Swath ???

[Matt.D]

Question... What happens with this boat when it hits a green wave of more then 1500mm, besides everyone being flung to the front of the boat?

[sabahcat]

A bit more than 1.5m?






http://www.theyachtmarket.com/boatIm...26logview%3dno

[Matt.D]

Not once its submerged.

[sabahcat]

Originally Posted by Matt.D

Not once its submerged.

Looking at the second picture
It looks that there is about 2 metres between the waterline and bridgedeck panel

I would imagine, that when it hits a wave, it would tend to cut through the wave until buoyancy takes over and gently lifts
http://www.swath.com/concept.htm



Nice bit of movie here
http://www.yachtsilvercloud.com/SSC/movies1.htm

Which would you rather be on? (not saying the above vessel performs the same way)

[Matt.D]

Yes true on the pics that youve attached, but on the pic i posted it has exposed crossmembers under wing deck and the super structure is shaped to dive down not up! with no reserve buoyancy. If google it there is a pic of a lady sitting on the pontoon while it is partly submerged and unless she is abnormaly talk its looks less then 2m.

[Ad Hoc]

In a short crested and irregular sea, she will slam. But so what?
What is really the issue, is the heave and pitch and vertical acceleration, ie its motions. The wet deck clearance is just a local slamming occurance issue, noisey and if heavy can make the ride "feel" uncomfortable. However, in following seas, can be prone to deck diving. The stern is wide, like a normal multihull catamaran (ie large WPA), thus, in following seas i would be very worried.

[Matt.D]

Yes i agree, i would be inclined to build in some wave dampering under the wing deck.
The other question will this design in a 50 or 60' make for a safe passage maker or does the exsesive drag of the hulls being submearged make it too Inefficient and would it work with a sail?

[Ad Hoc]

Originally Posted by Matt.D

The other question will this design in a 50 or 60' make for a safe passage maker or does the exsesive drag of the hulls being submearged make it too Inefficient and would it work with a sail?

Define ....safe passage maker?

If this boat can get from A to B, will all those onboard, safe and dry shod...then yes.

Everyones definition of "safe" and "safe passage maker" is different. Except from a purely legisative/technical point of view. Thus, it is subjective and anyone can have their own definition, above that which I've just noted.

Being submerged has nowt to do with. If the hulls were not submerged, you'd be in an aeroplane, not a boat, and all hulls have drag

[HReeve]

The original vessel in this thread is NOT a SWATH.

A SWATH has the hulls under the water, with reduced waterplane at the design waterline.

There are variants with either single or multiple vertical struts connecting the demihulls to the main deck. The struts are designed for minimal waterplane to reduce heave response, and shaped for resistance considerations. Certainly the aft most strut in the vessel pictured is not designed to be submerged.

SWATHS have more wetted surface area than traditional multihulls of comparable displacement, so yes, there is added resistance due to that. But if designed well, they make up for it with reduced wave making resistance (plus reduced motions). In practice, most SWATHS have active ride control by way of controllable horizontal fins forward and inboard of the hulls.

[CatBuilder]

I was thinking the same thing for a minute, Henry.

It is a SWATH though. Look at how low it sits in the water in other pictures. It appears to have a water ballast to drop it down to "SWATH mode" from "tall catamaran mode."

[rambat]

Hello,

I developed a more stylistic design for this inventors SWATH hull. What is not noted in the pictures is this design has the ability to fullly submerge the hulls AND de-water to allow catamaran speed and performance. It really is a most versatile yacht and we had great response from the more styled design which was covered in 2008? in Multihull, Yacht international and others.

We received immediate deposits but it was the old story about a inventor guy not familiar with the high cost of custom yacht building. I told him his idea of building it to any client other than himself for less that $800 K was a non-starter, he unfortunately never understood. Something new and proven like this is not required to be cost competitive with standard production yachts. It never went anywhere but I am interested in reviving my "yacht version" design if anyone is interested.

[tom28571]

Not my area of knowledge but, I don't see what the open area between struts add to the design. Looks like more drag than less than if there were a continuous hull on each side. There would be huge gain in reserve buoyancy also which would dampen plunging tendencies. Anybody know why the struts are separated?

To get that straight,

there was not ONE SWATH shown in the pictures, except those copied by Sabahcat.

The others are cats. In these cases inefficient cats.

To the Op´s question. A 50 or 60 ft SWATH is a joke, and will need approx 150 to 180% more power than a mono of equivalent displacement.

Regards
Richard

To get that straight,

there was not ONE SWATH shown in the pictures, except those copied by Sabahcat.

The others are cats. In these cases very inefficient cats. Ships do not "become" a SWATH when a cat hull is submerged. That is a completely different pot of fish.

To the Op´s question. A 50 or 60 ft SWATH is a joke, and will need approx 150 to 180% more power than a mono of equivalent displacement.

Regards
Richard

[cthippo]

These are the navy's (relatively) new SWATH SURTASS ships. The concept seems to work well, but there are concerns about the ability to drydock larger SWATH designs.