Semi-submersible Sailing vessel Ohanda One

[Ohanda Jay]

15, 000 tonnes is a very heavy vessel

True! What would you estimate for a vessel of that size?

What passenger ports can accommodate 11m - 23m draft?

I have no idea. It would be good to know what is the "standard" for cruise liners here. I think it should be possible to reduce the draft in a future iteration, especially when in "harbour mode" with fully air flooded ballast tanks.

 

[gonzo]

Yes, that's true for sure! In case of the existing 1:100 prototype when submerged the entire righting moment comes from the flapping fins and the automatic ajdustment of the ballast tanks on each side of the hull. I think that in a future version of Ohanda One one could add more static buoyancy and stability by increasing the vertical volumes, but due to the nature of the SWATH design in combimation with sails, the dynamic balancing will remain most relevant, I would say.

Dynamic balancing is energy intensive. How do you manage that system on w zero emmission vessel? By the way, zero emmision is OK for a sales brochure, but it is not possible.

 

[Ohanda Jay]

Dynamic balancing is energy intensive. How do you manage that system on w zero emmission vessel?

Thank you for making that point! I agree and I think that is the question, if it is worth the effort at all? Could a potential reduction of wave resistance and a gain in stability for the wind propulsion system justify the additional energy consumption? What would be the overall gain compared to a non-submerged system? How much power would it take to balance the ship? How could that be reduced by an improved design? Could this extra energy for balancing the structure be generated from solar systems and wind turbines? Could the water propellers be used for recuperation? How much battery capacity would it need in a worst case scenario? Is a gas turbine needed for backup? And so on.

By the way, zero emmision is OK for a sales brochure, but it is not possible.

Sure, agreed. What would be a better and yet catchy phrase to describe the goal in a headline? Any suggestions?

 

[gonzo]

If you can design a new system that is more efficient, the data will be the best advertisement. However, what you propose defies the laws of physics. Dynamic systems require energy input. Passive systems do not. You would have to design a submersible that is more efficient at the target speed that what current technology has. Further, it has to operate at the same conditions current design do, which includes zero speed. Finally, it has to be able to load and unload at commercial ports.

 

[Robert Biegler]

I don't know how committed you are to your present configuration. There is also the Small Waterplane Area Single Hull vessel:

The HYSWAS (Hybrid lift Small Waterplane Area Ship) takes the idea even further, but is completely unsuited for sail power, unless you wanted to sail Moth style, and passengers are unlikely to appreciate heeling:

If you are committed to small waterplane area, it seems to me that the most promising configuration would combine a single submerged hull with widely spaced foils for stabilisation, like Blue Arrow, a challenger for the America's Cup, had:

Give the vessel amas that touch the water at rest and provide static stability. Once you have enough speed, either let the foils or reduced ballast lift the vessel onto its stilts. The wider the spacing between foils, the less load you need for stabilisation, but also the more difficult docking becomes.

Using only the buoyancy of amas for stabilisation seems unlikely to work because that would just raise the central section until the submerged hull is no longer submerged.

Just as in your twin-hulled configuration, foils would need to provide longitudinal stability.

You could also sail a blimp or an airship:

That might not be as passenger-friendly a you aim for. Although you wouldn't need to worry about sea state, turbulence might cause worse movement of the craft.

Regarding the proa, I think it would move more in a seaway than what you are proposing, but it gets the most length and beam for a given amount of material, and I think it can tolerate a afford higher waterplane loading than a monohull carrying the same payload, so you should get less rolling, pitching and heave.

I don't know whether this is a design study, or the earliest stages of something that is intended to become reality eventually. If the latter, would a lower risk target be ferry traffic between ports with steady winds and generally rough seas, over distances too short for flight to be economical?

 

[Ohanda Jay]

You would have to design a submersible that is more efficient at the target speed that what current technology has. Further, it has to operate at the same conditions current design do, which includes zero speed. Finally, it has to be able to load and unload at commercial ports.

Yes, I agree, that is exactly the challenge. With our first version of the prototype, we just wanted to prove we can manage to semi-submerge the hull and keep it stable while driving. For zero speed we have to float the ballast tanks with air so that it fully emerges to the surface. The current behaviour of the shiplet is more like a modern airplane than like a ship, which I think is ok for now or at least while doing early 1:100 scale model prototyping.

For being more efficient than the existing, to my understanding the potential of a semi-submerged vessel design with dynamic fin and ballast stabilisation for larger ships - which could not just foil like a small racing yacht - lies in these two fields:

1. It has proven already that SWATH can be more efficient and faster at rough sea by reducing the wave resistance from sea disturbance, which usually is especially relevant at better wind conditions. But, as you already mentioned, without active stabilisation SWATH seems not really suitable for wind propulsion.

2. Wind based propulsion systems can be more efficient on more stable systems (plaforms) than on those with constant impact of increased roll, pitch and yaw affecting and changing the sail area, which is what usually happens to a sailing ship at increased sea disturbance at better wind conditions.

And last but not least another potential of the suggested design is, that a relevant number of people might prefer a journey on a vessel with improved stability rather than on a traditional sailing ship. If that vessel is then more energy efficient than the ones that these people would usually choose as an alternative, it might already be worth the effort, even if clearly not yet "zero-emission".

I think we agree that all this needs further exploration and scientific research. The aim of the Ohanda One project is to stimulate the conversation to challenge these ideas. We are aiming for amateur and academic support to substantiate or disprove it. I think your critical thinking is already of great help to further concretize. That's great!

 

[Ohanda Jay]

I don't know how committed you are to your present configuration.

Not at all. It was just the starting point for our first functioning scale model prototpye. In the meantime we have already learned a lot about potential improvemnts for a next version of it, that might look very different. To me a central and general questions that remains is TWIN vs. TRIPPLE hull. In your brilliant example of the "EXPLORER" the tripple hull seems to work quite well.

That might not be as passenger-friendly a you aim for. Although you wouldn't need to worry about sea state, turbulence might cause worse movement of the craft.

Though truly not what we are aiming for, this "Zeppy 2" is a brilliant example for actually thinking out of the box. I like it.

Regarding the proa, I think it would move more in a seaway than what you are proposing, but it gets the most length and beam for a given amount of material, and I think it can tolerate a afford higher waterplane loading than a monohull carrying the same payload, so you should get less rolling, pitching and heave.

To how I understand it, the "EXPLORER" designed by Abeking & Rasmussen also goes in that direction.

I don't know whether this is a design study, or the earliest stages of something that is intended to become reality eventually. If the latter, would a lower risk target be ferry traffic between ports with steady winds and generally rough seas, over distances too short for flight to be economical?

The current Ohanda One design is just a very early starting point to stimulate the conversion, as I also just wrote to @gonzo in above message. The use case between ports with steady winds and generally rough seas, over distances too short for flight to, might be the ideal starting point for a more concrete case study, e.g. Tenerife and the Canarian Islands come into my mind. But there must be many more spots with likewise conditions.

 

[gonzo]

1. It has proven already that SWATH can be more efficient and faster at rough sea by reducing the wave resistance from sea disturbance, which usually is especially relevant at better wind conditions. But, as you already mentioned, without active stabilisation SWATH seems not really suitable for wind propulsion

SWATH has keep the above water hull relatively light. A submerged vessel has to withstand high pressures, which makes it heavy and not conducive to foiling. Unless the hulls are submerged below the turbulent water surface, lower than the height of the waves, it will have more uncomfortable motions than a surface vessel.

 

[jehardiman]

What speeds do you anticipate under sail.....

These are all very good questions yet to be answered. Maybe we can gain more insights with a next iteration, since the balloon based balast tanks and other details of the 1:100 scale model do not aggregate the data we'd need to come up with reasonable results here, I suppose.

The type of rig is irrelevant if you can't make a design that has a significant righting moment.

Yes, that's true for sure! In case of the existing 1:100 prototype when submerged the entire righting moment comes from the flapping fins and the automatic ajdustment of the ballast tanks on each side of the hull. I think that in a future version of Ohanda One one could add more static buoyancy and stability by increasing the vertical volumes, but due to the nature of the SWATH design in combimation with sails, the dynamic balancing will remain most relevant, I would say.

<roll eyes> It will be slow, very slow, as from the responses it appears that the designers do not have a conceptual grasp on how much interference drag the struts and dynamic lift of the stabilizers will generate...as well as how much power a dynamic ballasting system will need. The concept itself is neither stupid nor promising; just not practicable. But it would be much better to build it as a SWATH with the whole topside a solar farm like the demonstrator TURANOR PLANETSOLAR.