Back in May I mentioned I was using Pete Bower's Fly Baby as the basis for Chugger's tail. At that time (ie, 16 May 2007) I uploaded the drawings for the rudder and vertical stabilizer box-spars, which use 1/8" plywood shear-webs and 3/8" square cap-strips (as opposed to the 1/2" square cap-strips used in the original design). Chugger's tail is smaller in both height and span but I've tried to retain the elegant curves Pete used.
To ensure the four shear-webs would be identical, after rough-cutting them 1/8" door-skins I tacked them together on their center-lines and sanded them to final size as a single 1/2" thick slab. Since door-skins have an inner and outer face, when stacking them I made sure the rough-sawn blanks were oriented with the inner faces against each other.
The horizontal stabilizers use a built-up C-section for both their spars and diagonals whereas the elevators use box spars. As you can see in the drawings the diagonals are of a different size than the spars and are best handled as a matched pair. The six shear-webs for the spars are identical in taper but the elevator shear-webs are shorter. I treated these as matched sets of three, cutting the elevator shear-webs to length after sanding the stack to the proper taper.
Interesting, R.S. For my FlyBaby's tail, I roughed out rectangles, measured and marked the ends, and let the 1/2 lumber define the taper. I dry-fit the filler blocks that support the hinges. After gluing it all up I trimmed and sanded the excess plywood flush.
ReplyDeleteSo far I've just done the elevator spars, not the stabs. I can see, though, there's a possible aerodynamic reason to do the elevator and stab spars as a matched set. But given the tolerances we're working with, is it that big a deal?