Air Lubrication Drag Reduction for Smaller Vessels

https://www.boatinternational.com/y...hon-lists-military-stealth-craft-ghost--28901

 

LOL...do you understand how big a "bubble" we are talking about here for a "Shkval"?

It 'flies' inside a fully submerged "bubble" about 20m long and 4m in diameter. The actual total area in contact with the water is about the twice the size of a human palm. It doesn't work on the surface...which would turn it into something like this....
(Edit: because I didn't look at all the links first...Portacruise for the Pop Sci article which had the illustration I googled to use.)

 

GHOST works with propulsion below the surface and without control issues or spiraling into the air like the second picture. But Ghost kind of underwhelming using 4,000 horsepower to speed along at only 30 knots? My guess is that even if there is a huge bubble for each 'torpedo', they don't maintain full air bubble coverage at such a low speed? I would think the ghost is too slow for the military work it was intended for, some conventional design racing boats go faster than that? Some conventional racers might possibly be tweeked to do Military Work requiring high speed?

 

Unlikely, real requirements are very different.
Old thread...
Military recon powerboat concept https://www.boatdesign.net/threads/military-recon-powerboat-concept.15137/#post-118574
New video...

 

Also noted on their website too:

Juliet Marine // http://www.julietmarine.com/

But I don't know what one of our designs is doing on their ticker tape of images!?

 

You should feel honored, John. ;-p

 

Typical "Go fast" boats have proven to be largely useless for most manned and unmanned naval/military applications for a multitude of reasons, the largest being the extreme motions in a seaway. Crews cannot function and are even injured, sensors degrade, weapon systems cannot be deployed, etc. The focus these days for most "smaller craft" platform designs is on stability.

 

Agree on the 'go fast' boat fallacy approach for defense. One article said the ghost was promoted and developed in response to the attack on the Cole, where many sailors died. Maybe this link shows a better way to go,

Air defense for $13 a shot? How lasers could revolutionize the way militaries counter enemy missiles and drones | CNN https://www.cnn.com/2024/03/13/europe/britain-air-defense-laser-dragonfire-intl-hnk-ml/index.html

 

Going back to air lubrication, I'd imagine the flat water model testing has been more successful than the real world because the planing surface in a flat water model, at a certain speed and loading will remain in the same place, but it moves around a lot in real boats/ real life.
However, with a landing craft style boat with a flat bottom, used in flat water (the only place you would want to use it)- I wonder whether there is a benefit and what testing people have conducted? I imagine a lot has been done on this as it's the place where you'd start- because a flat hull will tend to keep the air where its needed (underneath).

I've always wanted to build two otherwise identical landing craft type flat bottom hulls- one plain, but one with a curved slot just aft of the front of the planing area- effectively a false outer bow just in front of the existing bow. With shallow side walls at the edges of the planing area to keep the air from exiting until it gets to the transom. The idea wouldn't be to pump the air in under higher than atmospheric pressure, but to allow the forward motion of the boat to suck the slot empty of the water up to the surrounding waterline that would be in it at rest, then would it begin to suck air through like a larger version of self bailer on a racing dinghy that you can hear slurping air through once the boat is empty? If the front edge of the slot was a little below the main hull above it, I'd imagine it would create a low pressure area behind the slot exit that could empty the slot of water and could then begin sucking air.

I have attached a 30 second sketch on a post-it note!. WL is stationary WL, not planing obviously!