Designing a new type of fishing boat .

Discussion in 'Stability' started by helen07, Oct 28, 2009.

  1. baeckmo
    Joined: Jun 2009
    Posts: 1,134
    Likes: 122, Points: 63, Legacy Rep: 1165
    Location: Sweden

    baeckmo Hydrodynamics

    So, if pixels and electrones are with us today; here a few pic's of the "good" vessel I spoke about. It has an underwater shape resembling the red one you showed hanging in a crane. If you want to persue the search for short, wide fishing boats, you might look at Norway. They have a 15 m limit, forcing the design of rule cheaters. One of the most extreme I found has a L/B ratio of ~2.4:1.
     

    Attached Files:

    Last edited: Nov 6, 2009
  2. peter radclyffe
    Joined: Mar 2009
    Posts: 1,405
    Likes: 58, Points: 58, Legacy Rep: 680
    Location: europe

    peter radclyffe Senior Member

  3. Tad
    Joined: Mar 2002
    Posts: 2,303
    Likes: 184, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

    Short, fat, monohulls are subject to capsize according to this paper.....

    View attachment research_report_557 suitability stab FV.pdf

    Looking at a few wider monohull types, excessive and rapid motion seems to be a common complaint. Cousteau's Alcyone and the Ramform hull used by WHY are two examples.

    Thinking out loud I would suggest investigation of a Trihull similar to that shown below. The form is a catamaran with a large storage hull added on centerline. The shape and volume of each hull could be tuned to obtain better motion characteristics......perhaps. The platform is 15m by 7.5m, as shown the underside of the platform is 1.2m above waterline. I suspect one would want it higher forward and perhaps lower aft. Probably the space between the hulls could be partially filled.

    First though is that the center hull could be used to store your catch while the demi-hulls carry machinery. Fuel could be in the bottom of the center hull or in the demi's.....tuning again????

    Displacement to DWL is approximately 84,000 pounds, PPI is about 3500 pounds. So 4.5" down will see her at 100,000 pounds (45 L tons). The sterns of the demi-hulls need modification for props and rudders, etc.

    Newfishboatviews.jpg
     
  4. helen07
    Joined: Sep 2009
    Posts: 38
    Likes: 2, Points: 0, Legacy Rep: 60
    Location: UK

    helen07 Junior Member

    Thanks all , i haven't been able to reply my laptops fried .
    I have spoken to my guy about it over the weekend and it seems i am wasting my time . He said a trimaran would be the way to go but he'd have to rob the bank of england first , so thanks for the suggestion Tad .

    He also said British fishermen are fast becoming extinct , it's a toss up who hates them most , the UK Gov or Europe . And as far as safety goes every single suggestion put forward by so called experts makes the job more dangerous . To explain he would , if he needed a boat , look for a wooden boat too big to meet the rules , he would then take a chainsaw and make it short enough to keep the pen pushers happy . The rules have made suitable boats ridiculously expensive so buy a wreck chop it up some more and hope it floats long enough to earn the cost of a replacement wreck before it sinks with you on it ! . If it doesn't well a few dead fishermen will justify another few million being wasted on expert reports .
    Dipping a beam (beam trawlers) while leaving a tea boy at the wheel steaming home in heavy seas is the greatest cause of capsize in his opinion and no design of boat is built to withstand that kind of negative .

    Personally i have learned through this exercise that the only way to know what will and won't work is to try it and see the results . I'm told i cannot just increase the scale of a boat for all sorts of reasons - yet millions are spent testing "scale models" in tanks before millions more are spent building the model in real life scale ?

    It's been interesting though and i thank you all for your comments .
     
  5. peter radclyffe
    Joined: Mar 2009
    Posts: 1,405
    Likes: 58, Points: 58, Legacy Rep: 680
    Location: europe

    peter radclyffe Senior Member

    thanks Helen
     
  6. Tad
    Joined: Mar 2002
    Posts: 2,303
    Likes: 184, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

    I don't think anyone is wasting time talking about safety, economy, and the future of commercial fishing. These issues are just as important in every nation with a coastline. Here in Western Canada our fishermen are also endangered, due to mis-management, un-regulated fish farms, allocation of declining stocks to other parties....etc.

    Almost no one on this coast can imagine building a new boat aimed solely at commercial fishing. But there are endless refits going on to better adapt to current conditions. In a lot of cases these include sponsons and deck extensions to carry more pots.

    Helen....it's not that you cannot scale any hull up (or down) and not have a boat....you definitely will, but you cannot arbitrarily scale a hull equally in all three dimensions and expect to have the same performance...this will not happen.....as the testers of scale models will attest to!
     
  7. helen07
    Joined: Sep 2009
    Posts: 38
    Likes: 2, Points: 0, Legacy Rep: 60
    Location: UK

    helen07 Junior Member

    As i said earlier Tad , the only way to know what works and what doesn't is to put theory into practice and gauge the results . I have read the reports some members were kind enough to offer and many others besides , and in every case the report focuses on maybe 2 aspects relevant to fishing boats , this is despite the fact that fishing boats are subject to maybe 10 different inevitably interwoven aspects . This makes all calculations given in the 2 aspect reports utterly worthless .

    I can think of no other vehicle on land or sea that is exposed to the extremes of the average fishing boat , if the rule makers would just accept that fishermen , as hardy as they may be , do not want to die , fishing would be much safer . The current rules mean a skipper and 2 crew men can be hired at a decent wage for less than it cost to fuel a boat , this is without the constant maintenance , the cost of gear , depreciation , a fish market thats failing because fishermen are not allowed to deliver whats required , diseased shellfish caused by overpopulation of the grounds , and keeping the pen pushers happy .

    If the powers that rule want safer fishing then let the men who risk thier lives daily earn enough to buy a newer safer boat maybe once a decade .
     
  8. JRM
    Joined: May 2008
    Posts: 11
    Likes: 1, Points: 0, Legacy Rep: 14
    Location: UK

    JRM Junior Member

    Fortunately, that is not the way the real world works. Everybody would go bankrupt if they "tried things out" without designing them first. Fortunately, all ships and most boats are designed before they are built and largely do what they are meant to do. Some of these ships and boats have even been designed by people who have themselves worked on fishing boats.


    I dont think anybody told you that. You are dead right, model tests are used to examine the performance of full size boats.

    Finally, I agree with you that the UK fishing industry is being buried under a sea of bureacracy, with the UK MCA applying the full force of regulation to fishing vessels since they can no longer apply it to a huge UK merchant fleet. What they expect small 1 or 2 man businesses to do is unrealistic.

    And at the end of the day, for your problem, I dont think anybody could justify the financial investment in a newbuild boat built specially to solve the problems you started out by describing.

    The economic return would be too small. You would be better buying an old but large boat to do the job - however imperfectly. As you probably know, they can hardly give them away these days.
     
  9. helen07
    Joined: Sep 2009
    Posts: 38
    Likes: 2, Points: 0, Legacy Rep: 60
    Location: UK

    helen07 Junior Member

    A reply from my guy

    In the real world when profesionally designed equipment fails a jury rigged set up thrown together using whatever is available , shackles , nails , sleeping bags , fender tyres , cutlery , wellington boots , even underwear elastic has saved the day and perhaps the lives of just about every fisherman worth his salt . He says we buy what is supposed to work then hack it and chop it and weld it altogether again so it actually does work . The idea is then copied and sold back to us because we are considered to stupid to notice .

    From me , the lack of suitable used boats is bad now and it is only set to increase and a new build might soon be the only option for those who want to stay at sea . I was investigating possibilities only a new build might allow , but i agree completely that nobody can afford to buy new just to remedy problems even if the problems might prove fatal , such is today's fishing industry here in Britain .
     

  10. waldoswhere
    Joined: Nov 2009
    Posts: 24
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: mexico

    waldoswhere Junior Member

    boat design

    your design is what iam looking at ,,,for years 52x18x9ft with jets full displacment...all steel with fly bridge aft for offshore shrimp fishing here in mexico...looking for some on e to help with the cad end of it can do scale drawings ...am a boat builder by trade..just helped build five yachts in tacoma washungton...two for uhaul...we are thinking about a ship yard in mexico...material is 700---800dlls per ton
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.