BSDGuy

I decided I would do something radical, and build a balsa kit plane. I'm brand new to the hobby, and my flying before now and up to the point of getting this bird in the air (a cub) will be various toys and trainers.

The kit was plane only, and the suggested power system was a Great Planes speed 400, gearbox and 6 cells. It is a Dare Design Cub.

The specs for the plane indicate 500+ in wing area, 24 oz weight (I believe this includes the drive recommended, radio and batt).

So I downloaded motocalc and started looking at it's analysis.

Yes, I can make a 7 cell, geared s400 drive system, but it's always a bit marginal, no matter what motor, gear, and cell count I use. To slow, too little thrust, too little batt life, too hot, etc, etc.

So, I started "upping" the power system. I changed to NiMH battries, upped the cell counts, and moved up to a speed 500, then speed 600. I tried myriad combinations of prop size and pitch, along with gear ratios, etc.

I was looking to find something with good static thrust - more than 60% of expected weight. It seems that no matter how I go up in power, I get no farther. The stall speed of the plane keeps rising as weight goes up, and I continue to run into the warning that your prop pitch speed is low - or, warnings about the motor temperature, or, too little thrust. Or, I CAN sacrafice run time.

If I gear it up, put on a smaller prop, I get a "too low current" comment out of MC, and poor thrust figures.

I moved all the way up to a high output speed 600 and many cells. Each increase in power was accompanied by an increase in weight, and the relative performance of the craft actually began falling after a certain point.

I'm unfamiliar with much of what MC says, but it appeared to me that only LiPoly cells could make a dramatic performance increase.

Also, am I actually just making bad assumptions? When MC says something is typical of a trainer, does that mean it still flies well?

Just looking for feedback on MC's reports vs real life.... Any response appreciated...