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Old 04-11-2012, 11:26 PM   #1
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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
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Old 04-12-2012, 06:41 AM   #2
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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.

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Old 04-12-2012, 08:23 AM   #3
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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.
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Old 04-12-2012, 01:10 PM   #4
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Active stabilizers work great - except for anchoring

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

Paravanes are for all conditions.
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Old 04-12-2012, 05:09 PM   #5
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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.
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Old 04-12-2012, 07:17 PM   #6
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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.
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Old 04-12-2012, 07:29 PM   #7
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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?
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Old 04-13-2012, 12:30 AM   #8
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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.
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Old 04-13-2012, 07:26 AM   #9
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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.

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Old 04-13-2012, 08:48 AM   #10
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Quote:
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...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...
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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Old 04-13-2012, 10:34 AM   #11
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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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Old 04-13-2012, 11:48 AM   #12
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Shackel failure

Quote:
Originally Posted by Larry M View Post
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
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.
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Old 04-13-2012, 12:54 PM   #13
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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?) ...
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.
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Old 04-13-2012, 01:10 PM   #14
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Reference on stabilizers

http://www.google.com/url?sa=t&rct=j...Rl_ga3yoZV5big
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Old 04-13-2012, 01:58 PM   #15
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... 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...
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.
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Old 04-13-2012, 05:19 PM   #16
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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.
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.
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Old 04-13-2012, 05:43 PM   #17
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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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Old 04-13-2012, 05:49 PM   #18
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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.
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.
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Old 04-13-2012, 10:16 PM   #19
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Not to nit pick

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

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Old 04-13-2012, 10:42 PM   #20
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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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