Stringer Straightening

After fitting the fuselage forward skins I saw a problem.  Take a look at the picture at right.  Can you see it?

The fuselage top stringers, 240.3690 R&L, are kind of not at the same height at the aft end.  The right side is 3" higher then the left side.  What did I do wrong?

I measured the bulkhead member heights at 73.75 and 99.35.  Looks good there.  I placed a level across the upper fuselage stringers and it was level.  Must be something wrong with one of the parts.  Which one?

(Note:  This is very similar to RC model plane kits.  Sometimes the parts aren't right.  Close, but needing adjustment.  No problem.  Make the adjustment.)

This was a good time to take a break and reflect on the prints.  Which print are the upper stringers on?  Blarg!@#  Now I have to dig and find the prints!  Relax, you have time.  Don't panic.  Think.  How can I find the correct print?

 Oh yea...My fuselage reference mockup I made last fall.  Very handy to have hanging around.  I am glad I made it.

I was able to find the upper stringers were item #11 on the drawings.  Quick use of the legend at the top of the page and I found the correct print number for making the stringers.

I could see by the drawings there is suppose to be a 3" bend down just after station 99.35 bulkheads.  Now just how am I going to bend a 1"x 1" angle of 6061-T6 aluminum without "kinking" it?  I don't have any kind of a bender.

I made a quick call to Mustang Aero and told Chris Tieman of my dilemma.  Chris told me to clamp a pipe onto the aluminum angle so as not to kink it.  After talking to Chris I was full of confidence again.  I removed the right upper stringer from the plane and laid it on my flat work bench.  Yup!  It needed to be bent.    

The shot at right is after I bent the stringer 3" and removed most of the clamps.

I strapped a 1/2" electrical conduit right up to where station 99.35 bulkhead would be.  I secured the remainder of the aluminum angle to the bench.

The conduit held the angle in place so it wouldn't kink.  Worked pretty good.

Here is another shot of the setup after I bent the angle.

I clamped the angle back on the right side of the plane and it looked good.  Nice symmetrical fit with the left side stringer.

This is how it goes some times.  Testing & fitting parts together multiple times to get the best fit prior to final assembly.  This process is repeated several times for each piece.

If you are a little off in a measurement or proper fit by the time you get the other parts together you'll end up way off.  So, lots of double and triple checking.  Each day a little more progress.

Tomorrow, I will work on the firewall and try and have it clamped to the forward fuselage side skins by the end of the weekend.  I have to keep going.

Later,

Brian