Swath Hull Design

Unforgiven

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May 28, 2007
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Paging # juan, or anyone else who might know about these.

Have you heard anything about Swath hull boats? There are a couple out East I know and down in the States. I've been wondering if the effects are scalable and how effective the stabilization really is.

Any engineering buff care to put the thinkers on this thing?
 

#juan

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Aug 30, 2005
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I wish I could tell you something useful but my knowledge on this subject is very limited. I saw a picture a few years ago of a fairly large Swath design cat that was reportedly going 30 knots. The strange thing about it was that it was doing that speed without a deck angle of 45 or 50 degrees. It wasn't level by any means, but both hulls were in the water.
 

Unforgiven

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I like the thought of it and from what I've seen it's amazingly comfortable in ride, even in bigger seas. I saw a 60 footer for sale but I don't know if the extra expence would be worth it. The US military has one that does 60 knots.
 

#juan

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I've just done a bit of reading on the subject and it seems that SWATH designs are scalable in so far as the testing of several fairly large ship designs was carried out using small scale models. What is interesting is that these designs reduce not only resistance through the water but also reduce wave production. One of the things that helped kill the B.C. Ferry corp, "Fast Ferries" was the land erosion caused by the large waves produced by these boats. Here is a link that you have probably already seen. I found it very interesting.
http://www.rti.com/products/data_distribution/documents/LMCO_SeaSLICE.pdf
 

L Gilbert

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Nov 30, 2006
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That's kinda similar to the boats that start out with the hull entirely in the water and then as speed gets up the hull raises out of the water so the boat is riding on planes. Whatever happened to those boats? Think I read somewhere they had been clocked at over 40 knots.
 

#juan

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That's kinda similar to the boats that start out with the hull entirely in the water and then as speed gets up the hull raises out of the water so the boat is riding on planes. Whatever happened to those boats? Think I read somewhere they had been clocked at over 40 knots.

You are no doubt thinking of hydrofoils. Hydrofoil craft are probably not suited to B.C. coastal waters because of the piggish habits of our forrest industry, There are so many logs and deadheads in the water it is dangerous. I have seen a couple fiberglass boats get their bottom ripped off by running over a ten ton log at high speed.
 

Unforgiven

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May 28, 2007
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Hey thanks for the link #juan. I have been looking that over actually.

Swath hull isn't quite the same as a hydrofoil as the swath hull rides below the surface where all the turmoil is. They can also have the ballast pumped out so they ride up on the surface and provide a very shallow draft. Nice for the Caribbean moorings.

Blue water passage isn't a problem with them either if you can manage the fuel. I wonder if using a gas generator to power electric engines would be feasible in the 60 foot range?
 

Unforgiven

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SWATH was invented by a Canadian I believe, but the idea never caught on in Canada. See wikipedia

Oh yeah I read up on that. Sad story really. The inventor went from millionaire to pauper over this design. There was just a documentary on this subject and the way he ended up was quite tragic.
 

#juan

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Aug 30, 2005
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Hey thanks for the link #juan. I have been looking that over actually.

Swath hull isn't quite the same as a hydrofoil as the swath hull rides below the surface where all the turmoil is. They can also have the ballast pumped out so they ride up on the surface and provide a very shallow draft. Nice for the Caribbean moorings.

Blue water passage isn't a problem with them either if you can manage the fuel. I wonder if using a gas generator to power electric engines would be feasible in the 60 foot range?

I've always been a bit uncomfortable with gas engines on boats but it could be done. Have you any idea how much power you might be needing? I assume the power requirements would be something less than a planing hull of the same length. One problem with gas/electric or diesel/electric is the efficiency drop going from gas power to electrical, and then powering electric motors, but it would likely be cheaper than a specialized right angle gearboxes to drive the propellers. I don't know if you can buy something like that off the shelf or not but I'm sure they would be costly.
I'd like to see someone try this on a smaller boat because with the fuel cost at the moment, it is very close to ruling out motor boating for any but the very rich. My last boat could hit 30 knots at a cost of thirty gallons of gas per hour. Takes the fun right out of it.:roll::smile:
 

Adamentum

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Feb 10, 2009
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Kilo Moana

It a science research vessel owned by the US Navy and currently being used for scientific research by the University of Hawaii. It uses SWATH technology which provides a crazy stable platform while out at sea. Google the vessle and you can see detailed schematics of the vessel. I am interested in the application of SWATH TECH for tourism ventures. A stable platform such as this would make sailing more accessable. The largest vessel in the world that currently uses SWATH is the Raddison for one of their cruise ships.
 

CanadianLove

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Feb 7, 2009
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I have not knowingly seen a vessel of this exact design myself, but have seen a very nice spin off of in (although not in action).

Back in the 1990's there was a guy at the Kingston, Ont. drydock building a sailboat to sail around the World. He worked their to pay for his space and extra money. He was building it with two keels rather than one off the single hull. On the ends of the keel fins, which ran a good length of the hull, where the pontoons. I think he figured a 20-25% increase in speed due to the additional lift, but don't quote me on that it was a long time ago. The sailing vessel itself was a good 100' steel hull I believe.