I have stayed pretty focused all day today on trying to finish the
bulkhead/stringer structure on the bottom of the fuselage. I have always had
problems fairing in a group of stringers at the back end of the fuselage and
making them look right. To avoid this issue, I put in a solid balsa block at
the rear to serve as a tail cone which can be more easily trimmed to shape
than a bunch stringers! So before the 1/16" X 3/16" center bottom stringer
was glued on, a .063" inclined hole was drilled in a triangular soft balsa
block for the tail skid tube to slip through and the block was glued in
place as shown below. Then the center stringer was glued in the bulkhead
notches, which now butts up against the front of this tail cone.
Also an extra No. 3 bulkhead was glued on the back of the bulkhead
supporting the bottom forward strip planking as shown below. This provides
the location and support of the three 1/16" X 3/16" stringers that butt up
against the back of the forward planking.
Since the two pieces of white ABS tubing for securing the receiver mount are
on the centerline of the fuselage as shown below, the center stringer had to
be pieced in between and on either side of the two tubes.
A surface has to be provided around these tubes in order to have an area to
attach the bottom covering to. A No. 12 drill bit (.189") was used to drill
a hole in a piece of 3/16" balsa sheet. The balsa was trimmed and sanded
around the hole to form a .594" diameter flat disk shown below.
This disk was then split with the grain and a 1/16" wide piece removed from
Each half of the disk was then glued in on either side of the stringer
around the front tube as shown below.
This was also done around the second tube as shown below. These two disks
will be contoured to the shape of the bottom of the fuselage and serve as
areas to attach the covering material to.
All three of the bottom were glued in place and the two disks and tail
cone were contoured to the shape as the picture below shows.
This is close up of the tail cone.
This is a close up of the stringer fillets that were added at the stringer
attach point on the forward planking.
In the picture below, you can see that the bottom bulkhead/stringer
structure has added considerable depth to the fuselage giving it a more
attractive profile. I still have to add the fuselage block in front of the
wing leading edge up above the cabin and then do all of the finish sanding
on the fuselage before it is ready for covering.
There is one final decision I have to make on the bottom bulkhead/stringer
structure. The oval shaped bulkheads are an extension of the oval shape of
the bottom forward planking. However, the covering will stretch tight in a
straight line across each stringer and cause the edges of the oval bulkheads
to stick out under the covering. The oval bulkheads need to be sanded down
to form either a straight line between stringers or recessed concave between
stringers so as not to touch the covering at all. I am favoring the recess
concave approach, but would appreciate any comments or