High Quality Plan Sets and Laser Cut Partial Kits for Radio Control
Aircraft
Page 12
Antonio Arria's San Josè
Because
of the wide span of the tail and the slimness of the fuselage, the aft
fuselage is low in torsional rigidity. Kevlar thread
was chosen
to counter this.
Here the thread is
wrapped around to locate where holes should be drilled in the
longerons. I chose to go through all four longerons, which meant that the upper
stringers also had to be drilled in the proper locations.
Perhaps
installing the thread though the lower three longerons only would be
effective enough. It was decided to go
through the longerons instead of just wrapping around the structure so
that the thread would not show against the covering and also because of the better kevlar/balsa bonding in holes rather
than with a surface join. More photos of the
threading process are on page 16 of this build log, as well as links to
a source for the Kevlar thread.
The fuselage
is upside down in this photo. The kevlar has been threaded
though, starting at F7 and going to F8, and then back to F7 with
one continuous thread. Weights have been attached to both
free ends to tension the kevlar evenly, to prevent introducing a twist to
the fuselage caused by uneven tightening.
To
finish off the thread after gluing a second hole was drilled adjacent
to the start/finish hole and the kevlar ends were routed through and glued. All of the instances of kevlar passing
through balsa were glued with gel CA. There seems to be
sufficient rigidity in this bay now. You will see that an
adjustment was made to the upper longeron at F7. The notch
has been moved slightly on current parts but the fit will depend
on where against F8 you choose to end those stringers.
The
tail will be removable, almost a neccessity with the San Jose's 32 1/4
inch horizontal tail span. 1/4 square basswood block with vertical grain was
inserted on both sides just next to the leading edge and inner ribs.
A 3/32 ply plate was glued in underneath the side
longerons and 2-56 nut plates were pulled in and glued. The
nut plates are visible in the next photo.
A
hole was drilled for a 2-56 machine screw that will retain the fin.
Not visible is a 1/16 carbon fiber pin glued into the aft end
of the fin
assembly
that extends through
the stabilizer and into the end of the longerons. Some
adjustment
of the level of the stabilizer is possible by differential tightening
of the screws, but things are pretty rigid
because of the fin spar's extension down into the subfin. The
subfin has to be pretty straight.
