The
Weedhopper is a high drag design with several pounds of that drag being
generated by its four tubular wing struts. This drag is equivalent to
placing a two-foot square piece of wood out in the air stream. However,
a streamline, teardrop shape significantly reduces this drag by a factor
of 28, from 2 sq ft of flat surface area down to 0.07 sq ft (10 sq in).
Adding these wing strut fairings increased my cruise speed by 7 mph, thus increasing my fuel economy of my single carb, free-air cooled Rotax 503 by 6 mpg, going from an average of 14 mpg and 3 gph to 20 mpg and 1.75 gph (as measured during my first extended flight of 78 miles burning 3.75 gallons over 2 hours 15 minutes with rpms ranging from 4,200 to 5,400).
This page documents a common method of fitting such struts with a very light, cost-effective, easy-to-make, streamline fairing made of foam and tarp repair tape. Most of the directions are printed in the images below. Just click on the thumbnails to view the full sized image.
First, let's start with the materials.
- one block of DOW Blueboard insulating construction sytrofoam, 4 feet square x 3" thick.
- hot wire foam cutter (details of how I made one for less than $15 are shown below).
- four
35-yard rolls of 1 7/8" wide black vinyl Tarp Repair Tape made
by BAC Industries
(available for $3.10 each from Tarps Online). - a 4 inch square of scrap aluminum roof flashing.
- a printout of this streamline template form.
- six 1 1/2 inch long nails.
- 100 grit drywall sanding mesh.
- 1" wallpaper burnishing roller.
- Polyurethane glue (Elmers Ultimate Glue or Gorilla Glue).
- Spray bottle of water.
Homemade hot wire foam cutter:
Follow the instructions printed in the images below:
