[SAB]

On the question of propulsion for this type of hull, and since the concept behind the SABDES 70 (which we termed 'Sleek Princess'), is an attempt to create excitement for the guests 'yachting' experience, and also technical innovations like the hull design, then the propulsion might suit using a 360degree pod propulsion system like ABB have in their Compact Azipod product (see image). The hull form seems to lend itself to semi-displacement, as does the podded propulsion system. For higher speeds, 25+knots, the surface drive system would be a good option, noting your comments that waterjet propulsion would likely have intake aeration problems. The other advantage of using a podded electric propulsion system, is in allowing flexibilty for the location of the main generators, and increased manouverability, and having the props of the pods deep enough so as to avoid any aeration problems. To complement the innovations of the hull and propulsion system, why not also look at Fuel Cell System (like Ballard) to provide the energy. .. All possible and current technologies.. like James Bond! ... - SABDES

[Donald Blount]

Having designed vessels from 42 to 67 meters O A which have been built and sea trialed at speeds substantially above 50 knots, I question the buttock shapes of the monohull portion of the hull as being somewhat non-lifting in the hump and higher speed ranges. The monohull bottom shape is analogous to attempting to making a canoe plane. Negative dynamic hull bottom pressures will be developed beginning near 25 knots which may "pull down" the bow instead of lifting it.

My advice is to carefully study this hull form with realistic model tests before marketing energy takes control of decisions on committing large financial resources.

[SAB]

Thanks Donald for your review and sound advice. I agree with all your points, particularly that the main hull buttock shapes need refining.

In the interest of achieving a monohedron hull form, one proposal could be as per the new image I attach; At speeds <20kn the mainhull acts as a displacement hull, but as speeds increase >20kn + the addition of chine flats and running strakes aid lift. At the point where the main hull buttocks begin to curve upward, the chine flats and strakes stop and a step in the hull is added. The aft part of the main hull would lose resistance due to being recessed, and the hullform then becomes a 3 point planing surface, ie: main hull and aft sponsons. Weight distribution woud be critical for the correct trim angle, and the effects of the rooster tail would need careful consideration.

The SABDES 70 hullform in our later versions reverted back to a standard monohedron form, as can be seen in the attached early concept study image from 3/4 aft. Note the transom seen underwater.

Marketing wise, the idea for the hull form was not so much to reinvent the wheel while achieving high speeds, but an attempt to find a solution to create a hull form allowing the 'float-in-dock' without the need for constant flooding and draining. (as seen for eg on Princess Mariana, and some Naval Vessels). I came from a Naval design background, which was my inspiration in developing ideas for a 'float-in-dock' for tender deployment on Superyachts.

[SAB]

Amels have been producing a design where they split the Monohull aft into a Catamaran. They call it 'the STASH concept' (Single to Twin Aft Ship Hull).
Their basic idea is again to create an inside harbour for large tenders. Benefits are the tenders are located at the centreline, and the dock does not have the need to flood. The STASH was developed over a period of one year by the Amels Design Department with special contribution by Dirk Degroote, and was presented at 'Project 2004' Amsterdam Nov 2004.

[YachtForums]

The press release on Amel's tender handling concept can be seen here...

http://www.yachtforums.com/forums/showthread.php?t=2526

[Donald Blount]

Thanks for sharing the STASH information. I had a staff member at Project 2004 and will discuss with him the material presented there. It looks like it has possibilities for displacement motor yachts.

[SAB]

theres a good pdf document on the AMELS website about the STASH concept, showing tank tesing images, stability, resistance figures, wave interactions between the hulls. The concept for a Monohull to Catamaran hull was probably first seen on the 'Alcyone' (launched in 1985)... the Cousteau research ship which also had wind turbosails.

[SAB]

Don Burg, the inventor of a new patent-pending ship hull concept, the 'Ship with Wave Energy Engulfing Propulsors' or 'SWEEP', has combined the advantages of a bulbous bow with those of an air-lubricated ship (ALS) to significantly reduce the wave drag of displacemnt hull forms.The SWEEP concept takes advantage of the inward turning water around a bulbous bow, thereby sucking wave energy, thereby reducing wave drag, and accelerating the wave-making water flow into a high flow propulsor(s). The flow from the bow mounted waterjet is discharged into an air layer beneath the hull. The air layer needs very little blower power to be maintained. What this all means is that a SWEEP can be efficient over a large operating speed range. For example a 122m SWEEP can obtain a total drag reduction of around 15%-20% @ 20 knots, and a 40% reduction @ 45 knots. Studies carried out to date show the SWEEP concept is technically feasible and further analysis and model testing is planned as the next step in development.

[mp-willow]

After reading over the posts and the STASH info, I have a question, maybe I missed it, but the drive in always flooded tender garages, seem to be always open to the outside? If always flooded, in the case of the new project to swim in, are the tenders lifted up clear of the water?

The idea and hull design are very interesting, I hope to read more.

[Cooltop35]

How much would the 2002 70m design actually cost to build/fit out if you don't mind me asking?

She is a beauty by the way - well done!

[SAB]

Not much change short of 70M Euro is a good estimate.