Golden Era Model Service
High Quality Plan Sets for Radio Control Aircraft
74 inch San Josè
A 1948 design by Antonio Arria

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.

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