Designing a bay and open water fishing boat

Discussion in 'Boat Design' started by Tom Henslee, Aug 18, 2021.

  1. Tom Henslee
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    Tom Henslee Junior Member

    I am in the design stage of building a 32’ long x 102” wide all aluminum hull fishing boat. The boat will be a catamaran type hull. The interior of the hull will be one fishing deck on the bow with a fishing chair. There will be a number of storage lockers down each side with a 50 gallon fuel cell on each side of the boat at mid-ships. There will be a center cockpit console at 20 feet aft of bow. There will be an inboard engine compartment at the stern w/ 3 water jet pumps. There will be one 100 hp emergency outboard engine mounted just to the port of the inboard engine compartment. There will be 2 – 50 gallon fuel cells at the stern of the boat (one on each side). There will be no other inboard quarters in the boat. I need to know what type of engine and HP plus jet drive thrust and the number of drives needed to power this boat at 60 +- mph. It will be used mostly in freshwater but there will be often times in bay and open sea water in the southern USA Gulf of Mexico (Texas to Florida). Just guessing at this point with an approximate loaded weight of 10,000 to 15,000 lbs and possibly less depending on engine and jet thruster weights. If you can help me with this problem, I would much appreciate it.
     
  2. bajansailor
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    bajansailor Marine Surveyor

    Welcome to the Forum Tom.
    I am sorry, but I am totally baffled by your description above.

    You earlier mentioned a catamaran hull - but this now sounds more like a monohull?
    Why 3 water jets?
    And why would you need an emergency 100 hp outboard motor that is taking up a lot of weight and space, when you will have two (or more even) main propulsion engines?

    Can you post copies of any sketches that you have produced so far please?
    They would help a lot to explain what you are trying to do.
    Please be aware though that there is a LOT to consider if you want this boat to be capable of achieving 60+ mph.
     
  3. kapnD
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    kapnD Senior Member

    So you’re using three engines to drive the three pumps, and an additional outboard ?
    Sounds like a lot of redundancy and unnecessary weight.
    Why not just put a drive in each hull?
    Also 100 gallons of fuel won’t go far with that many power plants to feed.
    Better post some sketches of your concept, with some dimensions, your description is a little hard to sort.
     
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  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Twin outboards would be a whole lot easier, is there some very shallow shoal water you need to cross, encouraging you to think jet drive is needed ?
     
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  5. Tom Henslee
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    Tom Henslee Junior Member

    upload_2021-8-19_18-44-1.png
    Tried to upload a file but it would not work. This boat will also likely be used for nighttime bow hunting for gar and etc.
     
  6. Tom Henslee
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    Tom Henslee Junior Member

    This design may not need all the power I have suggested. That is also information that I need for planning power unit.
     
  7. Tom Henslee
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    Tom Henslee Junior Member

    An emergency motor is for when we go offshore and have a breakdown with bad weather coming in on us.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    It is a bit hard to tell from your drawing, but does the tunnel more or less "disappear" in the aft third of the boat ? I don't like that idea at all. I think rather than get into the detail of the boat design, first list what the tasks are this boat needs to perform, like distances covered, loads, speed, number of people aboard, and importantly, the type of conditions it is likely to encountered in serving its purpose.
     
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  9. kapnD
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    kapnD Senior Member

    The deep pointy hulls seem at odds with the obvious shallow water needs.
    Wouldn’t fat hulls with much shallower vee be better for this?
    Trying to understand the drawing in the lower right, do the catamaran hulls merge into a single hull at the stern?
    With so much weight concentrated there, it makes sense, but how will the transition be handled?
    Is there only one inboard motor, and if so, how will it drive three jets?
     
  10. Tom Henslee
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    Tom Henslee Junior Member

    The tunnel does disappear near the stern of the boat. The boat will be used in both shallow marsh waters (probably no less than two feet) as well as in lakes and offshore Gulf of Mexico. I am not a boat designer as you have noticed. I'm am just trying to common sense the design with the needs of the water conditions. I am not set on jet power. I want what is the best design for these needs. One reason the boat is this long is for sleeping over night on the gulf coast and during night time bow fishing. Typically, for my family there will be no more than 6 - 8 people. Night bow hunting may be as many as 8 - 10. There are six fixed places for fishing chairs. Water depths will not always be shallow. I need good first class information from those of you that know boat designs and power units.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Obviously you have selected 8'6" to keep it legally trailable, I can see if overnighting with a whole bunch of people aboard, you will need some space, but also a good eye on the weather, and any likelihood of rain. Because you want an offshore capable boat, as well as one for shallows, you are introducing some compromises. But I can't see any need for more than two engines, regardless what else you decide.
     
  12. bajansailor
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    bajansailor Marine Surveyor

    Here is a copy of Tom's sketch, rotated 90 degrees so that you don't have to rotate your laptop (or twist your neck) to see it properly.

    Tom, re your approx loaded weight of 10,000 - 15,000 lbs, have you done a rough weight estimate of all the aluminium hull and deck structure yet, along with all the outfit weight items?
    If not, you should - it is amazing how fast they all add up!
    And have you got a rough set of lines (and displacement calculations) to see if you have the buoyancy to support this weight?

    Tom Henslee's boat.png

    60 mph sounds very ambitious to me, not to mention possibly a tad dangerous, especially if you are operating in very shallow waters. Surely 25 - 30 mph would be more than enough speed for most purposes?
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    I agree 60 mph is way too fast for an essentially open boat, will lead to interesting hairdos for those not behind the centre console windscreen. Not to mention creates a problem of needing huge power that most of the time won't be used, and will result in extra cost, extra fuel etc.
     
  14. fallguy
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    fallguy Senior Member

    A few too many items on the wish list conflict.
     

  15. kapnD
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    kapnD Senior Member

    I can almost visualize this boat as a Texas flats boat style, very low freeboard, and a shallow tunnel hull with lots of light weight outboard horsepower.
    I just can’t wrap my head around a definite catamaran bow cleanly transitioning into a monohull stern.
    Does OP have any further drawings that portray this detail?
     
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