MPG chart.

[jvitiel]

So I was thinking - If high salinity increases buoyancy, does that improve fuel economy?...

[Destroyer]

Originally Posted by jvitiel

So I was thinking - If high salinity increases buoyancy, does that improve fuel economy?...

I have no idea,
BUT...
Anything that will reduce the amount of friction between the hull and the water as the hull passes thru it will increase either the fuel economy or the speed (in the case of a sailboat) That's why sailboats (Especially racing ones) use special coatings on their hulls to reduce friction.

So that being said... if we postulate that higher salinity increases buoyancy then it should stand to reason that there would be a lessening amount of friction on the hull, which should result in better fuel economy. But since a hull's density is a lot different than human tissue (that is primarily water anyways) I question how much the effect of higher salinity on fuel economy would actually be.

[jvitiel]

Agreed. There is probably no practical difference or even anything that the typical boater could measure (though I bet NASA could measure it).

I'm guessing that the difference in efficiency would be most apparent in a displacement hull or at least when a planing hull is not on plane. The boat would sit higher in the water and therefore have less to push out of its way. Somewhat similar to decreasing the rolling resistance of a tire by inflating it more.

Still, a mitigating factor could be that the smaller volume of water that has to be pushed out of the way would also require more energy to move due to its added density. Who knows.

Truly a topic that I wouldn't give a second thought to if my boat wasn't stuck under a tarp... :-)