Both sides are partially correct in this discussion. What's being left out is a discussion of what is attached to the winch.
First, the smaller the drum the greater the potential for mechanical advantage. At any given level of motor torque, a 1/2" radius drum will have the capability to develop twice the line pull of a 1" radius drum. Notwithstanding how much torque the motor can generate, however, the force of the line to the drum cannot exceed the force of the plane plus parasitic drag (grass, humps, turnarounds, retrievers etc.) in the opposite direction. Therefore, even if the motor/drum combination has the capability to pull at some level (let's say 200#), if the lift/drag vector of the glider on the line plus the parasitic drag is only 50# the motor/drum will only see 50# (I know this an oversimplification, but is is approximately right for this discussion). If you sit in a parked car and stick your hand out the window on a windless day there will be no aerodynamic force exerted on your hand. As you move the car faster and faster, the aerodynamic forces will increase. The same is true when you launch your glider. Notwithstanding the amount of preload that you crank in with the foot pedal prior to releasing the plane, at the very moment of release the only force the plane exerts on the line is the force of inertia required to begin accelerating the plane. With no windspeed, there is no aerodynamic force. This force comes into play as the plane accelerates and begins to fly. In this scenario, a small drum will likely accelerate the plane more slowly than a larger drum and thus less, rather than more force will be exerted on the plane until it is fully up to speed. Therefore it is likely, within some range depending on the combination of motor torque and speed, a larger drum will build up force faster than a smaller drum (it is likely that a 2" drum initially has less ability to utilize the torque available to accelerate the plane than a larger drum.) In addition to the relationship of plane speed to pull, you have to take into account the elasticity of the winch line and the usable energy it stores as you preload the winch. If you preload a winch to some particular force (say 200#) a stronger line will stretch less than a weaker line -- the energy stored in the stronger line will be released back to the system over a shorter distance than the weaker line. In the most extreme case a steel line with very, very low elasticity will return its stored energy over a very, very short distance and that stretch will likely be spent very shortly after the release and not really useful for acceleration. The opposite will be true for a very, very elastic line. (just ask the F3J guys) This is the front end of the effects that result from moving to higher and higher strength lines. The back end may be realized when the plane is moving fast enough to generate aerodynamic forces. It is possible that some breaks are the result of less elasticity, in spite of the greater strength of the line. It is at least theoretically possible for a plane to build up aerodynamic forces which, combined with sudden changes of direction exceed the line strength. With less elasticity in the line to absorb the force of the plane's acceleration, the plane's energy is more immediately and directly transmitted to the line. This doesn't seem to happen at the zoom point, but maybe the vectors during the climb accentuate the possibility of essentially jerking the line apart. -- dharban ------------------------------------------------------------------------ dharban's Profile: http://www.rcgroups.com/forums/member.php?u=31927 View this thread: http://www.rcgroups.com/forums/showthread.php?t=788940 RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
