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-   -   To The Hydrofoil,Robin! (http://boards.straightdope.com/sdmb/showthread.php?t=799039)

swampspruce 07-21-2016 12:46 PM

To The Hydrofoil,Robin!
 
Before I fell asleep last night my mind was idle and thinking about the Bras D'Or, another of those curious Canadian innovations that seem to constantly fall to the wayside due to politics.It got me thinking about all the advantages of the design and wondered how big a ship could you actually lift out of the water using today's propulsion, modelling and materials technologies?

Could you build a fast freighter the size of a small container ship for example, or a cruise ship (say 50000 tons) version of the Concorde, nautically speaking? Most of what I could find online seems limited to around 200 tons , is that the upper limit?

Doubticus 07-21-2016 12:59 PM

I'm sure it would be possible, but I'm not sure if the economics of such a craft would work in its favor. I've always thought there could be a market for a large ground effect craft https://en.wikipedia.org/wiki/Ground...iet_Union_GEVs , but who knows if it could be made fuel efficient enough or safe enough.

engineer_comp_geek 07-21-2016 02:37 PM

You've got the USS Plainview, which was 310 tons, so 200 tons clearly isn't the limit.
https://en.wikipedia.org/wiki/USS_Pl...w_%28AGEH-1%29

You might be able to build a larger one, but it's definitely not going to be a practical ship.

Hydrofoils have a deeper draft, which would make a large hydrofoil impractical in many harbors.

Hydrofoils work best in calm water. Rough seas (where a lot of shipping goes) are even rougher in a hydrofoil.

Not only do you have the extra cost of the hydrofoil, but the hull of the ship has to be a lot stronger as well, as the hull has to support the entire weight of the ship on the hydrofoil spars under a variety of loading conditions. And then you need bigger engines and more fuel, which takes away from your cargo carrying capacity. Hydrofoils are good for making light, fast ships. They aren't so good for heavy ships.

Hail Ants 07-21-2016 06:31 PM

Quote:

Originally Posted by Doubticus (Post 19495220)
I'm sure it would be possible, but I'm not sure if the economics of such a craft would work in its favor. I've always thought there could be a market for a large ground effect craft https://en.wikipedia.org/wiki/Ground...iet_Union_GEVs , but who knows if it could be made fuel efficient enough or safe enough.

Here's some video of it 'flying'. It was known as The Caspian Sea Monster when it was first spotted by US reconnaissance in the late 60s. Although its supporters had high hopes for it, supposedly when Brezhnev was finally shown film of it he was wholly unimpressed and ordered it cancelled.

scr4 07-21-2016 08:34 PM

Boeing proposed the Pelican ground effect transport vehicle in the 90s. It was designed to take off from a normal runway and capable of flying normally up to 20,000 ft altitude, but optimized for flying at very low altitude in ground effect. It never got built.

swampspruce 07-22-2016 09:54 AM

Looking through the links, I kind of like the appearance of the Bartini Beriev VVA-14 without the wings. I looks like some kind of futuristic Marine landing craft....
I didn't realize that the ekranoplans got that large! 500 tons is a lot of mass to be hauling through the sky 20 ft off the ground.

ecg, the link here proposes that they would be able to operate at Sea State 7 and that's not exactly calm water and 1100 ton craft to boot! I understand they work better under calm water, but that doesn't mean they can't work out in the open ocean.

I see your point about more robust construction, but wouldn't that be mitigated by using composites, and ti alloys to lighten the load? Assume you have several billion dollars to allocate to r&d; what would be the maximum practical size that a hydrofoil boat could be made? There are lots of deep draft ships that never go to port like the big cruise liners, so I don't really see that as an issue in my mind.


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