Paravanes

[heysteve]

There are very few naval architects that have any experience designing paravane stabilizers. Jeff. Leishman designs them for the Nordhavns but he is the only NA I recall with experience. It would be prohibitively expensive to have a NA start from scratch and analyze all the forces. You would be basically lying for them to learn.

The paravane stabilizers used on almost every commercial fishing boat in Alaska (gill netters excepted) are made by the owners themselves or some local welders who have seat-of-the-pants experience with the construction. The word "design" would hardly be what they would call their work. And these fishermen, who are at sea 24-7, have met worse conditions than most of us, without any rig failures.

These guys had paravanes designed and built in Port Townsend WA:

 

[Pascall]

Of course! Having seen your work I suspected as much.

Could you tell us more about them? Your own design? Materials? dimensions?

Hi Gilberto,
It is a design more or less of existing designs and adapted to my own insight.
It's still in the testing phase so I can't tell you that these are perfect, although the first test is well received.
The material of the fin is plywood 15 mm, this is impregnated with 4 layers of epoxy.
The remaining material is stainless steel.
The tube at the bottom is filled with lead, the whole weighs 7.5 kilos.
Only the front 8 holes are needed for use, then others are unnecessary.
The whole is still finished in two component paint.

Greeting

Pascal.

 

[Xlantic]

Pascal, thank-you for sharing, particularly the dimensions.

It looks similar to other plywood paravanes I have seen here in TF but maybe a bit lighter and more streamlined.

Keep us posted!

 

[Pascall]

Pascal, thank-you for sharing, particularly the dimensions.

It looks similar to other plywood paravanes I have seen here in TF but maybe a bit lighter and more streamlined.

Keep us posted!

You are welcome.

That's why I filled the space between the fin and the torpedo with putty, less turbulence I think.
Hesitated for a moment to make the paraphane in polycarbonate but did not have enough in house.
Very strong and no maintenance!

Greeting

Pascal.

 

[Larry M]

…Question, I have read that there are people who use a paravane in mild conditions and two in bad conditions, does anyone here on the forum have experience with that?

Pascal.

We tried it but it scared us. All it took was one roque wave and we quickly deployed the other fish. With only one fish in the water, as it dives down, there’s no counteracting force on the other side.

When we’d leave a marina we would typical would extend both poles. That helped the stability by themselves (our poles were stored vertically). If conditions warranted using the paravanes, we’d deploy both fish.

 

[balder8]

I have not seen them in Europe either, they are self-made.
Greet

Pascal.

Hallo Pascal, hello everybody,

Congratulation for your paravane project! From what I see, you are doing it in the Netherlands. As you say, this technical topic is really not a number one subject in Europe but thanks to this forum and knowledge from US west coast and pacific trawler owners, I learn a lot before starting also the same project after leaving the Netherlands where my steel trawler has been built. I have hydraulic stabs but wanted as well a simple and efficient back up. I went with foldaway paravanes arms ( NZ and australian design) and rigid pipe. I replaced the rigid pipe too heavy to handle by a classic dyneema rig with spring and "fish" self made with stainless steel and polypropylene white plate.

There is one question I have not solved and by the way, my project is not finished as yours: lenght of the cable from the top of paravane to keep the fish underwater ( many recommand here 15' at rest) and if flying as mentionned by others here, avoid to damage the cabin sides or the propeller. In this forum,you may read the story of this Nordhavn 40 crossing atlantic and damaged by one stabie.

I have decided to shorten a bit my arms to 6 meters , more or less 18 feet. From the top of my arms to sealevel I have 3,50 meters. With 8 meters lenght of running cable, the fish cannot hit the propulsion gear but may damage the hull!
If I reduce the lenght to 5 meters, no danger. It means that the stabie is 2 meters underwater.... may be not enough.

I do not know if you plan to motor offshore with your beautiful trawler of if you stay in the shallow waters of the georgeous Hollande? But what choice did you make for the running cable?

Below pictures in the varadero de Benicarlo where I am currently refitting Balder VIII ( new paints) with the arms open at 90 deg

 

[PierreR]

I know very well what is involved in your work and appreciate your work. I built my last trawler and had a paravane system on the boat. It worked very well.
Viewing your work third party, turns a mirror on me. It's nice to know someone else is cursed with the ability and an obsessive mind. I know the hours involved, the costs of the materials and equipment plus the level of mental draining that goes on. I also know the costs of buying off-the-shelf items and adapting. The problem with obsession is not properly valuing my time. Passion and hobby mentality cloud my judgement. I am to the point where I would just like to chill out but alas, why oh why can't I just write checks. One of these days I am going to hire something done on a boat. The clock is ticking, and I don't have many years left. I just bought another project.

 

[Pascall]

We tried it but it scared us. All it took was one roque wave and we quickly deployed the other fish. With only one fish in the water, as it dives down, there’s no counteracting force on the other side.

When we’d leave a marina we would typical would extend both poles. That helped the stability by themselves (our poles were stored vertically). If conditions warranted using the paravanes, we’d deploy both fish.

Thank you so much for your post Larry!
This confirms my doubts.
I'm going to start with the second boom.
Beautiful ship you have, nice line in!
In the Netherlands we mean by line (zeeg/ sieve ) I don't know the right word in English.

Pascal.

 

[Xlantic]

Sheer line, maybe?

 

[Pascall]

Hallo Pascal, hello everybody,

Congratulation for your paravane project! From what I see, you are doing it in the Netherlands. As you say, this technical topic is really not a number one subject in Europe but thanks to this forum and knowledge from US west coast and pacific trawler owners, I learn a lot before starting also the same project after leaving the Netherlands where my steel trawler has been built. I have hydraulic stabs but wanted as well a simple and efficient back up. I went with foldaway paravanes arms ( NZ and australian design) and rigid pipe. I replaced the rigid pipe too heavy to handle by a classic dyneema rig with spring and "fish" self made with stainless steel and polypropylene white plate.

There is one question I have not solved and by the way, my project is not finished as yours: lenght of the cable from the top of paravane to keep the fish underwater ( many recommand here 15' at rest) and if flying as mentionned by others here, avoid to damage the cabin sides or the propeller. In this forum,you may read the story of this Nordhavn 40 crossing atlantic and damaged by one stabie.

I have decided to shorten a bit my arms to 6 meters , more or less 18 feet. From the top of my arms to sealevel I have 3,50 meters. With 8 meters lenght of running cable, the fish cannot hit the propulsion gear but may damage the hull!
If I reduce the lenght to 5 meters, no danger. It means that the stabie is 2 meters underwater.... may be not enough.

I do not know if you plan to motor offshore with your beautiful trawler of if you stay in the shallow waters of the georgeous Hollande? But what choice did you make for the running cable?

Below pictures in the varadero de Benicarlo where I am currently refitting Balder VIII ( new paints) with the arms open at 90 deg

I have been following you for a while on this form, you make a special installation that I think also brings many benefits, very strong, you keep a low ship, and I think you can safely turn the paravanes in and out.
Beautiful ship, and special that bulp bow.
The booms protrude 4 meters from the hull and lie horizontally 2.50 meters above water.
The maximum listing I have ever measured is 43 degrees, I do not yet know how to translate this into practice with the booms, they should not touch the water.
I still have to work it out in the stability calculation, this is from our ship, see the picture.
The intention is to lower the paravanes with eclectic winches.
I think that the size of the boat also plays a role, in the end we have a small boat, everything in proportion.
We regularly sail on the North Sea and Baltic Sea

Pascal.

 

[balder8]

Thanks Pascall for your comment. To be honest, I am quite fed up with this project, and it is definetly more basic than yours.
Sorry for my broken american english, but I was curious to know how much deep you run your stabies underway, and if you take in consideration or not risk to see the fish flying and hit the cabin side or the cockpit in rough weather?

 

[Pascall]

Thanks Pascall for your comment. To be honest, I am quite fed up with this project, and it is definetly more basic than yours.
Sorry for my broken american english, but I was curious to know how much deep you run your stabies underway, and if you take in consideration or not risk to see the fish flying and hit the cabin side or the cockpit in rough weather?

May I ask why you are tired of your project?

As for the depth of the paravane, I will first carefully test how the paravane behaves in the water.
Maybe it goes wild like a wild young dog, or like the little mermaid, only then can I determine the depth.
For the time being the safe margin, 2 meters below the surface of the water, in calm weather.
Don't think your English is bad, I'm sure mine is!

Greeting

Pascal.

 

[hollywood8118]

I had paravanes on Volunteer. In the 9 years we had it the only time I saw the fish come close to breaking the surface was when I stupidly tried dropping the fish while at 8kts in flat water. I walked the fish to the stern at the aft limit of its cable and pointed it to the water and let it go. It swung through its arc and got within a few feet of coming out of the water. I had a "oh ****" moment when it looked like it was about to break the surface in its forward arc.
The previous owner (and builder) of the boat mentioned in passing when he first dialed in the paravanes he had a fish break the water and impale itself in the flybridge side wall. He experimented with different depths and settings on the running angle of the fish and "suggested" that I probably shouldn't mess with the system and just use it. Our fish ran at a depth of 16' which did not allow them to get anywhere near the running gear. I always wanted to add electric winches to lift the fish ( like the Nordhavn 46 system which works VERY well imho) as lifting the fish was tedious at best for me and almost impossible for my incredibly in shape 125lb multiple Ironman triathlon Admiral. I make the above statement because she can do around 50 push ups and is strong as a ox.
As others have mentioned the loads on the rig can be quite significant as the boat rolls and pitches much in the same way the rig on a sail boat changes significantly in a heavy sea way.

Richard on Dauntless had some issues on his paravanes ( as I seem to recall) on his Atlantic crossing and made some changes after he saw how the rig performed on the crossing.

Also do not under estimate the need for a downhaul and a aft guy to hold the poles in position as they will swing around wildly if they are unloaded without the fish down.
HOLLYWOOD

 

[balder8]

I had paravanes on Volunteer. In the 9 years we had it the only time I saw the fish come close to breaking the surface was when I stupidly tried dropping the fish while at 8kts in flat water. I walked the fish to the stern at the aft limit of its cable and pointed it to the water and let it go. It swung through its arc and got within a few feet of coming out of the water. I had a "oh ****" moment when it looked like it was about to break the surface in its forward arc.
The previous owner (and builder) of the boat mentioned in passing when he first dialed in the paravanes he had a fish break the water and impale itself in the flybridge side wall. He experimented with different depths and settings on the running angle of the fish and "suggested" that I probably shouldn't mess with the system and just use it. Our fish ran at a depth of 16' which did not allow them to get anywhere near the running gear. I always wanted to add electric winches to lift the fish ( like the Nordhavn 46 system which works VERY well imho) as lifting the fish was tedious at best for me and almost impossible for my incredibly in shape 125lb multiple Ironman triathlon Admiral. I make the above statement because she can do around 50 push ups and is strong as a ox.
As others have mentioned the loads on the rig can be quite significant as the boat rolls and pitches much in the same way the rig on a sail boat changes significantly in a heavy sea way.

Richard on Dauntless had some issues on his paravanes ( as I seem to recall) on his Atlantic crossing and made some changes after he saw how the rig performed on the crossing.

@Hollywood, I do not want to reply or divert the thread initiated by Pascall, but it is a real bonus to read your comment, as you like to have a real practice of this unknown
equipment here in Europe on our rare trawlers ( most of the named trawlers on this side of the atlantic are more semi planning classic motoryachts with some marketing
using words like explorer or long range which is not true, considering the Cpt Robert Beebe approach. These fakes are also more politically correct considering green blabla, less big engines, less noise underway, less bling bling new money style on the water or in marinas ....the truth is that it is in the Netherlands you can find sturdy heavy displcacment motoryachts, unfortunately most of them are more dedicated to rivers or canals and they have not the cat A rcd required to cross atlantic or sail offshore...
@ Pascall, I am sometimes tired of the project because as I you mentionned and others in this forum, paravanes are more or less a DIY concept project on a retrofit basis which may generate mistakes or misunderstanding... I like to finish a project and feel 100% confident. The only time when my hydraulics stabs stop running properly was few years ago in Med near Balerarics islands and the weather was reallynot fine. This is why I decided to have a back up.
About depth of fish in the water, I will test also like you recommand on the same careful approach....

 

[Pascall]

Very useful information by Balder8 indeed, my thanks for this.
Your project, persevere for a while, later you enjoy it and you think back on it very differently, then you enjoy your hard work.
There are quite a lot of steel yachts in the Netherlands with ocean certificate, but are usually very expensive.
A few examples, Mulder, Sturier, Van der Hoven, van der Valk, Doggersbank, Elling, Moone, Hakvoort, Koopmans, Bylgia and many others.

Greeting

Pascal.

 

[Pascall]

Continue with the paravane.

Decided to add two stainless steel wires so that the forces on the mast are better distributed.

Today the anchoring made for the steel cables to the wheelhouse roof.

And provide the paravane with a first coat of paint.

The second boom is now 4 layers in the epoxy.

Greeting

Pascal.

 

[Larry M]

I’d almost hate to put the fish in salt water. It’s a thing of beauty. Nice job!

 

[mvweebles]

I would suggest that you hire an engineer/naval architect to take a careful look at what you have built and the structural load paths thru your boat. Also look at the shift in cg with the equipment you are adding and stability of the boat. In my opinion you need an engineered solution which is not possible with just A number of suggestions from this forum. Goal is a safe design that accomplishes your requirements.

This boat was hauled a few days ago. Paravanes reminded me of this thread

I'm sure this rig hired a Naval Architect and had everything checked and verified by a certified engineer, then carefully constructed by skilled craftsmen to exacting measurements. And I'm sure the captain was careful not to overload the boat.

Peter

 

[DennisB1]

Question: What happens to the boat if a paravane hits something heavy when you are cruising at seven knots? Does the paravane breakaway with no further damage or does something else fail in the rig or maybe you capsize the boat. Some think to think about in the design build process.

 

[Pascall]

Question: What happens to the boat if a paravane hits something heavy when you are cruising at seven knots? Does the paravane breakaway with no further damage or does something else fail in the rig or maybe you capsize the boat. Some think to think about in the design build process.

That's a good question, I've been thinking about this too.
What is the weakest link in the whole?
For example, the line on the winch to which the paravane is attached has a breaking strength of 2380 kilos.
But what is the breaking strength of the bolts with which the winch is attached?
The chain is only as strong as its weakest link.
I'm thinking of placing a break line of, say, 500 kilos between the paravane and the winch cable, this to make sure that something breaks it is in the place where you want it.

Pascal.

 

[Larry M]

I hit a dead head straight on and also a 25 plus foot unlit fishing boat at 6.5-7 knots. Other than scaring the crap out of us there was no damage. In both the cases the boat pivoted slowly toward the side where the impact was. The 8’ of three strand that is part of the vertical rigging to the fish acted as a shock absorber. That and the fish traveling 15-20’ from the centerline of the boat really softened or damped the impact.

 

[Airstream345]

Question: What happens to the boat if a paravane hits something heavy when you are cruising at seven knots? Does the paravane breakaway with no further damage or does something else fail in the rig or maybe you capsize the boat. Some think to think about in the design build process.

I've read of several where there is a breaking line installed close to the fish. Losing a fish is much less expensive than wrenching your rigging.

 

[PierreR]

Question: What happens to the boat if a paravane hits something heavy when you are cruising at seven knots? Does the paravane breakaway with no further damage or does something else fail in the rig or maybe you capsize the boat. Some think to think about in the design build process.

I snagged bottom a couple of times with my vanes and all it did was spin me towards the side of the snag. Same as Larry M., No real damage.

 

[Fletcher500]

Question: What happens to the boat if a paravane hits something heavy when you are cruising at seven knots? Does the paravane breakaway with no further damage or does something else fail in the rig or maybe you capsize the boat. Some think to think about in the design build process.

I know a guy who travelled extensively in a Nordhavn 40 (recently sold it, and now they are back to a sailboat). He was off Mex with the fish out and the boat took a major roll. He ran aft and saw a Killer Whale wrapped up. Apparently the whale was able to untangle itself fairly quickly and was fine, along with his gear.

 

[Pascall]

I started to make the construction that the booms should attach to the boat.
Long thought about how I would do this.
In the end, the booms decided to attach to the mast base so not on the wheelhouse roof as I have said before.
This means a less invasive construction.
The starting point is, simple, strong, as light as possible and it should look good.

 

[Larry M]

I've read of several where there is a breaking line installed close to the fish. Losing a fish is much less expensive than wrenching your rigging.

I’ve heard that but have never actually talked to anyone including a navel architect who had engineered a “weak link” into the system.

On our paravanes, the 3 components from the poles to the fish have breaking strengths of 5,700 lbs for the 1/2” 3 strand, 6,400 lbs for the 1/4” ss aircraft cable/wire rope and 5,800 lbs for the ss chain. We had a swivel that failed under load and that did more damage to the rigging than anything we hit or got tangled up it. It was like a sling shot.

 

[Larry M]

Pascall: Are your sure you want to put any of that in salt water? Your fabrication is a work of art!

 

[PierreR]

Pascall, I have never had great luck using a hole saw to cut stainless. Can I ask what your speeds are and cutting oil? Stainless is a slow cut material.

 

[Bmarler]

Pascall, I have never had great luck using a hole saw to cut stainless. Can I ask what your speeds are and cutting oil? Stainless is a slow cut material.

I use a hole saw for stainless all the time. I tried a lot of different makers of saws and I find that a bimetal fine tooth does the best job on the tubing. Cutting flat Is tougher. I go through more saw blades when cutting flat with the drill press, so I usually choose the milling machine.
I try to keep my rpm’s low. 500 ish. A drill press with the third pulley is helpful. Have to keep the saw loaded so it keeps the blade cool as it removes material. If you don’t pull a chip you’ll overheat and just surface harden the workpiece. I use either rapid tap or tapmatic oil. I use that because it’s on hand. I sure there’s lots of oils that would work equally as well. Heck, I even keep a tin of bacon grease near the drill press. Sometimes it’s nice to have something that hardens when it cools so it holds the chips.
Cutting stainless is really a by feel sort of thing. Getting the right amount of pressure on the cutting surface is probably the most important thing.

 

[PierreR]

I use a hole saw for stainless all the time. I tried a lot of different makers of saws and I find that a bimetal fine tooth does the best job on the tubing. Cutting flat Is tougher. I go through more saw blades when cutting flat with the drill press, so I usually choose the milling machine.
I try to keep my rpm’s low. 500 ish. A drill press with the third pulley is helpful. Have to keep the saw loaded so it keeps the blade cool as it removes material. If you don’t pull a chip you’ll overheat and just surface harden the workpiece. I use either rapid tap or tapmatic oil. I use that because it’s on hand. I sure there’s lots of oils that would work equally as well. Heck, I even keep a tin of bacon grease near the drill press. Sometimes it’s nice to have something that hardens when it cools so it holds the chips.
Cutting stainless is really a by feel sort of thing. Getting the right amount of pressure on the cutting surface is probably the most important thing.

I have a 480V 3Ph drill press that can go a little as 20 rpm. Everything I have tried to cut was flat and probably 316. I actually found that compressed air works well instead of oil but never tried to cut through a pipe tube that way. Will try it. That hole saw look like a plain Milwaukee.