Paravanes vs. Sea Gyro vs. Active Fins

Scary, thank you for the great article! That link was chalked full of great information.
the author seems pretty positive about "passive fins". this looks like a valid option.
My question is "why is it you don't ever see these on any boats?"
Thanks all for the comments.

Taras

Seeing the "Perfect Storm" kinda put me off them...

ParaVane are ok in my book

Peter B said:

Seeing the "Perfect Storm" kinda put me off them...

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just remember... anything you see in a movie is never embellished!!

I had the good fortune to deal with para vanes for nine years... with the exception of the down cables picking up stuff every now and then they worked remarkably well.. in the open ocean set and forget was the norm. The worst thing that ever happened was snagging a log in the Strait of Georgia in less than ideal conditions.. I noticed the boat was applying a lot of port rudder to maintain course then noticed the stbd. vane was trailing much further aft causing loads of drag to stbd. It took about a hour to get the waterlogged log up out of the water and to use a hatchet to cut the log free of the cable. I think chain down lines would of solved this and a slight harmonic sound caused by the s.s. cable slicing through the water, Nordhavn paravane rigs use chain and I can see why.
We did have a set of flopper stoppers that could be rigged at anchor to reduce swell roll... but they never really were worth the hassle of rigging at anchor. My kids did really like to use the rig poles to hang a rope swing for use at anchor too.
HOLLYWOOD

I love my Paravane Stabilizers.
SD

I wonder why more manufacturers' do not build their hulls with bilge keels. They are basically free stabilizers. There is a coefficient equation, with the waterplane entered into it, that tells you the size of bilge keel that can be added to a hull for maximum stability as it is related to drag. Most bilge keels on full displacement hulls are about 50-75% of the total hull length and greatly reduce roll and add to tracking. Just a thought.

rpackard said:

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

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Kolstrand Marine Supply, Seattle. 206-784-2500

If you email me yur email address I will email you information that I have.

Plan on adding bilge keels before Fish Stabilizers. The keels are to reduce the roll but also help to keep the Eagle up right when grounded and/or on the hard/grid.

Good Question

Taras said:

Scary, thank you for the great article! That link was chalked full of great information.
the author seems pretty positive about "passive fins". this looks like a valid option.
My question is "why is it you don't ever see these on any boats?"
Thanks all for the comments.

Taras

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It seems to me this would be a fairly simple addition to many boats. I suspect that appearance when not in use may have something to do with it. This an Australian study and I have to say from experience that Australians have approached boating in innovative ways. they were among the first to really champion high speed catamarans and have always thought out of the box when it comes to small sailboats. I think there is a lot of things we do out of tradition without really thinking things out. If those passive fins are as effective as their study implies they would be a very cost effective way of controling roll. We certainly have the ability to build foil shaped centerboards that same technology could be used to built passive foils for fins. I lose 1/2 knot and fuel economy running my active fins, if these work close to as well and cost a fraction of the active stabilizers why not give them a try. From my experience sailing small boats with centerboards, this system should have seemed obvious. It also fits in well with those of us that are minimalist and want to keep it simple.

Taras said:

Scary, thank you for the great article! That link was chalked full of great information.
the author seems pretty positive about "passive fins". this looks like a valid option.
My question is "why is it you don't ever see these on any boats?"
Thanks all for the comments.

Taras

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Because fish stabilizers are UGLY and require activation/deployment/retrieval. Fish stabilizers are active not passive by definition. You do see them on commercial and trawler type looking boat like the Eagle. I mean the Eagle is ugly already so a little more ugly will not hurt.

Because fish stabilizers are UGLY and require activation/deployment/retrieval. Fish stabilizers are active not passive by definition. You do see them on commercial and trawler type looking boat like the Eagle. I mean the Eagle is ugly already so a little more ugly will not hurt.

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I won't call pavanes ugly. They're just an other piece of boat hardware. We keep the rigging up to date so it looks good IMHO. I get more questions about what they are. Most cruisers don't realize that we run with them under way. They think there just flopper stoppers. If I've had a few beers I just tell people they're "sissy bars".

I won't call paravanes active but passive. Ours require no activation other than me putting them in the water.

Don't let Eagle here you call her ugly. She could get even with you when you least expect it.

Passive Fins are fixed to the hull and except when up.

Take the time to read the article on Stabilizers I posted earlier. It's an Australian research article on fishing stabilizers. These are located like active fines but fixed. Like having apposed centerboards on a sailboat.

Scary said:

Take the time to read the article on Stabilizers I posted earlier. It's an Australian research article on fishing stabilizers. These are located like active fines but fixed. Like having apposed centerboards on a sailboat.

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That is sort of what I call Bilge/Twin Keels as they are about 8 to 10 ft long and hang down even/level with the main keel. So they are like bilge keels but wider and not as long. So if a ground or on the hard/grid it will help keep the Eagle up right. The Eagle has a round hull and for round hull boat they tend to roll on its side usually causing more damage than the actual grounding. I have a chart that bilge keels are about 50% to 75% of paravanes which require to not activating/deployment/retrieval. I am hoping the bilge keels will be enough as the Eagle does have a slow comfortable roll.

I would much rather have passive rathern than active.

If I didn't have the active stabilizers I doubt I would front the money for them. The Australian fins are long and thin, high aspect, not unlike a dagger board for a sailing dingy. I don't think they would double as props to stabilize a grounded boat. They are supposed to be close to drag free, again I'm just quoting this report. Bilge keels are supposed to have 10-15% drag. Somehow intuition say's this is high. As to grounding and needing to stand upright, you have a really good point. A lot of grounded round bottom boats fill with water before they right themselves and float. There are a couple of examples by the mothball fleet near Benicia CA. Non of the bilge keels I've seen are anywhere near as large as your describing. There may be a reason.

Scary said:

... There are a couple of examples by the mothball fleet near Benicia CA. Non of the bilge keels I've seen are anywhere near as large as your describing. There may be a reason.

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That was quick

Just the one i was thinking of.

Phil Fill said:

Kolstrand Marine Supply, Seattle. 206-784-2500

If you email me yur email address I will email you information that I have.

Plan on adding bilge keels before Fish Stabilizers. The keels are to reduce the roll but also help to keep the Eagle up right when grounded and/or on the hard/grid.

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bilge keels also adds permanent drag to the hull. Some say up to 10%..and it cannot be removed, whereas paravanes/fish can.

When we built Hoa we already fit two daggerboards you can see them
on the side of the wheelhouse.
Dérives - Le blog de long-cours
But the roll attenuation is very limited...

Have only home made model tests , but I believe a simple sailboat style centerboard would be ideal for most cruisers.

The board case is created wider than for a sail boat so the board (with a different pin and location) can be given about a 5deg angle by a ram.

An Air ram is ideal as air cylinders are cheap and really fast.

And leaks do not get pumped overboard to get the sheene police excited.

When not in use or on a grounding (cruising boat right?) the board simply retracts.

Cheap to build , cheap to maintain , but probably to costly for most boat assemblers to install, as it is not seen.

FF

Very interesting

longcours62 said:

When we built Hoa we already fit two daggerboards you can see them
on the side of the wheelhouse.
Dérives - Le blog de long-cours
But the roll attenuation is very limited...

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What a clever location to install dagger boards , on what looks like a very interesting boat. I'm guessing but your boat appears to have hard chines and not a round bilge. If that is the case, you may have so much primary stability and lift generated by the chines that the fins aren't capable of controlling roll. Or maybe the correct term should be pitching. I think boats with really rounded hull shapes, like the Nordhavns benefit the greatest from stabilizers. How far can you extend your centerboards. I would like to more about your boat.

Our dagger board

Actually we can extend them 5'9" under the water line
We are thinking make them longer
But like we wrote (sorry in French)on our blog , their first target was help to keep the right course and put less 'near 0°) angle of rudder when we motoring on just one engine.
For that they work very well, they are asymmetric (I hope it is the same word in English)

Paravanes

Tested the stabilizer/fish setup this past Saturday. Once they were in the water they worked great. The biggest lesson I learned is to have all systems ready to go before you hit the rough water. I was alone on this test run and had to get on the cabin roof to get the fish out of the slotted holder, not fun at all. Then getting the poles deployed was a big pia because I had to climb around the side of the boat on the narrow catwalk and yank them outboard. I was smart enough to wear a life jacket and put the gear in neutral. Pretty nice test run after that, what normally (without fish) would have been a rolly uncomfortable ride was pretty smooth. Tested the fish at all points of the compass.
Mike
Baton Rouge

Glad they are working for you Mike. Good post and it is important you are sharing your experience. From your post I can see, once again, the hazards of "fish." There are many people happy with them but just be careful. The risk, disapperance and injury potential from deployment and rigging failure is real.

All true SC, moving slow and cautious with the fish is the way to go. That being said, it's almost like having a new boat with a smooth ride, so well worth the hassle.

GC I got your Pm. Just getting back in myself. didn't need my paravanes this weekend myself.
You asked about tight turns and the fish swinging into the side of the boat. Did you test that out?

At 8 knts, the speed I cruise at. I never had an issue with it.

I don't know how fast you cruise.

When next I am out I will try some close quarter manuvering with the vanes deployed.

They do do the trick when It ges snotty out.
SD

SD:
I cruise at 7 kn, 1600 rpm. I did try a few fairly tight turns, no problem. I also snagged a crab trap float, thought for sure it was going to swing into the running gear so I put the boat in neutral and coasted to almost a stop and the float came loose from the fish, got lucky.
Mike

Paravanes scare the heck put of me! I installed a new thick wall aluminum mast, beefed up the stays, have the fish and poles. But I really want to try the twin bilge keels first. For some reason I have the gut feeling/fear that I am going to ground the Eagle on purpose. I guess its having memories of BC Canadian coast line, rapid change in depth of 100+ ft, rugged coast and big tide swings.


You might want to look at an ART, Anti Roll Tank, which is a tank that is mounted on the roof with baffles to times the move of water back and forth to counter the roll. A 58 sister boat cross the Pacific to Hawaii with an ART. He mounted it on the pilot house roof about 8 ft long and 3 ft wide. He made a ply box and played with the baffles and them fiber glassed the box and baffles in place.

Some boats/ships have flumes built in their bilge hull to counter the roll, but on the roof seems to work also. So the idea been around for a long time.

Paravanes

Very interesting to heard about your news paravanes .
Because what I read about them on the site of the Canadian Ministry is quiet scary .
(capsize after a loss of one fish)
Must be remove in case of realy bad wheather is it true or not ?
Because for us it could be very interesting for one very good reason....not expensive way for get a smoother ride !
For the tank on the roof , I am affraid by the loss of stability : adding weight so high and also the effect of this 'carene liquide'.
On some paravanes systems I saw the poole cant be gooing back because one 'wire" is replaced by a tube , is it better or worst to use ?

Gulf Comanche where we could have more details concerning your boat ?
I am always curious !

LC62:
My boat is 38' long, 12' wide, 60 hp Perkins 4-236 engine. Anything else you want to know?
GC

Phil Fill said:

You might want to look at an ART, Anti Roll Tank, which is a tank that is mounted on the roof with baffles to times the move of water back and forth to counter the roll. A 58 sister boat cross the Pacific to Hawaii with an ART. He mounted it on the pilot house roof about 8 ft long and 3 ft wide. He made a ply box and played with the baffles and them fiber glassed the box and baffles in place.

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Would fear this could make matters worse, not better. Wouldn't this increase the potential for instability by raising the center of gravity? Wave frequency is also variable so wouldn't counter "sloshing" potentially increase roll if the baffles are not adjusted for wave frequency?

" potentially increase roll if the baffles are not adjusted for wave frequency?

There you go mark getting all technical.

I'm sure there is a web site to calculate wave frequency.

I think I will let you handle that one I'm going fishing.

Sd