Brain Teaser – An 8-inch model screw

An 8-inch model screw, tested in a water tunnel at a rotational speed of 22.5 revolutions per second and a velocity of flow of 12 feet per second, yields a measured thrust of 28.5 pounds, a torque of 3.45 pounds and an efficiency of 70 per cent.

If the model scale is 1:25, what should be the equivalent rotational speed, thrust and power of the prototype when the speed of the ship is 15 knots? What will be the approximate velocity of the prototype slipstream?

How to open a briefcase| Back – Next | A Manager’s dilemma