Water ballast revisited
Jim Pope did a good job of explaining the way water ballast affects a
sailing vessel, and it's advantages over, say lead.
One important thing to keep in mind when talking about water as ballast
is that it needs to be contained in some form of tank and as low in the
hull as possible. Otherwise it sloshes up the side of the hull as the
boat rolls. The boat may sit lower then without the water, but without
a containment tank it will sit low in any attitude.
Earlier I noted water's lower specific gravity then lead or steel,
meaning that to accomplish the same amount of ballasting you need to
use more water, a lot more than compared to lead. If ballast is to be
carried internally and space is at a premium then lead will take up
significantly less room for the same effect. If the ballast is carried
externally then the problem is a trade off of the increased wetted
surface area of a large external water chamber, say an open keel, or
the smaller surface area of a lead fin.
Both are equally effective at creating ballast, but not space
efficiency. And as Jim pointed out, in a boat meant to be stored on a
trailer the water ballast makes the job of getting the boat out much
easier.
Peter
sailing vessel, and it's advantages over, say lead.
One important thing to keep in mind when talking about water as ballast
is that it needs to be contained in some form of tank and as low in the
hull as possible. Otherwise it sloshes up the side of the hull as the
boat rolls. The boat may sit lower then without the water, but without
a containment tank it will sit low in any attitude.
Earlier I noted water's lower specific gravity then lead or steel,
meaning that to accomplish the same amount of ballasting you need to
use more water, a lot more than compared to lead. If ballast is to be
carried internally and space is at a premium then lead will take up
significantly less room for the same effect. If the ballast is carried
externally then the problem is a trade off of the increased wetted
surface area of a large external water chamber, say an open keel, or
the smaller surface area of a lead fin.
Both are equally effective at creating ballast, but not space
efficiency. And as Jim pointed out, in a boat meant to be stored on a
trailer the water ballast makes the job of getting the boat out much
easier.
Peter