Saturday, May 02, 2009

Gary Hinze from California on the Delta Dart

Hi John,
I came across your Transformation and Development Program.  The Oakland Cloud Dusters use the equivalent AMA Cub in our youth program.
I have made a couple improvements to the construction instructions.
The 1/16" x 1/8" balsa pieces are sorted by weight.  Flexing them is a good indication, the stiffer ones generally will be heavier.  The heaviest pieces go to the wing leading edge, the lightest go to the tailplane and fin trailing edge, everything else in between according to weight.
The entire fuselage assembly, fin, tailplane, prop and rubber motor, is completed before joining the main wing.  The entire assembly is balanced on a loop of thread and the CG is marked on the side at the top of the stick.  The center wing rib is marked at its midpoint.  A couple pins are pushed into the wing center rib about 1/2" from the ends at 45 degree angles.  Glue is applied to 1/4" of the ends of the center rib and then it is pinned to the stick with the center of the rib mark corresponding to the CG mark.  Then the plane is inverted over the board, propped up on the fin and propeller, the wingtips are pinned down and the wing spars are glued to the sides of the stick and center rib.  I glue twice, forming strong fillets.  Care must be taken that the tailplane is parallel with the wing.
I also make a right handed pigtail from the pin for the rear motor pin.  The rubber is less likely to twist itself off the right handed pigtail.  I cut the head off the pin, file the end round, bend a right handed loop, a straight piece and a reverse angle for the sharp end to go into the balsa.  The straight piece is glued over the tailplane spars to space the rubber farther from the stick to prevent rubbing.  A picture is worth a thousand words.

With the 1/8" rubber strip provided, the Cub easily hits the ceiling of our gym with much less than maximum turns.  I recommended replacing the 18" strip of 1/8" rubber with 24" of 3/32" strip.  The thinner motor takes more turns per inch, and it has more inches.  It will still hit the ceiling, but much more of the energy can be used for flight with much longer flight times.  I recently found that 1/16" strip works better.  An 11" loop will give flights of more than a minute outdoors.  I'm afraid to try anything longer, because I nearly lost my daughter's Cub out of the park with 80% turns on the 11" motor.
Gary Hinze
San Jose, California

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