The line length and diameter are critical for getting good performance. The current favorites, .018 x ~65ft is optimum for a largish, 60 oz plane, .015x ~60 ft for smaller planes around 48 oz.
The lap time is not really important. We are looking for a specific airspeed. Almost all stunters fly at about 52-55 mph. You have to adjust the line length so the plane flies properly. Longer lines make the plane more sensitive to the controls. Shorter lines make it more stable. Going too long makes the plane very difficult to fly overhead in the RWO and OH 8's. Going too short makes it hard to get the corners to fit in the square maneuvers. Going longer on the lines can make the plane harder to handle in sharp corners. The lines drag behind the plane, and the weight of the lines can swing the plane around as it goes through the corners.
Use one of the line rake calculators to set an initial point for the adjustable leadout guide. The optimum seems to be about 2 deg. of rake. Longer lines require more rake, shorter lines less. When you change line length the LO guide and tip weight may need to be changed too. Most people start a couple feet long and shorten the lines 6 inches or so at a time. When you get to a good length it will be pretty obvious. Shortening the lines a foot more than needed will cause less problems than leaving them a foot too long, especially when it get a bit windy.
As an example, I helped a buddy trim out a new Vector. He started with 65ft(c/l to c/l) .018 lines, 'cause that is what he had. The plane only had an OS 40 in it. It was a real handful. Way slow, poor line tension, wobbled around in maneuvers, required real coaxing to do a RWO. Switched to .015x60 ft and it became very flyable. A few tweaks to the flaps, tip weight, and balance point and it was flying well.
Topic: Line Length (Read 1573 times)