Sport fishing boat design

Discussion in 'Boat Design' started by seapassionate, Feb 1, 2025 at 12:01 PM.

  1. seapassionate
    Joined: May 2024
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    seapassionate Junior Member

    Can anyone tell that aftdeck wall height ( internal from deck to bulwark) is there a minimum recommended height?
    Let's say 70 cm for a boat of 12 m. length with 3,2 m. beam is acceptable ?
    Thanks your comments will be appreciated
     
  2. bajansailor
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    bajansailor Marine Surveyor

    Have you sketched out any proposals yet for your sports fishing boat?

    If you have, it might be easier if you post a drawing or two showing what you are proposing, rather than asking what the minimum acceptable freeboard on a 12 metre boat 'should' be.
     
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  3. TANSL
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    TANSL Senior Member

    @bajansailor, he is not asking for freeboard : "(internal from deck to bulwark)" .
    He, I think, is asking about the height from the cockpit sole to the gunwale
     
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  4. bajansailor
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    bajansailor Marine Surveyor

    Ah yes, sorry, I missed that.
    Freeboard does come into it as well though, as for a 12 metre boat one would expect it to have a self draining cockpit.
    So if there is a minimum possible height from the gunwhale to the cockpit sole, based perhaps on ergonomics and safety (high enough so that people do not fall overboard too easily), then that will affect the minimum freeboard that the cockpit has to have.
    And they want to have enough freeboard so that if they are enthusiastically backing down on a fish, they don't accidentally swamp the cockpit - that could rather ruin one's day.

    These guys appear to be a bit too enthusiastic when they were backing down....
    https://www.youtube.com/shorts/vLJiJWrEgMk
     
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  5. Rumars
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    Rumars Senior Member

    "From deck to bulwark" isn't a phrase that makes sense because the bulwark is an extension of the topside, so that distance is usually zero, with the exception of the freeing ports (openings to let out water that gets on deck).

    Now if we interpret that phrase to mean "from deck to the top of the bulwark", aka. bulwark height, we have several cases. Vessels under SOLAS must use a minimum height of 1m. Vessels not under SOLAS are subject to either local regulations or free from any. Most local regulations for passenger carrying boats orient themselves either by SOLAS (1m) or very close to. Boats not falling under those regulations can use whatever height the designer wants.
     
  6. ziper1221
    Joined: May 2018
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    ziper1221 Junior Member

    Waist high. That way you can still brace yourself while fishing, but can lean over to gaff a fish.
     
  7. TANSL
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    TANSL Senior Member

    Ships designed according to ISO 12217-1 must meet minimum values for freeboard and must meet certain buoyancy requirements which make the height of the bulwark (which is what limits the total amount of water that can be taken on board) also have certain minimum values. When the ship is completely filled with water, two-thirds of the length of the top of the gunwale must remain above water. Positive buoyancy even with the ship completely flooded.
     
  8. seapassionate
    Joined: May 2024
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    seapassionate Junior Member

    Thanks a lot to all of you for your efforts:)
    Am about discussing with friends about that data... some say lower but I insist that there must be minimum height requirement and I say that 70 cm should be OK and not lower
    To make easier to understand it is better to show some pictures about what I mean by my question, not free board of course but internally from deck level to top Sheerline, topplank...
    Actually mainly matter to ease the anglers It would be matter of a rather modern sport fishing boat design of approx 12 m length similar to this:
    Appreciate your kind comments again.
     

    Attached Files:

  9. bajansailor
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    bajansailor Marine Surveyor

    @seapassionate are you planning on having inboard or outboard engines on your boat?
    What is your plan once it is designed - are you going to build it for yourself or for somebody else - or will somebody else build it?

    You could use other similar 12 metre boats for general guidance re your preliminary design, while also ensuring that you have enough freeboard.
    However as Tansl notes above, you should make sure that you comply with the applicable rules.

    If you have outboard engines in a well (I presume as per your first attachment in your last post above), rather than a bracket on the swim platform (as shown in the aerial screenshot photo), then in addition to sufficient freeboard you will need to ensure that the depth of the well is sufficient for containing water (and draining it overboard quickly) if (for example) a wave comes over the transom (this can easily happen if you are backing down on a fish, as per the video I posted above).
     
  10. Waterwitch
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    Waterwitch Senior Member

  11. seapassionate
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    seapassionate Junior Member

    Thanks a lot again for all your suggestions.
    I think an answer to my simple question might become too tricky?!
    OK let me post the question like this:
    Independently from the fact the classification society or ISO most probably in this case will give a minimum height.......

    What is the standard / average/suggested height ( internal aft deck gunwale from deck level to top plank included i.e. max height) in USA or so for a similar boats of 12 m length with obms and live well?
    I am talking about the best comfortable height required by professional big game anglers!
    Unfortunately I cant find out this data from the web and since there must be hundreds and hundreds of such boats floating around on the water.... this data
    shouldn't be too difficult especially for anybody involved in the sportfishing sector :)
    Hope my question this time is more simple to understand....
    Look forward to your farther comments.
    Thanks
     

  12. fallguy
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    fallguy Boat Builder

    More important to consider broaching wave or backing hard into the sea to chase a big marlin. Both require massive scuppers and oriented to flow when backing means out the sides.

    For passenger safety not related to ingress, you can also use railings.

    The height of one meter is a bit much for either while 70cm might be a bit short and still want a railing. The railing offers more than the bulwark. It is a handhold.
     
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