Chapter 21: Assembling Ribs and Bulkheads


The plans method has you flox all ribs, bulkheads, and bottom skin into place all in the same session.  It doesn't take a rocket scientist to see that is like herding cats!  Norm Muzzy suggested to me that I flox the R33 and R57 ribs one night, then flox in the rest of the bulkheads the next night.  Norm is a smart man!  I actually floxed the ribs in one night, the leading edge bulkheads the next night, and the interior bulkheads the final night.  

I dispensed with the tapered pine strip in favor of using dental floss for aligning the rib tips and the leading edge bulkheads to 17.4 inch water mark.  I drilled small holes at the 17.4-inch water marks in the fuselage FS60 location and in the wing's leading edge near the cuff, then strung the dental floss from the fuselage to the leading edge cuff..  I like dental floss because it won't sag under its own weight when s-t-r-e-t-c-h-e-d over long distances.  The dental floss allowed me to set the ribs to the exact height and will make my strakes match the wings exactly. It takes away the guess-work of trying to set the distance-above-table dimensions outlined in the plans.

    

I held everything in place with various bricks, clamps, and other "persuasive" devices.  Getting the leading edge bulkheads installed straight took a bit of jigging and fiddling.  As you can see in this picture, I used a length of iron angle supported in place by wood blocks and shims.  There are spacers between the iron angle and the TLE and BLE for the iron angle to clear the R33 and R57 tips.

If I were to do this over again, I'd seriously consider making the TLE and BLE bulkheads into a single piece spanning from the fuselage to the outboard edge of the R57 rib, and I'd cut off the R33 and R57 nose tips on the aft dotted line shown on the rib template.  The rationale is simple -- easier installation, easier to cure straight, and less chance for leakage around the nose tips.  After the top and bottom skins are in place, then I'd simply flox and tape the nose tips back on.  (Addendum:  I did indeed saw off the nose tips prior to glassing the outside surfaces, which requires overlapping the fiberglass cloth onto the leading edge bulkheads.)


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