Originally Posted by Pblais
.... In the extreme example comes the answer. It all depends on how much of the above and below the water
is exposed vs the mass of the boat.....
Mass of the boat is a factor, but I think the area exposed under the water
to catch the current
vs. above the water in the wind
is most significant. Another extreme example:
River rafters in my area run into this situation frequently. Often a very strong afternoon wind
blows upsteam. A river raft (even heavily loaded) tends to have a big area exposed above the water, but draws only a few inches below the water. In many cases the wind is strong enough that one needs to row hard
downstream to make any progress at all. This has important safety
implications if someone falls in. A swimmer has much less mass than the raft, but only a small area exposed above the water in the wind. Most of the person is below the water and pushed by the current
. It can be impossible to rescue
a swimmer in these conditions because they will be carried down stream much faster than the raft can travel even when being rowed hard.
Bottom line is that it is a contest between the area below the water being pushed by the current vs. the area above the water being pushed by the wind. Thus very different for each vessel. From experience one could no doubt come up with a rule
of thumb for an individual boat or class of boats ("a Catalina 30
will do thus and thus..."), but I would be very skeptical
of any general rule
of thumb that claims to be even approximately correct for all boats.