The Magnus effect

I thought I would take moment and introduce an ongoing thread here for an upcoming project.

LIBRA will be headed to the shed in Port Angeles in March for, among other things, the fitting of a pair of Magnus Rotors for roll dampening.

The equipment has been purchased from DMS Holland and the work will be performed by Platypus Marine. This may be the first US installation of this equipment.

Any comments or advice from forum members with experience with this equipment will be appreciated.

I will supply photographic support of our project as it proceeds. Now that I have committed to this project and accepted that it is senseless and risky, I am pretty jazzed to get going.

Yours may be far from the first Magnus system in the US, though.
https://quantumstabilizers.com/products/maglift-magnus-effect-rotor-ship-stabilizers/

Is this for Domino? I didn't think stabilizers work on multi hulls? To counter roll, you basically have to lift or sink the opposing hull. With a mono hull, all it needs to do is roll the hull. Is DMS saying this is good for a multi hull?

twistedtree said:

Is this for Domino? I didn't think stabilizers work on multi hulls? To counter roll, you basically have to lift or sink the opposing hull. With a mono hull, all it needs to do is roll the hull. Is DMS saying this is good for a multi hull?

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No, no, no! This is for LIBRA. DOMINO and the comfort of her cruise is likely the reason we finally committed to this move on the heavy slow boat. Now we are spoiled.

klee wyck said:

No, no, no! This is for LIBRA. DOMINO and the comfort of her cruise is likely the reason we finally committed to this move on the heavy slow boat. Now we are spoiled.

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Got it, thanks. Makes sense now.

twistedtree said:

Got it, thanks. Makes sense now.

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Libra is quite heavily ballasted so has a pretty nice motion that I sort of enjoy.
But, one day this past Summer we were crossing the Strait of Juan de Fuca with my daughter and grandson aboard. After a particularly sporty section, she, with him in her arms, asked "can you make this stop?".
I thought to myself later, I think I can, actually.
So here we are.

I had them quote but it is far too big a system for my boat. The wanted to come and do all the work themselves, but they would agree to only sending a technician at commissioning time. I'd personally want to be there for all the work, because you will need to know everything about it eventually.

The equipment for the DMS Holland stabilizer installs arrived in the US this week. We moved LIBRA up to Port Angeles on Thursday and hauled her into the Platypus yard on Friday.
For those of you in the region, you might note the condition of the bottom after two+ years in salt water and having never seen a diver during that period. Virtually zero growth on the hull. The paint was Seahawk Bio-cop.
The Propspeed was three years old and beginning to fail but still functioning reasonably well.

Do those also work at anchor? I think I read somewhere that they do.

No effect at anchor for the rotors.
Due to flow requirements over the rotors, they are effective over the range of 3-12 knots. They are actually set up to park themselves parallel to the hull at speed outside of that range.
Mine will park nestled right up alongside the bilge keels and should be protected from strikes in that position.

If comparing Magnus to fins to gyros (Magnus master, Humprees, SeaKeeper) what are the +/- s is your view?
Electric draw, service requirements, expense, ease of use, risk of use etc. Think you’re a thoughtful person so did your due diligence so respect your decision matrix.

Hippocampus said:

If comparing Magnus to fins to gyros (Magnus master, Humprees, SeaKeeper) what are the +/- s is your view?
Electric draw, service requirements, expense, ease of use, risk of use etc. Think you’re a thoughtful person so did your due diligence so respect your decision matrix.

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Everything is a compromise and many things on a boat are more personal than clear cut, of course.

The reasons that rotors came out on top for include:
Ease of installation in a retrofit
Low power consumption. (1000W of AC power per rotor (two in this case) allows the system to run via inverter and alternator can keep up without a need to run the generator while cruising.)
Power efficiency. (Predicted 70+ roll reduction on a 136000# boat on 2000 watts)
Low profile/low drag and retractable. (Libra is already slow I would like to avoid making her much slower)
Instant on and instant off with no physical input.
Electric rather than hydraulic is preferable for my situation even though I have high flow, high pressure hydraulics already available on LIBRA.

And finally, I am genuinely curious about how this low power application can effectively reduce the effect of the sea on a boat this heavy. There are quite a few of these in operation, especially in Europe. The videos and testimonials are pretty impressive. The whole idea makes sense to me and I really want to see it in action. Libra is heavy and heavily ballasted. She already does pretty well in terms of roll in most conditions. Crossing the Strait in front of my house with beam seas is often not pleasant though, with wind and current often in opposition and this should open up more days and more hours for that common route with guests aboard.

Nobody in their right mind would stick this kind of money in this boat, but I am looking forward to this just the same.

So I'll ask the question.
Why these compared to batwings seeing as they both stick out the side of the boat.

Batwings don't require power to operate and do work quite well at anchor.

Simi 60 said:

So I'll ask the question.
Why these compared to batwings seeing as they both stick out the side of the boat.

Batwings don't require power to operate and do work quite well at anchor.

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Hopefully the photos will provide my answer. Batwings never made my list for serious consideration. Different strokes and all. I guess 'stick out' is a pretty broad terms for some folks.

Yes, "cosmetically" one is prettier than the other but that wasn't what I was getting at.

I didn’t know about this style of stabilization. Very interesting. I looked at the quantum version and it looks like they work at anchor by swinging the rotors fore and aft, not spinning as when underway.

Currently have gyro. This made sense for us in our current coastal skinny water world but really liked Magnus. Couldn’t find a single boat on the market to check it out in the real world so moved on. However if I ever get the opportunity to build another boat think it has many pluses. Would be curious if you would be kind enough to post what impact it has on boat speed and fuel consumption as you gain more travel time.

And how good you feel they work...

I have several friends who sail with the DMS system.
All are very satisfied with the operation of it.
As far as resistance is concerned, not working it costs about 1/2 kilometer per hour, in operation about 1 kilometer per hour.
Smaller ships, about 11.00 meters 15 tons, one system is sufficient, slightly larger ships it is common with two systems.
There are even large ships equipped with four systems.

Pascall said:

I have several friends who sail with the DMS system.
All are very satisfied with the operation of it.
As far as resistance is concerned, not working it costs about 1/2 kilometer per hour, in operation about 1 kilometer per hour.
Smaller ships, about 11.00 meters 15 tons, one system is sufficient, slightly larger ships it is common with two systems.
There are even large ships equipped with four systems.

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This matches with what I have been told to expect for drag and the relatively low drag of the system was a significant consideration for choosing this system. Basically, a quarter of a knot loss when parked and half a knot when deployed. I imagine that for our vessel and cruising conditions, they would be deployed less than a quarter of the time. So, for a 200-hour cruising season, this would add around 7 hours to cover the same distance. Seems like a fair trade to add the capability to increase comfort for those crossings.

I thought both the DMS system and the Rotorswing advertised zero speed stabilization. Certainly Rotorswing does (they call it the Zerospeed for that reason). It is technically possible (you have to wave them back and forth), and should be more effective than fins.

DDW said:

I thought both the DMS system and the Rotorswing advertised zero speed stabilization. Certainly Rotorswing does (they call it the Zerospeed for that reason). It is technically possible (you have to wave them back and forth), and should be more effective than fins.

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Magnus does have a zero-speed system. I did not choose that one for reasons of cost and complexity.

Thanks for the posts everyone. The DMS rep (Tim) in the UK has looked at the Helmsman 46 hull design and made recommendations for locations in the lazarette. I'm working with Helmsman on preparing the hull. Klee wyck, please keep posting on your installation. Good stuff!!

Hippocampus said:

Currently have gyro. This made sense for us in our current coastal skinny water world but really liked Magnus. Couldn’t find a single boat on the market to check it out in the real world so moved on. However if I ever get the opportunity to build another boat think it has many pluses. Would be curious if you would be kind enough to post what impact it has on boat speed and fuel consumption as you gain more travel time.

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If you go to Youtube and find the videos on the Magnus you will find one owner in the US. Am sure that Magnus will be more than happy to get you in contact with him.

klee wyck said:

Magnus does have a zero-speed system. I did not choose that one for reasons of cost and complexity.

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I also spoke with Magnus (DMS) during my search for stabilizers. Indeed the reason for not choosing them was the fact that they don't function below a speed of roughly 3 kts. The system itself however is very cleaverly thought of and you don't always need to have 2 of them. You can get away with just one.

The zero speed system is also highly modern, but not suitable for the smaller boats. They told me you need to have a boat of at least 70' (in that region) to be able to install them. And my boat is only 49', so that made it a non starter. Pity.
The design did win quite a few maritime awards though.

DDW said:

I thought both the DMS system and the Rotorswing advertised zero speed stabilization. Certainly Rotorswing does (they call it the Zerospeed for that reason). It is technically possible (you have to wave them back and forth), and should be more effective than fins.

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Unfortunately a rotor is not effective when there is no waterflow over the rotor. A boat on anchor does not have any waterflow, unless it is lying in a strong current.
The system itself works very efficient when the boat is underway, but after I spoke with was left with some issues.
1. What happens if you sail through a debris or weed field ? Will they clog up and if so, how do you clean them ?
2. What happens if you hit a log or snatch a line from a fishing pod ?
3. How can you get them back in the stored position after you caught a line, hit something through which the system is deformed ?

I did not really get clear answers to those questions. I don't want to draw the conclusion the system does not function, on the contrary, it is a genius system, but the absence of a zero speed option was for me the reason not to pick them.

klee wyck said:

No effect at anchor for the rotors.
Due to flow requirements over the rotors, they are effective over the range of 3-12 knots. They are actually set up to park themselves parallel to the hull at speed outside of that range.
Mine will park nestled right up alongside the bilge keels and should be protected from strikes in that position.

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That is not what their promotional video shows. That says they work at anchor in a different way than underway. The rotors actively swing back and forth in the at-anchor mode.

Mambo42 said:

Unfortunately a rotor is not effective when there is no waterflow over the rotor. A boat on anchor does not have any waterflow, unless it is lying in a strong current.

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As I said you have to swing the rotors back and form to generate waterflow, and that is what they do. Zero speed fins try to do the same thing, but I think with less efficiency, they are just oars in the water and generate drag but no lift. On the Magnus rotors, quite a little more energy is required at anchor, since the rotors have to be spun up and actively swung, but they do generate lift.

Curious as to the structural requirements. Please keep posting

Bigsalmonfish said:

Curious as to the structural requirements. Please keep posting

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The structure is quite simple and I suppose this is partly due to Libra being steel of 10 mm thickness.
There is a 10 inch steel ‘bushing’ that gets welded vertical through the hull in the first chine(this ‘bushing looks like a piece of 10 inch steel pipe that is around 16 inches tall).
The rotor then bolts to the bottom of the bushing and the drive motor to the ertop and these are coupled inside the bushing. The bushing is also tied to two structural members on either side of it. That is it. Other work is the electrical panel in the engine room with cabling to the opposite side and to the control panel at the helm.
I cannot imagine how this will be more than a week to ten days worth of work in a good yard. Cable runs are short and straightforward. I already have the single phase, 230 volt, 50 hertz power that it needs from the inverter.