Questions about paravanes

[North Baltic sea]

Here is the picture of this canadian fishing boat with wings

Hi,

Much the same idea of ​​what I have seen the construction of large cruise ships stabilisator, these can be turned in to hull, when there is a need for convenient and, unfortunately, expensive to implement.

NBs

 

[Whodgins]

Rich aka Wxx3 chimed in with a lot of good info. I would also contact CruisingSeaVenture here or on youtube. They recently underwent a refit and added a custom one-off paravane set up on their cruiser.

Thanks Ben, we are in touch with both now and will continue to update here on this thread.

 

[Whodgins]

We have them on MOJO and use them anytime the boat is rolling. They work great. Easy to launch, just push the poles out, run the down wire back to the flopper stoppers which are stored on brackets on the aft rail, shackle it on, slow the boat down and drop each bird overboard. They go to work immediately and are somewhat fascinating to watch! Ours hang 16' down, but when underway are probably running about 12' under the surface. Retrieval is by stopping the boat, pulling the poles up to near vertical then hauling each bird up over the rail and walking it back to it's storage bracket. What would I do differently? I'd rig a way to raise each bird out of the water (probably with a small winch) while the poles are fully extended, and have some sort of bracket a the top of the pole to hold the bird so it wouldn't bang around on the pole. This would make it faster to get the birds up, and also allow me to bring the poles vertical with the bird up at the top. I could then lower the birds down and store them at my convenience. This is not something difficult to rig, just one of those "round tuits". We don't do much offshore cruising anymore so it hasn't bubbled to the top of my priority list yet. You can see pictures of the A-frame rig, the birds and their storage braclets on our web site, www.mvmojo.com on the exterior tour page.

Thanks for the great info here and on your site MoJo. We have the A-Frame style booms and what I'd call from my sailing days as the "standing rigging" for getting the A-Frame booms in/out or deployed/stowed all designed and approved so we are all set there.

What I'm now working on and the primary purpose of Christine's OP is the rigging for launching, retrieving and adjusting the paravanes/fish/birds. The rigging for getting poles/booms deployed/stowed seems pretty straightforward and my plan is to use a block/tackle arrangement for controlled in/out movement and then a fixed length line from the top of the boom/pole to the upper arch corner. If we were to use a fixed length line from the top end of the boom/pole down to the fish that would be straightforward as well.

What I am trying to add now are two capabilities; adjustable control of the fish/bird from the end of the boom and a winch assisted retrieval of the birds/fish.

The first is the same ability you are looking to add of being able to adjust the length of the up/down line to the fish. Like you, we would have a manual winch that could take this Up/Down line and would run it through a clutch to hold any given position. I'm not sure I would use this to raise the birds all the way up to the ends of the booms unless it was very calm and I do see the utility in this as you point out of being able to get the poles/booms vertical with the fish/birds at the top and then lower them down into their holders.

My primary purpose of having an adjustable winchable line down to the fish is to be able to retrieve them and bring them aboard under reasonable control in rolling conditions and without having to manually lift them aboard. I haven't worked out the exact weight of our foil shaped CNC aluminium birds yet and will keep them as light as possible but suspect they might get up to 30-40kg/70-80lbs range and be more than we would like to have to depend upon manual lifting to bring aboard.

As you noted, I think this rigging will be fairly straightforward to design and I'm paying the most attention to getting a pulley/block setup at the end of the booms that will be bullet proof and not prone to fouling. In addition to retrieval I think the ability to adjust the depth of the fish/birds while they are deployed, boat stationary, without having to retrieve them.

We are full time live aboards and passage making is our norm so this system is a high priority for us.

I will post some renderings of the system I've got in mind and you and others here can let me know what you think.

Thanks again for all your help so far.

-Wayne

 

[Whodgins]

In our area, paravanes are often connected via stainless steel rods at an optimum length. (This means that they can't be adjusted, as Richard mentioned.) The fishermen who run these claim that the advantages are that boom and rods can be sized so fouling any part of the ship is not possible; there is little sound and no vibration from the system, and retrieving is safer/simpler.

Thanks Kit. SS rods are interesting and would be low drag and very strong but present more challenges when retrieving I think and not be adjustable. So I currently plan to go wtih synthetic line such as Dyneema/amsteel for all our rigging. Some others using this have reported them to be very quiet compared to the SS wire or chain they had been using. So I think we will try this out and see what our results are with noise and drag.

 

[Whodgins]

Visuals certainly help with these kinds of discussions so here are some quick renderings of the rigging setup for our A-Frame paravane booms so far. I've included the A-Frame booms in both stowed and deployed positions and the rigging is all in orange.

As per my note in #33 to Mojo I think we have the A-Frame booms, Arch and their respective hardware all done now and this is from our brilliant NZ based designer and NA and his structural engineer. My focus now is getting the rigging right and my requirements are to have rigging for well controlled, safe and easy deployment and retrieval of both the booms and the paravanes/fish/birds using the mechanical advantages of triple blocks, a manual winch with clutches and/or cleats to hold lines in position.

Not shown is a scissor style pole between side of the Arch and midways along the boom to lock the booms in their down/deployed position and angle of about 30 degrees off the water. Boom length from hinge pin to end pulley is about 4.3m/14ft

Rather than having a fixed length line from the end of the booms down to the birds/fish I want to have a system that allows me to adjust their vertical position up and down while they are deployed in the water, boat stopped. This would be most often used to retrieve the fish by bringing the booms up so the fish/birds are closer to side of the boat and then winching the birds/fish up to deck level and brought aboard as well as enabling the depth under the water to be changed for different conditions and locations.

I'm thinking I will build holders for the fish/birds onto the outer edge of the vertical pole such that they can be left there while the booms are deployed and then pulled out by pulling on the fish/bird up/down line so they fall into the water. Getting them back into these holders on the boom can also be aided by using the winch to raise them up the vertical pole and then lowered down into the holder.

Paravanes/fish/birds themselves are being CNC milled aluminium based on NASA foil type design by Michael Kastens for lowest weight and least drag. All lines will be Dyneema/Amsteel. Boat is 24m/78' all aluminium, beam 5.1m/16.7', displacement w/ half tanks about 40 metric tonne. Full time home for my wife and I to continue sailing the world's more remote locations.

Open to all suggestions, questions and critique and thanks again for all your help so far.

-Wayne

 

[ben2go]

Thanks Ben, we are in touch with both now and will continue to update here on this thread.

You're welcome. I look forward to your updates.

 

[balder8]

Those wings don't look like they can be that effective, but possibly the added surface area compensates for the lower moment arm.

Balder, in the Canaries, besides the best steaks, you should be able to find a good sailboat rigger. That's who did my paravanes, though i told them the lenght of the poles and the size of the birds.

Hi Richard,

May I ask you to email me contact with the rigger who worked for you on your trawler in Canary Islands, was it in Gran Canaria or Lanzarote?

Thanks by advance!
Dominique
M/V Balder VIII
mmsi 227 399 280

 

[Snapdragon III]

That looks like a sweet plan to me. The only thing I would be worried about is chafe at the block at the end of the boom if you were crossing an ocean. Once the block and tackle is all the way pulled in, it looks like the fish is still underwater? I assume the plan it to pull the booms up at that point to pull it out of the water, but definitely put some thought into the scenario of rough water right outside of a marina you are entering, pitching the boat around and making that fish want to swing around wildly once it is out of the water. I have found that solid railings to lean against are very helpful when manhandling my fish out of the water. Make sure you have good ones right were the outriggers are. Another possible idea might be to get rid of the block and tackle that controls the depth of the fish, and put a nice winch on the deck instead to raise and lower it with a single line. It would eliminate some blocks and shackles that could fail, and clang around at anchor, and might be nice to have for some docking situations as well.

Also, make a plan for removing the back guy wire on the pole if it is going to be in the way of launching your dingy. This is an issue on my boat with the poles folded up or down. I replaced the cable that it came with with amsteel and put a quick release shackle like the sailboat racers use for spinnaker sheets on the end. Big improvement over messing with the cable and stainless shacked it came with, that I always needed a tool to loosen, and was always worried I would drop parts.

 

[Nightsky]

We are fine tuning the paravane system for our under-construction 24m aluminum powerboat. We are former sailors and neither of us has been on a boat with paravanes. We've studied designs and talked to folks we've encountered cruising, but I thought I would reach out to this group to start a discussion.

I'm looking for people who have blue water experience running with paravanes.

How deep do you run your fish?
How difficult is it to launch and retrieve your fish?
Could you post a picture of your actual paravanes?
If you could redesign your system, how would you do it?
What words of wisdom can you pass on from your experience?

Thanks in advance for any help you can offer.

Christine
Blog: Mobius World

If you haven't already seen this youtube video, it might be worth a few minutes of your time...

Some comments regarding your drawings: 14' poles are too short, IMO. The further out from the side of the boat, the greater force the paravane can apply against the roll. This can be compensated for by having larger paravanes, but these will increase stress on the rigging. I personally would not have the weight and stress of the paravane relying on the strength of the blocks, but rather off fixed points on the pole. This would of course require you to find another method of lifting or adjusting the depth of the paravane. I do have a concern that paravanes might not even be a good solution for your size of boat, the size of the paravane required to do an adequate job might be so large as to make it to difficult to work out the logistics of lifting, storing and deploying as to make it more trouble than it is worth. I speak from some experience. I had a 93', aft wheelhouse, steel tuna schooner that was so "stiff" that it would throw me out of the helm chair on occasion when the boat righted itself after a particularly steep beam sea. My solution was to try paravanes (which I was quite familiar with coming from a salmon trolling background). To be somewhat effective at roll damping, I ended up with paravanes that were 4' along the back edge and had,iirc, 100 lbs of lead on the nose. I only used those for 1 season before ditching that idea and going to a welded bilge keel (rolling chocks). Best of luck with your new boat.

 

[Larry M]

I agree with Nightsky on the pole length. We have 20’ poles mounted about 3’ from the water. They’re deployed at about 45 degrees. With shorter poles, in large seas, I’d also be concerned about the lines/fish tracking too close to the hull and running gear. In the first picture, we’re in pretty quite conditions with a cross current tracking right to left. You can see how the fish were tracking.

We retrieve the fish with the poles extended. Once, I started to bring a pole in with the fish still running. When the pole was within maybe 5’ of vertical, the boat rolled in a swell, the pole now went past vertical and with the downward force of the fish, the pole slammed against the A-frame. If you can mechanicaly retrieve the poles, not by lines like we do, you should be ok.

Here’s a stress analysis from one of Beebe’s book for a 36’ vessel. The numbers were an eye opener on the loading. We had a swivel let go once and thought a gun went off.

Good luck on your project and thanks for posting.

 

[balder8]

Canadian research Paravanes VS wings

Thank for posting your drawing!

Here is a link about the canadian research done for fishing boats ( goal: security and comfort)

The link is in ENGLISH!!


https://www.irsst.qc.ca/media/documents/PubIRSST/R-870.pdf?v=2019-01-29

 

[bogranjac1]

Thank for posting your drawing!

Here is a link about the canadian research done for fishing boats ( goal: security and comfort)

The link is in ENGLISH!!


https://www.irsst.qc.ca/media/documents/PubIRSST/R-870.pdf?v=2019-01-29

A great read ,thx for posting.
The foldup keels look a further improvement on 'bat wings'.
Maybe one of the two systems discussed will go the way of the 8 track.

 

[Wxx3]

That's why I used the word "overdamped" some roll attenuation is probably a good thing from a comfort point of view but in reality that's all it is the boat doesn't need it, you do. Paravanes don't make a boat more seaworthy, they make a seaworthy boat more comfortable for it's crew, but the roll damping can be overdone and limit a vessels ability to respond to sea conditions in a safe manner.

Yes. I understand now.
And with paravane birds, there is only so much force they can exert with a sfc area of only 250 sq inches.

And my system was purposely made with the weak link being the aluminum poles.

Which reminds me, we snagged an entire line of pots off the Mexican coast. Obviously old, but the tension was so great, the bird was 2 feet out of the water.

I'll have to write a blog post about that fiasco.

 

[hollywood8118]

There is a direct correlation between the angle of the poles off the water, the length of the poles regarding how high they are at the tip off the water and how far the attachment point is away from the boat.. and the depth the fish run.

Most important is that the fish is too short to connect with the prop!


The second is the ability of the fish if it every gets airborne not to go through the cabin side ( The builder of our old boat had this happen when he thought he was doing the right thing by shortening the line.. until it launched out the face of a wave and impaled itself in the flybridge side.)

Our system worked well and seemed to be a bit less complicated than what you propose. The Nordhavn winch system works well and I have used is alot, it's about as easy as it gets ( although in the video above the buttons are in the wrong spot as it has the lady leaning over the side in what appears to be a dangerous position.)

I think the ability to adjust depth is unnecessary and adds additional failure points to the system. Also I think the need to machine a wing is not needed as the design uses drag to slow the lift of the unit and when the speed/angle of attack goes neutral the fish doesn't need a airfoil shape.. less drag is preferable when not resisting roll.

Keep in mind the poles when deployed also slow the roll of the boat.. even without the fish.. so the Nordhavn system works great leaving the poles out and bringing the fish up while still underway... we learned this on our old boat that dead slow was the best for retrieval.

HOLLYWOOD

 

[balder8]

rock and roll attitude

There is a direct correlation between the angle of the poles off the water, the length of the poles regarding how high they are at the tip off the water and how far the attachment point is away from the boat.. and the depth the fish run.

Most important is that the fish is too short to connect with the prop!


The second is the ability of the fish if it every gets airborne not to go through the cabin side ( The builder of our old boat had this happen when he thought he was doing the right thing by shortening the line.. until it launched out the face of a wave and impaled itself in the flybridge side.)

Our system worked well and seemed to be a bit less complicated than what you propose. The Nordhavn winch system works well and I have used is alot, it's about as easy as it gets ( although in the video above the buttons are in the wrong spot as it has the lady leaning over the side in what appears to be a dangerous position.)

I think the ability to adjust depth is unnecessary and adds additional failure points to the system. Also I think the need to machine a wing is not needed as the design uses drag to slow the lift of the unit and when the speed/angle of attack goes neutral the fish doesn't need a airfoil shape.. less drag is preferable when not resisting roll.

Keep in mind the poles when deployed also slow the roll of the boat.. even without the fish.. so the Nordhavn system works great leaving the poles out and bringing the fish up while still underway... we learned this on our old boat that dead slow was the best for retrieval.

HOLLYWOOD

Paravanes with no fish at the end of poles! Why not, like on the picture with our french world champion?

 

[Ventana]

The Krogen we just purchased has vanes, looks like a similar setup to what Larry has on Hobo. We used them a couple times bringing the boat up from Seattle in November, 10-12' steep following seas with about 40kn from behind and the boat was snap rolling too much without them. For the longer swells we didn't feel we needed them.
I also fished up here in the Gulf and we always used vanes. On the fishing boat we had an extra spool on the hydraulic gurdies used to raise and lower the vanes and it was a great setup. On our current Krogen it is done by hand, setting them is not bad (just drop them in) but they are heavy and I'm not sure my wife could get them back aboard herself. Once we are away from the dock for the summers I don't see us bringing them back in often so it may not be a big issue. A small simple winch on each side would do it if we decide we need it.

I agree with the others that said your poles look too short. (The jokes from that alone could go on and on...) Also, I'm not sure you need the line aft. Maybe someone else can explain why you would, but most of the force will be pulling down, or some aft on the bow fitting because of drag. There shouldn't be any force pulling forward unless you had following seas big enough to catch a pole as it went by, and the aft lines will be in the way.

 

[Whodgins]

If you haven't already seen this youtube video, it might be worth a few minutes of your time...

Some comments regarding your drawings: 14' poles are too short, IMO. The further out from the side of the boat, the greater force the paravane can apply against the roll. This can be compensated for by having larger paravanes, but these will increase stress on the rigging. I personally would not have the weight and stress of the paravane relying on the strength of the blocks, but rather off fixed points on the pole. This would of course require you to find another method of lifting or adjusting the depth of the paravane. I do have a concern that paravanes might not even be a good solution for your size of boat, the size of the paravane required to do an adequate job might be so large as to make it to difficult to work out the logistics of lifting, storing and deploying as to make it more trouble than it is worth. I speak from some experience. I had a 93', aft wheelhouse, steel tuna schooner that was so "stiff" that it would throw me out of the helm chair on occasion when the boat righted itself after a particularly steep beam sea. My solution was to try paravanes (which I was quite familiar with coming from a salmon trolling background). To be somewhat effective at roll damping, I ended up with paravanes that were 4' along the back edge and had,iirc, 100 lbs of lead on the nose. I only used those for 1 season before ditching that idea and going to a welded bilge keel (rolling chocks). Best of luck with your new boat.

Wow! Can't thank you enough for providing the link to the video of Norman and Clairise on mv Sailish Aire with them walking us all through the whole launch and retrieval process for their paravanes. Much appreciated and really helped clarify the process with their kind of aft stowed paravane setup. As described in my previous post I'll be stowing our paravanes in a similar kind of holder but this will be located on the outside of our A-Frame poles/booms which I think will make it even easier to retrieve and launch them from there on the sides of our boat rather than off the transom.

Thanks too for you critique and suggestions based on your significant experiences with paravanes on various boats. Since my previous posting I've decided to make several changes based on similar concerns you and others have pointed out. One is to increase the length of the poles as you suggest. I had been thinking that I should keep the tops of the poles when stowed vertically to be no more than the height of the top of our arch but the bulb finally went on that there is no good answer to the question Why? There would be several feet more of gear such as Radar and antennae at least and not good reason to limit the height to this either so I'm now thinking of increasing the length of the poles to about 6m/20ft which will significantly reduce the surface area size and weight of the fish.

I have also changed to a fixed length line from the end of the poles down to the top of the fish out of the same concerns you expressed for a variable length line I had been thinking of. A fixed length line is a much more KISS (Keep It Simple & Safe) solution which we strive for in designing all our systems. As several others have pointed out as well, being able to adjust the depth of the fish under the WL is of limited use and especially with some human error thrown in could prove to be problematic in some situations or tempt you to run the paravanes in places and situations you shouldn’t in the first place.

Sharing your concern about relying on the strengths of blocks I've done away with all of the 3:1 blocks and will use continuous lines led to the winch mounted at the base of the vertical Arch legs just above where they are welded to the upper half of the big hinge plates. Right now I think we will go with the same basic idea of bringing two lines down to each of these winches, one for the in/out control of the A-Frame boom/poles and the other for the fish launch/retrieval line. My current design for this L/R line is that the bitter end of it will run from the winch area up the Arch through a turning pulley out to another turning pulley on the end of the poles and then down to an attachment point on the fixed length pole/paravane line. This line could be used to reduce the underwater depth of the fish but that is not their purpose. Instead these lines would be primarily used for bringing the fish in and out of their stowing brackets. On retrieval we would bring the poles up to vertical, or close to it which will bring the fish up but not out of the water and the fixed length line would be just off the side of Rub Rails, and then use this L/R line to winch the fish up out of the water to a height where the nose can be tilted down into the cylindrical bracket on the outside of the pole and then lowered fully into the holder. To launch we would leave the fish in their holders and get the A-Frame booms/poles out and secured and then use this L/R line to pull the fish out of their brackets and fall down into the water. Launching would be completed by releasing this line from the winch and letting it out till the fixed length pole to fish line goes taut and the fish are fully working at depth. The L/R line can then be tied off with a bit of slack in it and be ready for the next retrieval. Doing it this way means that there is only the main fixed length fish to pole line in the water, no 3:1 blocks, and the ability to use the winch to lift the fish up out of the water and into their brackets.

Our calculations with the 3D model show that paravanes should work quite well on our very long skinny hull as it is not very stiff at all and so the forces needed for roll attenuation are relatively small which along with the longer poles results in relatively small and light fish. We will run roll tests on the model once I have the new design changes and dimensions setup and see how this works out but my napkin sketch numbers look good so far.

Thanks again for your most helpful thoughts and that link. My sister lives in Comox, brother in Ladner and I taught at Ladner High School for over ten years back in the 70's and 80's so it was fun to have this additional connection with a fellow BC’er.

 

[Whodgins]

Thank for posting your drawing!

Here is a link about the canadian research done for fishing boats ( goal: security and comfort)

The link is in ENGLISH!!


https://www.irsst.qc.ca/media/documents/PubIRSST/R-870.pdf?v=2019-01-29

Merci beaucoup Balder! I'd read this paper several years ago when I was first researching roll attenuation for our boat and this type of hinged fin design was a very tempting. After experimenting with these in our 3D model we decided paravanes were the best overall fit for us. Nothing "wrong" with the hinged fins just a combination of factors such as the overall balance between efficiency of the roll attenuation and the efficiency through the water or the drag, the overall build and maintenance costs, etc. So we have decided to go with paravanes and will have to wait for sea trials to find out how well these work for us.

I suspect though that this hinged fin design will catch on and we will see more and more of them being used which will also help to refine and improve the design so we'll keep an eye on their evolution as well.

Thanks again for the link.

 

[Whodgins]

Here is a picture of the setup on my boat. It works super good. the difference between having them deployed and not is night and day. We have not crossed any oceans with them, but we did the west coast of Vancouver island I couple years ago, and they worked great. They have 5/8" three strand nylon from the end of the pole to the waterline, for some stretch, and originally had cable about 15' long from the waterline to the fish. A broken strand on the cable cut the heck out of my hand when I was retrieving them and I replaced it with amsteel rope from the waterline to the fish. I also like the thought that I could cut the rope loose easier if I ever had to if I became entangled with a big log, which I am always nervous about in the PNW. The small yellow line hanging slack is what I use to retrieve them, it just has a clip that attaches to the shackle between the Nylon line and the Amsteel. I use it to pull it in so I can get ahold of the main line, then just manhandle it up out of the water. My boat is only 40' and if the fish was much bigger, manhandling would be too much, but I like the simplicity of it. I really like the way the central support mast is put together on my system. I wish they had mounted all the radar, spotlights, horns, etc, up there.

Thanks for sharing your first hand experiences with your very effective paravane setup, much appreciated. As I explained in my previous post my current design will use a similar retrieval line as the yellow line you have though rigged differently. I'm not sure yet of the need for a two part fixed length line between the end of the poles and the fish with the upper section having some shock mitigating stretch to it but our retrieval line will be attached in a similar position as yours to be just above the WL when the fish are fully submerged.

I have 2 different ways of rigging this Launch/Retrieval line that I'm experimenting with. One that would have the L/R line go up to a turning pulley at the end of the pole and over to another turning pulley near the top corner of the Arch and down to the winches near the bases of the vertical legs of our Arch. Or the 2nd design is to just bring this L/R line direct from where it attaches to the middle of the pole to paravane line over to the turning pulley on the top corner of the arch and down to the winch. Either design let's us use the winch to easily lift the fish out of the water near the side of the boat and up into their holders on the outboard side of the A-Frame poles. And this same setup lets us launch the fish after the poles are fully secured in their down position by using the L/R line to pull the fish out of their holders and fall directly down into the water. Letting out this line lets the fish move away from the side and down to their full depth with the full length paravane line taking up the load while they are in the water working.

We will do all our rigging with synthetic line such as Dyneema or Amsteel as we think this will be much safer, longer lasting and less noisy that chain or SS.

Thanks for the suggestions and explanations of your system. Stay tuned as ours evolves and gets built.

 

[Whodgins]

That looks like a sweet plan to me. The only thing I would be worried about is chafe at the block at the end of the boom if you were crossing an ocean. Once the block and tackle is all the way pulled in, it looks like the fish is still underwater? I assume the plan it to pull the booms up at that point to pull it out of the water, but definitely put some thought into the scenario of rough water right outside of a marina you are entering, pitching the boat around and making that fish want to swing around wildly once it is out of the water. I have found that solid railings to lean against are very helpful when manhandling my fish out of the water. Make sure you have good ones right were the outriggers are. Another possible idea might be to get rid of the block and tackle that controls the depth of the fish, and put a nice winch on the deck instead to raise and lower it with a single line. It would eliminate some blocks and shackles that could fail, and clang around at anchor, and might be nice to have for some docking situations as well.

Also, make a plan for removing the back guy wire on the pole if it is going to be in the way of launching your dingy. This is an issue on my boat with the poles folded up or down. I replaced the cable that it came with with amsteel and put a quick release shackle like the sailboat racers use for spinnaker sheets on the end. Big improvement over messing with the cable and stainless shacked it came with, that I always needed a tool to loosen, and was always worried I would drop parts.

Thanks for the great set of suggestions Snapdragon and I have already updated my design to deal with most of these so see what you think.

I’ve eliminated all the 3:1 blocks and will use single direct lines instead, all synthetic Dyneema/Amsteel type, which lead to a winch that I’ll mount at the base of the vertical legs of our Arch just above where they meet the top plate of the big hinges which allow the Arch to be folded down to “Hunkered Down Mode” on a few occasions. The paravane A-Frames will also come down when we convert to this kind of hunkered down mode for situations such as prepping for hits from hurricanes or for very low Air Draft when exploring canals of the world with low fixed bridges, but I digress.

I’ve increased the length of the A-Frame poles/booms by about 2m/6ft right now and will possibly lengthen them further as I run some tests in the 3D model. I had been thinking I should keep their height when stowed to be no more than the top of the Arch or the top of the Radar and antennae up there but had a bit of a forehead slap moment when I asked myself Why? and realised that there is no good reason for keeping them low and significant advantages of making them longer. Longer levers mean smaller and lighter fish and our very long very skinny hull doesn’t require much righting force so we should be able to have relatively small and light fish which is a big plus.

I have also decided to change the main pole end to fish line to be a single fixed length line for its KISS factor. I’m working my way through the pros/cons of having a shock mitigating function in this line by having the first section from the pole end to just above the WL be nylon or something that provides shock mitigating stretch and then use Dyneema/Amsteel the rest of the way down to the attachment to the fish. I see the initial logic of this but I think I will keep this a single length of non stretching synthetic for now and see how it behaves and what the loads are like in sea trials. Easy enough to add in a segment with some stretch at a later time.

For retrieval there will be a dedicated Launch/Retrieval line which attaches to a point along the fixed length pole end to fish line that will be a foot or so above the WL when the fish are fully submerged. I’m playing with 2 ways of rigging this L/R line, one setup that would take this line up to a turning pulley at the end of the poles or a 2nd design where this line would go directly to a turning pulley at the top corners of the Arch and then down to the winch. Both designs enable us to use the winch to lift the fish out of the water to just above their holders on the outboard sides of the poles and then be let down into those holders to securely stow them. Launching would be quite straightforward as well, lower and secure the A-Frame boom/poles and then use this L/R line to pull the fish out of their holders and splash into the water. Letting this L/R line out let the fish travel out to the sides and down to their fully submerged depth where the fixed length pole end to fish line takes over and the L/R line can be tied off with a bit of slack in it and ready for the next retrieval.

I try to do as much scenario based designing as possible and one of those is the exact scenario you describe of retrieving the fish in rough seas. So I share your concern about raising the fish up out of the water and flailing away in rough seas when you are retrieving them. My solution so far is to keep the fish in the water until the poles are fully vertical or near to it and then once they are near the sides of the hull be able to use the winch to lift them out of the water and up into their stowing brackets as noted above. Our Rub Rails are about 2m/6ft above the WL so not a big distance and you would have your hand on the line the fish are hanging from to allow you to control the fish a bit as you raise them high enough to grab onto, tip nose down into their brackets and lower in place.

Agreed as well of the benefits and safety of solid railings for doing this work and we have a very solid railing just aft of the vertical A-Frame pole that is just over 1m above the deck and made from thick walled 40mm OD aluminium tube with base sockets welded all the way through the beefy Rub Rails which holds all our railings and stanchions very solidly. In the space between the two A-Frame poles there are two stanchions with Dyneema/Amsteel lifelines between them but have the option of converting these to solid railings if desired.

I have an Aft Guy line in the model and I think I will leave the design of the pole end plate as is with a shackle pin hole in it for an After Guy, but I’m not sure this line will be needed in our setup. Easy enough to rig one up out of Amsteel as you did if sea trials show a need and lots of good attachment points on the stern so I will wait to see what the sea trials tell us by trying some runs with and without an Aft Guy.

So thanks much for the great suggestions and sharing some of your experiences with paravanes and please do add more as you see our design evolve.
-Wayne

 

[Whodgins]

I agree with Nightsky on the pole length. We have 20’ poles mounted about 3’ from the water. They’re deployed at about 45 degrees. With shorter poles, in large seas, I’d also be concerned about the lines/fish tracking too close to the hull and running gear. In the first picture, we’re in pretty quite conditions with a cross current tracking right to left. You can see how the fish were tracking.

We retrieve the fish with the poles extended. Once, I started to bring a pole in with the fish still running. When the pole was within maybe 5’ of vertical, the boat rolled in a swell, the pole now went past vertical and with the downward force of the fish, the pole slammed against the A-frame. If you can mechanicaly retrieve the poles, not by lines like we do, you should be ok.

Here’s a stress analysis from one of Beebe’s book for a 36’ vessel. The numbers were an eye opener on the loading. We had a swivel let go once and thought a gun went off.

Good luck on your project and thanks for posting.

Thanks for sharing your expertise with us Larry, much appreciated. I have indeed lengthened our “poles” which as you see in the renderings I posted are A-Frame type booms more so than single poles. I had been thinking I should keep the tops of these A-Frame poles to be less than the height of our Arch and Radar but realised there is really no good reason for such a limit and lots of benefits from increasing the length of the paravane poles. Right now I’ve changed them in the 3D model to be about 6m/20ft and will be running some tests with this and can easily add more as I play with the roll attenuation numbers, fish size and weights and other factors to end up with the best setup for us.

You have me thinking more about the scenario you described of your pole being pushed past vertical in a large swell to hit your mast. With our design the poles will stow vertically being captured by a strong horizontal holder coming off the top sides of our big Arch so in a similar sea state our poles can not go past vertical so we are a bit better off. But I can see several benefits and higher safety of having a setup where we would retrieve the fish first and pull the poles in last, so I will be playing with this idea in the model now and see what this reveals.

We are able to run stress analysis simulations in the 3D model which tell us what the loads on any line or pole are going to be in a given configuration of the paravane pole length, angle, depth of fish etc. and with our very long very slender round hull these forces are much lower than for a beamier flatter bottomed boat so that helps. However as with all parts of the design we are eXtremely over engineering them and will definitely be heeding your advise of doing so with the paravane system.

Thanks again for your expert advise and please do continue to add more as our design and build evolves.
-Wayne

 

[Whodgins]

There is a direct correlation between the angle of the poles off the water, the length of the poles regarding how high they are at the tip off the water and how far the attachment point is away from the boat.. and the depth the fish run.

Most important is that the fish is too short to connect with the prop!


The second is the ability of the fish if it every gets airborne not to go through the cabin side ( The builder of our old boat had this happen when he thought he was doing the right thing by shortening the line.. until it launched out the face of a wave and impaled itself in the flybridge side.)

Our system worked well and seemed to be a bit less complicated than what you propose. The Nordhavn winch system works well and I have used is alot, it's about as easy as it gets ( although in the video above the buttons are in the wrong spot as it has the lady leaning over the side in what appears to be a dangerous position.)

I think the ability to adjust depth is unnecessary and adds additional failure points to the system. Also I think the need to machine a wing is not needed as the design uses drag to slow the lift of the unit and when the speed/angle of attack goes neutral the fish doesn't need a airfoil shape.. less drag is preferable when not resisting roll.

Keep in mind the poles when deployed also slow the roll of the boat.. even without the fish.. so the Nordhavn system works great leaving the poles out and bringing the fish up while still underway... we learned this on our old boat that dead slow was the best for retrieval.

HOLLYWOOD

Thanks for the wise advise based on your experiences with paravanes Hollywood. Being able to try out all these designs and dimensions in the 3D model is a huge help and enables us to run all sorts of simulations and checks of things such as how close the fish could possibly come to the prop tips, how their depth below the water changes as we bring the poles in, etc. We are currently well clear of the fish being able to get anywhere close to the prop tips and are designing for a running depth of 16-20ft below the WL so I think the odds of a "flying fish" to come into contact with the boat are being managed as well as possible though never zero.

To your other points I think I've now removed a good deal of the complexity of the initial design by going with direct lines led to a winch rather than 3:1 blocks, going with a single fixed length line for the pole end to fish line, lengthening the poles to 6m or more, etc.

I think that being able to retrieve our fish directly below the ends of the poles rather than close to the stern also reduces some complexity and improves the geometry of the rigging allowing us to do a straight lift of the fish out of the water when using the winch to bring in the Launch/Retrieval line.

I don't quite follow your comment about how ".... the design uses drag to slow the lift of the unit.... " so perhaps you can explain that further? Based on my research and talking with others reducing the drag by improving the hydrodynamics of the fish "flying" through the water is a good thing in terms of reducing the drag loads which paravanes place on a boat and thus reduce fuel consumption for any given speed. My current plan is to use NACA foil based design we currently have to CNC machine our fish out of aluminium to reduce their resistance through the water and their weight significantly. We will then run some experiments with different attachment points on the vertical fish vane to find the best angle they fly at when fully deployed.

We have experienced the roll attenuation benefits of poles out to the side when at anchor on some of our previous sailboats and look forward to the significant degree we can have this "tight rope walker" assistance with just the poles out.

Thanks again for taking the time to share your experiences and assist with the design of our paravane system.

-Wayne

 

[Whodgins]

The Krogen we just purchased has vanes, looks like a similar setup to what Larry has on Hobo. We used them a couple times bringing the boat up from Seattle in November, 10-12' steep following seas with about 40kn from behind and the boat was snap rolling too much without them. For the longer swells we didn't feel we needed them.
I also fished up here in the Gulf and we always used vanes. On the fishing boat we had an extra spool on the hydraulic gurdies used to raise and lower the vanes and it was a great setup. On our current Krogen it is done by hand, setting them is not bad (just drop them in) but they are heavy and I'm not sure my wife could get them back aboard herself. Once we are away from the dock for the summers I don't see us bringing them back in often so it may not be a big issue. A small simple winch on each side would do it if we decide we need it.

I agree with the others that said your poles look too short. (The jokes from that alone could go on and on...) Also, I'm not sure you need the line aft. Maybe someone else can explain why you would, but most of the force will be pulling down, or some aft on the bow fitting because of drag. There shouldn't be any force pulling forward unless you had following seas big enough to catch a pole as it went by, and the aft lines will be in the way.

Thanks Stripper and I think we have implemented changes in our design that deal with most of your observations. Poles are now going to be at least 2m longer at about 6m and we are running tests on the model to find the best length balance. Also eliminated the 3:1 blocks and gone with direct lines led to a small winch mounted near the base of the vertical legs of our Arch.

I also question the need for the Aft Guy line that was in the renders I posted as my logic matches yours in not seeing the need for them. I will still machine the AL plate at the pole ends with the hole for an Aft Guy shackle and it will be easy to whip up a Dyneema/Amsteel line from there to one of several attachment points back near the stern if we find an Aft Guy is helpful when we are doing sea trials. But like you, with our very over engineered A-Frame type hinged booms I don't see much need for the Aft Guy line and less is always better when it comes to lines and rigging I think.

- Wayne

 

[Kit_L]

Wow: this thread has grown since I last checked in.

To the paravane gurus out there: assuming a fish is suspended from its intended hole, what downward angle are we looking for at rest? The way the fish have been re-designed, we can easily set any angle we want by moving the bullet fore/aft, on land.

I'd like to get this angle right before we test at sea.

 

[FF]

"Keep in mind the poles when deployed also slow the roll of the boat.. even without the fish.."


The old schooners that worked the banks in the north Atlantic would frequently hoist their heavy anchor part way up the fore mast to ease the riding conditions before a blow.

 

[Larry M]

Wow: this thread has grown since I last checked in.

To the paravane gurus out there: assuming a fish is suspended from its intended hole, what downward angle are we looking for at rest? The way the fish have been re-designed, we can easily set any angle we want by moving the bullet fore/aft, on land.

I'd like to get this angle right before we test at sea.

Part would depend on the fish design. We use the middle hole on ours and average 6.5 knots. The forward hole is for up to around 9-10 knots and the rear hole is for slow speeds such as trolling for salmon in the Pacific North West. I’d be concerned that too much downward angel could overload the design at a given speed. So for testing, I’d start so the fish is pretty close to horizontal at rest and start from there.

 

[Larry M]

Here are couple of pictures while underway in calm conditions. The fish are 15' below the water at rest so they can't foul the running gear.

 

[balder8]

Hello,
As "promised", some pictures of my paravane project currently underway.
We decided to go on the "Aussie" way, no vertical poles, chain and cable but an horizontal arm ( 23 feet) with a tube and the fish able to move on a bidirectional way, with a fixed length, making impossible to hit the hull, the cabin or the propeller.
We used heavy jauge galva steel pipes which will be painted soon. the articulation of the arm is around a 25mm full stainless steel tube rotating in two bronze rings inserted in the vertical upright of the A-structure. Two electric 24 Volts cylinders ensure the 90 ° opening of the two arms controlled from the wheelhouse and the fold over the roof with a stop (not yet visible in the photo).The green ropes are only to block the arms, I have prepared to 10mm dyneema stays to control and limit the rotation and another piece to be fitted on the wheelhouse to stop and tignt the pole.
Now we have to test the angle if necessar of the fish welded for the trial at 90° on the tube.
I may say design and build these paravanes are an headache, very rarely used here in Europe, and some lack of infos, non considering this brillant forum.Thanks by the way to Lary M, Sea Venture and Tidapah who gave me interesting ideas and comments!

 

[Ventana]

We will do all our rigging with synthetic line such as Dyneema or Amsteel as we think this will be much safer, longer lasting and less noisy that chain or SS.

.

Ours are set up with the two guy wires made out of SS wire, and the line to the fish is braided nylon on the upper half and chain on the lower half. The previous owner set it up like that, his reasoning being that SS wire would “hum” at certain speeds. I guess he experimented with different materials and found that the chain produced a bit of drag but didn’t produce the vibration regardless of the boat speed. Just something to keep in mind, and easy enough to change if you do start getting a vibration.