Originally Posted by dmksails
came the the rig pictured. Not sure of it's intended purpose, but I want to use it to hoist my dinghy. I googled this and it should be giving me a 4-1 advantage over simply lifting the dinghy. The dinghy weighs 60-lbs - I can easily lift it with two hands. I thought that I should be able to use just one hand to pull it up with the pulleys - nope. Seems to take the same effort as lifting it. All pulleys involved are free wheeling and the rope
is not in the clamp. What's wrong?
I absolutely guarantee that if every sheave is freely turning and the line is not too stiff or too big pulling down on the free end with 15 lbs force will result a lifting force of 60lbs.
However there is always some loss due to friction. Double check that. And it's unlikely but those sheaves might turn freely when not loaded but become sticky when a load is on them due to wear.
Mostly, on boats, the friction losses add up quickly. A 6:1 system for a mainsheet, going around several cheek blocks to get to a cabin
, will often feel like worse than 1:1 due to all the friction.
Small diameter lines and good, new, small line will help.
However, I'd make a suggestion: For raising a dingy if you can use a masthead halyard
led to a winch
(with very few blocks) it will probably be easier than rigging
that 4:1 block and tackle you have every time.