In my youth I flew small model aircraft powered by miniature two cycle gas engines. The planes were controlled by two lines and flew only in a circle. Friends had a couple of planes and we flew them in the open area out behind our houses. Sometimes we would stand back-to-back to race them to see whose plane was faster. Most of the planes were plastic prebuilt models of pre-existing aircraft. I realized that there were flying wing kits of wood and paper designed to fly faster and began building those. These planes were faster and could do simple stunts. Soon we were building and flying these.
All of us used a three bladed propeller on the theory that more blades would bring more speed, produce more thrust that two bladed propellers. At some point, however, I saw a power output chart for our small engines, known as ½A engines. The engines were rated for maximum power output at 22,500 RPM. And achieving that rotation rate required using a two bladed propeller known as a five and a quarter four.
I eventually found a five and quarter four propeller in a local hobby shop. The propeller was smaller than our three bladed props we used. So when I came out into the flight area with my too small prop my friends laughed. I was worried too – I could not see how a smaller propeller with one fewer blade was going to improve the speed of my plane. I flipped the prop with the prop spring and adjusted the needle valve until the engine was screaming at a pitch not before heard in the flight area. A friend launched the plane and from the get go the plane was hands down the fastest any of us had ever seen. I was being spun around at a dizzying speed by the plane until the fuel ran out. As the plane landed in the grass my friends all wanted to know what kind of propeller I was using. Smaller, only two blades, but the result was the engine could hit a far higher rate of rotation and generate even more thrust.
Some time back I had purchased an electric string trimmer for my daughter – she had really wanted one for the yard. After she headed off island for college a nephew -in-law had come over a couple times to weed whack the lawn. He seemed to have trouble with the line feed mechanism. The line had been recommended by a chap at the local hardware store based on the trimmer model we have. I hadn’t been with on that particular run to the hardware store.
I recently tried to use the electric string trimmer myself in the garden, but the line feed mechanism was not working. Every time my line broke I had to take the head off, pop open the reel case, and manually feed the line. I figured the line feed mechanism must be broken. I spent that day whacking a couple of feet, then manually feeding more line, whacking two more feet.
I hadn’t paid much attention to the line since the line was the one recommended to my wife. The string was a hexagonally edged “maxi-edge” line. As the trimmer line was running out, I went to the hardware store today to pick up more line. I knew that the edged line could be more problematic and that the electric string trimmer used the lightest of lines at 0.065 inches. I picked up some smooth round 0.065 inch line to see if that might work better than the edged line.
Within a few feet the line had split off, but when, just for the heck of it, I pressed the line feed button, the line suddenly fed. I was surprised. Not once during the day did I have to manually feed the line. The machine whirred and purred feeding line. Only when I took a break to reload the reel did I realize that the old orange hex line was 0.095 line – the wrong size. Not to mention that the lighter weight electric trimmer is designed for the round, non-edged line.
The lighter line lasted longer and fed properly, making far quicker work of the lawn. Smaller was exactly what the string trimmer needed. The lighter line also seemed to let the head spin faster, providing a much cleaner cut line that the heavier 0.095 inch line had been able to produce.
Thus I was reminded of the five and a quarter four propeller once again after many years of not having thought about that time in my life. There is some deeper lesson about the right tools for a job, the right accessories for the tool, but for now I can just sit on the porch and enjoy the trimmed lawn.
danaleeling 