What defines an Expedition Yacht?

I am glad you mentioned she has some control over her draft which could very well put her back on my short list.

How much do you think she could raise herself to reduce her draft for docking or anchoring in shallower water?

But it is butt ugly...

Her optimum draft for stability during cruise is 13 feet 5.4 inches

Her minimum draft for mooring (torpedos reaching the surface) is 11 feet 5.76 inches.

Still a lot, but almost in the normal range of large yachts of her volume.
The standard 180 ft power displacement yacht has around 11 feet draft.

This little drawing explains the concept of her stability in the waves.

The easiest way to understand her principle, is to compare it with a submarine, perfectly balanced on periscope depths. In our case there are only two submarines with two airfoil shaped struts each, instead of a tower combined with a bridge deck and superstructure. That explains the fact, that a SWATH has no excess buoyancy, in only must have the buoyancy needed for the optimum draft. All buoyancy has to come from the torpedos and the struts.

So, if fuel is used up and potable water is being used, the skipper has to compensate for that loss of weight by pumping ballast water in. On Sea Cloud that is done by pushbutton control. Plus the 4 stabilizing fins work for roll and pitch.

Will say, during cruise, her draft has to be as such, that her torpedos are below the waves. The wetted surfaces of those 4 struts are so small, that the whole ship is almost not affected by the waves. The rest is done by the stabs.

Small waterplane area twin hull

It is interesting... that the resistance to Brian's cat multihull suggestions have disappeared when they are submerged...

I have to admit... just love those machinery spaces in the submerged part... very submarine like... which if you have followed my posts this is a favorite with me... and sort of makes the whole submerged torpedo / submarine pod into a POD DRIVE... see the diesel electric thread we have been hashing that over... this is like a big pod... and somehow that solves the problem as everything then becomes very conventional... interesting. Best of all worlds... cake and eating it and even seconds all without guilt.

http://www.yachtforums.com/forums/technical-discussion/2229-diesel-electric-propulsion-11.html

Someone mentioned more than 2 pods / torpedos / submarines somewhere... wonder about 3 or 4 rather than just 2... ???

No one has much liked my "SWATH" mono-hull deal... is just totally ignored! I suppose it does have some technical issues to solve...

The question I have is that could the beam of the cat SWATH be reduced into something that would be acceptable in a tony marina, and still predominately work... just wondering about beam to length ratios I suppose?

The issue is that the swath concept only works if there is no reserve buoyancy. Almost all the buoyant force is located in the pod (the COB being the exact center of the round pod). That means that the center of mass needs to be below the cob if it's a single pod, and that is difficult. Even a tiny deck is going to have a huge lever arm advantage over any internal ballast, and you need a lot of said internal ballast. At that point you've just got a semi-submersible, why not just go full submarine?

The SWATH uses the stability boost off the multihull configuration to put your living spaces up where they can be used to see. A monohull could not copy that without coming so close to the surface that wave action would kick back up.

Monoswath

Here gentleman is the Abeking & Rasmussen Monoswath. The prototype of 20 by 12 m is under construction at A&R. It is a commercial application. I do not know any more details. Looks unconventional, to be friendly spoken.

WOW... and they are building a prototype!

Guess I am not going to be filing any patents...

This is almost exactly what I was thinking...

The center pod would have the machinery, storage and maybe crew spaces... maybe viewing windows underwater too... prove very interesting

It could be very simple with a single prop out back and use a combination of vertical and horizontal fins for steering with some on the side mini pods for transverse stability.

I even thought of having the side pods mounted off horizontal wings off the mono hull. Then the above water yacht would be much like a standard yacht and be more familiar and arranged more conventionally like a yacht than a floating house.

Maybe I need to get Tom Perkins to fund the development of a prototype... and leech off that ground breaking experience... with his underwater submersible and technical interests he might be game.

There is no reason the center pod has to be circular in cross section... might be better to be flat bottom triangular is section!

Circular reduces the weted surface, and also provides a stronger shape, thus requiring comparatively less reinforcement. It also allows the water to flow around it with the least resistance. I'm not sure where the benefits from any other shape would come, other than perhaps a bit less affinity for rolling compared to the waves (which could be a bad thing).

Also, I'd consider this a trimaran if the outer struts touch the water, which I'm quite sure they would do.

Monoswath

Here are a few more details of this Monoswath. I think, Opcn is correct. It is more a trimaran with a center buoyancy body of SWATH design. A design, one has to get used to.

The pictures are press releases of A&R, so, no industrional espionage.

SWATH Comparison1 - YouTube

Silver Cloud running video.

I am so excited about the SWASH... mono hull swath

Concept video
SWASH by Abeking & Rasmussen - YouTube

Actual finished ship running level and true in ocean
Late March 2013
SWASH@A&R "EXPLORER" - YouTube
Early April 2013
PILOT EXPLORER - YouTube

Operating as pilot boat on river I think these are the first trials as it seems not to have enough aft horizontal fin area
Late February 2013
EXPLORER - YouTube
EXPLORER - YouTube

I can see a longer version with the same beam being even better. I think the outrigger verticals could be made much shorter if the horizontal fin area were increased and torpedo pods used small diameter but going forward from a aft of ship mounted outrigger and the horizontal fins at the aft end...
This could be enough like a normal monohull yacht it would not be too noticeable. In fact it could look a lot like a standard motor yacht above the water line... with a large central pod... maybe the yacht part could be composite of aluminum and in marina the pod submerges more and you could hardly tell... needs really deep berth but us snail boat guys already know about that.

This thread should probably be split into two threads as well. The swatch info is very interesting, but not really inline with the expedition yacht thread.

!

I disagree... the SWATH yacht built by A&R was built specifically for use as an explorer / expedition yacht... and likely the best yacht ever built for that use because of the SWATH design.

Its just real hard to imagine something like a submerged cat or pontoon boat being the ideal...

Just like it will be hard to accept a SWASH on the Riviera... but it will happen and likely take over... as more landlubbers get into yachting !

Hi,

Well put.

The SC Team went to some great places in less than great conditions many were far away from the normal Riviera Cruising spots so Kudos to the Owner, A & R and the team that took it to the extremes and back again.

The fact that SWATH (and SWASH) technology makes for a great expedition yacht doesn't mean that listing all the characteristics and hypothesising about the future is particularly relevant to the question of 'What defines an expedition yacht?'. It's around topic for sure, but not on topic. I think a thread split is in order. It's not as if the SWATH topic will die in its own thread, it will just get to be what it wants to be.

I actually do NOT think the lastest America's Cup will do much for the advancement of multihulls nor sailing. The foiling aspects, and the wing-rigs, are just not that transferable/translatable to ocean sailing.

I think those great big French multihulls racing around the world thru all sorts of open ocean conditions, include the roaring 40's are the real goal setters.....and those Volvo monohulls doing the same.

Swath design and expedition yacht

For the pleasure / expedition, the commercial and the military applications, the SWATH design were taken for common reasons. For their extraordinary seaworthyness and their special stable behavior in the waves. The conceptually higher draft and the wider beam based on its multihull design is IMO not a disadvantage. As a pay off, you will get enormous deckspace and internal volume. The only problem a large SWATH will have during a cruise, is entering small and shallow harbours. But I believe, med type mooring in Portofino is not the prefered goal for her owner. He will have other destinations. Large monohulls with comparable volume will have trouble finding a mooring position too. The external design may need more effort to create a beauty and the issues as far as weight control is concerned, will need more emphasys on the naval architecture part. But under the bottom line, the SWATH concept is one of the most ideal designs for an expedition yacht, an explorer yacht or just a yacht for the motion sickness sensitive owner or passenger or even the nervous helicopter pilot who is afraid of an unstable landing spot.

Below examples of commercial and military SWATH designs with obviously no emphasys on beauty (form follows function). Please do not blame A&R for the design of that military vessel. The third vessel is the military research vessel Planet, it even has real torpedo tubes in its buoyancy bodys.

REDEFINING THE EXPEDITION EXPLORER YACHT

No Opcn... I am not posting this just to aggravate you...anyway, up early cannot sleep so might as well get up... and cannot stop thinking about this new idea.

The SWASH just does not lend itself to convention thought on "style" but then something styled like the Wally Why... is made for the SWASH setup... and it really would be pretty decent looking... but the Why deal would have to be shrunk down to a reasonable size... and maybe a little less beam in proportion.

Make the "WHY" for the upper or super structure out of sandwich composite and have the submarine pods bolt on like keels and make them out of some kind of metal... steel or aluminum... with the big pod the center on and two small pods with controlled balancing fins. I think being a submerged structure steel might be the best and cheapest choice... or basically just the A&R setup would be perfect but with the Wally Why styled superstructure... it really works... beginning to get real excited about this whole new definition of an explorer style.

Anyway my really big idea is the forward nose of the center pod could be either a fiberglass nose cone like nuclear subs... but WHY not make it a clear bubble observation area... wow... the perfect explorer / expedition yacht.

Really neat for watching the sea life and exploring... the ideas are finally gelling...

And, it could be a motor sailer... actually perfect for that... naturally is very stable and already has a bulb keel.

Not the least of it... it would wow them on the Riviera... !

I was reading on the A&R SWASH and somewhere it refers to class society required the side vertical 'pods'... wonder what that is about? But it is perfect with the WHY concept.

I'm not annoyed by it at all. I think it's fantastic and think that the conversation should go on. I just think the thread should be split, not that either conversation should slow down.

The problem with a clear bubble for the bulb keel is that that is probably the most vulnerable part of the whole boat, so a big acrylic dome is going to be an additional risk for sinking the ship. Building a few watertight bulkheads in is a start, but in general I'm not in love with the notion of a lot of glass under the water on a boat. Smaller is better I think.