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Old 02-01-2014, 07:52 PM   #1
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SWATH to SWASH

Sigh...would be an interesting platform to play with...

SWATH - Small Waterplane Area Twin Hull
SWASH - Small Waterplane Area Single Hull


http://www.bluebird-electric.net/SWA...ingle_Hull.htm
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“One of the main restrictions on building smaller Swaths was the difficulty of access and the space available for the engines that are located in the underwater torpedo shaped hulls,” said Nils Olschner of A & R, “So with this new concept we have taken one of the underwater Swath hull units and added slim side hulls or stabilisers. The result is a design that we hope will have all the benefits of the Swath and allow smaller sizes for which we see a considerable demand”.

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Old 02-04-2014, 06:39 AM   #2
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North Sea, last September on the way from Borkum Island (DE) to Lauwersoog (NL).

The “World Passat” changed course and has come closer to look at us! Why? This happens occasionaly, as an Austrian Trawler is not a common sight on the North Sea. A very good thing about these vessels is, that they do not make a big wake when overtaking with +20 Knots.
Our fleet of SWATH vessels. Offshore support, offshore rescue, standby and maintenance vessels

The second picture shows an “ordinary” vessel with a catamaran hull. The “Bayard 4” crossed our course the same day.
Fred. Olsen Windcarrier | Bayard class

Karl
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Old 12-18-2014, 09:52 PM   #3
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Found this SWATH vs monohull video today;

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Old 12-18-2014, 10:04 PM   #4
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You can charter this luxury version "Silver Cloud".
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Old 12-18-2014, 10:45 PM   #5
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Pretty amazing how much less affected by sea conditions the SWATH hull(s) are. Sail catamarans have been known to flip over, but if the torque of the mast/sail is removed, and a bunch of engine ballast is added, chances are this design could be pretty stable.
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Old 12-19-2014, 12:38 AM   #6
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Ah yes, SWATHs. I remember them!!! I ran a small 38' SWATH boat as a video platform for the '95 America's Cup in San Diego. It was magic when at speed (~16 kts), as all it's dynamic stability systems (interceptors, foils, water ballast, etc.) had significant dynamic pressure to work with. At speeds less than ~8 kts, it was an absolute dog, having very little transverse and fore-and-aft stability, due to the self-same small waterplane that makes SWATHs such able platforms within their (very) narrow design envelopes.

For example, underway at slow speed, a person walking forward would require immediate re-ballasting to compensate. Given I couldn't pump water fast enough, she would inevitably dip her bows, allowing green water to flood the walkway on whatever side that person walked upon. Ditto when walking aft. If the crew stayed put, all was well, at least in the benign sea states I worked in.

Fortunately, I had an engineer that was a little, tiny, skinny guy that could crawl down into the submerged hulls for engine service. Me, I could SEE the engines, I could (with difficulty) TOUCH the tops of the engines, but no way, no how, could I work on them.

I also worked at the Naval Undersea Center, when one of the 1st SWATH ships (KAIMALINO) was built by the Navy for evaluation. With two gas turbines on deck, driving the propellers via daisy-chained chain drives down the aft legs of the hulls, the noise underway was truly epic! Again, magic when operated in her very narrow range of speed and load parameters, but ultimately unsuccessful as a general work platform.

Be careful when you think of "stability" and "SWATH" in the same moment. They act much more like aircraft than ships. As with aircraft, when they're out of their operating envelope, with little dynamic pressure available to augment stability, they behave more like bricks.

Regards,

Pete
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Old 12-19-2014, 01:26 AM   #7
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Quote:
Originally Posted by jungpeter View Post
Ah yes, SWATHs. I remember them!!! I ran a small 38' SWATH boat as a video platform for the '95 America's Cup in San Diego....
Check out the SWASH link above...it's what one company found to work better with "smaller" vessels.
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