boat crane weight vs. boat theortical weight

[Ron]

I read on the sailnet site a question about boat weight. According to the specs, my 1994 C320 should displace 11,700 pounds. Each year it has been crane-weighed at about 14,000 lb. This an empty boat with no mast. At our club, the maximum crane weight for a boat is 10,000 lb. If you are over this, commercial cranes come in for the day and launch all the heavy boats. If this is a common finding, someone might think their boat is within local crane limits and might actually be dangerously over the safety capacity of their crane. Anyone else have big discrepencies like this ?

 

[r taylor]

displacement is not weight

did you ever notice that a rock weighs a lot more on land than in the water? the same thing is going on here. i believe the displacement is the weight of water that your boat displaces, not the actual dry weight. i am an engineer and used to have a grip on exactly what the difference is. if you need the exact definition, just google it up.

 

[Garry@S/V TASHTEGO]

Displacement vs weight

I'm not an engineer but I do know that the displacement is exactly the same as the weight of the boat. I guess we have to assume that manufacturers may shade the truth about the weight/displacement of their boats and that the true weight includes any fuel and/or water in the tanks and any add-ons like outboards and sails. You might also have a badly calibrated crane scale. But generally she weighs what she weighs - whatever the manufacturer says.

 

[Ron]

OOPS - other forum please

Sorry for the double posting. I have this on the "Ask All Sailors" forum. Please check out the great responses over there as well.