Spar Installation


With the doors more or less complete, it was time to move on to something else.  Why not install the spar?  The only thing holding me back was the idea that I would have to relinquish 100% of the garage space to the airplane, and park my car outside.  Or would I?  With some strategic planning, perhaps I would still be able to both vehicles in there.  So I took some measurements and built an AutoCAD drawing.  I found that moving my bowling-alley-work-bench into the corner, and putting the fuselage at an angle would still allow me to fit the car in there, although it was pretty tight.  So I had my friend Brad come over and help me position the fuselage on the leveling jig in a pre-measured location.  What a deal... I bought myself a few more months of getting into a warm, dry car in the mornings.

Alrighty then... time to break out the sabre saw again and do some more cutting.  There's something a little disturbing about cutting big chunks out of one's nifty fuselage, but it was necessary.  The spar fits into these "slots."  In the far left photo, you can see the NACA inlet in place.  Actually it was just resting there when I took the photo.  It gets installed later.

You've probably heard the expression "measure twice, cut once."  Well, when it comes to positioning the spar in place, I altered the phase somewhat: my version is "measure 66 times, glue once."  It's kind of important that the spar go in level and normal.  I used water levels, digital levels, tape measures and plumb bobs to make sure everything was groovy before mixing up the flox.  The fuselage was leveled on the leveling jig, and the spar supported and shimmed on saw horses.

Once I was satisfied with the spar alignment, I mixed up some flox and bonded the thing in place.  That was followed by 2 plies of S2 glass around all the joints, both inside and outside the fuselage.  And there you have it... one spar installation.

 

 


A little later (after the firewall and NACA Scoop had been installed) it was time to cut out the spar center sections.  This is done to allow access for systems installations (hydraulic lines & electrical components) later.  Pretty easy work using a hole saw and sabre saw, but when I removed the panels I found a problem:  The inside face of this panel was bare core.  I was expecting to see fiberglass in there.  "This could be bad" I thought, so I called the factory.  Indeed, their first response was "we'll send you a new spar."  Huh?  A nice gesture considering it's a $4,000 part, but good grief, removing the spar at this stage would be highly destructive to my fuselage and firewall.  In actuality the panel did have the correct number of plies installed, it's just that they were all on the forward side of the core with none on the aft side.

I needed to try and fix this thing in place.  But how?  The missing plies extended from centerline to 40 inches outboard in each direction.  Even with my nifty new cutouts I couldn't reach that far outboard.

My solution:  Cut two additional access holes mid-spar (1 per side) to allow me to get my hands in there.  It was difficult using mirrors and working around corners, but I managed to get the area cleaned and prepped, and 2 plies of S2 glass layed up in all missing areas.  I put 2 additional plies inside to strengthen the access holes, and once the access panels are bonded back in place, I'll put 3 more plies over the outside.  Not only is strength critical in this area, but it needs to be fuel resistant too.  For now I'm leaving the access panels off because it allows better access to install landing gear hydraulic lines and wing wiring.

The finished project is shown at right.  For clarification, this shot is of the R/H spar, while the prior shot (above it) is of the L/H spar.  It took 28 hours of unplanned construction time, but at least I didn't have to remove the spar from the aircraft.

 

 

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