Midwater Longliners – Fishing Vessel

DELFTship forum Hull modeling Midwater Longliners – Fishing Vessel

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    • #37111
      duÅ ¡an

      Hi, I’m graduate student of Naval Architecture and for my M.Sc. thesis i have to project this type of fishing vessel (maximum lenght 30m). I was trying to find some body plans for midwater longliners, but it was without results.

      Here is some characteristics of this kind of fishing vessel (copied from FAO):

      Deck Type – Decked vessels.
      Overview – Midwater longliner are generally medium sized vessels operating worldwide and purpose built to catch large pelagics. The line hauler is usually placed on the star-board side forward and a gate in the rail is provided to haul in the fish. A baiting table and a chute are located on the stern, from where the lines are set. The basic requirements of this type of vessels are:
      adequate speed to reach far away fishing grounds,
      enough endurance to conduct continued fishing in distant oceans,
      facility for very efficient freezing storage to keep the highly valued catch,
      suitable machineries to shoot and haul up longlines quickly and proper storage facilities for keeping the fishing gears and accessories.
      Deck Arrangement – The wheelhouse can be situated aft or forward, but on larger vessels the bridge is generally placed aft. In typical arrangements the gear is hauled from the bow or from the side with a mechanical or hydraulic line hauler and the lines are set over the stern. To avoid incidental catches of seabirds outboard setting funnel are installed on longliners. This funnel guides the line from the setting position on the stern down to 1-2 m depth.
      Catch Handling and Processing Equipment – Freezing.


      Deck Equipment – In general the longline systems consists of rail roller, dehooker and hook cleaner, line hauler, hook separator, storage rack or drum. Different types of baiting machines makes the operation more efficient. Brine freezing tanks are typical equipment for midwater longliner.
      Fish Detection Equipment – More important as echosounders are temperature sensors in midwater longlining.
      Fishing Gear – Midwater longlines.

      Does anyone know where can i find some body plans?

      Thanks in advance!

    • #37136
      Ralph Grothe

      You could try to contact shipyards that build or have built such vessels.

      That worked for me when I conducted a ship design as part of my intermediate examination during my studies of naval architecture.
      Our German shipyards were very helpful and supplied me with all sorts of plans that I requested.
      However, this was in the late 80s and many of them have disappeared from the shipbuilding market since then.
      But I would give it a try anyway.

      Apart from that you could scour the Internet, what you have done with little avail, as you wrote.
      Maybe you haven’t searched carefully enough?

      A while ago I had drawn a lines plan in DS of a 50m longliner – so a wee bit larger than your project’s dimensions.
      I think that I even have made it public in some forum for model makers who might be interested.
      I had approximated the hull lines from a specs sheet of the Norwegian yard that had built her which contained apart from the main data and particulars a small GA plan.
      For unknown reasons the builders have removed this specs file from their webserver and now only offer a meager one-page specs file that lacks the small GA plan.

      You may find my lines plan approximation attached to this post (if they uploaded correctly and appear here)

      Just now I have also found this interesting Video on YouTube with some footage on the vessel’s moon pool and how it is used to retrieve the long line with the hooked catch.





      Then I had also drawn a hull of a 30m vanilla trawler on request by a fellow model boater in two variants,
      one with and one without a bulbous bow.

      As you can see, if you can’t find any body plans on the Net, it is quite easy to draw your owns after photos, specs, and small GA drawings which can be found in abundance on the Net
      (e.g. just do a search on Google Images)


    • #37137
      duÅ ¡an

      thank you very much for help!!!
      first one is very interesting, so i have to ask you, do you know why keel looks like that?

    • #37138
      Ralph Grothe

      I have no practical experience in ship design, for when I finished uni I somehow found a job in a completely different area (viz. IT).

      Therefore I can only answer you what I assume might be the reason.

      Fishing vessels traditionally have a rake of keel.
      Don’t know how to translate our German NA term “Kielfall” into the proper English term.
      What is meant is that the in the side elevation or sheer plan (or buttocks) view the keel exhibits a slope so that the vessel’s draft aft is deepest,
      whereas commonly ships have a flat, unsloped or unraked keel so that the lower edge of the keel usually constitutes the basis of the grid.

      Also it is common for fishing vessels to have a bar keel, which unlike a flat keel protrudes from the faired bottom with a crease edge or knuckle.

      I assume that both constructional features are to give the rather short and clumsy vessels better directional and yawing stability, especially when they are trawling a net or a line.
      What also contributes greatly in this respect is the rather extended area of a deadwood or skeg.
      The rake of keel also gives some kind of protection to the prop and rudder-nozzle arrangement against grounding.

      Especially, the cut-away or recess in the bar keel closely aft of the LCB is the spot where the moon pool penetrates the keel.
      The thing that you can watch in the video that I linked to above.

      I hope my assumptions are right, or that someone who knows better will correct me.

    • #37139
      Robert Holme


      Your description of “Keilfall” leads me to believe the English term is Trim which can be by the bow or by the stern. The Delftship manual has a full explanation.

      Hope this helps

      Best Regards

    • #37140
      Robert Holme

      Oops, forgot to say that the design of the keel above would suggest that this vessel uses keel cooling as a means of heat exchange for the main engine. i.e. instead of having a tube type heat exchanger fitted in the engine room and supplied with a seawater pump, the engines fresh water pump supplies tubes fitted in the keel and the vessels motion provides the heat exchange. This means one less pump to be powered and maintained. This is very common in Australian trawlers.

      Best Regards

    • #37141
      giorgio zuppin

      здравствуй – Sorry, hello bob!
      First of all compliments to deadwood: nice drawings.
      let’s go to the point, for first time I’m involved in something I’m really in – in a shore term only – could you quantify, as a rule of thumb, the advantage of that arrangement ( cooling system )?
      I fully understand the absence of suctions portholes and hyghly corrosive salt water tubing and heater exchanger means a relief to maintanence – pumps are reliable and you take almost a spare – but …
      Having a massive line of tubing almost uninspectable – as they are positioned – and they sheer size, I can quantify a 20% efficiency loss compared to a usual heather exchanger, it’s worth the while?
      There are other reasons I’m unaware?
      So, пока for now, and thanks of course.

    • #37143
      Robert Holme

      Hi Jurgen,

      My wife is Russian hence my use of snippets of it.

      All that you have said about keel cooling is correct and my term of tubes was misleading. What is actually done is the keel box is baffled similar to the attached jpg.

      Another form, is to weld half sections of say 100mm tube to the outside of the hull such as to form a grid on the hull as a heat exchanger.

      I personally see many more disadvantages with this system than advantages. The 1st which comes to mind is grounding!!

      Best Regards

    • #37144
      giorgio zuppin

      Hi Bob, my regards to your wife, Мне жаль ( i’m sorry ), it was a small courtesy presuming some russian ascendancy.
      Anyway, It makes sense, the idea is not wrong and it could be perfect if you can arrange an heat exchanger to cope hullforms AND with pipes or water passages sinked in it or included in a moulding to maximize exchange efficiency.
      It will turn out very expensive though.
      It’s another case of “Jim will fix it” idea applied on small scale: in my business I saw it many times.
      Btw Yelta drawings are on progress, has caught me…
      By, Jurgen.

    • #37145
      Robert Holme

      Hi Jurgen,

      Don’t be sorry, it’s good practice for me with my adopted 2nd Language.

      Thanks to you I have made a deal of progress with Yelta. I’m slowly coming to grips with the way delftship handles layers, extrusions and faces. Interior edges had me for a while but now I see how to use it to fair the hull and in a few more days, (between honey do’s), I hope to offer something for you to critique.

    • #37152
      Ralph Grothe

      I just wanted to provide a link to the website of McDuff longliner designs, where each design is accompanied by a tiny GA plan,
      to our anonymous prospective naval architect.

      Since all of them seem to exhibit a box/bar keel I presume this is a state-of-the-art design feature of this type of vessel nowadays.

      Merry Advent
      (or Seasonal Greetings as they say pc denominational neutral in the US)


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