Wing Build Page
I'm following the second spar designn for the M-19 Flying Squirrel, namely the "Barnard Composite Spar" or BCS. Intended to save money, weight AND ease getting appropriate building materials, Marvin designed a built-up spar to replace the 7" * 3/4" * 11' plank used in his prototype. Oscar ran engineering trials on a test spar I built to confirm Marvin's design. Read about that test.
I built box beam spars for the KR2 and figured this was an appropriate design change for my iteration of the Flying Squirrel. Combined with the taller fuselage cabin height, I'm calling my project an M-19b.

Spar wood scarfing & lamination

Bottom spar cap being scarfed on the table saw

Fitting the sections together & bonding with T88. I pinned the scarf joints with aircraft nails to prevent slipping under clamping pressure; removed the nails post-cure.

Spar dimensional layout

Visualizing the root & lift strut sections in place & cutting the fish mouth transitions

Spar structural construction

To build spars, a flat work surface is good. My table is within 1/16" across the 12' length. As good as I could do.
I got the baseline straight edge to 1/32" according to my thread guide line stretched along the table edge and that meets Marvin's design spec.
The 1/16" should work itself out when it gets bonded to the XPS foam factory edge. Assuming I pay attention at that stage.
Kind of fun, this stuff!

Final layout and Glue-up
 

T88 Glue test sample looks good

John bonding the right main spar (record shot for the Repairman Certificate)

T88 applied & glue closing up

Clamps applied and top weighted for curing

Another T88 sample block with excessive clamping & squeeze out to trial shear destructive test

Finally, the first spar blank is out of the clamps and cleaned up.

    XPS plug insertions

    WAF placements and drillings

    FG layups on the bias