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Comment by mk_stjames | Hacker News Reader

For the one design, a supercavitating foil is mentioned. There have been torpedoes that use supercavitation sustained by onboard gas-generators feeding strategically located ports on the skin.

But that begs the question- would that type of cavitation induction be considered 'cheating' in the sense of being used on a sailboat that is supposed to be solely powered by the wind? The gas bubbles wouldn't be providing thrust, but a stored bottle of gas or electric pumps or any other stored energy device is just that....

The line between what tech gets used and what isn't allowed in these completely unsanctioned 'record attempts' is interesting to ponder.

In this case, it seems they are using a passive system (it is possible to get a foil to supercavitate without extra powered manipulation).

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A number of offshore records don’t allow the use of stored power not generated by a human. It’s common to see electric winches and hydraulic controls on 100 footers, with the diesel running the whole race to power the winches and hydraulics, saves on bodies. However the 100 footers designed to beat ocean records have more people and more winches as they must be entirely human powered.

See Comanche. After she broke a bunch of records her winches and grinding pedestals got pulled and hydraulics installed.

A lot of large ships use air lubrication systems to reduce fuel use, it's typically a system of compressors connected to ports with lots of tiny holes at the bottom of the hull. As I understand it, it reduces effective wetted area and thus surface tension drag.

So if you used a wind turbine to drive the compressor then it's fair game I guess? Maybe that makes it more of a windmill ship than a sailboat though.

You could just have a dude on an exercise bike powering the compressor too. A well-conditioned athlete can sustain 300 watts, which is 0.4 HP, or enough to drive something like 2.5 cfm?

Some AC75 designs (The British one I believe), used cyclists as their grinders, to drive the onboard hydraulics.

Depends on the competition. The 2024 RRS disallow hull lubricant, but as you said, this is an unsanctioned record attempt.

If the pressure on the upper surface of the foil is below atmospheric, this could be used to suck air down a tube. I have no idea if this is feasible, or would be useful if it were.

I wonder if they are going fast enough for ram-induction to generate the pressures needed?

You could always generate the power for the compression using wind.

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