just how heavy is it

Hi all
I am confused, not an entirely unusual state, about the meaning of the terms displacement and ballast in the weights shown in the specifications of sailboats. Displacement for me was the weight of the water displaced by the boat in the water rigged and ready which included the weight of the ballast. Now my confusion came from the scale reading when I hauled my buccaneer home, of 16,000 pounds at the scale, which if one subtracts 2000 for the trailer, gives 14,000 pounds of displacement. This can only be achieved if one adds the displacement spec weight of 10,500 to the ballast spec weight of 3,500. All round figures. This is not a really healthy situation where the Departments of Transportation are concerned. Does anyone have any idea what I am missing?
John

 

What was in the boat? How long has it been in the water? Most advertised displacements are for "as delivered" with normal fuel and water. Boats, like people, gain weight over time and also tend to soak up water.

 

Displacement should be the total weight of the displaced (as the terms says) volume of water, including of course ballast.
Many times, though, the displacement you read in the brochures refers to a half load condition.

 

"Half load condition" applies to the normal displacement from the factory with additional allowances for stores/supplies carried for a "voyage" - the term refers to the midpoint of the assumed weight for these stores. The 14,000 pounds would be 10,500 pounds of boat, + added pounds of water, fuel, food, sails, anchor chain, accumulated paint, dirt.... etc. Math seems off!

The factory would forecast and report performance based upon an assumed (and stated) allowance. The big question is how you found space for 3500 pounds of stuff? That's a pretty conservative choice of ground tackle

It seems reasonable to wonder if the displacement was indeed 'misquoted' by not adding in the ballast. How trustworthy was your quoted displacement?

 

The boat's a Buccaneer 305 I'm guessing? That one was cored right? I would expect that a crusier that old that has been in the water a long time would gain that much weight. Where is the waterline scum line WRT the scribed waterline?

 

nemo: Many times, though, the displacement you read in the brochures refers to a half load condition.

How often is "many times"? And how do you know what a full load is? With or without the smarmy misinterpretation of "load".

 

Thankyou all. I have since checked the numpers and a Practical Sailor spec lists the thing as 10,000 lbs with 3,500 lbs of ballast. I bought the thing out of the water and do not remember the skum line as being above the waterline but at the waterline any change in height would represent a significant change in the weight. There had been an extreemly poor repair done to a crunch that had compromised the outer skin but not the inner one so there was ample opportunity for water intrusion into the core. Since the displacement is about a boat provisioned the actual weight of the boat empty as delivered from the factory should be less yet. So like jehardiman says boats like people gain weight with age methinks also like to fib about it a bit and since there was nothing much in the boat as hauled that must be the water in the core. I stand causioned on hauling cored boats and wonder if this might be an intresting method of determining the condition of the core of an older boat. Thanks again
John

 

Gaining weight

Hi!

Well, the weight gain due to water in the GRP can be measured to little, some 50 kilos max. The differens is mainly due to the optimistic spec in the brochures and the actual gear loaded in the boat.

BUT, what puzzles me is the comment " ample opportunity for water intrusion into the core " -is it a hull made of sandwich (core is balsa wood or foam)?

If so and the water has/can penetrate into the sandwich material you have
a) a very heavy boat (calculate the volume between the hull/skins)
b) a monstrous task to dry out and replace damaged material. I hope you do not have frost as we face in Sweden soon -that will cause a delamination if the water still is there and then we talk a snake excercise -i.e. shift the outer skin. This I don't wish yoo!

Deck is sandwich? If so, how is that? Screws OK sealed and massive epoxy or tubes between the skins to keep the distance and avoid the core to be compressed?
Water will eventuelly cause delamination and thus less structural strength.

-Jörgen

 

I'm afraid that Nemo describes a best-case scenario, often the displacement claimed is the number that was expected when the boat was being designed without any regard for reality, and sometimes the number comes directly from 'twixt the buttocks.

Yoke.