Green Cruiser 50

Very unique design made with bamboo/epoxy composite featuring a translating keel where the bulb is mounted on tracks on the underside of large wings coming off a fairly short keel fin:
http://www.styacht.com/
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Comment on the keel first published on SA:
"An innovative keel system which has been specially thought through, developed and now patented, allows the boat to have a translating bulb mounted on a fixed winged keel. The advantages of a 'traditional' canting keel come along without the typical drawbacks. Draft is limited to 2 meters. The keel attachment to the hull is completely standard and the wings prevent the need for daggerboards. As a consequence nothing is affecting the interior space."
http://www.sailinganarchy.com/fringe/2009/tav-6-keel-exploded-view.jpg
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the VERY unique rudder:
http://www.sailinganarchy.com/fringe/2009/0814-rudder-asm-3d.jpg

 

Looks like an interesting keel design... I wonder how it will hold up. I also wonder what kind of PHRF rating it will get.

Reed

 

What a load of crap! Really! The typical cruiser doesn't really even know how to properly use a vang or a main traveler properly, much less take advantage of a few degrees of advantage that a wing will provide. A much less vulnerable wing keel showed up a few years back and was a complete failure in the cruising world.
And the claims to canting keel and daggerboard performance are so lame they are embarrassing. Really Doug you are a snakeoil salesmens dream.
That thing won't even make a minor appearance on the scene...thank God!

 

You mean unique like these rudders that have been around for many years?

There is also a powering device for kayaks that is a trolling motor integrated with a removable, stern hung rudder.

Doug, this is not new. It's a great idea and these guys bagged it for big boats.

Perhaps, getting out more often and looking at all kinds of boats and not just foilers would keep you more informed?

 

Well, Green cruiser 50 is meant to bring some technology down into the cruising boat world both for comfort and performance.
Deck layout allows the skipper to take under control all the manoeuvres.All lines are led to this point beneath the deck. In this way, the seating area of the cockpit and the stern sun deck remain accessible and free of potential dangers.
Keel System allows to move 2.5tons bulb by almost 3 m across the boat.
We developed this device to have a gain in total boat performance and lower down the displacement (less lead).
We have run a comparative VPP study ( feed with CDF derived polars of the appendages) using as a reference the same boat, with the same righting moment, the same draft, but fix keel (so heavier displacement) . The results, (see polar diagram attached: blue –standard keel; red – winged movable ball. TWS: 5-10-15-20-25 Kts) show similar performances in the range 0-10kts (TWS) . Above that range the gain in performance is very visible especially beam reaching.
The system if compared to a standard canting keel is less efficient in increasing the performances of the boat but has important and unique advantages:
-standard keel to hull attachment.
-low draft
-no interior space required
-lower energy consumption. Bulb moves side wise in a almost horizontal plane when boat heels.
-no daggerboards required

This means, for example that if you want to make your boat (whatever boat) lighter, keeping very similar stability properties, you can, and you'll go faster!

Please continue to give your comments. Would be great if they are very critical. We'll try think about, to answer or explain our vision.

 

Green 50

Davide, thanks very much for posting here. Very innovative thinking! Is there a concern about the bulb track under the wings getting fouled with sea growth?

 

One way is mechanical: a flexible little plate in front of every sheeve of the bulb car can clean the sea growth at every movement of the bulb. To prevent problems an automatic bulb movement should be implemented in the PLC of the control system. Power consumption for that purpose is not a problem because the boat is a little power plant it self.
I'm getting info about other suitable chemical protection for mechanical movable parts.

 

Doesn't the complete structure of the arrayed fins, when coupled with the bulb, act as one very efficient weed collector?

What provisions are there within the design to handle repeated keel fouling in locations where weed is a significant issue?

Perhaps a set of images showing the mechanical strategy for keeping the track clean would be appropriate so that the readers here can more fully understand the system?

What is the strategy for boat handling should the bulb be stuck in the track at the far end of its movement?

How susceptible is the system to track misalignment, should the keel form be struck by an underwater obstacle? Have any tests been done in this area for such a potential?

If misalignment occurs and the bulb becomes locked in place, what are the procedures for the typical cruising sailors and their wide latitude of experience in boat handling?

Have any structural changes been applied to the fixed fin and the hull to handle the enhanced drag induced torque on the structure?

Thank you,

 

1) Giving the LE edge of the keel blade some degrees of sweep back and using the bulb as a weed cutter
2) 3) I will give you some images of the flexible plates sliding on the rails just in front the sheeves
4) Car system is detachable from the bulb so it can be handled easily. sliding rails are split at centerplane. you need to remove rails from one side, attach the driving steel wire cables and screw the rails in again. Than you assemble the bulb
5)-6) Car is designed to have sheeves rolling on each surfaces to prevent undue movements and locking issues. The attachement plate on the bulb is mounted and a high load rubber damper. To smooth out load peeks and vibrations.The system is meant to accomplish the ABS rules about grounding
minimum safety factors.

 

Twin Rudders&saildrives combined

Right, this is not a new idea. Maybe is a new application for big boats.
The beauty of the system, at least as I see, is when it is applied to a 2 rudders boat.
Here some pros
- Electric engine allow the idea to be used because low vibrations
- Electric engines allow to have 2 counter rotating propellers.( port and starboard). =>> no evolutionary effect !
- No bow truster, but 2 engines consolle
- more efficient way to use the rudder stock ( usually on round stock are loded only side wise)
- less holes on the boat shell
- less overall drag (saildrive underwater support avoided)
- better boat manuverability.

 

Listen...there is no one that likes the tech stuff more than me. I love seeing innovation. But really get a grip here and consider the reality of such a contraption under a "cruising" boat.
First off, the problems with moving parts underwater are overwhelming. The compatibility, corrosion and fouling issues are huge. Even with the highest strength materials we use (carbon, kevlar, titanium etc.) that setup would be nothing less than fragile at best. And saying the word cruising implies grounding. A gentle encounter with mud would be costly. Even if it didn't break, you would be stuck, as healing the boat would not help and any struggling would dig a hole and stick you worse. This is something I saw a lot of with the Beneteau charter boats with wing keels that were being used in the Caribbean. They sometimes had to hire a diver to dig a trench to get the boat out!!
I have worked around some the best technical boat builders in the world. I can say without hesitation that any one of them would whoop with joy if they got that thing to function in the shop environment, but I don't think any of them would tell you with a straight face that they would expect it to function in the marine environment.
It is a great intellectual exercise in design, at best, but the reality is silliness really.

 

Davide, will the wings develop vertical lift when the boat is sailed relatively level-or is the lift down? I'm guessing that the lift would be down so that the leeward foil "lifts" to windward and so the windward foil adds a bit to RM...

 

Davide,

To solve a question raised in another thread, can you tell us the angle(s) of the wings (either the angle away from the vertical keel portion, or the angle between the two keel wings)?
I'm guessing:
1. 110*
2. 140*

...someone else guessed closer to:
1. 135*
2. 90*

Who was closer in their estimation?

 

I must say this concept and the word cruising do not go together. Cruisers value seaworthiness, ruggedness, simplicity, economy, practicality, which this concept is the very opposite of, and all just for a fractional increase in speed on reaches, close and broad.

I'm not dissing it as it is always neat to see people try new stuff though.

But now performance; Drop the boom so it is a few centimeters off the deck and you gain sail coefficient of lift , halve mainsail induced drag, get more sail area low down where it makes almost no difference to heel and for about 0.1% (a few square meter extra cloth) the cost of the keel apparatus...

Ok , so I think the sliding bulb keel actually needs to be continuous loop so the bulb wraps around (the foil goes through the bulb) the foil because i see a lot of parasitic drag between the foil and the bulb which is no doubt why the polars show no difference where it matters most; at VMG angles. I know the polars are CFD , as in theoretical, but assuming they' re accurate. Continuous loop also gives two attachment points which is a lot stronger, for this "pushing what we can do with materials to the limit" kind of thing.

 

Right! And from a cruisers point of view, as already mentioned above:
what a load of crap..........
And, sorry, whats so green here? The bucks one can get from the dumb?

Regards
Richard