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Old 12-13-2019, 06:39 AM   #1
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paravane stabilizer: solid foldaway arms design

Hi!
Bonjour tous,

First of all, thanks to all boaters and trawler owners who are posting pics, drawings, comments and explanations concerning this very crucial subject on passagemaker trawlers: the paravane design as unique system for stbailization underway or as a back up for long range cruising.

I think trawlerforum is certainly the only one forum where you can find this level of quality! With a very friendly atmosphere!

So, I have decided to go with paravanes as a back up ( I have Keypower stabs installed) for my next ocean crossing aboard Balder VIII, north sea trawler 57' built by excellent Dutch boat yard Tinnemans'BV.

Instead of considering an extra A frame design with mast etc, as used on Nordhavn, KageyKrogen and described in the fantastic book " Voyaging under power", I am planning to retrofit a stainless steel rigid structure based on an horizontal solid foldaway arms/stabilizer design as shown below on the picture of the australian fishing boat shown on M/V Dirona blog ( thanks to them!)

On my plan, paravanes are 20' long. An engineer is calculating the diameter and sizes of all this rig, may be in stain less steel.
Here some pictures of my project.

Is it necessar to say that all comments or advices will be welcome and appreciated???

Kind regards
Dominique
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Old 12-13-2019, 09:07 AM   #2
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You are going to be pushing our collective memory of statics class!
There is a likely heavy load, alternating, on the base supports. That fixed bottom blue tube will load the bottom vertical supports quite significantly, I believe, with both a bending moment and a shear force. So, those are significant anchor requirements. Is the superstructure Al or steel?

Beyond that, consider the arms of titanium, or is money limited?
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Old 12-13-2019, 09:45 AM   #3
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Yes, diver dave is correct as above. The bending moment will be taken care of by the horizontal truss structure. But the vertical and sheer force on that blue member will be quite significant.

So make sure someone looks at the underlying structure below those blue members as well as the design of the arms and truss.

David
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Old 12-13-2019, 11:01 AM   #4
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Thank you Diver Dave, thank you DJ Marchand!

Yes I know there will be a serious load on the underlaying structure!

Hull and superstructure of Balder VIII are built from marine steel 6 to 8 mm.

I wish the calculation should be accurate to avoid transform my beloved trawler in a convertible one in rough seas!

Seriously, I want to avoid the vertical pole, chain or cable as well, adding weigth in the heights.

The picture below from a Trawlerforum member is also typical of this design.
About Titanium, I am paying too much taxes in France to afford this kind of material, as well gooooold!
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Old 12-13-2019, 11:07 AM   #5
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Also, in the retracted position: Be sure to support the movable arm from below, well aft. Otherwise there is a significant bending moment to aft on the lone vertical support pole that has no strut bracing in this direction. This is obviously the same port and starboard. Even with this, a high seas transition from retracted to extended will stress these masts. You might think about a strut guy or even conventional wire rope guys up high.
Note that your two example pictures show pole attachment high and low.
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Old 12-13-2019, 11:15 AM   #6
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Quote:
Originally Posted by diver dave View Post
Also, in the retracted position: Be sure to support the movable arm from below, well aft. Otherwise there is a significant bending moment to aft on the lone vertical support pole that has no strut bracing in this direction. This is obviously the same port and starboard. Even with this, a high seas transition from retracted to extended will stress these masts. You might think about a strut guy or even conventional wire rope guys up high.
Note that your two example pictures show pole attachment high and low.
Yes it is exact. I am waiting for the calculation of the Bureau d'Etude.
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Old 12-13-2019, 11:28 AM   #7
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I have added the red triangle, forgotten.
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Old 12-13-2019, 11:38 AM   #8
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Originally Posted by balder8 View Post
I have added the red triangle, forgotten.


Intending any mainsail from the foremast? I suppose only a closehauled situation? Or, will paravanes eliminate future use of sail?

Oh sorry; was confused by vessel behind.
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Old 12-13-2019, 02:06 PM   #9
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Quote:
Originally Posted by balder8 View Post
.

The picture below from a Trawlerforum member is also typical of this design.
About Titanium, I am paying too much taxes in France to afford this kind of material, as well gooooold!
M.V.Lifeline
Tragic story there and vessel is still up in Kota Kinabalu I think.

You will notice their top beam/truss arrangement has a horizontal top and bottom whereas you only have a bottom drawn.
On yours I believe you will get upwards bending from the centre unless you ad a top beam.
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Old 12-13-2019, 02:10 PM   #10
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Well said above.

Fascinating approach. As mentioned above, bending moment and shear forces abound. If it were my boat, I’d see the solution as two separate problems. One, I’d want to consider what it would take to transfer the forces from the bird through the boom and to the points of attachment as a force requiring a material and structure of one yield strength, and the forces placed on the center mast section attached to the boat as forces requiring a separate and much higher yield strength material, integrated with the boat’s structure.

The boom design as shown looks adequate for this sort of stress constructed from simple schedule 40 tubular aluminum. But to transfer that much leverage through that center section design as an add-on, non-integrated accessory with no compression mast or direct connection across the farthest points of leverage....shew! I’d sure need to have a lot of faith in my boat. Interesting challenge.

I know you’re just opening to feedback here, but at the very least, I’d want a glaring green light from a darned good naval architect. Please keep us updated!
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Old 12-13-2019, 05:59 PM   #11
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Originally Posted by Simi 60 View Post
M.V.Lifeline
Tragic story there and vessel is still up in Kota Kinabalu I think.

You will notice their top beam/truss arrangement has a horizontal top and bottom whereas you only have a bottom drawn.
On yours I believe you will get upwards bending from the centre unless you ad a top beam.
"Tragic story there"... I do not want to be impolite, I believe you know something very sad about this vessel or the owners or family...

"On yours I believe you will get upwards bending from the centre unless you ad a top beam". Thanks a lot for this comment, I will try to translate it and transmit to the technician.
To Healhustler,
Well said again.. the problem for me as an european boat owner, quite experienced as well, is that we know nothing about paravanes, rig and all the stuff. Because, here, fishing boats are not using these kind of stabies.And by the way, trawlers owners do not share or reply their experiences.
When I compare the US culture and the Australian or NZ practices , the big difference is the way you are rigging the arms: vertically in US and more horizontally in Pacific. Horizontally folding with rigid arms looks more easy to deploy and retrieve, isn'it?
Of course, lack of A Frame or mast means more solid structure to support the load.
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Old 06-02-2020, 10:56 AM   #12
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Quote:
Originally Posted by healhustler View Post
Well said above.

Fascinating approach. As mentioned above, bending moment and shear forces abound. If it were my boat, Id see the solution as two separate problems. One, Id want to consider what it would take to transfer the forces from the bird through the boom and to the points of attachment as a force requiring a material and structure of one yield strength, and the forces placed on the center mast section attached to the boat as forces requiring a separate and much higher yield strength material, integrated with the boats structure.

The boom design as shown looks adequate for this sort of stress constructed from simple schedule 40 tubular aluminum. But to transfer that much leverage through that center section design as an add-on, non-integrated accessory with no compression mast or direct connection across the farthest points of leverage....shew! Id sure need to have a lot of faith in my boat. Interesting challenge.

I know youre just opening to feedback here, but at the very least, Id want a glaring green light from a darned good naval architect. Please keep us updated!
Well, after two months, back aboard to finish my paravane project!
Here is the result, but the birds are not done. Plywood or steel, I try to find the best solution and drawing: 300 sq inches or more?. Before COVID 19 flu, I expected to order from Kolstrand but shipping cost was too expansive. Will weld or build locally.
Also , very difficult to imagine which angle for the swivel attachment hole???
Any suggestion appreciated!
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Old 06-02-2020, 01:28 PM   #13
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I'd go with the 3/4" plywood that you have in the drawing. If they come in contact while deploying or retrieving, the wood won't scratch the side of your boat. Ours uses stainless steal with 27.5 lb lead weight up front. For scaling purposes, ours measure ~28" across the back and we displace 44,000 lbs. I'd consider going up to 32" size based on the size of your boat.

Here's a picture of how ours are attached, while underway and who we bought them from.

https://www.englundmarine.com/produc...CSNO-STAB.html

Nice job by the way!
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Old 06-03-2020, 04:57 AM   #14
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I'd go with the 3/4" plywood that you have in the drawing. If they come in contact while deploying or retrieving, the wood won't scratch the side of your boat. Ours uses stainless steal with 27.5 lb lead weight up front. For scaling purposes, ours measure ~28" across the back and we displace 44,000 lbs. I'd consider going up to 32" size based on the size of your boat.

Here's a picture of how ours are attached, while underway and who we bought them from.

https://www.englundmarine.com/produc...CSNO-STAB.html

Nice job by the way!
Bonjour Larry M,
Thank you very much for your kind comment!
I have spent a lot of time reading your posts and looking at your pictures before starting my project! As mentionned, here, in Europe, even naval architects know nothing about paravanes...and most of people consider it is uggly... I assume my choice and if I cross Atlantic next winter ( depending of bloody flu, situation in US, taxation here to support economy, to resume all good news to come may be in the next six months, etc...)I will be happy to have a back up to my hydraulic stabilizers.
One more question, going to with plywood 32" local made (Englund does n't ship oversea and I have no chance, sadly, to visit my house in Qubec...), is the vertical stabilizer really usefull or may I follow the drawing in my post?
Last but not least, on my boat, we have fitted a rigid pipe with a welded plate like they do in NZ but I think it is too heavy. So these plywood paravane with high density lead ballast look more easy to use.
Last , would you only recommand dyneema rope to connect from the paravane to the bird instead of chain??
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Old 06-03-2020, 05:16 AM   #15
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Originally Posted by healhustler View Post
Well said above.

Fascinating approach. As mentioned above, bending moment and shear forces abound. If it were my boat, Id see the solution as two separate problems. One, Id want to consider what it would take to transfer the forces from the bird through the boom and to the points of attachment as a force requiring a material and structure of one yield strength, and the forces placed on the center mast section attached to the boat as forces requiring a separate and much higher yield strength material, integrated with the boats structure.

The boom design as shown looks adequate for this sort of stress constructed from simple schedule 40 tubular aluminum. But to transfer that much leverage through that center section design as an add-on, non-integrated accessory with no compression mast or direct connection across the farthest points of leverage....shew! Id sure need to have a lot of faith in my boat. Interesting challenge.

I know youre just opening to feedback here, but at the very least, Id want a glaring green light from a darned good naval architect. Please keep us updated!
Yes indeed,
Some details of the fitting ( not already tested to be honest)
The supports on starboard and portside are bolded with 4 cm diameter bolts. counterplate in 7mm hull more or less in the gravity center position.
The arms are articulated with a solid stainless tube 25mm inserted in two bronze rings. Material is galva steel.
Hope my google translation from french is ok!!!
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Old 06-03-2020, 01:45 PM   #16
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... is the vertical stabilizer really useful or may I follow the drawing in my post?

I’ve never run with out the vertical stabilizer. I have tuned them though. Based on current and wave height, I’ve bent the stabilizer slightly to track parallel to the boat.

You could start without the stabilizers and easily add them later
.

Last but not least, on my boat, we have fitted a rigid pipe with a welded plate like they do in NZ but I think it is too heavy. So these plywood paravane with high density lead ballast look more easy to use.


I’ve used both. I like the plywood. As I mentioned, they are more user friendly when they come in contact with anything. I have seen where others have replaced the plywood with high density polyethylene/plastic for longevity. I was getting about five plus years before I had to replace the plywood.


Last , would you only recommend dyneema rope to connect from the paravane to the bird instead of chain??

I think it depends on your retrieval method. I bring the fish along the side of the boat and manually lift them. I’m not sure my hands could get a tight enough grip on the dyneema to lift the fish over the cap rail. The dyneema would definitely have less drag though.
Dominique: The picture is what happens after the plywood has been soaking for 5 plus years and fails when fully loaded.

Here's the contact information for the guy who makes the stabilizers for Englund Marine Supply. Maybe he can ship what you want with out the lead?

Harold Williams, F/V Snapper Products
360-580-0114

Larry
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Old 06-08-2020, 01:27 AM   #17
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I use Dyneema rope on my stabilizers and it has worked out great. Much better than the stainless cable they were rigged with when I got the boat. I pull them up by hand. I have a pair of heavy duty rubber gloves I put on before I pull them up. One thing that worries me about having the fish in the water is the possibility of accidentally snagging one on something while in shallow water and near rocks, (I have kissed the bottom before, but never got stuck.) I like the idea that Dyeneema could be cut easily in an emergency situation. Much easier than chain or cable.
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Old 06-09-2020, 03:50 AM   #18
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Thank you again Larry, thank you Snapdragon for your replies!
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Old 06-18-2020, 11:17 PM   #19
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Can you share your cost for this project? Thanks.
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Old 06-19-2020, 05:30 AM   #20
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Hello,

Why you don't ,partially at less, use the existing structure ?

To low ?
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