Survivable Electric Combat Part II

The Windrider Bat is a slope soaring flying wing glider.  To convert it to electric pusher propulsion the 1/8" plywood center rib shown at right was created.  In the front on the bottom it droops down to form a grip point for launching.  There is a hole behind the rear compartment.  That is where the carbon fiber spar goes though the rib keying it to the wing halves.

The Bat is shown here partially assembled.  The wings are not glued to the center rib, instead they are held together with strapping tape supplied in the kit.  The vertical fins shown here are made from 4mm coropast and will be glued onto the wing once colored tape is applied.  The glue that works best to adhere coro to tape is GOOP.

The completed bat before colored tape is applied. The ailerons are molded into the wings.  You simply cut the ends of the ailerons free and put tape on the top of the wing to form a hinge.  As shown here strapping tape is applied to the center section to hold the wing halves to each other, and is applied for strength on the leading and trailing edges.

The Agony of Defeat: The finished bat weighed 23 ounces but required an additional 8 ounces of lead for balance. The first power on launches were followed by removing almost all of the lead, then reflexing the ailerons up. The only way it would launch was with power on.  Then the prop tip vortices sucked the fins into the prop.  The result was broken props and splintered carbon fiber extension shafts.  CG still needs to be worked out.

A new rear bearing support was designed made from basswood and maple.  Two servo control horns were used a bearings.  The mount was also designed to stiffen the vertical fins.  The prior design fins did not have enough stiffness to keep them from being drawn into the spinning prop.

This view shows the new vertical fins which are made from foamboard instead of coroplast.  The horizontal brace has two plywood end plates on it which are attached to the vertical fins with tape.  This has proven to be a strong system and will soon be tested in flight.

This is the Generation II Bat with new fins, and more robust rear shaft support.  As shown it is 24 ounces.  The CG will need to be worked out.  I will test glide it until the weight and elevon up reflex are correct. Should be able to test this upcoming weekend.