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nial · 13-03-2013, 12:34

I'm puzzled about what "displacement" of a sailboat means. Is it the weight of the boat with mast, rigging, sails, fuel, water, etc. or does it exclude any or all of those items. Perhaps there is an industry standard as to what boat builders mean when they give this figure but I haven't been able to find it.

SkiprJohn · 13-03-2013, 12:40

I can only say that it is usually the weight of the amount of water it displaces when it is unloaded. It usually does include mast, rigging, minimal sails and engine but doesn't normally include water, fuel electronics and food.

That's just my interpretation and I'm certain others will chime in and maybe we'll get someone who is a designer or in the boat business to help you with this question.

kind regards,

Kettlewell · 13-03-2013, 12:49

Boats displace a certain amount of water when they are afloat. If you could weigh every drop of water displaced when your boat is afloat, it would equal the weight of the boat. So, displacement is essentially the weight of your entire boat, and it goes up when you fill it with fuel, water, etc.

transformer · 13-03-2013, 13:25

This is primary schools stuff...
Displacement is the actual weight of a vessel and everything onboard at the time of measurement
Light displacement - is empty vessel. The displacement will change with any additional weight. IE. if you add 100m of heavy chain the boat will displace more water. But the displacement will always equal the overall weight.

As previously said Archimedes Law - A body immersed in water appears to suffer loss of weight equal to its own weight

Paul L · 13-03-2013, 13:31

Displacement is sometimes spec'd as half-weight displacement. This means the displacement of the vessel with rig (weight of the water displaced) when the fuel and water tanks are half full.

**boatman61** · 13-03-2013, 13:38

Lets keep this simple.. ferget the crap 'sailors' are gonna come out with...
When you've filled yer bath... draw a line... when your in and settled... draw another line... the gap is how much water your body displaced.. same with boats..

Hope that cuts down on the armchair Googler's..

Get enuf boats they'll call it Global Warming

transformer · 13-03-2013, 13:47

Quote:

Originally Posted by boatman61

Lets keep this simple.. ferget the crap 'sailors' are gonna come out with...
When you've filled yer bath... draw a line... when your in and settled... draw another line... the gap is how much water your body displaced.. same with boats..

Hope that cuts down on the armchair Googler's..

Get enuf boats they'll call it Global Warming

...and you just invented the wheel. those previous posts were talking about agriculture.

**boatman61** · 13-03-2013, 13:59

Quote:

Originally Posted by transformer

...and you just invented the wheel. those previous posts were talking about agriculture.

Cheers mate... 2 outa 3 aint bad...

SkiprJohn · 13-03-2013, 14:30

So, with all the answers we've come up with maybe we should as the poster what answer he really wanted. Light displacement, displacement or volume? Maybe he was looking at an ad for a boat and it gave displacement and he wanted to know if that meant loaded or light displacement.

Eumelia · 13-03-2013, 14:41

Displacement = weight
Period

**boatman61** · 13-03-2013, 14:46

Quote:

Originally Posted by transformer

...and you just invented the wheel. those previous posts were talking about agriculture.

PS... I'm a Newbie and try to keep things within my limited inteligence level... sorry if I caused offense... just trying to help..

Tell me when to stop grovelling

clockwork orange · 13-03-2013, 16:08

When you design a boat it is typical to include tanks half full, the volume is calculated at the load waterline, LWL or designed waterline,DWL, (which are both the same thing) which is just a line drawn on the drawing but it is an important one as this is this is where all those numbers that sailors are so keen on looking up online are generated from, when you start adding all the crap everyone carries these days that waterline dissapears underwater and those numbers become meaningless. It is unfortunate that there is not an industry standard for publishing displacement, many marketting departments will publish the lightship displacement because it makes the boat look faster.

Steve.

sabray · 13-03-2013, 17:03

It's not weight it's displacement that confuses me. If I am in a tub of salt water do I displace less then I did when I was in fresh water. If yes then most women might be prefer to have a saltwater displacement then a true weight.
Never mind no women is going to tell you her displacement ever.