I have built a 12 vdc powered winch to help launch RC sailplanes. Currently the power is applied by tapping a foot controlled switch which in turn acts to pulse the automobile starter motor which powers the winch. A constant ON would cause excessive strain on the wings of the sailplanes and they would most likely "pancake". The foot controlled switch activates a dc solenoid, which in turn handles the load from the battery to the motor. I would appreciate any advice on how to incorporate an adjustable pulsed signal, so a constant press of the foot switch would yield a pulsed control output to the solenoid. I would like to be able to either increase or decrease the speed of the pulse while in use to facilitate the required torque to get the sailplane safely launched.