With no sheet or halyard winches aboard a smack, tackles and their power are important. Apart from the pleasure of using the correct name for a tackle, the information below on how much work can be expected from a fit crew combined with the table of what that work will achieve when applied to a tackle is of design interest when rigging a smack. Two single blocks, the upper, a tail block, made fast.
Power gain is double less friction.
With just the top block it would be a single whip tackle with no power advantage. One direction of force we all agreed on was pulling down on a line which would be the person's body weight when their feet left the ground. Forces in other directions produced a variety of answers tempered by the unknowns such as size of rope, wet or dry deck and pure muscle power. Reading a friend's copy of The Admiralty's Manual of Seamanship Volume III, I came upon the following under the chapter dealing with Extempore Handling of Heavy Weights. It is of interest to owners of old boats because the information relates to strop or iron bound, plain bearing blocks and more relevant than the information provided by modern manufacturers.