Magnus Stabilizer for a ST 52

[Mr. Blu]

Hi all,
As you perhaps know I am already looking quiet some time for a stabilizer system which I could have built in my ST 52. I have considered the MC Quick system, a gyro system which had the advantage that it is very compact, I looked at several fin systems from Naiad and others, but they were all very vulnerable to my opinion and I also considered the Seakeeper but that has to my opinion the disadvantage of slow starting and a long time running after shutting off. And it would take to much space in the first place.
But the main problem, building these systems in a second hand motoryacht is that you will have to sacrifice a lot of space and even sacrifice things like a watermaker. And also the costs for adjusting a GRP motoryacht, -making necessary enforcements and adjustments- are very high in comparison to building a system in a new motoryacht. And you can only spend a dollar or euro once.
The best way is to have a new ship built and get all the options that you want. But I like my ST 52 very much and it meets to most of my wishes. So I left idea of the project “Stabilisers” for what it was for some time.
However recently I found an article on the internet about a Swedish shipyard which had built in a so called Magnus system in a Beneteau Swift Trawler 52. It does not use fins but a kind of spinning tubes, which use the so called Magnus effect to stabilize the ship. These tubes are retractable so when they are not used these tubes are folded along the hull.
The system works at speeds up to 12 knots. At anchor (zero speed) it does not have any effect. Although the ST’s are capable of going much faster we do not use (as most forum members do) our ST as fast going motoryacht.
Interesting for me in the article was that the owner of the shipyard pointed out that to his opinion there was a large market for refitting ST 52 with this system. It had not been a one of a kind job.
Also were interesting the photo’s of the installation of the system in the engine room. It takes little room and to my humble opinion it can be built in rather easy.
I went to Boot Düsseldorf (Europe's largest indoor boat show) where the manufacturer (a Dutch company to my surprise) demonstrated the system. It was so impressive that I ordered a system for my ST 52. It will be built in in April or March.
I think that also for smaller ST the system will fit.
I add some photo’s of the Swedish guy where you can see for yourself. Of course I will make lot’s of pictures when the system is build in my ST but that will only be in a few months. My ST is at the moment in Croatia and has to come to the Netherlands first. But that is another story.

 

[twistedtree]

I look forward to seeing progress on this project, and hearing about how it performs. Thanks for sharing.

 

[caltexflanc]

Looks very interesting indeed. At average consumption of 1000 watts per rotor (2000w total) 1500 peak (3000 ttl) it sounds like you would need the generator running, much like the gyros. At 24 volts that's about 80 amps, so to run without the genset, that's a big bank devoted to the stabs. A lot to like though. Any view as to cost?
https://www.dmsholland.com/wp-content/uploads/2019/05/Flyer-MM-Algemeen-UK-1904.pdf

 

[Mr. Blu]

A few photo's

What I understand is that it is not necessary to have the generator run. We have an inverter of 3000 Watt. The alternator of the engines supplies enough power in combination with the inverter. As you look at the photo's the little space that is used in the engine rooms is remarkable.

 

[Arc]

Is this a marine version of a curve ball?

 

[Mr. Blu]

Magnus effect is often used by people not knowing that they are using it. Baseball, soccer, tennis, you name it.

 

[caltexflanc]

What I understand is that it is not necessary to have the generator run. We have an inverter of 3000 Watt. The alternator of the engines supplies enough power in combination with the inverter

I'd check that carefully with Magnus. Are your alternators 24 volt? How many amps? Your inverter is at the limit of what these thing draw. Anyway, I am sure they will help you get the right set up. I really look forward to your updates!

 

[MurrayM]

I contacted them a year or so ago and they weren't available in North America. Anybody hear whisperings to this?

 

[Fletcher500]

You stated you looked at various fins from Naid and others, but found them “vulnerable”. Are you saying that large L shaped thing sticking out of the hull in the first photo is less vulnerable than a Naid fin?

Regarding Seakeepers, agree, you need internal space for it. We had a large empty spot in the aft portion of the engine room and it fit in there well. As far as start up time, it takes about 30 mins for it to spool up to engagement speed. Not a big deal, I just start it at the dock prior to leaving while on shore power and shift over to the Gen, or start it on our way out and it’s ready to go. Spool down time down is about 4 hours and it’s a non issue. The raw water cooling pump for the antifreeze heat exchanger runs about 15 mins, then shuts off. It just slowly winds down on its own, and the noise is barely audible. Not saying the Seakeeper is a better system because I don’t know anything about the one you are referring to, but I find people on TF have some opinions about Seakeepers and have little to no interaction with them except for what they heard second hand on the docks.

 

[MurrayM]

You stated you looked at various fins from Naid and others, but found them “vulnerable”. Are you saying that large L shaped thing sticking out of the hull in the first photo is less vulnerable than a Naid fin that runs parallel to the hull?

When not in operation they swing back and lay along the hull.

 

[Fletcher500]

When not in operation they swing back and lay along the hull.

Copy, I noticed that in the other photo and edited my response. My original question regarding the OP’s assertion that it’s less vulnerable than a Naid fin still stands.

 

[MurrayM]

Copy, I noticed that in the other photo and edited my response. My original question regarding the OP’s assertion that it’s less vulnerable than a Naid fin still stands.

My guess would be that fins are always 'out there' even in calm conditions whereas the Magnus Stabilizer rotors could fold back when conditions were calm...you would be less likely to damage them compared to fins if you were ripping along (in a trawler sense) and there were objects like deadheads in the water.

 

[caltexflanc]

but I find people on TF have some opinions about Seakeepers and have little to no interaction with them except for what they heard second hand on the docks.

Among about a 1000 or so other things.

 

[Mr. Blu]

I understand that the people of DSM Holland are in contact with Canadian dealers.
I will inform about theNorth American market.

 

[MurrayM]

I understand that the people of DSM Holland are in contact with Canadian dealers.
I will inform about theNorth American market.

PM me when you find out, please. Probably won't be able to afford them, but it's nice to Dream.

 

[PM]

Folded back or out in operation they just look awfully "vulnerable" to me. And those elbows, they look like an awfully lot of added "drag"

pete

 

[MurrayM]

Folded back or out in operation they just look awfully "vulnerable" to me. And those elbows, they look like an awfully lot of added "drag"

pete

Anything sticking out of the hull would be vulnerable and that vulnerability would increase as the size of the object increases. These seem smaller than fins. I'd be inclined to fashion some sort of sloped "hull to elbow" deflector, just in case. Would probably help with drag.

Would be interesting to compare the drag of these to that of fins and paravanes.

 

[MurrayM]

In the case of a direct destructive hit, do they break away outside the hull, leaving the hull intact?

I've heard of boats going down after a fin got ripped off.

 

[caltexflanc]

I've heard of boats going down after a fin got ripped off.

Heard where? On Naiads, it would have to be an otherwise catastrophic grounding at speed to begin with. Think about the geometric relation of the fins vs, the hull. The fiberglass fin is designed to sacrifice itself and in its own way act as something of a deflector. Here's a picture I took at a boat yard, wherein they had broken the fin off several thousand miles before... by the way, he said that the system still had been stabilizing just fine for the conditions they'd been in, as the other fin was intact.

 

[twistedtree]

How long is the Magnus tube? I’m wondering how far it sticks out when deployed, compared to a fin?

I have owned fin stabilized boats for quite a few years now, and only snagged a lobster pot once. That boat didn’t have cutters/deflectors at the leading edge of the fin, and the line got between the top of the fin and the hull. It was no big deal to get it out, but showed the value of those deflector/cutters, and I have had them on subsequent boats.

 

[MurrayM]

Heard where?...

I think it was within the last year, here on TF, somewhere in Ontario.

 

[Crusty Chief]

This system was recently installed on a Selene 40 in Europe. Owner states the system works like magic and is very pleased with the results. Did say that he lost approximately .5 Knot speed, similar to active fin stabilization. Weight of the system was a concern as it was installed in the port side of lazerett, and had to add 350 KG of ballest to starboard side to compensate. So a total of 700 KG or 1550 pounds. Would appear to be comparable to active fins.
Nice setup and takes very little space. The company doesn’t know when they will be able to provide the system in the US yet.

 

[MurrayM]

This system was recently installed on a Selene 40 in Europe. Owner states the system works like magic and is very pleased with the results. Did say that he lost approximately .5 Knot speed, similar to active fin stabilization. Weight of the system was a concern as it was installed in the port side of lazerett, and had to add 350 KG of ballest to starboard side to compensate. So a total of 700 KG or 1550 pounds. Would appear to be comparable to active fins.
Nice setup and takes very little space. The company doesn’t know when they will be able to provide the system in the US yet.

Yikes! I thought they were electrically driven...why so much weight?

 

[Crusty Chief]

Pretty sure its the mass inside the tube that is the heavy part, kinda like a gyro I suspect. And yes the system is powered with the main, genny not required.
He did say that as the size of the boat increases, adding another tube may be required.

 

[MurrayM]

Pretty sure its the mass inside the tube that is the heavy part, kinda like a gyro I suspect. And yes the system is powered with the main, genny not required.
He did say that as the size of the boat increases, adding another tube may be required.

One tube? are you sure we're talking about the same system? They make 3 different kinds.

 

[twistedtree]

This system was recently installed on a Selene 40 in Europe. Owner states the system works like magic and is very pleased with the results. Did say that he lost approximately .5 Knot speed, similar to active fin stabilization. Weight of the system was a concern as it was installed in the port side of lazerett, and had to add 350 KG of ballest to starboard side to compensate. So a total of 700 KG or 1550 pounds. Would appear to be comparable to active fins.
Nice setup and takes very little space. The company doesn’t know when they will be able to provide the system in the US yet.

Sorry, which type of system does this reference? Magnus, or a seakeeper-like unit?

 

[Crusty Chief]

The Magnus, pics from the Selene Owners site, hope the owner doesn’t mind.

 

[Woodland Hills]

When I was boat shopping a couple of years ago there was a steel trawler on the market that had a pair of these mounted on the transom. They had brackets on each end and didn’t swing in and out like these. It looked like they hung just below the hull in clean flowing water.

Does anyone know how they work? Do they spin along the long axis and reverse direction of rotation to reverse the force? Or does the spin resist movement in both directions? Is it essentially just a type of long skinny gyroscope?

 

[MurrayM]

When I was boat shopping a couple of years ago there was a steel trawler on the market that had a pair of these mounted on the transom. They had brackets on each end and didn’t swing in and out like these. It looked like they hung just below the hull in clean flowing water.

They have 3 distinct systems. The one I'm pretty sure we're talking about here is the MagnusMaster: https://www.dmsholland.com/en/

Does anyone know how they work? Do they spin along the long axis and reverse direction of rotation to reverse the force?...

Yes. Think tennis ball...top spin dives, bottom spin rises.

 

[MurrayM]

Pretty sure its the mass inside the tube that is the heavy part, kinda like a gyro I suspect. And yes the system is powered with the main, genny not required.
He did say that as the size of the boat increases, adding another tube may be required.

Weird. That's so counter intuitive. Why does there need to be so much mass when the system operates on surface effects of a spinning object in water?

Putting a top or bottom spin on a ping pong ball has the same effect???

Maybe the weight is in the controller, mounting hardware, and spinning mechanism. Interesting that they don't seem to list the weights on their website.