On Tue, 22 Jun 2010 12:22:12 -0400, W1TEF
wrote:

No - he misunderstood the nature of the answer. Yes, the weight is
still 350 pounds. What you are effectively doing is reducing the
amount of energy required to move the 350 pounds by the use of
mechanical advantage. It seems like you are only lifting 35 pounds.

Yeah, I got that... I thought he was talking about 35 pounds on the boom
holding the tackle..

I'd have to ask Wayne, but I think he uses the boom for the rib and
that whole rig has to weigh in at or around 350 lbs - maybe not.

We use a block and tackle arrangement to lift the boom (tilt it up)
with the RIB dinghy attached. The RIB with full fuel tanks, two
small anchors, security locks/cables, safety gear, etc., weighs
somewhere around 400 pounds. Because the block and tackle is pulling
diagonally from the top of the trawler mast, the actual initial force
required is greater than 400 lbs if you solve the vector diagram. For
discussion purposes, let's call it 500 pounds. The block and tackle
is in two parts: a 7 to 1 pulling a 2 to 1 for a theoretical total
mechanical advantage of 14 to 1. Our old nemesis friction steps into
the picture however and reduces the advantage by some significant
amount, probably around 30% which results in a real advantage of
about 10 to 1, requiring a 50 pound downward pull to lift the boom. As
the boom rises above horizontal the vectors add up more favorably so
that by the time the boom is at 45 degrees, the pull required is less
than 30 pounds.