Bay boat hybrid hull design

Discussion in 'Boat Design' started by PBC, Aug 17, 2020.

  1. PBC
    Joined: Aug 2020
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    Location: South Africa

    PBC Junior Member

    Hi,
    I am developing a hybrid “bay boat” with offshore capabilities. The boat will be produced commercially and hopefully for profit at some point. Construction will be GRP using vacuum resin infusion.
    I am using Delftship to design the hull, 3 d printing prototypes and then I will build a 1/3 scale model / plug from mdf. Plug will be built from stations and panels cnc cut from delftship outputs.
    Currently LOA is 6.7 m .
    Max beam will be 2.5 m and beam on waterline will be 2.215 m. Beam can not exceed 2.5 meter due to road regulations.
    Dead rise is around 18 degrees transom angle of 15 degrees. The boat has a reverse hook on the stern.
    I am looking for input on the Bow entry : I have 2 versions both are convex between strakes. But with different entries. I would like to sharpen the bow entry As in the blue hull. any advantages or pitfalls associated with this. I am mainly concerned with broaching in big following seas and unpredictability in tight turns.
    Thanks
     

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    Last edited: Aug 17, 2020
  2. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    I'm not convinced anyone has build a better one than the old(ish) Aquasports.

    upload_2020-8-17_15-24-42.jpeg


    upload_2020-8-17_15-25-11.jpeg


    For heavier twin OB, inboard or I/O installation - more offshore oriented, look at the old(ish) Stamas hulls.

    [​IMG]

    [​IMG]
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    The "reverse hook" idea can't be seen in the pics, but is best avoided, if you want to get satisfactory results. Trim tabs are a better way to have the option of extra stern lift. Perhaps you should explain what you are trying to do, develop something for your own use, or to market it ? What material is the boat intended to be built from ? Hulls of this type are pretty well evolved, and unless you are very knowledgeable about what makes them "tick", it is unlikely you will come up with something that is as able, let alone better. I would say as a general observation that a deep forefoot is not as useful for improving ride, as some extra deadrise around the mid-body, and the stability won't be much different. It also encourages broaching, and is generally wetter, because a deep forefoot implies steeper buttock line forward.
     
  4. PBC
    Joined: Aug 2020
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    PBC Junior Member

    Thanks!
    I have edited my initial post. Also to clarify I am looking to design and build a plug to produce boats rather that attempt to design something revolutionary.
    I will get some clearer photos . On version one the keel rises up from the baseline at around 3.3 meters from stern. Version 2 (blue hull)it rises up at around 4.7 meter giving the deeper forefoot and more dead rise forward of midship. You prefer version 1 in this instance? I suspect I can keep the keel on the baseline a little longer without the boat broaching...
    I will upload picture and more detail of reverse hook.
    Thanks
     
  5. PBC
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    PBC Junior Member

    Thanks !
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    Sounds like a substantial amount of work and expense involved, is their a substantial market for high-spec ( infusion moulded) boats ? Do you have many local boats over there that are built that way ?
     
  7. PBC
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    PBC Junior Member

    Aware of all the work and the expense. I think there is a viable market. Tooling cost for infusion will be roughly the same as for hand lay up. Infusion will allow me to work cleaner and have less labour And overheads. There are a few builders here that are experienced with infusion so I have access to experience in that department.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    You might be better to 'flop' a good one, it is fairly common practice in Australia, to copy the best hulls of yesteryear, and adapt more modern lay-up techniques. Just make sure it can't attract legal action !
     
  9. PBC
    Joined: Aug 2020
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    PBC Junior Member

    Here is our progress so far- would be interested to hear opinions. thanks
     

    Attached Files:

  10. PBC
    Joined: Aug 2020
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    PBC Junior Member

    Busy with sanding. Will be fairing with mixfill 80 epoxy.Then epoxy primer followed by duratec vinyl ester primer and top coat. Tooling resin was going to be polylite but will now use a vinyl ester. Opinions appreciated. Thanks
     

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    BMcF likes this.
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Unusual looking boat, that forefoot and bow area has me a little worried.
     
  12. PBC
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    PBC Junior Member

    Side view of the forefoot.
     

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  13. Mr Efficiency
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    Mr Efficiency Senior Member

    The pictures of the bow area at the framing stage looks different to the pictures you posted a short while after. A bit of an optical illusion. Is there a lines drawing to show ?
     
  14. PBC
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    PBC Junior Member

    Lines drawings.
    Thanks
     

    Attached Files:


  15. Mr Efficiency
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    Mr Efficiency Senior Member

    That is a very, very complex shape indeed. I've never seen one like it. So there is no plan to use a test boat as the plug, and only make the mould if it performs to your satisfaction ? My first impression is that running down-sea it will dive into the back of waves before abruptly "bogging". It is quite fine in the waterlines forward, low down, but develops fullness very rapidly higher up.
     
    bajansailor likes this.
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