Air Lubrication for Ships

OK well, given that there’s apparently little left to say in the field of AWE this week, and with kite-ships seemingly a forgotten topic in the face of Magnus/Flettner rotors, Sharp rotors, rigid sails, etc., I figured I’d mention a fuel-saving concept that seems to be catching on, having been installed on many ships at this point.
What is Air Lubrication? - Silverstream Technologies (
The company claims 5% - 10% fuel savings, OR they say you can just go faster using the same amount of fuel. My question then was, if you are going faster, using the same amount of fuel, doesn’t that mean you’ll arrive at the destination sooner, thereby STILL saving fuel?

They say you can immediately see the fuel savings the moment you turn on the air, as the ship goes faster while putting less load on the propeller. But I wonder if the air injection apparatus might cause some drag itself, so sure, after it is installed, you almost HAVE to run it cuz now, unless you run the air-injection system, your fuel use would be MORE than if you had never installed it? You notice they don’t compare against an identical ship with no injection system installed. They only compare the ship with itself, AFTER the system is installed, and only compare that ship with the system running or not running, and also conveniently forget to mention how much power it USES, and where that power comes from…

Now don’t get me wrong, I’m not totally doubting whether the air bubbles might help the ship along by reducing skin friction over the wetted area. This concept has been discussed for several years that I can remember. But when I see “5% - 10%”, I’m thinking the real number they’re hoping for is the 5% figure, and maybe even THAT is a high estimate? Plus, as with Flettner/Savonius spinning sails, we know it would TAKE some power to run the air injection system, right? So maybe the ship goes a little faster, but you’re having to add power to accomplish that… They don’t mention how much… Anyway, this Silverstream system seems to have many ships using it.

Whether it saves fuel or not, the ships are enjoying some financial benefits by the mere appearance of “saving fuel”. And I suppose someone like JoeF could once again try to redefine the word “kite” sufficiently that a ship using air lubrication “is really” “a kite” - I guess the propeller could be “the tether”, and it’s floating on air, so - kitepower! Anyway, sorry to take it into the land of mental derangement, but back down to Earth here - it’s supposedly way beyond “experimental” and being run and installed on a lot of ships. So let’s place it in the same basket as kite-ships, Magnus/Flettner rotor-sails, rigid sails, and, well, I guess nobody is using regular cloth sails of any kind. I wonder why? I mean, if someone wants to use sails to help a ship save fuel, what’s wrong with just using sails for sails?

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