RIB - Dive Boat - First Boat Build - Help Please!

Discussion in 'Boat Design' started by CodeS, Jan 25, 2020.

  1. CodeS
    Joined: Jan 2020
    Posts: 12
    Likes: 1, Points: 3
    Location: Sydney

    CodeS Junior Member

    So, I want to build a boat. My main trouble is that I don't have much boating experience so I don't know what boat is going to be best for me.

    I have a pretty well equipt fabrication workshop, so from a construction standpoint I'm good to go.

    Let me tell you about a few of my requirements, and then what I am currently thinking. Here is a list:

    - Be light to tow long distances (as it will be mainly used on trips away up/down the NSW coast)

    - Fit 3 divers (+) with heavy, technical diving gear.

    - Be able to travel offshore, in NSW Australia, upto 20km trips each way (without having to wait for the perfect day).


    Currently I am thinking a 5-6m Aluminium RIB with hard foam collar with a 90hp + outboard. I am thinking a hard foam collar is going to be the easiest thing for me to build.

    So my questions are:

    * What would you build (with photos and rough measurements/key design points if at all possible)?

    * What would something like what I describe weigh?

    * Am I heading in the right direction?

    * Any questions I haven't asked/more info needed?

    Thanks in advance.
    CodeS
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    What do you mean by a "hard foam collar" ? I noticed the title says "RIB" which I assume is "rigid inflatable boat", do you mean a foam collar instead of inflatable ? I expect you won't be much short of 2 tons towing weight with a boat capable of handling three divers and their gear, offshore. First thing to consider is the towing capacity of your vehicle.
     
  3. CodeS
    Joined: Jan 2020
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    Location: Sydney

    CodeS Junior Member

    Yes that is indeed what I meant, please excuse my ignorance. I have 3500kg towing capacity on my car but was hoping to not need anywhere near that to reduce wear and tear/fuel costs.

    Thanks for the response.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

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  5. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    Maybe something like that might interest you.
    Main Particulars:
    LOA = 5.26 m
    LH (hull) = 4,394 m
    Lbp = 3,904 m
    Lwl = 3,926 m
    Bmax = 2,590 m
    Bwl = 1,670 m
    Draft full load = 0.330 m
    Disp full load = 1100 kg

    RIB 526.jpg
     
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  6. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

  7. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    A 6 meter RIB or one with a hard collar is going to be small for three divers with technical gear. We use a 20' (6m) aluminum jon boat for commercial diving in protected waters and it is cramped. The collar will probable take 30% of the interior space. I assume you want to build a boat for the experience of it and not to save money.
     
  8. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Certainly the desire to be creative is admissible to some extent, but if the main game is the diving offshore, you need a proven hull design. There are still a few of these old things around with dive doors, and with judicious selection ( they are getting old) around hull condition and engines, you have a boat that will completely eclipse the performance any 6 metre vee-hull offshore. I'm not au fait with the preferences of divers re inflatables or "soft" collared boats vs "hard" boats with dive doors, though.
    CAT.jpg
     
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  9. CodeS
    Joined: Jan 2020
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    Location: Sydney

    CodeS Junior Member

    Yes going for an alloy build as a preference, unless there is a lighter way :)

    I had looked at the Specmar boats in the past, my trouble was trying to get an idea on final weights.
     
  10. CodeS
    Joined: Jan 2020
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    Location: Sydney

    CodeS Junior Member

    Thanks for the image TANSL, yes that is the sort of information I was after.

    It looks like there is an inboard on that design? Is roughly that included in the 1100kg? I steered away from an inboard due to additional weight considerations, although it would make for easy access from the rear. I'd probably be keen to keep the internal area a bit more clear also, opting for standing/a small fold away seat with a minimalist dash.
     
  11. CodeS
    Joined: Jan 2020
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    Location: Sydney

    CodeS Junior Member

  12. CodeS
    Joined: Jan 2020
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    Location: Sydney

    CodeS Junior Member

    Yes, I do want to build it for the fun of it and also so I get things the way I want them.
     
  13. CodeS
    Joined: Jan 2020
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    Location: Sydney

    CodeS Junior Member

    Yes I have been on a number of boats similar to that, what sort of tow weights do they get?
     
  14. CodeS
    Joined: Jan 2020
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    Location: Sydney

    CodeS Junior Member

    I have been loving the look and design of the 'life proof boats' range like attached. As I understand they use a foam collar vs fabric tubes. I'd only be able to budget for a much smaller version however (which they don't build).

    Anyone have any idea on towing weight on a 5-6m version of these (even an educated guess)?
     

    Attached Files:


  15. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    The boat of post # 5 has a waterjet type propulsion because it was thought that it would be safer for divers. The stem, somewhat higher than normal, allows attacking waves of greater height. The total length, 5.26 m could be increased very easily to 5.86 m although the Bwl / Lwl ratio would be somewhat small.
    @CodeS, displacement full load is 1100 kg. If you would like more information, please send me a PM.
     
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