Monday, June 6, 2011

LWX & LWY Stringers...

Step 5 of Ch 5 started with the lower longerons (previous post) and then went on to installing the so-called LWX and LWY wooden stringers in the aft section.  These stringers form an important structural section that carries loads from both the center wing spar and the main landing gear.

The biggest issue I had here was that when the two stringers were lined up according to the proper measurements, the angles that were cut to fit the intersection of the two stringers (middle of pic) and the intersection of LWX and the lower longeron (bottom right in pic) didn't fit nice and flush.  I'm not blaming the plans here...I'll take the full blame on behalf of my cheapo miter guage.

The important thing was to make sure the 3 key measurements were correct: 5.5" from the aft edge to the vertical support, 8.7" down and parallel to the bottom of the top longeron, and 16.3" from the aft edge to the intersection at the lower longeron.  After those were solid, I adjusted the intersecting angles as best I could to get a better fit and let flox fill any minor gaps.   The pic shows the wooden stringers in place as well as the beginning work of step 6...which includes securing the electrical conduit cover and filling the voids with foam.  Next is securing the foam in place with micro, filling the gaps, sanding the section level, and glassing over this area to make it one solid enclosed structure.

It's not an illusion that my electrical conduit covers are slightly curved.  When doing some double checking, I realized that I failed to cut the conduit channel at the "recommended" 14.7" down from the longeron and instead cut them according to the plans 14.5".  The problem is that at the plans measurement, the conduit opening at the firewall will likely interfere with the rudder pulley mounted on the firewall.   The easy solution was to shape the aft part of the conduit cover with an ever so slight bend in order to exit the firewall below the pulley assembly.

OK.  I'm in the last step of Ch 5.  I'll have some fuselage sides done very soon.


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