Stabilizers: A Must for Passage-Making?

[Simi 60]

Haven't seen raising batwings.
The wings I am familiar with are horizontal sheet steel, 1/2" or so, affixed beneath the keel, extending to the maximum beam and secured in place by verticals that are bolted to the hull above the WL. They work well on FD boats with round hulls. Always in use, little or no drag losses.

These

 

[LeoKa]

I had rolling chocks installed, carefully measuring before and after cruise speeds and consumption vs. rpm. There was no measurable difference at any rpm.. They will not do the same job as active stabilization but do make a difference. They cost me $4K to have installed..

How did you manage to have the chocks for only 4K? I had a quote recently by a welder/fabricator for 10K. Was your 4K the total price?

 

[Xlantic]

Nice one but steel boat makes things easier therefore cheaper
and the mast was already there I'm guessing

But to add a mast to a boat without one or framework to support those loads especially if bulkheads aren't in the right place to support it will add a whole new magnitude of $$

Still sticking with our $30,000 guestimate based on others that have done the design and framework from scratch
And that framework will then be shading our solar as well
So not as easy or cheap for some unfortunately

Simi, your boat is so tall you may not need a mast or strongback to support the paravane poles. Just make the poles long enough (for the angle you use) to reach the level of the flying bridge roof and connect them with horizontal stays to chainplates attached to the roof.

You can use two or three stays to distribute the stress on the roof and keep the booms centred fore-and-aft.

Something like this:

 

[rslifkin]

Simi, your boat is so tall you may not need a mast or strongback to support the paravane poles. Just make the poles long enough (for the angle you use) to reach the level of the flying bridge roof and connect them with horizontal stays to chainplates attached to the roof.

You can use two or three stays to distribute the stress on the roof and keep the booms centred fore-and-aft.

Something like this:

I was thinking the same, just reinforce the roof to handle the loads and attach there.

 

[DDW]

How did you manage to have the chocks for only 4K? I had a quote recently by a welder/fabricator for 10K. Was your 4K the total price?

That was the total installed price. It was done in one day by Roy Brown out of Coombs, BC. Fiberglass moldings were pre-made and fitted to the chines. He's done hundreds of them.

 

[Airstream345]

Simi, your boat is so tall you may not need a mast or strongback to support the paravane poles. Just make the poles long enough (for the angle you use) to reach the level of the flying bridge roof and connect them with horizontal stays to chainplates attached to the roof.

You can use two or three stays to distribute the stress on the roof and keep the booms centred fore-and-aft.

Something like this:

Those appear to be more flopper stoppers than paravanes. Are they used underway?

 

[Airstream345]

Also, went down the ART rabbit hole and found this document from the Navy in 1962:

https://apps.dtic.mil/sti/pdfs/ADA423062.pdf

Interesting stuff with a lot of calculations.

 

[Simi 60]

Simi, your boat is so tall you may not need a mast or strongback to support the paravane poles. Just make the poles long enough (for the angle you use) to reach the level of the flying bridge roof and connect them with horizontal stays to chainplates attached to the roof.

You can use two or three stays to distribute the stress on the roof and keep the booms centred fore-and-aft.

Something like this:

I had thought of that and we did just have these made for flopper stoppers at anchor

They are half lengths of 80x3 tube
Thought of going full lengths of 80x6 tube but kept being told about these huge loads and didn't want to go tearing the cabin apart.
I guess I could have built a fuse into the system in the arm to paravanes rope.

Another part of the puzsle was the actual paravanes
I didn't want the steel ones, to bloody heavy and boat damaging but that is all there is here
I could make a set out of ply or composite easy enough but can find no info on dimensions and fin/hole placements so it keeps getting put in the too hard basket

 

[Xlantic]

Those appear to be more flopper stoppers than paravanes. Are they used underway?

Yes, currently just used at rest.

 

[LeoKa]

That was the total installed price. It was done in one day by Roy Brown out of Coombs, BC. Fiberglass moldings were pre-made and fitted to the chines. He's done hundreds of them.

I wonder, if the price I was quoted is due to steel fabrication for my steel boat? If they had molds available in BC, that makes it easier to install on a fiberglass boat.

 

[Xlantic]

I had thought of that and we did just have these made for flopper stoppers at anchor

They are half lengths of 80x3 tube
Thought of going full lengths of 80x6 tube but kept being told about these huge loads and didn't want to go tearing the cabin apart.
I guess I could have built a fuse into the system in the arm to paravanes rope.

Another part of the puzsle was the actual paravanes
I didn't want the steel ones, to bloody heavy and boat damaging but that is all there is here
I could make a set out of ply or composite easy enough but can find no info on dimensions and fin/hole placements so it keeps getting put in the too hard basket

With the poles at a 45º angle the (horizontal) sideways pull on the roof would be equal to the downward pull of the paravanes. Using chainplates for the stays and maybe using two or three stays per pole should distribute the load enough for the roof to handle it.

(In my boat the roof is made up of two glued layers of 1" plywood and is strong enough to take the weight of the loaded mast with limited support from beneath.)

I would also like to obtain the dimensions for the plywood paravanes as well. I have only managed to find those for the metal parts from the Mobius site.

 

[Hippocampus]

Why do you want stabilization? Think there’s two reasons.
One is comfort.
The other is to prevent things from shifting or falling or failing to function. Some heaters won’t tolerate high lean angles and some engines don’t like them much either.
Safety isn’t one of them. Regardless of technique none improve AVS nor have a material effect on stability (using naval architecture lexicon). Indirect effect of increasing comfort may impact safety but it’s not a direct effect.
Folks are sensitive to heave, pitchpoling and roll. All techniques primarily effect roll but not the other two unless multiple devices are employed. Displacement is the major factor in heave and hull shape along with meta center/gyradius in pitchpoling.
Folks tend to divide into those sensitive to rapid oscillations and those more sensitive to slow. Due to the physics fins, fish/birds, rotors and gyros do well with slow. There is some literature suggesting rotors and gyros do better with rapid oscillations and as well or better with slow. Both have a shorter latency to effect. Tanks would appear to have the longest latency and least effect followed by fish/birds.
All have significant limitations to the average cruiser.
Although rolling tanks require no additional power they can decrease AVS and are least effective. The rest require power input.
Rolling tanks and gyros have not external appendages and should not effect speed. The rest can. Some fin arrangements create lift sufficient to increase speed by decreasing wetted surface but aren’t applicable to many cruising designs.
Birds/fish are limited by the need to have sufficiently deep water for deployment. For cruisers usually around 18-20’.at a minimum. Often greater due to wave action. Failure of one can produce catastrophic decrease in AVS resulting in capsize.
Gyros are not instant on and require more energy to spin up.
Fins and fish increase drag. Modern fin design mitigates this to some degree.
So you pick your poison.
Think for most mom and pops fish are a poor choice. Cheapest by far but the most trouble to use and unusable in many commonly encountered cruising settings.
Fins continue to lead the pack for BWBs with Magnus rotors a close second.
Rolling chocks and tanks have the least effect with tanks not being practical on many cruising designs.
Gyros make sense for the coastal cruiser. Especially those in debris laden or skinny water. Rotors probably second.
My two cents.
Interesting to note in this thread those to have eschewed stabilization either have a program where it’s not required or boats with a high so called comfort quotient.

 

[sjisailor]

Very nice summary and discussion, Hippocampus!

 

[Airstream345]

Failure of one can produce catastrophic decrease in AVS resulting in capsize.

Is this true? I've heard of many who lost one fish but continued on with one. Others who cruise with one intentionally. Generally they rigging is designed with a weak point that allows the fish to break free in an overload, sparing the rigging. I can't imagine a system designed to release under extremes would also result in a capsize.

 

[mvweebles]

Is this true? I've heard of many who lost one fish but continued on with one. Others who cruise with one intentionally. Generally they rigging is designed with a weak point that allows the fish to break free in an overload, sparing the rigging. I can't imagine a system designed to release under extremes would also result in a capsize.

Good catch. A rigging failure - whether for paravanes or sail-plan (an under-discussed form of stabilization) - is not necessarily catastrophic (as evidenced by the recent N40 crossing the Atlantic that had a rigging failure), but a major inconvenience and expense.

In the end, there is no one perfect stabilization system for all people, use-cases, and budgets. But there is near universal agreement by those who have cruised a stabilized boat that the effort/expense is worth it and they would not cruise a non-stabilized powerboat.

That said, Kevin Sanders in his Bayliner 4788 makes a good point: some wide-body/relatively low profile planing sedan-layout hulls such as Bayliner, Tiara, or Sunseeker type boats make decent sea boats up to moderate conditions simply because they are so wide and relatively low (so-called 'form stability').

There are pros and cons for each form of stabilization. The Exam Question from the OP was: Is stabilization a must for passage-making? The answer is yes. Which form of stabilization is right for any person/circumstance is hotly debated, but the answer is something is needed.

Peter

 

[Hippocampus]

Is this true? I've heard of many who lost one fish but continued on with one. Others who cruise with one intentionally. Generally they rigging is designed with a weak point that allows the fish to break free in an overload, sparing the rigging. I can't imagine a system designed to release under extremes would also result in a capsize.

Yes this is true. The Canadian government propagated a statement advising of this risk. It’s logical this risk could occur. Rotors and fins work by pushing one side up and the other down. Fish work by delaying one side from rising. In effect pushing one side down. They are effective has which side is in play alternates. If one side of a rotor or fin pair fail the other will still work out of synchrony to the wave chain. If one side of paravanes fail it will work both against but also with wave induced motion. The single paravane will also create unbalanced drag on one side only increasing the risk of broaching. This unbalanced effect can also increase the risk of being overwhelmed. Due to losses the Canadians came out with their statement.
Here are some of the other risks
https://tc.canada.ca/en/marine-tran...ety/ship-safety-bulletins/bulletin-no-15-2000

The addition of any anti-roll system, except bilge keels, would be a major modification and should only be undertaken after the vessel’s stability has been assessed, as they usually reduce the vessel’s reserves of stability. A system of paravane stabilizers reduces its reserves of statical stability because of all the added weight relatively high up in the vessel. Once fitted, on a vessel, the outriggers should be lowered to the operational position while at sea, even if the paravanes are not deployed. This improves the vessel’s stability because, in the operational position, it lowers the center of gravity. Please refer to Figure 3.3
Paravane stabilizers present a potential risk to the vessels stability due to the introduction of large capsizing forces, resulting from:
The loss of one paravane (fish).
Failure of a fixture or rigging, resulting in the loss an outrigger boom.
Failure of an outrigger hinge apparatus, or fracture of the outrigger itself.
One paravane becoming entangled in fishing gear or other obstruction.
If operating in icing conditions, the extra booms and riggings increase potential ice accretion area.
There are personal and vessel safety hazards associated with one paravane ‘broaching’ or breaking the surface of the water while in heavy sea conditions. Similarly if a stabilizer (outrigger) should dip into a wave while the vessel is steaming, it could easily fracture.
Potential vertical and horizontal movement of the outrigger boom must be minimized by appropriate placement of riggings, in line with the outrigger configuration.
All associated riggings, hardware and mounting point fixtures should be checked regularly for deterioration and fatigue.


Figure 3.3:
Paravane stabilizers use the forces of resistance created by the paravanes (fish) to reduce the roll, however their installation and operation actually reduces the statical stability reserves of the vessel.
(Courtesy of the Canadian Council of Professional Fish Harvesters).


Checklist items (q): Stability considerations for hull mounted fin roll-reduction systems:

 

[Xlantic]

Is this the advise?

https://tc.canada.ca/en/marine-tran...ety/ship-safety-bulletins/bulletin-no-15-2000

 

[Hippocampus]

Would note we rejected one N40 and a diesel duck from purchase due to the presence of only fish(paravanes) for stability.
Most small motor pleasure craft have poor AVS as compared to blue water sailboats. Have no interest in making it worst. The downside of gyros is weight. The upside is in most installations they are placed on the stringers so if anything improve AVS. Would similarly reject any vessel modified to accept rolling tanks unless the installation was signed off by a reputable naval architect as not having a significant deleterious effect on AVS.

 

[Hippocampus]

Yup and from my limited understanding they are looked at as a risk from non governmental entities as well. We need to consider we are mostly on small boats not ships. Although repetitively here people state their belief that with modern weather forecasting you can reliably avoid weather. I have no such faith and continue to believe for any passage over five days adverse weather is possible and any prediction will not be timely enough to allow avoidance. Personally I would not own a vessel with paravanes. I doubt I will ever own a vessel stiff enough and large enough where rolling tanks would be appropriate. Odds for the lottery aren’t that good.similarly rolling tanks are more effective the higher up they are. So you are adding weight where it must decrease static stability and AVS. No thank you. There’s a reason you see neither paravanes nor rolling tanks on new construction recreational pleasure craft. It’s called physics.

 

[sunchaser]

Would note we rejected one N40 and a diesel duck from purchase due to the presence of only fish(paravanes) for stability.
Most small motor pleasure craft have poor AVS as compared to blue water sailboats. Would similarly reject any vessel modified to accept rolling tanks unless the installation was signed off by a reputable naval architect as not having a significant deleterious effect on AVS.

As an aside, active stabilizers on a well-found popular brand boat help the sale and price.

 

[socalrider]

This continues to be a fascinating discussion.

The more I think about roll tanks the more they frighten me. We were just heading down the back side of Catalina a few days ago with 4-5' long period swells on our 3/4 stern. Of course, the rolling motion of our boat was very slow compared to what we'd encounter if they were off our bow. So how do you "tune" a roll tank given the different frequency at which a boat rolls underway? A long slow roll would result in all that liquid sloshing down to the low side of the boat, exacerbating the roll, reducing stability & comfort & in survival conditions increasing the chance of capsize. I can imagine it would be quite frightening for the crew even in non-survival conditions.

I can understand how failure of a single paravane could be dangerous in survival conditions (more relevant to fishing boats than most cruisers). That could be rectified pretty quickly by cutting a line or pulling up the fish - overall it seems like a manageable risk for a competent crew, but I take your point @Hippocampus that they have operational disadvantages for a cruiser in some conditions. They're still appealing to me as we have very deep water here, limited debris in the water, long passages (but not necessarily multi-day), and rolly anchorages. And I'm cheap.

 

[Jeff F]

That said, Kevin Sanders in his Bayliner 4788 makes a good point: some wide-body/relatively low profile planing sedan-layout hulls such as Bayliner, Tiara, or Sunseeker type boats make decent sea boats up to moderate conditions simply because they are so wide and relatively low (so-called 'form stability').

My experience with semi-displacement boats is that comfort and sea keeping abilities increase with speed. I think Kevin has made this point before. The form stability underway comes in large part from the lift that's provided at higher speeds.

I think that's a benefit of SD designs that's not talked about much. The higher speed capabilities often can be used to increase comfort and control in moderate conditions.

Sent from my moto g play (2021) using Trawler Forum mobile app

 

[rslifkin]

My experience with semi-displacement boats is that comfort and sea keeping abilities increase with speed. I think Kevin has made this point before. The form stability underway comes in large part from the lift that's provided at higher speeds.

I think that's a benefit of SD designs that's not talked about much. The higher speed capabilities often can be used to increase comfort and control in moderate conditions.

That's a big factor with a good SD or planing hull and one of the reasons they're so range limited for long distance cruising in many cases. When the going gets tough, you have to let the conditions dictate the correct speed for best comfort and handling. A bit less so if the boat is stabilized, but there are still times where (fuel permitting) the best thing to do is just go faster.

 

[Hippocampus]

Or change direction slightly. Corkscrewing makes people puke more than any other motion on a boat. Even in prior sailboat with AVS of 130 when crew got listless and lethargic well before they showed other signs of motion sickness would change angle of attack. Would do this even if it meant tacking or gybing.
Dashew was those to popularize the idea of speed improving comfort (and safety) on a cruising boat. His treatise on storm tactics is a worthwhile read even if you never have the resources to own a boat like that. Some of his thinking is counterintuitive until you understand the rationale and physics. We lost our genset on our first long transit. We were time limited and it was sloppy. So kept it at 10-12kts. It was fine. Our fuel burn is much better at 7.4k with the genset on with the SeaKeeper running. So it’s not about speed but rather comfort for us.
I get nervous when surfing. Worry about broaching. Don’t even trust the AP then. Find running a simgin faster than the wave train (depending upon wave height) gives better control. So it’s not only about comfort.

 

[mvweebles]

....Personally I would not own a vessel with paravanes...... There’s a reason you see neither paravanes nor rolling tanks on new construction recreational pleasure craft. It’s called physics.

Diesel Ducks, Nordhavns, and many new boats out of the PNW can be purchased with paravanes. I'd venture more new powerboats offer paravanes than sail plans. By way of example, the recent N40 that lost its infrastructure was inconvenienced, but not imperiled. Just as Hippocampus was when he lost his generator, or I was when my old Vosper fins aged-out.

Honestly, a gyro system is about the last stabilization system I'd ever install simply because I cannot see myself as a 24/7 generator boat. Nothing wrong with the system, just not how I roll (so to speak). The wrong technology for me.

For a single engine trawler such as mine or Hippocampus') Nordic Tug that will get cruised some distance, there's an argument for a sail plan for both stability and auxiliary propulsion - not much harder to deploy than paravanes I'd reckon. But tradeoff is air draft - just like most paravane setups.

It takes some thought to figure out what system is best for any given individual. The good news is there are several viable solutions all with slightly different benefits and disadvantages. Just depends on how you will use the boat.

Peter

 

[Marco Flamingo]

The key is just to get the water to roll 180° out of sync with your boat.

It actually is less than 180 degrees out of sync. As the boat tips to port, it "loads up" the force that is going to right the vessel and (especially if timed with a synchronous wave that aids the righting force) whips over to starboard. We've all felt that condition where the first tipping to one side isn't the issue. It's the feeling that the next roll is going to be worse. If, when the boat tips to port, just after the vessel begins to right itself some additional weight is added to the port side, the effect of the righting force is dampened. The roll would be diminished and the roll period would be lengthened. But the "wave" in the tank only needs to arrive a moment after full roll to port, not necessarily 180 degrees out of sync. Too soon is bad as it would increase the roll. Too late is much less effective or even ineffective.

And it isn't just the weight transfer of the fluid. It is also the momentum. The wave smacks into the low side of the tank just after the tank (and the entire vessel) is beginning to right itself. The larger the roll, the bigger the smack. The further the tank end is from the center of buoyancy, the more effect of the smack.

Timing the smack is everything and, without adding complexity to an ART, it appears that one must choose which roll amplitude to most effectively minimize. One might think that they should concentrate on minimizing a monstrous 45 degree roll, whereas in reality it is the 10 degree nuisance roll that is frequent. I would love to really stifle a 10 degree roll even if it meant only slightly reducing a 45 degree roll (which I've never experienced in a trawler). Probably the best way to minimize a 45 degree roll is by using my mooring lines and watching the weather.

Are ARTs dangerous? Yes, they can be. It's like having somebody jumping back and forth on the flying bridge. If the person weighs over 2,000 pounds and times their jump incorrectly, they might cause the boat to tip over. One could do a risk assessment as to whether they would prefer to have an ART capsize their boat or to have an active stabilizer fin tear loose and sink their boat. I haven't yet thought of a Henny Penny fear of paravanes but I'm sure that there is one.

That U.S. Navy study is a perfect example of the rabbit hole. My eyes glazed over by page 5.

 

[hollywood8118]

Would note we rejected one N40 and a diesel duck from purchase due to the presence of only fish(paravanes) for stability.
Most small motor pleasure craft have poor AVS as compared to blue water sailboats. Have no interest in making it worst. The downside of gyros is weight. The upside is in most installations they are placed on the stringers so if anything improve AVS. Would similarly reject any vessel modified to accept rolling tanks unless the installation was signed off by a reputable naval architect as not having a significant deleterious effect on AVS.

We get it you don't like paravanes!


But... those of us who have ACTUALLY cruised boats with them offshore and have actual knowledge of how they work on a recreational power boat like them. Years ago I read the Canadian info and this was relevant to commercial boats who are out in crap weather that the rest of us "pleasure" boaters chose to sit tied to the dock. Not to mention that the overall stability of lots of commercial boats changes drastically due to gear on deck, product in the hold or holds ballasted down to help the stability if empty. Keep in mind this report was also geared to the crowd that on a relatively frequent basis rolls boats over do to many other factors not related to paravanes.


We also get it you love your gyro, personally I would not own a boat where the genset has to run all the time to make the boat ride better.


Many have I guess been lucky to survive just having one fish in the water, I personally have deployed just one at times due to needing to take the edge off the roll .. or because I was just lazy and the boat didn't need both.
Lots of boats do just fine with paravanes, some folks prefer them for the simplicity.
HOLLYWOOD

 

[Simi 60]

We get it you don't like paravanes!


But... those of us who have ACTUALLY cruised boats with them offshore and have actual knowledge of how they work on a recreational power boat like them. Years ago I read the Canadian info and this was relevant to commercial boats who are out in crap weather that the rest of us "pleasure" boaters chose to sit tied to the dock. Not to mention that the overall stability of lots of commercial boats changes drastically due to gear on deck, product in the hold or holds ballasted down to help the stability if empty. Keep in mind this report was also geared to the crowd that on a relatively frequent basis rolls boats over do to many other factors not related to paravanes.


We also get it you love your gyro, personally I would not own a boat where the genset has to run all the time to make the boat ride better.


Many have I guess been lucky to survive just having one fish in the water, I personally have deployed just one at times due to needing to take the edge off the roll .. or because I was just lazy and the boat didn't need both.
Lots of boats do just fine with paravanes, some folks prefer them for the simplicity.
HOLLYWOOD

I've read that same report a few times and that is my take on it as well

I'll also add that in my eyes any vessel that actually needs an add on like stabilisation to be safe or useable has design issues imho.

And if having to go the big spend and then running Genset full time for comfort I'd change vessel and put the extra towards a large commercial style power cat.

Ex ferries in Aluminium are great candidates, they can carry the payload of 100+ passengers out to the reef and islands and are often delivered to other counties on their own bottoms.

Something like this - she's been for sale for a while
Cheeky offer with a 3 in front of it?
https://yachthub.com/list/boats-for...atamaran-21-m-alumunium-ferry-pleasure/250930

 

[mvweebles]

I've read that same report a few times and that is my take on it as well



I'll also add that in my eyes any vessel that actually needs an add on like stabilisation to be safe or useable has design issues imho.



And if having to go the big spend and then running Genset full time for comfort I'd change vessel and put the extra towards a large commercial style power cat.



Ex ferries in Aluminium are great candidates, they can carry the payload of 100+ passengers out to the reef and islands and are often delivered to other counties on their own bottoms.



Something like this - she's been for sale for a while

Cheeky offer with a 3 in front of it?

https://yachthub.com/list/boats-for...atamaran-21-m-alumunium-ferry-pleasure/250930

Cool idea. Looks interesting and a decent project. Wouldn't be hard to create a suitable living and work space.

I've crewed on a friend's 52 foot power cat and I have to say, I'm not overly fond of the tide, especially with anything approaching beam seas. Great at anchor and has an amazing cockpit area. But both the owner and myself feel a stabilized monohull has a better ride. His wife suffers horribly from seasickness and had hoped the power cat would assist. No noticeable effect.

I think stabilization is more of a comfort item which bleeds into crew safety in a way. A recent episode of Below Decks showed a super yacht with failed stabilizers. Guessing over 80-meter yacht that easily went to 25-30 degrees on either side.

Peter

 

[ofer]

thinking of installing something like this. any comments appreciated