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Old 28-08-2009, 21:01   #16
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sorry that link, is www.austal.com
state of the art shipbuilding
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Old 28-08-2009, 21:04   #17
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le sigh,

None of the three earthrace hulls have flat bottoms. Check this video link at 1:15.



Also, I never said your boat actually did plane. I said it is likely that it is generating lift and raising the stern.

Please explain triflection.
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Old 28-08-2009, 21:32   #18
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A good article from the late Malcolm Tennant on hull shapes

Catamaran Comparisons by Malcolm Tennant

Talks about the "earthrace" Craig Loomes hulls and Gold Coast Catamarans.
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Old 28-08-2009, 21:37   #19
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Quote:
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sorry that link, is www.austal.com
state of the art shipbuilding
Very much like White Rabbit
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Old 28-08-2009, 22:01   #20
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Woods Designs Sailing Catamarans
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Old 30-08-2009, 21:32   #21
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further information.
Built in Aluminium
39ft X 8 ft will fit inside a 40 ft shipping container
Oceanic lateen sail for low cost downwind cruising.
Motors 2 X 30 hp Honda outboards to be upgraded to 2x90 hp for 20 knots plus.
Narrow entry non planing/ fast displacement hull, shallow draft (9 inches)
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Old 30-08-2009, 22:15   #22
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how much weight are the outriggers supporting on flat water?
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Old 31-08-2009, 00:50   #23
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I have never checked the actual % of weight supported by the outriggers but unlike sailing trimarans both outriggers are in the water at all times.(bow down) (necessary)

There is at all times a NEGATIVE angle of attack, ie. the bottom of the boat is flat but tilted forward and the bow is always the deepest part of the boat in the water when underway. (1-1.5 ft, deep)
The wide stern just touches the water.
This does create a degree of bow steering, which was an initial concern with the prototypes (Five 15 ft prototypes have been built)
This has also been a problem with some of the multhull fast displacement ferries (from personal experience)
This is where I found that using a Trimaran configuration was preferable to a mono or catamaran design plus the addition of a decent rudder or stern keel.(daggerboard)

Aft of midway along the hull, under way, if you throw ash (or other floating material) on the water the ash is sucked under the hull.

Initially there is a stern wake but once the boat reaches speed, the stern wave flattens out, and there is little or no wake with little or no interference with other boats in the vicinity.

Driving straight into the waves (90 degress) is its best point underway, there is little or no lifting to waves (in moderate seas) and no hobby horsing which is very common with fine hulled catamarans.
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Old 31-08-2009, 01:23   #24
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Well, discovering how much the outriggers are carrying isnt too hard (since they are not curved). Measure the draft, multiply that by the surface area of the bottom, multiply again by the weight of water per unit by whatever unit area you're using (make sure you are consistant). I'm interested to know this.
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