Sunday, February 9, 2014

(page 15-02) Wing OCD (obsessive-compulsive deburring)

Deburring all the wing ribs is a bigger job than I previously suspected.  The lightening holes require use of the little curved, freely-rotating deburring blades (I don't know what they're officially called), the small flange cut-outs require a tiny rat-tail file, and I'm doing the flange edges on a Scotch-Brite wheel mounted to a drill
press (visible in the previous post).  The build manual calls for flattening all the ribs via fluting, and I quickly learned that it's easier to debur before the fluting process.  The edges of the flanges are cut in a scalloped pattern so the flanges are scalloped in two dimensions after fluting.  The picture at right shows the fluting tool and the tool I used to remove fluting.  After fluting the first 10 or so nose ribs, I settled on this procedure which went more quickly: lightly flute every bay between holes, then decrease or increase the fluting where needed as indicated by laying each rib flat on the work bench.  The main ribs require a lot less fluting.  I found that lightly fluting the seven bays between the embossed stiffeners in the web was near perfect with no correction.

Since the fluting didn't require and solvents or lubricants and didn't produce any aluminum chips, I was able to escape the horrendous cold that has descended on the sunny south by moving the fluting operation into the house.  The Spousal Unit (my beautiful and patient wife Karen) was none too pleased but allowed it considering the temperature in the garage.

The description in the build manual of the various operations to be performed on the ribs is somewhat confusing, and the situation was not helped by viewing the Homebuilt Help videos, which don't agree with the manual.  I couldn't find a revision on Van's site which would explain this discrepancy, so I went with my best interpretation of the manual.

The bare ribs come in two flavors labeled W-1208-R and W-1208-L.  I assumed, of course, that the L referred to ribs for the left wing and the R referred to ribs for the right wing.  Wrong.  All the nose ribs for the left wing are labeled R with one exception.

Off topic  The engine for my antique car recently came off the dyno: 544 hp @ 6600 rpm, 486 ft-lbf at 5000 rpm.  I was a bit disappointed in the torque number, but it'll probably be hard to get it to hook up anyway given the limited rim width.