davids0865
Well-Known Member
I can't buy MBY in France, any chance of a link to RSS please
Van der Valk 23M in build
- Thread starter Yoeri
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I can't buy MBY in France, any chance of a link to RSS please
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Deleted User YDKXO
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I don't recall that Marsh's retirement has been flagged up anywhere in MBY so I guess thats why it hasn't been mentioned on the forum. Fair play to him. Is he going back to naval architecture? There was an unsubstantiated rumour going around that our very own jfm was in the latter stages of high level contract negotiations at MBY Towers to take over from Mr Marsh.
Regarding the Rotor Swing Stabs, they have one major disadvantage AFAIK in that they don't work at zero speed because flow is required across the rotors to achieve the Magnus effect on which they operate. However if they are cheaper than gyros and fins, I guess they'll find a place in the market
Yoeri
Well-Known Member
It seems that the RotorSwing has a zero-speed option. I will ask the Dutch distributor for some more info about this. I know they are also working on a new collapsible system (zero-speed) for yachts of 30m and over.
Yoeri
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True Nick!
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Deleted User YDKXO
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Er, wassat? Somebody else help please!
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Deleted User YDKXO
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How can they work at zero speed when they need water flow across them to work? I'm all ears!
davids0865
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Nick_H
Well-Known Member
Yes, it said that in the article, just below the bit where it said the magnus effect only works with water flow over the cylinders
Maybe the cylinders will swing forward at the same time as spinning to get the water flow.The article also said that Rotorswing had come up with a completely new idea for yacht stabilisation, whereas in fact they've just scaled down the existing product which Quantum have been offering for years on larger craft.
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Deleted User YDKXO
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Quite impressive video here although woe betide you if you leave them extended when parkingYes, it said that in the article, just below the bit where it said the magnus effect only works with water flow over the cylinders
The article also said that Rotorswing had come up with a completely new idea for yacht stabilisation, whereas in fact they've just scaled down the existing product which Quantum have been offering for years on larger craft.
http://www.youtube.com/watch?v=0dxNaS8p1rI
Yoeri
Well-Known Member
Yes, it said that in the article, just below the bit where it said the magnus effect only works with water flow over the cylinders
The article also said that Rotorswing had come up with a completely new idea for yacht stabilisation, whereas in fact they've just scaled down the existing product which Quantum have been offering for years on larger craft.
True Nick! I've just been in contact with one of the Rotorswing developers and it seems that the system (when activated at zero-speed) will swing horizontal forward-backward-forward etc. to get water flow.
Until now they were not suitable for aluminum yachts as they were partly made out of massive steel, but they are working on a version made out of stainless steel.
Yoeri
stillwaters
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Deleted User YDKXO
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Interesting website and it seems that the concept was designed by somebody who knows a thing or two about stabilisers. Looking at the installation though, it does look rather tall and bulky and I wonder how easy it would be to install these stabilisers in a typical planing boat where underfloor space is limited
MapisM
Well-Known Member
Well, not only the concept, but also the equipment itself has actually been around for decades.
In fact, it rather looks as a simplified version of the original one, which - being FULLY retractable - was much more interesting, imho.
I even wonder if in this new version the total drag is really much lower than with fins, whose hydrodynamic shape is surely more efficient, though of course the overall surface is higher.
Anyway, I'm intrigued by the explanations on the background shown in the "Intro" section:
By 1982, Theo had already designed the first line of retractable Magnus effect stabilizers with his company, KoopNautic Holland. Although his first prototypes were very effective at the time, the sealing technology against the seawater was still a challenge. A few of the initial installations that were delivered are still in operation, however, the maintenance on the rotary seals of these systems requires regular attention from the owners. KoopNautic Holland had to stop the production of the initial stabilizers due to the aforementioned sealing issues.
Since Theo’s first installations, sealing technologies have improved drastically. Having sold his stabilizer company and retiring, Theo got the urge to start again with a new stabilizer that utilizes the Magnus effect
Now, I'm struggling a bit with such justification.
Propulsion shafts have been efficiently sealed since some time now... I wonder why sealing those things should be much harder.
In fact, it rather looks as a simplified version of the original one, which - being FULLY retractable - was much more interesting, imho.
I even wonder if in this new version the total drag is really much lower than with fins, whose hydrodynamic shape is surely more efficient, though of course the overall surface is higher.
Anyway, I'm intrigued by the explanations on the background shown in the "Intro" section:
By 1982, Theo had already designed the first line of retractable Magnus effect stabilizers with his company, KoopNautic Holland. Although his first prototypes were very effective at the time, the sealing technology against the seawater was still a challenge. A few of the initial installations that were delivered are still in operation, however, the maintenance on the rotary seals of these systems requires regular attention from the owners. KoopNautic Holland had to stop the production of the initial stabilizers due to the aforementioned sealing issues.
Since Theo’s first installations, sealing technologies have improved drastically. Having sold his stabilizer company and retiring, Theo got the urge to start again with a new stabilizer that utilizes the Magnus effect
Now, I'm struggling a bit with such justification.
Propulsion shafts have been efficiently sealed since some time now... I wonder why sealing those things should be much harder.
MapisM
Well-Known Member
Interesting numbers indeed.
A 10% loss in top speed is quite relevant. To the point of requiring slightly shorter props, I suppose?
I can't see why IPS as such should be more affected than shafts, though.
Maybe it has more to see with the fact that a 3 engines configuration requires the external props to be nearer to the chines than twin engines? Just a thought.
Re. the fuel burn, of course it's correct - based on your numbers - to say that it's 10% higher (which is a helluva lot of fuel!), but only at WOT.
Since drag increases exponentially with speed, that difference is surely lower at normal cruising speed (20kts or so, I guess?), and probably becomes almost negligible at D speed.
It would have been VERY interesting if you checked (and if you're willing to disclose those numbers, of course) the curves with rpm/speed/engines load/fuel burn "before and after" fitting the fins!
Yoeri
Well-Known Member
Hi MapisM,
Exactly this!
Because a conventional drive usually has no more than 2 shafts, they are generally closer to the keel.
In this case, there are 3 IPS drives of which the two outer partially are in line with the stabilization fins.
So there may be turbulence and thus affect the incoming waterflow.
Especially when you compare that with a Seakeeper which will not cause any swirls/turbulence underwater.
These are indeed serious significant figures, and indeed this is at top speed causing maximum possible drag for this particular ship. I find it hard to fully blame the stabilizers because I can not see how full the fuel tank has been etc. on both test days. But a large part of the loss is due to the big stabilizer fins.
I will have to check if we have such a table/graph available, if so, I will definitely post it!
Yoeri
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MapisM
Well-Known Member
Well, I suppose you should have them, being an essential part of any proper sea trial.
Otoh, I said "if you're willing to disclose those numbers" for a reason, 'cause not many builders are keen on publishing much more than the max speed - and even then, with all the usual disclaimers...
...in fact, IIRC, so far we've never seen a full sea trial table posted around here.
Yoeri
Well-Known Member
Well, I suppose you should have them, being an essential part of any proper sea trial.
Otoh, I said "if you're willing to disclose those numbers" for a reason, 'cause not many builders are keen on publishing much more than the max speed - and even then, with all the usual disclaimers...
...in fact, IIRC, so far we've never seen a full sea trial table posted around here.
Naturally we have sea trial tables
But I'm not sure if they contain differences between speeds with or without fins mounted. In the meantime I have found the final rates during the seatrial having the fins mounted. Until now I cannot find rates without the fins mounted unfortunately.
Yoeri
Edit: This is a Continental II 23.00 Flybridge (ext. wheelhouse) 23.00 x 5.60 with a triple IPS-1050 stack.
Note that the fuel rate is the total fuel consumption of the 3 engines together.
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MapisM
Well-Known Member
Wow, that's a "première" disclosure in this forum, as I recall.
Very interesting numbers too, many thanks.
Very interesting numbers too, many thanks.
acbruce
Well-Known Member
Interesting fuel consumption figures. Can I be cheeky and ask JFM (if he reads this) how they would compare with Match? Does IPS show any fuel consumption benefits in a triple installation?
Do you have to run all three engines when running at low speeds? Can you just run on centre or on Port and Starboard engines?
Do you have to run all three engines when running at low speeds? Can you just run on centre or on Port and Starboard engines?
Yoeri
Well-Known Member
Anytime MapisM!
As far as I remember there is also one in the beginning of this tread regarding a CII 23.00 Fly with a triple IPS-800 stack! Should be this one:
As far as I remember there is also one in the beginning of this tread regarding a CII 23.00 Fly with a triple IPS-800 stack! Should be this one:
