitch 40 instead of 50mm on the B2 tube for the same reason. Finally,
I installed a top skin of 0.020" in thickness instead of the mandated
0.016". This also helps. (note that my rear skin is also 0.020" just
because I ran out of 0.016")
||The corner gusset
This was fairly easy to install, but make sure you don't attempt to install it
square with the baggage shelf corner stiffener. The last rivet hole may
be closer to the upper longeron than you wish.