Naiad Marine Systems info

[yacht picasso]

Hi guys,

what can you tell me about Naiad Marine Systems and their "advanced anti-rolling system VT" at Anchor and the "DATUM control system"'? in short words, what do they do?

how useful are they on boats 62m long upwards?

[BMcF]

The so-called 'Zero Speed" or S@A systems make use of the force produced by a fin when it is quickly moved through its range of motion while the vessel is at rest and there are no forward-velocity lift forces present. Unlike what the fins are doing underway (being positioned dynamically in response to combination of roll acceleration/roll rate/roll angle measurements, suitably processed), in the case of the zero-speed control, the fin is 'cocked' at one limit position and 'fired' to the other limit position at a high angular rate when a roll rate threshold is exceed. There it remains, having discharged its 'impulse', which is a combination of viscous and added-mass damping forces on the fin blade and vortex shedding effects (akin to sculling), until a roll rate in the opposite direction again exceeds the programmed threshold value and the fin is 'fired' again.

Zero-speed roll damping requires higher fin rates (and benefits from fins specifically designed for zero-sped control..but can't give out those details.sorry), more robust fin hardware and larger accumulators than do conventional roll damping fin systems; some 'retrofit' zero-speed installations have experienced problems with performance and equipment reliability, but the systems installed that were suitably sized right from the start for that control objective ahve been gaining wide acceptance..and for some very large yachts too, certainly well over 62m.

The control alogrithms required to implement zero-speed control are a bit tricky..and proprietary of course. The current leader in the design and installation of zero-speed and low-speed roll control systems for very large yachts is actually Quantum Marine Engineering, but Naiad has many out there too. The hull form and roll period thereof are also very important..zero-speed does not work well for hard-chine, fairly stiff and short-period hulls (very general statement...).

[Guillermo]

One of devastating simplicity has been designed and developed by my friend Iñigo Echenique: his Stabtech system consists of unfolding doors in the hull that become “Super Bilge Keels” which damp the motion, actuated by a gyroscopic stabilising system, offering the advantage of having no drag-inducing appendages when under way. This makes the system particularly interesting for fast yachts that may not normally need active stabilising fins at speed.

Unluckily I cannot find now where Stabtech's webpages are....

Cheers.

[BMcF]

Sounds interesting..sort of a 'zero-speed' version of an active roll control concept that emerged some years ago whereby fins with fixed angle of attack (one or a pair with positive lift and one or a pari with negative lift) were extended in to the flow or retracted in to the hull in repons to the magnitude and polarity of the vessels roll rate.

The inherent drawback fo the solution you describe is the same as with any passive solution...to develop a damping force requires a cross-flow velocity be present across the 'device' from ship's motion...meaning, of course, that the ship must be rolling to develop the damping force on those 'doors'..and it is the reduction/elimination of that rolling that is the control objective in the first place. Active systems such as the Naiad or Quantum zero-peed fin packages develop the maximum damping force they are capable of regardless of the roll angle or rte threshold values and thus are not as dependent on rolling motion to create control forces. Theoretically, at least, that makes it possible to reduce the roll amplitude to 'near' zero with an active solution...

In practive, any damping force, appropriately applied and 'timed' will reduce the rolling of a vessel that is ligthly damped in that axis of motion, so your firend's solution, convetnional bilge keels, flume tanks, etc all work to some degree (of course..or they would not be 'out there' working ).

[Guillermo]

Stabtech system is not passive but active. There was a very interesting presentation at the web site showing the doors unfolding and acting like fishes' pectoral fins, but I'm not able to find it now!
I've written Iñigo Echenique asking him about this.

Cheers.

P.S. I have found a presentation Iñigo did in Vigo some months ago. From there I attach down here a video clip on the system. It was installed aboard an Azimuth 68, but the correspondent video is too heavy to be attached here.

[BMcF]

Originally Posted by Guillermo

Stabtech system is not passive but active. There was a very interesting presentation at the web site showing the doors unfolding and acting like fishes' pectoral fins, but I'm not able to find it now!
I've written Iñigo Echenique asking him about this.

Cheers.

I understand the concept and I see that it would work..but what I was getting at is that (as I understand it ) there are no roll damping forces produced without a significant roll velocity ocurring to produce them. In other words, the force on the 'active bilge keels' is still proportioanl to a velocity created by ship motion. That is what is different from the Naiad/Quantum systems that produce a damping force independently of the magnitude of the vessel roll rate, at least to the point where the roll rate is below some trigger threshhold that cannot be measured...

[Guillermo]

Originally Posted by BMcF

I understand the concept and I see that it would work..but what I was getting at is that (as I understand it ) there are no roll damping forces produced without a significant roll velocity ocurring to produce them. In other words, the force on the 'active bilge keels' is still proportioanl to a velocity created by ship motion. That is what is different from the Naiad/Quantum systems that produce a damping force independently of the magnitude of the vessel roll rate, at least to the point where the roll rate is below some trigger threshhold that cannot be measured...

The system has been tested in real life and worked fine. It's a pity I cannot load the video where two identic Azimuth/Benetti 68' yachts can be seen rolling side by side, at zero speed, one with and the other without the system. Let's see if Iñigo can direct us to where visualize it.

Cheers.

[BMcF]

Originally Posted by Guillermo

The system has been tested in real life and worked fine. It's a pity I cannot load the video where two identic Azimuth/Benetti 68' yachts can be seen rolling side by side, at zero speed, one with and the other without the system. Let's see if Iñigo can direct us to where visualize it.

Cheers.

Would love to see it if you can lay your hands on it.

[expedition]

Yacht Picasso,

Before you look at NAIAD, read the discusson on Yachtforums.com where end users compara NAIAD with Quantum Hydraulics.

[Guillermo]

I forgot to tell you Iñigo told me there is no web page at this moment for his Stabtech system, although he continues to produce and install it on big yachts. If any of you is interested, you can contact Íñigo through his company's web pages at: http://personal.telefonica.terra.es/...tech/esp1.html
Cheers.