Monday, June 23, 2014

Herr Champ First Flights

Building a rubber powered model free flight model airplane that looks like a full-scale airplane is fun and challenging for me.  It can be frustrating at times as there is a good chance the model will be broken from clumsy fingers during the construction process. Covering the many surfaces without wrinkles or warps is not easy for someone new to this either. Adjusting the model can take considerably more effort compared to the rubber powered beginners models. When it all comes together and the model that looks like a full-scale plane is making perfect circles in the sky with no control from the ground it is well worth the effort.

One of the common challenges comes from the fact that the full-scale airplane has this heavy motor in the front while your rubber model only has a propeller in front and the rubber motor is located along the length of the fuselage back almost to the tail. If possible, building the tail as light as possible saves having to add excessive weight in the nose to balance the airplane and reduces the overall weight. On the Guillow's Super Cub I built the tail by curving the wood while wet to create lightweight tail surfaces, this plane flies very well without any nose weight.

Other challenges come from the lack of dihedral and the smaller tail surfaces when building a model that looks closer to it's full-size counter part. In the links below are short videos of some my previous rubber scale airplanes that did not fly too well at first. With some adjustments the planes all flew better but not perfect. It has been a learning process and I try minimize problems during the building phase based on my previous experiences if possible.

Last winter I constructed the Herr Engineering Aeronca Champ rubber powered airplane. Plans are adequate but not as detailed as with some kits, the wood was good but not excessively light. When completed I thought it looked fairly well for my skill level but I am no master builder.

Start of the Construction

For the first flights it became apparent the plane had too much turn to the right, in the field the only way I had to correct was clay on the left wing tip. With a gentle right turn the plane would climb very steep and hang on the propeller resulting in a stall to the ground. Clay was added to the nose until the climb seemed about right, this put the CG as indicated on the plans. As seen in the video clip I took the flight path is rather wobbly yet, I am trying washout in the wing for the next flights.

IMP Model Flew Perfect With No Adjustments 
The Easy-Built IMP model pictured above is a typical beginner's model for comparison. Lower wing loading, more dihedral, higher lift wing, and larger tail surfaces make for an airplane that flies slower and was easy to adjust.

Hopefully I can get another video clip when this plane is flying smooth.

Bill Kuhl

Flight Videos of Some of My Other Rubber Models

Guillow's Super Cub
Guillow's Cessna 180 - bad flight
Dumas Curtis Robin - some stalling
Minnow ROG - flies perfect every flight

1 comment:

  1. I have given up on this airplane for now as it needs a major repair. It is my opinion that the airplane is just too heavy. Someone had built this plane a few grams lighter and it flew very well for them.