aerodynamics - Why is it rare for small aircraft to have winglets ...
I thought I might clarify the process I used to build Hoerner tips and
correct one misstatement I made if anyone considers building them for
simplicity.
I started by sanding the top surface of the wing with the foam extension
I added to the 36" rib. I then glassed the top surface of the wing.
That gave me the entire top surface of the wing finished including the
tip. When cured I sanded the tip straight at 90 degrees to the spar /
36" rib (not the lead edge). Next sand the bottom foam to shape but
don't glass at this time. With the wing up side down I used a hacksaw
blade to cut the tip to shape. I biased the blade along the hard finish
of the top surface glass and followed a glue line on the foam blocks on
the bottom side for a straight cut. As you approach the trailing edge
the angle keeps getting flatter until it is nearly zero degrees. See
photo. Radius the front and rear corners and sand the front corner to a
smooth curve shape by eye. You'll know when it looks right. Before
glassing the bottom surface remove about 3/8" of foam from the entire
top surface edge. Fill the void with resin rich flox and glass. This
gives a nice sharp edge to the top surface with a good glass to glass
bond. If you plan on installing a wingtip light or ADS-B unit on the
wing tip I'd suggest you embed a hardwood block in the tip before
glassing. I used a 2" cut back on the bottom. If doing again I'd
probably go with a 3" or 4" for a sharper angle although 4" may be
getting too extreme. Your call on that one.
I used this process to easily build two identical tips and didn't
realize until finished that if was a Hoerner tip with advantages. Makes
me wonder if Mr. Hoerner didn't stumble on this as I did. As
always...........................
Larry Flesner
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