Trawler Rocking, Rolling and Stability

[Mambo42]

Agreed the electric CMC look great. Various web pages list them as "starting" at $45600 USD for 12 meter vessels, e.g. https://www.nauticexpo.com/prod/cmc-marine/product-29020-556763.html I mostly see the same price regardless of model number so I assume that's for the smallest size, ~40 foot vessel.

Those prices are indeed correct. But as I heard from several other owners it is advisable to go one size up if you are a trawler at slow speed. The faster the boat goes the more effective the stabilizers will be. Many producers tell you the size is based on roughly 10 kts minimum speed and that is something we never reach.
So we went for 1 size larger, the Stab 25. On paper it uses more electricity, but since they are more effective in the end the electricity usage will roughly be the same as the stab 20, which has to work a max power all the time.

 

[Southern Boater]

https://www.flopstopper.com/FlopStopper/Home.html

These are the ones. It's very hard to quantify improvement unfortunately; this is SoCal, Channel Islands and Catalina - anchorages can be quite roll-y indeed.

We did a season with nothing, then a season with those orange cones - four per side. They were almost useless - no real discernible difference.

Bit the bullet and got a single flop stopper ($$). It made a significant improvement in comfort - mainly by damping out the roll much more quickly than the boat's natural motion.

We got the second and used it for two more seasons - another step up in improvement; roll damping is much faster since damping occurs on both sides.

Again, I have no measurements, but with nothing, it could be tough to walk around and make dinner. With two, you still feel some motion, but it's much more controlled. I think polls will be another big step up - I've seen some boats with just a single flop stopper and a long pole and they seem to do better than us with two off the midship cleats.

Cheers SoCal, appreciate the feedback

 

[ronobrien]

Most trawlers have a mast and boom. While it is NG for propulsion, at anchor a small sail can help keep the boat head to the wind, which is generally where the swell will be from. Underway a roll does suck, but it makes sleeping almost impossible.

 

[Hippocampus]

Mentioned north swell above. In the Caribbean you occasionally get north swell with trade winds coming in from the east. Sails make motion worst. In New England prevailing winds are commonly from the southwest but the swell from the east. Again lining up to the wind means you’re not lined up to the swell or chop.

Understand one individual above is strongly against gyros but they work better than fins, fish, flapper stoppers, rolling chocks or anything else except possibly Magnus that can oscillate deployment. I’d rather have the genset on and sleep like a baby putting up with the nominal cost of this rare condition than be pissy, crappy and not be on my best game the following morning. Fatigue boating or driving is every bit as dangerous as being drunk. My genset like most is in the ER. It has its own enclosure. It doesn’t interrupt anyone’s sleep. Even its exhaust doesn’t splash.

 

[ronobrien]

I lived aboard in the Caribbean and found it worked pretty well. The worst nights were when there was no wind at all.

 

[Hippocampus]

On sail or power? Can see some benefit to a riding sail if big enough and far enough aft. Do know a gyro just plain works. Even in small deep Vs while they’re bottom fishing.

 

[long-cours.62]

Thanks

Here in Oz they cost I would hazard a guess at $30,000 for a 60fter
Still way cheaper than actives or gyro
And they do work well both underway and at anchor going on observations of boats that have had them near us.

Around the cost proposed by DMS to upgrade our Vetus hydraulic fin.
May be less effective but no need of energy (on the way not a problem) but at anchor could be interesting.

 

[Mambo42]

Most trawlers have a mast and boom. While it is NG for propulsion, at anchor a small sail can help keep the boat head to the wind, which is generally where the swell will be from. Underway a roll does suck, but it makes sleeping almost impossible.

Unfortunately I don't have a mast and a boom. The mast that I have is more 'show' than really supporting anything. Yes the radar and antennas are attached to the mast, but I would not want to try to attach some flopper stopper booms to it. That mast would just simply be ripped off the boat in the first roll the boat makes.

 

[Mambo42]

Understand one individual above is strongly against gyros but they work better than fins, fish, flapper stoppers, rolling chocks or anything else except possibly Magnus that can oscillate deployment. I’d rather have the genset on and sleep like a baby putting up with the nominal cost of this rare condition than be pissy, crappy and not be on my best game the following morning. Fatigue boating or driving is every bit as dangerous as being drunk. My genset like most is in the ER. It has its own enclosure. It doesn’t interrupt anyone’s sleep. Even its exhaust doesn’t splash.

I guess you meant me with regard to the gyros.

After talking to several producers of gyros I could only draw one conclusion and that was they are not for me. Reasons ?

1. The whole thing takes up quite a bit of space, which I don't have available. If I put it in the boat it means I won't be able to access certain parts of the boat (ER) anymore. That was a no go for me.

2. The spool up time is around 45 min and that means that, if the wind picks up suddenly (like e.g. the Meltemi does in the Med) you won't be able to get the boat stabilized. A gyro that starts up needs to be in a stable condition, otherwise it cannot determine what is the 'horizontal' position. You actually might end up with a list.
For me that was unacceptable since I want to have instantaneous stabilization when conditions change and in the Med that can happen in an instance.

3. Electricity usage of the gyros is high. First of all about 4 to 5 Kw to spool up the system and then about 2 Kw per hour to keep the gyro going in bad weather. For me that means running the generator at night while I am asleep and there cannot be a bigger no-no than running a generator when nobody is guarding it. There is no automatic shut off, there is no fail safe system and since parts in a generator can fail it is a hazard on board, which means someone has to be awake if a generator is running. So I want to run stabilizers from the batteries and that means the lowest electricity use possible. The electric fins have an anchor mode where they are slightly less sensitive and react a bit slower. That reduces the electricity usage and that means I can run them off the batteries.

4. The fourth reason is the bearings. We spend about 7 - 8 months or almost 6000 hours each year on the boat and most of it is on anchor. We would have that gyro on basically every trip and most nights when we would be in the Aegean sea. That would mean the gyro would be running about 3000 - 4000 hours each season. And the bearings have a life expectancy of about 3000 - 6000 hours. In order to change the bearings the whole gyro system needs to be taken apart and that costs a fortune. The producers of the gyro don't tell you that in their sales pitch, but when you ask a bit further they will tell you. If you only use your boat 200 hours each year it is not a problem, but when you use your boat in mostly rough waters for months at the time...............it is something to take into consideration.

Based on those 4 reasons and the fact that the cost of a gyro is not so different from other stabilizers, I decided against gyros. I fully understand the way the system works and I agree it is a good way to stabilize the boat since it will oppose any movement of the boat immediately. But that also brings in another worry that I have, of which I have not enough knowledge, but since I had already taken my decision I did not dive deeper into that subject.
The gyro is bolted to the boat in order to be able to get the boat stabilized. Unlike the stabilizer fins, which excercise their force on a reinforced hull, the gyro will create a torque effect in the hull. As a result you will get a different torque moment close to the gyro as opposed to, let's say the bow. In other words you continuously put stress on the hull in a corkscrew motion and I don't know if the boat was designed to take that force.
But ok, perhaps I am over estimating this 5th reason, but if anyone knows the answer, I would like to hear it.

Anyway, like I said, that is my choice, but I fully understand if someone else makes a different assumption or decision. I know there are loads of people who happily switch on the generator and go to sleep without anyone guarding it. A large part of my life I have been trained not to do that, for safety reasons. Maybe I am too serious, but I am former military, also a pilot, I like safety

 

[cfr]

i know one yardowner in Holland who built three Vryburg 61 , first with fins, second with magnus plus one year later a gyro, number three with fin and zero speed option......he cruises from Holland to Norway fir 5 month a year. Last one is the best solution for him. I use a flopper stop on a spinnaker pole with my sailboat in the Med, because most nights yre calm and the swell is comming from everywhere, and a sailboat is rolling same as a trawler in an anchorage and downwind sailing too, and motoring also even with sails up......only from 10 to 30 kn wind and upwind or beam sailing its very nice.....

 

[Simi 60]

Unfortunately I don't have a mast and a boom. The mast that I have is more 'show' than really supporting anything. Yes the radar and antennas are attached to the mast, but I would not want to try to attach some flopper stopper booms to it. That mast would just simply be ripped off the boat in the first roll the boat makes.

Whilst it possibly could be the loads really aren't that much.

I can grab the 1/4 inch Dyneema on ours, pull some belly in the rope and pretty much hold it with one hand during a big roll.
If I actually tried with both I could do it easily.

To me that says it can't possibly be more than about 50kg (110lb)

 

[mvweebles]

Whilst it possibly could be the loads really aren't that much.

I can grab the 1/4 inch Dyneema on ours, pull some belly in the rope and pretty much hold it with one hand during a big roll.
If I actually tried with both I could do it easily.

To me that says it can't possibly be more than about 50kg (110lb)

I agree with you Simi - for at-anchor flopper stoppers, I don't think the loads are that great because the deep 'pendulum' oscillations that would load-up rigging never develop.

That said, what I can't quite reconcile is the instructions that came with my Magma hinged plates that say the plates should over 10-feet below the surface of the water. It can't be because there is risk of them being airborne - must be a water density issue. Best I can surmise is the lawyers reviewed the marketing copy for liability, but only a hunch.

Peter

PS - if you can lift 25kg at the end of a very slippery 1/4" Dyneema line by hand, hats off to you.

 

[Hippocampus]

If I was still doing blue water I’d not have the SeaKeeper as my first choice. But I’m coastal.
In this environment using the generator isn’t a problem.
Weather is accurate enough and I’m always shorter than the 3-5d window where accuracy deteriorates. So the windup is a non issue.
The SeaKeeper sits on the two main stringers. Same ones as the engine. They run the length of the boat. There’s no flexing and I think no possibility of torque damage to any part of the boat. SeaKeeper was put in 2011. Still hasn’t had the vacuum cracked open.
We aren’t in the med. We have the SeaKeeper on <20% of the time overall. Find it unnecessary at anchor in our travels except very rare occasions. So far this year we’ve done about 2500nm but all very near shore or totally protected in the AICW. SeaKeeper has gone on 1h before crossing bays, large inlets, rivers and very near shore ( coast of NJ, SC etc.).
Fins wouldn’t be as good a choice for us. We’re often in skinny water or weedy, or full of traps or full of debris. Do rare continuous transits. A rare 24-48h one. Nothing longer. Each evening when anchored or slipped check the strainer baskets. Not uncommon to see a lot of stuff in them. Fins produce drag even when not active and lower top speed. Fish aren’t practical either because commonly in depths insufficient for safe deployment.
So for our current use pattern we’re left with gyro or Magnus . With a single screw and nothing sticking out not that concerned when I hear a bump or can’t avoid a weed field.
Have no issue with your choice. For a boat always in deep water and rarely dealing with debris, weed or traps makes perfect sense. Some drive G wagons. Some drive Lamborghinis. Would suggest gyro makes no sense for you but might be the best choice for others.

 

[rslifkin]

To me the biggest issue with the Seakeeper in a lot of boats is "where the heck do I put it?" On my own boat, for example, I can't come up with a good place where the Seakeeper would fit without majorly blocking engine access. There's no lazarette, the aft cabin floor sits right on the stringers (so no room below) and you can only put it so far forward in the boat (both due to effectiveness and weight).

Paravanes carry some of the same "how do I actually install this on X boat?" problems. Especially if cruising in areas where air draft is a problem. Fins can be a similar challenge on some boats depending on where tanks are placed, etc. But fins do generally require less internal space than a gyro, so if there's room for the actuators you'll generally be able to make an install work.

Other than cost (which isn't any worse than other fin options) and them only taking 24v DC and 230V AC input (neither of which I have on board currently), the Waveless fins mentioned earlier in this thread look like a nice option, as the actuators aren't huge and you don't have to get big hydraulic lines to them (or find space to mount hydraulic pumps on the mains).

 

[mvweebles]

There is no perfect stabilization system, but there is one universal truth: stabilizers work and those who have cruised with them are loath to go without.

People with Seakeepers seem pretty happy with them. Concerns about service intervals seem most prolific from the bleachers, not the owners. Fins and fish both require maintenance. Some of the early Seakeeper installs suffered from being too small. As far as at-anchor, nothing says you can't put out flopper stoppers if you don't want to run the generator. Mind you that many boats in hot humid climates run their generators 24/7 so there's really no penalty. Install space aside, if I were a 24/7 generator boat, Seakeeper might be my first choice for active stabilization.

In open water, I run my stabilizers less than half the time. Fins are nice in places where wake traffic comes though because they can be activated in seconds. The install space is considerable however, just distributed. The oil tank especially is pretty sizeable. I'm very interested in the newer electrical motors being developed using technology advanced in the e-car space.

My point being that preference and choice of one type of stabilization system or another is personal and use dependent. Emphasis on choosing one system over another, not choosing one or nothing.

Although Hippocampus' only uses his 20% of the time, guessing he's damn happy he has them. Be curious to hear whether it would be a requirement on a "next boat."

Peter

 

[slowgoesit]

2. The spool up time is around 45 min and that means that, if the wind picks up suddenly (like e.g. the Meltemi does in the Med) you won't be able to get the boat stabilized. A gyro that starts up needs to be in a stable condition, otherwise it cannot determine what is the 'horizontal' position. You actually might end up with a list.
For me that was unacceptable since I want to have instantaneous stabilization when conditions change and in the Med that can happen in an instance.

I was also told by a Seakeeper rep at the boat show that you also shouldn't shut down the gyros in "rough conditions" or you would risk damaging the bearings, and it wouldn't be covered under warranty . . . . Soooo, Here's a scenario:

You finally get in to an anchorage after a rough passage where you were running the gyro non-stop, you tie up to a humongous mooring ball that won't move with anything less than the Queen Mary tied to it, and you want to go ashore for a week. . . . but the conditions are still "rough". Based on what the salesman told me, you have to continue to run the generator because you can't afford to risk damage to the gyro bearings by shutting the gyro down in "rough conditions"? Seriously?

It's a mute point for us anyway, as we're happy with out current stabilization, but would probably preclude me from purchasing because of this alone . . .

 

[cfr]

there is another manufacturer than seekeeper

https://www.quickitaly.com/en/home/

 

[bkcorwin]

I may be missing some prior context here, but in general vertical wave action decreases as a function of depth up to the "wave base" at which point wave induced activity is pretty much gone.

Deeper the better so that the plates are in water that is not oscillating vertically.

I agree with you Simi - for at-anchor flopper stoppers, I don't think the loads are that great because the deep 'pendulum' oscillations that would load-up rigging never develop.

That said, what I can't quite reconcile is the instructions that came with my Magma hinged plates that say the plates should over 10-feet below the surface of the water. It can't be because there is risk of them being airborne - must be a water density issue. Best I can surmise is the lawyers reviewed the marketing copy for liability, but only a hunch.

Peter

PS - if you can lift 25kg at the end of a very slippery 1/4" Dyneema line by hand, hats off to you.

 

[dannc]

Paravanes can be designed so that they do not have an air draft issue. Some designs can fold down and others just don't have an air draft. Though, to be fair, the air draft with the paravane setups that one normally sees, is still well short of most sail boats. Having the structure where the paravanes should be mounted is certainly an issue.

Just another one of those boat design issues.

Later,
Dan

 

[rslifkin]

Paravanes can be designed so that they do not have an air draft issue. Some designs can fold down and others just don't have an air draft. Though, to be fair, the air draft with the paravane setups that one normally sees, is still well short of most sail boats. Having the structure where the paravanes should be mounted is certainly an issue.

Just another one of those boat design issues.

Later,
Dan

Yes, having the structure is a big concern. But when I think of air draft limited areas, I'm thinking of places sailboats can't go with the mast up. Like the NY Canals. Depending on what sections you want to travel, you need to fit under either a 21 foot, 17 foot, or 15.5 foot bridge. I can't say I've ever seen a paravane setup that would stay under 15.5 feet.

 

[dannc]

Yes, having the structure is a big concern. But when I think of air draft limited areas, I'm thinking of places sailboats can't go with the mast up. Like the NY Canals. Depending on what sections you want to travel, you need to fit under either a 21 foot, 17 foot, or 15.5 foot bridge. I can't say I've ever seen a paravane setup that would stay under 15.5 feet.

Mobious and some of the Artnautica LRC's have a paravane design that fold down or normally store along the side of the boat.

I have seen some that are bit different than the Artnautica designs. There are some photos here, https://www.trawlerforum.com/forums/s3/paravane-stabilizer-solid-foldaway-arms-design-48062.html, but mainly this one, https://www.trawlerforum.com/forums/attachment.php?attachmentid=97496&stc=1&thumb=1&d=1576252746, that are similar to what I have seen on real fishing trawlers.

Later,
Dan

 

[Hippocampus]

Guys let me tell you again I’m now coastal.

The SeaKeeper is automatically locked and not moving until it has adequate rpms to be fully operational. The issue of damage in heavy seas isn’t even a possibility for me. If weather report says I’m going to need it it goes on well before we leave. If I’m transitioning from protected to open waters it’s turned on an hour before we get there.

Seems you folks are in an open water mindset for a coastal SD cruiser. Been there, done that, have the T shirt. I’m now doing something else.

Even so Peter is absolutely correct (usually is). I would never own a power vessel that wasn’t stabilized except if it was on a small lake. Know multi hulls are wonderful but don’t like their motion except in small outboard fish boats so I’m stuck with mono hulls. So far my take is
Skinny junky water - gyro or Magnus with gyro in the lead.
Deep water - fins (fish scare me) with perhaps fish as a backup and to allow flapper stoppers. Seems tech has moved along so electric not hydraulic.
Mixed - Magnus with fins a close second

Yup a personal opinion but just want to suggest one size doesn’t fit all and all have their issues and strengths.

 

[Don L]

Sounds $$$$$$$$

 

[Mambo42]

The SeaKeeper is automatically locked and not moving until it has adequate rpms to be fully operational.

I understand it is locked, it also has to be locked, but there is something I don't understand, perhaps you or someone else can shed a light on this.

In my flying years we obviously also had gyro's and they usually took about 7 - 10 min to spool up. During that period you were not allowed to move at all. Reason was simle, the gyro has to establish what is level on all the axes. If you would move the plane before the gyro was at speed you would find the gyro was not level. You could later gage the system, but in order to do that you needed to have level flight.

The gyro onboard a boat takes about 40 min to spool up, but even if it is locked, something has to tell the gyro what is level and what is not. The last thing you want is that the gyro thinks a 10 degree starboard list is 'level'. So the question becomes: 'how does the gyro know what is level when the boat is rocking and rolling ?'
Can you gage this gyro as well ?

 

[Hippocampus]

Not at all similar to a gyro compass or other like device. While it spools up it’s locked. When unlocked it responds to horizontal changes and opposes them. My understanding is it doesn’t matter which direction( starboard or port). I think if you have a prolonged sustained list the gimbals and sensors might settle down with that orientation so you would get precession force with changes from that list. However even with waves directly on our beam the inclinometer shows us level and without a list. This has been a non issue to date.

To my mind there’s several reasons a gyro wouldn’t be my first choice if I was doing open ocean voyaging. Among them is the way the thing works is by the force generated by precession. It has two hydraulic arms to allow that. Once they hit their limit righting is gone. Unlike fish where if you lose a fish the one still in the water can put your rail down the gyro doesn’t present a risk. But with monstrous seas its limits maybe exceeded. Even if your sideways fins should provide some continued beneficial effect. Same with Magnus. For both fins and Magnus as long as one is in the water you’d get some benefit and no detrimental effects. Gyros no benefit once precession exceeded but no detrimental effect. Fish detrimental effects unless both in the water and working.

 

[Mambo42]

Sounds $$$$$$$$

Yep, stabilization is expensive, but if you are sailing in an area with rough seas on an average basis, then it can become very uncomfortable onboard. Actually to the point where you cannot go out anymore. This week I arrived at the marina, to put the boat back into the water and was talking with a fellow trawler owner. He told me a couple of years ago he had to stay put on the south side of Mykonos for almost 1 month due to the Meltemi winds and the subsequent rough seas.
That is not my idea of fun, I don't want to be stuck in one location because the boat is not stabilized and yet we do want to visit that region. But when the wife and dogs are all hanging over the railing because of sea sickness, there is little fun in seeing the islands. So basically we have no other option and unfortunately that does cost a lot of money.

 

[Mambo42]

Not at all similar to a gyro compass or other like device. While it spools up it’s locked. When unlocked it responds to horizontal changes and opposes them. My understanding is it doesn’t matter which direction( starboard or port). I think if you have a prolonged sustained list the gimbals and sensors might settle down with that orientation so you would get precession force with changes from that list. However even with waves directly on our beam the inclinometer shows us level and without a list. This has been a non issue to date.

It is clear the gyro is locked during spool up, it has to be. Once it is on speed you unlock it, however during the spool up time the boat should remain level, in other words no rolling or pitching. Locking the gyro's means the axes are locked into position, in other words, the sphere will roll identical to the boat roll. That movement creates extreme forces on the gimbals, so my guess is there is a limit of roll when you want to start up the gyro. If you find yourself all of a sudden in a heavy sea and you don't have the gyro running, my guess is you will be out of luck, there won't be any stabilization.
Once unlocked the gyroscopic effect of the sphere will oppose all movement of the boat. The sphere wants to stay in the 'level' position and the boat just moves around the gyro. That will work in all directions, so also pitch which is something fins won't do.
However, if you spool up the gyro while the boat is rolling you may end up calling 10 degrees list to starboard as the level position. From that moment on the gyro will think 10 degrees list over starboard is the level position and then will try to keep the boat in that position.
I am sure they have found a way around it, but am very curious how they did it and what limits they have with regard to spool up ?

It has two hydraulic arms to allow that. Once they hit their limit righting is gone.

When a gyro goes in gimbal lock it indeed does not function anymore, it will spin, but can't get out of the gimbal lock. Then you have to re gage the gyro, tell it again what is level. However, a 500 or 1000 kg gyro is not that easy to gage.

 

[Hippocampus]

Thanks for that post Mambo but think the devil in in the details. I have found although the SeaKeeper is totally amazing in decreasing roll it has little if any effect on pitch. The hydraulic arms will force the vacuum contained gyro to move in the AP direction(forward and aft) but has no degree of motion in the transverse plane ( athwart ship). In short it has minimal if any effect on pitch. Best I can tell the gimbals allow it to swivel only in one plane.
The fact it can’t pivot in the athwart ship plane is how it resists roll.
We haven’t spun it up in big seas but have in chop up to ~3’ even if on the same course for hours and hours it works fine and keeps us level. Haven’t spun it up when there’s already a list so don’t know if it would keep us on that list but think it might. So far when I hit the button to get it working after spin up if there’s chop head directly in to it so we’re pretty level. I say it again we are now coastal. Spin it up in a slip or at anchor. Have had it up to 3-4’ short period chop as well as swells and it’s amazing. Can’t say anything more from personal experience.
What we really need is a good engineering mind more familiar with the device or contributions from others who have gyros. My understanding is that if you have a sustained list before going off or while underway there’s a possibility in will try to preserve that list. Given being beam on is lousy on power or sail in the past when on sail we would zigzag to improve the ride quality. Still do that to the extent possible. Have yet to have the SeaKeeper induce a list.
In short I don’t think it ever knows what’s level.

 

[Hippocampus]

look,at it another way.
Fish don’t know what’s level they have no inclinometer but to the limited extent they work they work just fine without one.
I think fins and Magnus devices must have some sort of fancy pants inclinometer to know which way to turn.
But think as regards this issue gyroscopes are more like fish. They just resist roll. Do it pretty damn good up to,85% reduction.

 

[Mako]

Seems tech has moved along so electric not hydraulic.

I was just thinking about what you said and how thoughts on electricity have evolved in 30-40 years. Back then, the Pardeys were my heroes for remote exploring, and electricity was a 4-letter word. I don't think they even allowed flashlights on their boat. Maybe that was over-cautious, as they also refused to install a seacock and had to cr@p in a cedar bucket.

Today, electricity is very reliable, safely managed, and personally I would replace hydraulic systems with 48VDC or 230VAC electric in anything under 65 feet.

Anyway, just mulling on a Saturday morning.