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Electric BUHOR - Wing Modifications

Began by building BUHOR's wing using a simple,
no-adhesive method.

Modifications from original (.40 glow version)
BUHOR wing: plywood spar, new folding jig,
heat-to-fold, no-adhesive method.


Spar: Used 1/4 inch plywood spar in place of yardstick hoping for a bit more strength. Kept 60 inch
span & 12 inch chord. Made spar 1.75 inch wide
to give thick airfoil. Made this jig to keep
spar perpendicular and aligned while shaping the
airfoil by screwing plywood spar to two pieces
of 3/4 inch thick ("one-by...") lumber.

Jig to form coroplast wing airfoil.


Airfoil:

First attempts to shape the airfoil failed
completely. The flutes just wouldn't bend
smoothly over the spar nor hold their shape in
anything like an airfoil form. I finally tried
heating the coroplast over the spar with a
Bernz-O-Matic torch while making the bend and
this worked a lot better. Some of the flutes
sagged a bit while hot but regained their
firmness when they cooled.

Heat coroplast wing to make airfoil.


After testing all of the recommended adhesives
and techniques for gluing coroplast without
being able to make any of them work (including
heat treating and Windex), I went with large
staples and small machine screws instead.
Used the staples to attach the coroplast to the
spar...

Coroplast wing - staple coroplast to spar

...and small machine screws with nuts to
"stitch" trailing edge together. Note (in photo below)
rectangles of PVC siding to give strength under
screw heads. These are also used on the nut
side. Since you'll need a lot of these, it's
worth mass producing them drilling a bunch of
evenly spaced holes in a scrap piece of PVC
siding then cutting them apart with metal snips.
(I uses 30 in the wing alone, and you'll need a
few more for the tail mounting, control horns,
etc.)

Coroplast wing built with machine screws


Coroplast center wrap was made with both staples
(bent over with pliers) and screw-and-nut
attachments.

Wing wrap / reinforcement stapled


And here's the finished wing temporarily mounted
on a PVC pipe frame.

Completed coroplast wing on temporary mount


Coming next: rudder, elevator, receiver and
servos...     [Next article]

 

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