Plimsoll line for yachts ?

[rickwat]

Does the payload for yachts vary much in hot climates or is it just for ships where the cargo is heavier in relation to the vessel ?

Thanks in advance for any replies.

Rick

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[aph]

Nothing to do with temperature. Draft increases in fresh water. On a large ship FWA (fresh water allowance) is on the draft marks and allows more cargo to be loaded say in a river. On a yacht its of no significance.

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[Guest]

In further response to the query regarding “Plimsole lines” I’m afraid it is not quite as simple as APH suggests. The original query regarded temperature, this can be considered in two ways. Firstly, water temperature does have an effect on a vessels draft for any given displacement, this however is very small indeed and would only be considered by the most pedantic of cargo/draft surveyors when assessing the amount of cargo on board a vessel prior to or on completion of cargo operations. The other area where temperature can come into the equation is by putting temperature into the mixing bowl of weather generally and from this we move onto seasons and zones of operation.

The Plimsole Line, the circle with the horizontal line through it, is equal to the minimum permissible freeboard that the vessel can load to so that it can operate in the summertime in non tropical waters and in salt water RD 1.025. From this line there may be calculated numerous variations that the vessel can load to depending on where it is trading to, from or through; the time of year; the nature of it’s cargo (timber) and as mentioned by APH the density of the water. All the variations that are applicable to any particular vessel are indicated by the vertical line with various horizontal lines marked on the ships side just forward of the Plimsole line. These will be identified by such lettering as WNA (winter north atlantic), F (fresh) TF (tropical fresh) to name a few and all of which can be prefixed with L for vessels in the timber trade. It is the distance between S and F that is the FWA referred to by APH.


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[AndrewB]

No, but ...

... don't let that stop you painting one on the side of the yacht, just to impress the wanabees!

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[heerenleed]

Frresh water makes a lot of difference

Fresh water does make a lot of difference, also for yachts. As for many Dutch yachts, we are on a permanent fresh water mooring, but do most of our week end sailing and all of our holiday sailing in sea water. When our boat is heavily loaded she tends to sink through her water line in fresh water and loses speed measurably. We do not bothger too much, as the distance through fresh water to sea water is short. But as soon as we reach sea water she speeds up with half a knot in normal (F4-5) conditions.
If your conclusion is, that a cargo ship can carry more load on a river, then this may only be because the water is more sheltered. Sea water is heavier than fresh water, therefore a boat sinks deeper into fresh water than into sea water.

<hr width=100% size=1>Peter a/b SV Heerenleed, Steenbergen, Netherlands

 

[aph]

Re: Fresh water makes a lot of difference

I am surprised you notice the difference. Having traversed a lot of canals throughout the years I didnt notice much difference but we only displace 12 tons. 40000 ton bulk carrier has a FWA allowance of around 18 inches so a yacht maybe sinks an inch or so. As for loading........... a ship loads in a river to her her fw marks (or somewhere in between depending on density) so that she is at regulatory freeboard when reaching open water. If ship loaded to SW marks in a river there would be a shortfall in cargo. (and revenue)

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[heerenleed]

Re: Fresh water makes a lot of difference

As you say, the difference is not that much, only an inch and a half approx.
But this is quite sufficient to affect the sailing performance.


<hr width=100% size=1>Peter a/b SV Heerenleed, Steenbergen, Netherlands