Paravanes vs. Sea Gyro vs. Active Fins

Hi All,
I will eventually be adding stabilizers to my 52' Trawler. Paravanes are way cheap compared to Active Fins or the Sea Keeper / Sea Gyro. I see lots of advantages to the Sea Gyro but I'm not too excited about having to run the Genny all the time to power it.
The real question I have is "how effective are the 3 systems in attenuating Roll?" Does anyone have any data on the percent of roll attenuation, etc... for each these 3 systems?

Thanks all,

Taras

You might as well ask which is better one engine or two,
OR why would anyone anchor with anything but a Danforth, or CQR or .....?

ALL the mfg will claim the most success for their product .

To my mind the ability to repair a flopper stopper setup ,
with out flying in a gaggle of "experts" and a truck load of parts wins.

For testimonials just read some marine motorist cruising accounts , to keep track of effectiveness and repair history and costs.

And of course hull fins have knocked BIG holes in some cruisers hulls.

FF

I don't have any data but I can tell from personal experience we like the paravains. From Alaska to Colombia the only failure was when we hit a dead head and destroyed one of the fish off the Oregon Coast. We carry 2 spares. We have been tangled up in nets but no damage. You can have a cup of coffee in the pilot house without it tipping over underway (in most seas). They work great at anchor.

The down side: How they are retrieved and deployed, each fish weighs about 30 lbs and are about 320 sq" in size so they're awkward and heavy. We loose about 3/4 of knot when they're in the water and you can't run in real shallow water. They travel at 15' below the surface in flat water so we don't deploy them in water less than 25' to 30'.

In the last 4 years I don't remember seeing a boat that have both active and passive systems. We do see a lot of boats that have active stabilizers and flopper stoppers/roll stabilizers for when they are at anchor like the system sold by ForeSpar.

Active stabilizers work great - except for anchoring

Gyros are mainly for "lighter sea state conditions" and anchoring.

Paravanes are for all conditions.

ABT has a new STaR system, which is the active fin type with larger fins than standard, which they say will work at anchor. No idea how that could work.

I have Niad Active Stabilizers

Active Stabilizers are relatively trouble free but they cost at least 40K for parts alone. They have the ability to improve tracking in following and quartering sea conditions as they actively check the yaw as a boat starts to broach. My Hatteras 48 tracks straight as an arrow in heavy conditions. The down side is they slow the boat about 1/2 a knot and need some forward motion to work. The seals on the fin shafts should be replaced every 10 years or so. The Gyro option is even more pricy and has limitations in really rough conditions and actually need to be shut down at some point. They also require a fairly large generator running constantly. They do have the advantage of stabilizing at anchor if you don't mind running the generator 24/7. Paravanes have there own problems besides fouling on crab pots and such. They too can hole a boat as happened to a good friend of mine off the Mendocino coast. They also if not carefully handled can foul your running gear with disastrous results. What hasn't been mentioned is a stay sail which has some benefit depending on size and wind force. I have a friend with a Nordhavn 40 with both paravanes, active stabilizers and a stay sail. In his case he's still not happy with the ride so I guess you just can't completely control all motion in some boats.

I am thinking about adding active stabilisers since I already have a large capacity constant flow hydraulic system running off the main engine. It used to haul nets but now only runs the anchor windlass and bow thruster. I guess I would just need the actuators and a control unit. Does anyone have an opinion if this would be practical or cost effective?

The pump is just the begining

You will have to talk to Niad. The hydraulic pump is just the beginning. But it might be convient to use. I highly recommend active stabilizers. I have 6sgft blades on 9sgft machinery. My boat weighs 66'000lb and the ride is wonderful with the stabilizers on.. The big gain as I mentioned is down wind tracking. As following waves overtake my boat from either quarter as the stern lifts and the boat starts to heel and turn, the stabilizers correct the heel driving the boat in a straight line down the face of the waves. Obviously the stabilizers do nothing about up and down fore and aft movement but there is very little roll. Beam seas are often the most comfortable ride. They can be noisy in really rough seas as the rams hit their stops when functioning though the full range of travel. I was in 10-12 foot wind waves standing unbraced in my pilot house door taking photos of a Hans Christian 43 getting beat up with a 200mm telephoto lens on a 2xe telextender. You have to feel them to believe how well they work. I believe they have some benefit at anchor as the two big blades act like bilge keels and at least dampen some of the roll. If you compare the total surface area it is not much different that a daisy chain of flopper stoppers.

Does anyone have an opinion if this would be practical or cost effective?

Big question is weather you can get to the area the fins are installed , and can easily beef up the hull in the local area.

FF

Scary said:

...Paravanes have there own problems besides fouling on crab pots and such. They too can hole a boat as happened to a good friend of mine off the Mendocino coast. They also if not carefully handled can foul your running gear with disastrous results...

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I agree that paravanes and all stabilizers have their own problems besides fouling crab pots and such. But how can paravains hole a boat? If properly designed and installed, the fish should not be able to foul the running gear. The length of the poles and the length of the three strand/wire rope/chain prevents under any conditions the fish making contact with the running gear

Once above 46 or so feet paravanes fall out of favor. It is hard to find paravanes on a new build (Coot noted of course Mark, but when will you give them a workout in deep water?) except the Buehler type designs. Five years or so ago the paravanes on a Nordhavn hooked a sailboat's anchor line pulling the sailboat up to the deck of the Nordhavn and killing the owner's wife who was trying to fend off the approaching sailboat. The ultimate paravane boat of course is a sailing vessel without all the debris attracting tethered fish swimming alongside. I've yet to sag anything other than kelp with my active stabilizers.

Shackel failure

Larry M said:

I agree that paravanes and all stabilizers have their own problems besides fouling crab pots and such. But how can paravains hole a boat? If properly designed and installed, the fish should not be able to foul the running gear. The length of the poles and the length of the three strand/wire rope/chain prevents under any conditions the fish making contact with the running gear

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Greg Yocum, Bringing his 50' wooden salmon trawler back from Alaska had a bird come loose and swing into his hull. It was so rough that by the time he got it under control they had holed and fractured several planks at the water line. He and his brother bailed 36hrs with 5 gallon buckets from Mendocino to Moss Landing. For some reason the sea conditions wouldn't let them make landfall sooner. Most fishing boats set up their paravanes so they can't foul running gear so if they come loose from the boom they can't reach the prop which means they can swing into the hull sides. In this case the line towing the paravane held and the shackle attached to the line from the boom failed and the bird swung into the hull at waterline depth. Greg said it was too rough to get on the fore deck and try to retrieve the bird. They ended up cutting the cable but the damage was done. If you check out the birds on fishing boats you will see many of them are made out of plywood or that white plastic boat board. Most of the fishermen have there own set of tricks to make them fly smoothly. When I was researching ways to stabilize I spent a couple of day's talking to fishermen about how to effectively set up booms and paravanes. These are the guy's using them to make a living. There are probably as many ways as there are fishermen. To my knowledge there are no fish boats using active stabilizers as most fear fouling them in pots nets or fish lines. Every fisherman said it would be impossible to work with out paravanes.

sunchaser said:

Once above 46 or so feet paravanes fall out of favor. It is hard to find paravanes on a new build (Coot noted of course Mark, but when will you give them a workout in deep water?) ...

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The Coot has no paravanes. Mine does have two small sails. They were an option offered by the builder for $6500 (paravanes weren't). I believe two of the six Coots built have stabilizing sails.

Reference on stabilizers

http://www.google.com/url?sa=t&rct=...fOoja7eVbI2eysQeA&sig2=e_GGN47-Rl_ga3yoZV5big

Scary said:

... If you check out the birds on fishing boats you will see many of them are made out of plywood or that white plastic boat board. Most of the fishermen have there own set of tricks to make them fly smoothly...

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Ours are made of plywood and the lead on the bottom is 1/2 of a 55 lb down rigger ball. We like the plywood for it's easy on the fiberglass if you touch the side during retrieval or deployment. You can buy them complete for less than $200 from Alaska down to CA and you can also just buy the parts. We paint/seal the fish every year or so and "tune" them occasional to keep them running true.

That had to be a scary ride for Greg. Something I hope we never have to experience. Thanks for the story.

sunchaser said:

Once above 46 or so feet paravanes fall out of favor. It is hard to find paravanes on a new build (Coot noted of course Mark, but when will you give them a workout in deep water?) except the Buehler type designs. Five years or so ago the paravanes on a Nordhavn hooked a sailboat's anchor line pulling the sailboat up to the deck of the Nordhavn and killing the owner's wife who was trying to fend off the approaching sailboat. The ultimate paravane boat of course is a sailing vessel without all the debris attracting tethered fish swimming alongside. I've yet to sag anything other than kelp with my active stabilizers.

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Above 46 feet fall out of favor? Back in the Northeast...about every seagoing fishing vessel has them from 40 feet to well over a hundred feet.

Gee ps, I thought this was a pleasure boat discussion. Silly me. But since you raised the topic, what pleasure craft new build (excepting Buehler hippie type designs) over 46' uses paravanes? Certainly not new build "pure" trawlers along the Nordhavn, Krogen, Northern Marine or Watson lines.

sunchaser said:

Gee ps, I thought this was a pleasure boat discussion. Silly me. But since you raised the topic, what pleasure craft new build (excepting Buehler hippie type designs) over 46' uses paravanes? Certainly not new build "pure" trawlers along the Nordhavn, Krogen, Northern Marine or Watson lines.

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OK..fair enough...just pointing out that they are popular for what they are and can be fitted on larger vessels. Sometimes the trawler crowd takes a lead from the comms as much as the yachties.

Not to nit pick

Some of the larger over 50' Nordhavns use paravanes as well as active stabilizers.

.

After the early 2000s, few if any Nordhavn 50s, 52s, 55s, 57s, 60s or 62s had them installed. They were quite common on the early 62s but with better active stabilizer designs and increasing reliability, paravanes went kaput.

Why not just get a catamaran and be done with it? But then, that wouldn't be a trawler, would it? ... I'll stick with sails and avoid the inherent difficulties of gyroscopes, protuberances, and "wild" paravanes.

"Why not just get a catamaran and be done with it? "

CATS CAPSIZE

And give a hideous ride in a beam sea.

Like being in a box barge , the cat takes up the wave shape even quicker as they are usually light.

"After the early 2000s, few if any Nordhavn 50s, 52s, 55s, 57s, 60s or 62s had them installed. They were quite common on the early 62s but with better active stabilizer designs and increasing reliability, paravanes went kaput."

Perhaps the new trawler folks had no concept on their use?
And no use for offshore stability , just a boat that looks "offshore"?

For a lumpy ICW or short coastal cruise the hyd setup is perhaps better as it is simply switched ON , not deployed.
And a MR Fix It is only a phone call at the next marina

FF

FF said:

Does anyone have an opinion if this would be practical or cost effective?

Big question is weather you can get to the area the fins are installed , and can easily beef up the hull in the local area.

FF

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I have calculated where the fins/actuators need to be mounted and fortunately it's just forward of the fuel tanks - in a relatively clear area. The solid glass hull, with frames and stringers, at close centres will be easily reinforced at this location.This is work I am confident to do myself after I get someone to determine the layup required. I will do more investigation re cost of parts - it may be gross overcapitalization!

I too have thought about catamarans but they make me sick (literally).

sunchaser said:

After the early 2000s, few if any Nordhavn 50s, 52s, 55s, 57s, 60s or 62s had them installed. They were quite common on the early 62s but with better active stabilizer designs and increasing reliability, paravanes went kaput.

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Seems it all depends on how much money you have.

Cheep and low tec.

High tec and expensive.

SD

Bendit said:

I have calculated where the fins/actuators need to be mounted and fortunately it's just forward of the fuel tanks - in a relatively clear area. The solid glass hull, with frames and stringers, at close centres will be easily reinforced at this location.This is work I am confident to do myself after I get someone to determine the layup required. I will do more investigation re cost of parts - it may be gross overcapitalization!

I too have thought about catamarans but they make me sick (literally).

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My parts from Niad 11 years ago 6' blades and 9' machinery came to over $35k and the last I heard was it was over $40k. the Installation is involved as there is a lot more than just a pump and reservoir

If they were to be located in a close to "vertical position", they will actually alo work as rudders and can therefore influence the steering system. They should be installed as close to horizontal to avoid this.

paravane

Can you be specific about where you can purchase these paravanes?

FF

Call Jim Leishman at Nordhavn and inform him his boat purchasers (the biggest group of MV world travelers by brand yet) have no concept of paravane operation and you have just the way to instruct them. I can't see the paravanes in your boat picture, Where do you have them attached?

Sunchaser,


i have not posted any pictures of my paravane system

Richard P

Active fin angle

Singleprop said:

If they were to be located in a close to "vertical position", they will actually alo work as rudders and can therefore influence the steering system. They should be installed as close to horizontal to avoid this.

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My Niad active fins are on about a 60deg angle from horizontal so thirty deg from vertical. One of the reasons for this is so the vanes don't protrude beyond the gunnels. The vanes are set with a lot of tow in, close to 10deg by estimate, maybe more. The fins are located at about the center of effort or turning point of the boat. Not at either end so there is little rudder effect. They are self centering and have to lock in center position when backing down. They do effect steering but maybe not in the way you would expect at first thought. Many round bilge boat lean out under hard turns, the opposite of banking like a planing hull. So do Cats for that matter. The stabilizer vanes stop the heeling and keep the boat near perfectly vertical. When running in large following seas that tend to broach many boats as the stern is lifted and the bow starts down the wave face. When the boat starts to turn and broach the fins correct the heel and direct the boat in a straight line. Hands off no steering needed. My boat tracks like it's on rails in following seas regardless of whether the wave are quartering or directly astern. I can literally set my auto pilot on a course heading and the boat will track straight and true with almost no cross track error. If you can afford them and have room they make an incredible difference on a round bilge boat. I'm not as certain that will work as dramatically on a semi-planing hull form because of the extra primary stability of a hard chin / rounded chine boat.