Monday, July 16, 2018

Nats Free Flight Next Week - Getting Ready

My summer has been really busy, yet I have not done as much as in past summers, or at least not a thing with students or demonstrations. The College for Kids program that I taught for many years is taking a breather this summer and planning for next year. I feel this summer I have been the student, trying to teach myself new things.  This winter I started building my first larger glow powered free flight, the Witch Hawk 500 from a BMJR kit. Building a larger balsa plane was not that hard for me in that I have built several wood RC sailplanes 2 meter or larger. What took more time was that I used an airbrush system to spray the Polyspan covering and had to spray two different types of dope with a color dye in between. The airbrush worked fine but it is a rather small system for spraying a plane that size.

Witch Hawk 500

Red Cap Bladder
Compressor for Spray Painting

This was the first time for me running a glow engine on a bladder pressure. I ran the motor first on suction on test stand and then tested a bladder made from plugging one end of tubing. It ran alright but it was easy to flood the engine.  I then tried a bladder made from a product to seal the end of a caulking gun known as “Red Cap”. This created a little less pressure but appears to work fine with my engine; K&B .19 Greenhead. I was told with more pressure it might be necessary to use a needle with finer threads, I purchased an OS .20 needle valve but have not used it. 

With an engine running on pressure I decided I needed an electric starter on a stand with a foot switch. From my glow RC planes I had a starter but needed it to be stationary. I found a small plastic foot stool that I attached the starter to and wired in the foot pedal switch designed for electric trolling motor. It seemed to work well when I started the motor on the plane. I have not flown it yet but did some test glides that looked good.

1/2 A Streak

My intentions were to build the two One Design models for the 2018 Nats Streak and Smarty, only the Streak was completed but the Smarty is well along.  Power for the Streak is a K&B .049 running on suction with the tank below the motor. I have run the motor several times and flown it more and it runs perfect.  The plane I think I am just getting adjusted properly, some of the first flights were rather exciting in that the plane banked too much right, stalled going straight up as motor quit or did a loop under power. Almost no damage and the last time out the climb was much better and it landed gently from the glide.

Eureka e36

New for this year was another e36 electric model the Eureka which is based on a glow model from the 1950’s. Trimming this model has gone pretty well except two times it went too much right after launch into the ground. Damage was minimal; I added more left thrust and have not had another crash. This past weekend I am guessing I made 20 flights with this plane. The rudder tab and stab are screw adjustable and I tried tiny tweaks to get power and glide patterns closer to ideal. 

It is my hope that I will do a little better in competition at the Nats this year but mainly just hope to learn more and see people I have not seen since last year.

Bill Kuhl