Best stabilization

[Cruising Sea Venture]

I'd say a very high percentage of Nordhavn's are equipped for flopper stoppers, and a much smaller percentage, mostly older boats, are equipped with paravanes. So it can be hard to distinguish just looking at the boat. But I don't know if the structural needs are the same for both, and whether you could rig either way.

The structural requirements for working paravanes while cruising is entirely different then what is needed for flopper stoppers at anchor. I know our system, when designed by the naval architect, was made to withstand up to 10,000 lbs of downward pressure on the end of the 26' long poles, alternating every 3 seconds between full force downward and upward pressure.

Note, some folks use these terms interchangeably. When I say paravanes I mean the triangular units with a heavy weight at the front. Flopper stoppers are much larger, light weight units that usually have some type of hinged door that allows them to sink at anchor then resist coming up, but only light pressure. In Alaska, where we are now, the fisherman call paravanes "fish". I believe in the NE, the fishing boats call them "birds".

Jim
M/V Sea Venture
www.youtube.com/CruisingSeaVenture

 

[oscar]

F. It was mentioned in severe weather they are a liability. I also mentioned a yard worker telling me about a case of cracked frames on a boat. Don’t remember exact details but think it was on a big searay.

"Have heard" "Was told".... By a yard worker.... with an engineering degree from MIT?

And you use structural damage on a SEARAY as "data" for making definitive statements on the blue water suitability of a piece of equipment.

Right.

Dude, I mean this as constructive criticism. You don't know what you don't know. So you come here and ask questions, which is good, but then you argue the answers. You need to listen more and talk less.

 

[Cruising Sea Venture]

If interested in seeing paravanes deployed, operating in 3-5 foot seas with a roll of under 3 degrees, and being retrieved - all three are in our newest YouTube Video.

It's a short segment in the video - starting at 0:38 seconds in.

Thanks,
Jim
M/V Sea Venture
www.youtube.com/CruisingSeaVenture

 

[markpierce]

Thank goodness for inland/protected waters with little concern for high-effort stabilization.

 

[offshoreskiff]

Also, they do nothing at anchor, and paravanes work just as well at anchor as they do cruising.

....One thing is for certain, once you have a boat with stabilization you will not ever go back.

Jim
M/V Sea Venture
www.youtube.com/cruisingseaventure

Paravanes work while moving but have a fairly small effect while at anchor. When we are on on the hook we move to passive roll stabablization, flopper stoppers. We've found that a louvered panel works the best here.

I agree that when you find a good solution for stabilization under way or at anchor that it can greatly increace your comfort on the water.

 

[Hippocampus]

Try to be pretty upfront about stuff. Intentionally reveal sources so you can judge how robust they are. Think that’s simple honesty and I try to stay well aware of what I don’t know. Think my posts demonstrate that. Please chill. Disclosed the brand of the vessel knowing full well it further weakened the strength of the report and strengthen my quest for more knowledgeable answers.
Nordhavn assigns you a “guy”. Their guys are divided by region. For years now have dealt with the same “guy” every time I go to the Hinckley yard. Doesn’t matter why I go there. Nordhavn seems set up the same way. I”ll ask my Nordhavn “guy” when next we speak. I think (but don’t know) the knockout piece you see on the bulwark is to accept a pole for either paravanes or flopperstoppers. If he doesn’t know will ask on Dreamers.
BTW-Melita should be on the interesting boat thread. Looks to be a gorgeous and serious vessel.

 

[Hippocampus]

Great vids sea venture. Informative rather then just being a travel log.

 

[BandB]

Don't for one moment think any system is 100% safe and without potential risks. I've seen cases of paravanes breaking at sea, fins doing the same.

That said, I do not like having to handle or fool with paravanes so dismiss them, although I've never used them.

I do have considerable experience with fins. I'm used Naiad and Naiad Zero Speed and always been very pleased. I've also fallen in love with Sidepower Vector fins. Incredible and I've done over 9000 miles using them. I would choose them over Gyros because they're superior at speed and you avoid the spool up. That gets to a key element of discussion. Gyros outperform Fins at anchor, but by a small amount on some newer fins. I've been out in boats with gyros and felt great at slow speed but when at planing speeds over 20 knots I felt like they had been turned off as their help was so diminished. For this reason, many large builders, 100'+, are putting both fins and gyros on boats so you can have the best of both worlds.

I've only heard good on ABT Trac. I've heard good on the performance of Wesmar but similar to Weebles on communication with them. However, if you have a dependable yard you get them from, then communication issue is eliminated.

I've heard nothing more regarding problems with Gyros than any other type and most owners echo Fletcher. They are definitely no longer a novelty as they're on huge numbers of boats worldwide. Like any stabilizer they can be a challenge retrofitting with the need of strengthening and even moving equipment around not uncommon. If the builder is still around they can generally advise you well. It's older boats where you don't have drawings or specifications and the builder is long gone that may challenge you. Just keep in mind that they are less effective at planing speeds, just as many fins are less effective at anchor.

Today, all stabilizers have been refined and work well, it's just matching one up to your boat and your needs.

 

[Gordon J]

I am very pleased with Trac support and the system in general. I have completed two six year services on the stabilizers and found customer service excellent. I have never failed to get a technician on the phone to answer questions. Parts support is excellent, best I have seen for any system.

I have had the boat four and a half years. I serviced the stabs when I first bought and again a couple of months ago. I pushed up the service because we are planning to take the boat to Europe and I figured better here than there.

Since owning the boat I have rebuilt both hydraulic pistons that drive the fins. One started to leak after about 1400 hours of use. I rebuilt the non-leaking cylinder during the service because I figured now better than later. My system has two hydraulic pumps, one on each engine. Only one is used at a time. I had to rebuild one. Pistons and pumps are about $100 each to rebuild. I also had to replace a computer board last year! Cost about $1200.

Which ever hydraulic system you buy, ensure you have adequate fitting to fit on ends of hoses during repair.

My system now has about 1600 hours on it. I wouldn’t own a trawler without them.

Gordon

 

[CaptainSEA]

I am using ABT with STAR (Stab At Rest) on my Selene, they work extremely well, most part of new 100+ ft yachts are now using both Gyros and active fins (ABT sounds to be the most popular as far as I can see in my marina), quite often two to four gyros and fins, I guess there are pros and cons for each solutions also depending on the yachts they are fitted. One thing for sure, Stab at anchor is a game changer for my wife!!!

 

[Simi 60]

I'm going to put the question out there.....
In Beebe's book there is the implication from memory, of around 3 tonne of load on the cables and fish therefore structure.
Sounds a bit.

Yet Cruising Sea Venture and others run plywood fish.
Surely if you took one of those plywood fish, clamped 50% it to a bench and plonked a F150 ute on the overhanging half of the fish it would collapse.
I daresay it would collapse if hanging a hell of a lot less than that.
Surely then, there can not be "that much" load on the gear.

Just a thought.

 

[mvweebles]

Simi - two items. First, long lever of the poles multiples the force. There is not 3 tons on the fish. Second, operating in a viscous medium (water) provides partial resistance, not a brake force. Similar to why a fisherman can land a 300 lb marlin in 50 lb monofilament line that would snap a non-stretch line of equal rating. A vessel the size of Sea Venture (or yours) likely weighs at least 50 tons, perhaps much more. The resistive force must go somewhere. 10k lbs for design parameter does not sound unreasonable to me.

Peter

 

[Hippocampus]

Please correct if wrong. Isn’t it a simple vector diagram. The vertical force goes up the line from fish. Force is determined by load on the fish. How fast it’s moving and it’s surface area. That force is divided at the point at the end of the pole into compression on the pole and extension on the segment of line going up to the mast or midline structure where it’s attached. Other horizontal force is either on a foreguy or other structure stabilizing the pole preventing motion in the horizontal axis.
So forces involved change depending upon how big a fish and how fast the boat rocks and how much the boat weighs. So a smaller fish on a longer pole will develop the same vertical force as a bigger fish on a shorter pole. But the vertical force is the same if you want the same amount of roll prevention.

 

[Hippocampus]

Above needs a correction. Forgot to add in heave. Heave plus roll need to be considered when thinking about force on that first line from the fish. Especially if the fish isn’t in the same wind wave.

 

[FF]

Complication is not on every ones list to avoid and I love hydraulics for operating gear , but the few photos on the web have assured me that fins can be dangerous.

Sure the mfg. claim there is a breakaway ability should an errant log or Sealand box be struck underway , but part of cruising is once in a while running aground and having a big hole on the hull where the fin has poked thru has cost boats.

I see downsides to the paravane system (more work ,not pretty) but at least a system failure should not endanger the hull.

 

[Hippocampus]

They say about running aground “it’s not if but when” so your point is well taken FF. We visited a beautiful N40 that ended up having their entire fin system redone after catching the mooring pendant on a fin. Saw that boat with intention to buy it. Unfortunately due to the money owners put into it for that and other updating the price is unreasonable and they refused our offer. Could also see that happening with an anchor line especially if not all chain. So that’s another vulnerability.
However have read several stories where fish got out of control either due to operator error or seastate and caused damage. Could also envision serious injury should a cable snap.

 

[Hippocampus]

There’s a DD for sale in Turkey. Has Seakeeper and paravanes and sails. That maybe the best of all worlds. Adding flopperrs to a preexisting fish set up is a trivial expense. By picking what appropriate to the setting get around the weaknesses of each.

 

[Larry M]

This is from Beebe's first edition (1975). It gives you a good idea on the loading for paravanes.

 

[mvweebles]

We visited a beautiful N40 that ended up having their entire fin system redone after catching the mooring pendant on a fin.

I have to wonder what kind of Cirque du Soleil maneuver managed that bit of customization. I suspect this is the type of stuff people without fins worry about.....

In the end, there are pluses and minuses to each system.

Hydraulic Fins. Most convenient option for underway stabilization. Except for recent advances in zero-speed stabilization (which requires a significant power source), at-anchor stability is fairly easy to deliver via a relatively inexpensive flopper stopper system. It does require periodic maintenance which is fairly significant - boat must be hauled, fins dropped, and some specialty parts replaced.

Paravanes are simple and effective, but require some work/effort to set, so are best suited for longer runs. Most designs increase air-draft beyond limits of Loop, and they need to be pulled-in when running inlets/bars. Running in the shallow waters of Florida is not always practical. For at-anchor, fitting with an appropriate flat-plate flopper-stopper is easy and an inexpensive addition.

Gyro's are popular with those who have them and are the only system that have no appendages outside the hull and thus do not constrict air draft or drag, and present zero risk of a snag or impact damage. They are not usually a good refit option to an existing boat, but a strong contender for new-build applications for which they are increasingly popular. To operate, they require a constant source of power so generator must be running. Being the new-kid-on-the-block, they seem to have an unfair share of tomatoes being thrown at them by pundits.

Sail. I think a reasonably sized sail-plan (vs a useless steadying sail) is an under-rated option. Based on personal experience, I find steadying sails to be cute but mostly worthless for stability. But I do think a decent sail plan similar to a DD has merit for a cruising trawler. A sail rig with roller furling may very well be the most expensive option of the lot, and will 'set' the boat on a heel vs stabilize it level, and is not effective on some points of sail (indeed, dead downwind the tall mast may exacerbate roll), but it should be considered, especially for single-engine trawlers with no auxiliary power, albeit it's 'get-somewhere' power vs get-home propulsion. At-anchor stability would require some additional rigging, though fairly simple. There are no hull-appendages, though relatively low risk of losing rig overboard and the accompanying damage should not be ignored. It is also the only stability solution that also provides entertainment. Of all the options, Sail requires the most skill and learning curve, but not extreme. It is also the only system that has a sizeable positive impact on fuel efficiency.

So pick your poison. I don't think one system is the best or the worst. Some are more appropriate for certain types of travel or cruising. All have a long history of many satisfied owners who agree on at least one thing: Whatever you chose, stabilization is rarely viewed as optional, at least for cruising purposes outside of protected waters.

Peter

 

[Hippocampus]

Other thing I wonder about with gyros is this business of gensets. Just like most electrical devices they take considerable energy to get going but once up to the required rpm energy requirements fall significantly. Was taught when you run the genset it’s good to have a decent load on it. Usually at anchor your AP is off and many turn off their entire nav system. Unless you’re going in/out of the frig/freezer all the time the compressor loads are about the same. Most times you don’t need or want HVAC running. In fact often just a couple of solar panels is enough at anchor. So does that mean to get full use out of a gyro you need to run a genset at low load and decrease it’s service life?
See this differently for mega yachts where the air handlers are always on or ships but I’m a small time operator so wouldn’t this apply?

 

[Hippocampus]

If you’re interested the involved boat is Sea Trek. Owners are delightful, honest and open people. Boat is Bristol. Don’t know exact details just the outcome. In my travels have had frequent occasion to pick up a pendant which was gross from lying underwater allowing growth. So some add their own with two snubbed lines. Now it’s longer. With a tide or wind shift can see how you can get entangled. We’ve taken to just not using their pendant and going straight to the ball. That avoids the possibility of entanglement.

 

[Porgy]

One can play “what if” all day long about fins but, anecdotally I’ve run aground in mud a couple times with no damage, once having to be dragged sideways and heeled over by a tow for a couple hundred yards. Wrapped a mooring pennant once, hit a log or something in the ICW. I know of a Nordhavn 40 that hit rip rap in Portsmouth, RI with no damage and there’s a semi-famous photo, maybe a 50’ perched on the rocks propped up on a fin like it was a bike’s kickstand.

The fin is fiberglass and it bolts to the shaft way up in there. You need a two foot socket extension to get the nut off. One is much more likely to splinter the fin itself before getting a bullseye hit to the shaft.

On the other hand, I know of an otherwise passagemaking 50’ sailboat that ran aground on rocks recently and ripped it’s skeg and rudder off, very nearly sank. So be careful, those rudders can be dangerous.

 

[Hippocampus]

Like your attitude Porgy. Speaks of experience and reality.

 

[moparharn]

Has anyone mentioned ballast box? VUP mentions them and speaks somewhat favorably about them. They look a little strange when retrofitted, but has any builder included them in an original design? Completely passive and low maintenance. Would be interested to know if anyone has experience with them.

 

[MurrayM]

Best stabilization? Why not built in, rather than added on?

NEEL sailing trimarans is now producing LEEN power trimarans:

(These guys are rather 'top end', but there are more frugal designs out there)

LEEN-TRIMARANS - LEEN-TRIMARANS

 

[mvweebles]

Best stabilization? Why not built in, rather than added on?

NEEL sailing trimarans is now producing LEEN power trimarans:

(These guys are rather 'top end', but there are more frugal designs out there)

LEEN-TRIMARANS - LEEN-TRIMARANS

I was sort of waiting for idea of a multi hull. Many such as myself who have spent any appreciable time on a multi hull do not care for the ride in a seaway. Some call it snappy, I call it jerky. Nice space and nice at anchor, but underway? I prefer a monohull. A close friend with a very hi end power cat will return to a stabilized monohull.

And we haven't even gotten to discussion docking the dang thing.

Peter

 

[MurrayM]

...And we haven't even gotten to discussion docking the dang thing.

Electric pods in ama's.

This one is top heavy, in that living space square footage has been maximized. I'd prefer a more 'frugal' design.

There is no perfect boat, just one that has the least amount of compromises for each owner. Trimarans resolve a lot of issues for me.

 

[Hippocampus]

Maine cats seem more reasonable for mom & pop cruisers in my opinion . Unfortunately hard to find a good one for sail.

 

[Simi 60]

Simi - two items. First, long lever of the poles multiples the force. There is not 3 tons on the fish. Second, operating in a viscous medium (water) provides partial resistance, not a brake force. Similar to why a fisherman can land a 300 lb marlin in 50 lb monofilament line that would snap a non-stretch line of equal rating. A vessel the size of Sea Venture (or yours) likely weighs at least 50 tons, perhaps much more. The resistive force must go somewhere. 10k lbs for design parameter does not sound unreasonable to me.

Peter

But surely the weak point in the design would be the plywood fish?

Arms are aluminium supported by struts or dyneema - strong
Arms to fish are dyneema, cable or chain - strong
Fish are plywood with a compromising slot on the centreline - comparatively weak.

I really would have thought the fish to be the "fuse" and they would simply fold down the centreline where the slot is if large loads were applied.........yet they don't

Trying to get a handle on it as I am in a position next week to build folding h frame arms but can really only run a 1/2 inch eyebolt in close to cabin side, through the top deck roof beams which are laminated 3 inch x 3 inch and less than 1 ft apart , to support down loads.
Cabin side in column for compression loads and eyebolt arm would be at or very near a bulkhead position.

Load fore and aft is easy with dyneema running to a plate towards the bow

Obviously don't want to tear cabin off but in theory, it should be strong, its essentially a cube

A supporting mast structure is still trying to tear chain plates out of cabin side but the mast is more for height/angle of attack.
I am thinking our cabin height already gets us that height that others try and get from a mast.

 

[mvweebles]

But surely the weak point in the design would be the plywood fish?

Arms are aluminium supported by struts or dyneema - strong
Arms to fish are dyneema, cable or chain - strong
Fish are plywood with a compromising slot on the centreline - comparatively weak.

I really would have thought the fish to be the "fuse" and they would simply fold down the centreline where the slot is if large loads were applied.........yet they don't

Trying to get a handle on it as I am in a position next week to build folding h frame arms but can really only run a 1/2 inch eyebolt in close to cabin side, through the top deck roof beams which are laminated 3 inch x 3 inch and less than 1 ft apart , to support down loads.
Cabin side in column for compression loads and eyebolt arm would be at or very near a bulkhead position.

Load fore and aft is easy with dyneema running to a plate towards the bow

Obviously don't want to tear cabin off but in theory, it should be strong, its essentially a cube

A supporting mast structure is still trying to tear chain plates out of cabin side but the mast is more for height/angle of attack.
I am thinking our cabin height already gets us that height that others try and get from a mast.

Good point about plywood fish. The Kolstrand galvanized ones are readily available in the US. Wonder why bother with plywood?