Displacement powercat single 40hp

Discussion in 'Boat Design' started by Saqa, Oct 8, 2014.

  1. groper
    Joined: Jun 2011
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    Location: australia

    groper Senior Member

    Yeah nice jack mate, tops the biggest one ive caught...

    Im not sure whats left to discuss on the matter too bads, aluminium works fine, ally boats are everywhere... All you have to do is figure out a preliminary design based on how you think youll build it. Then youll need to estimate the weight, and weight distribution, and from there we can estimate the performance based on a few tools we have at our disposal - i can help you with that later. BUt for now, you really need to draw something up to get your ideas across or you dont have anything to converge upon...

    Ive shown you a few designs ideas which i think would work well for this purpose. I really dont like the single outboard approach tho, the lack of maneuverability when fishing would be a real handicap. If you have other ideas then show us...
     
  2. Saqa
    Joined: Oct 2013
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    Location: Hervey Bay

    Saqa Senior Member

    Single outboard is out mate. Going twin, max twin 40hp

    Will show some lines soon of what I think I can make with alloy without too much pain, cheers
     
  3. Saqa
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    Saqa Senior Member

    Turnpoint, mate I have a request. Do you have any build progress pics that you can share? I would really appreciate seeing some under boat pics and such but I understand if its something proprietary. M just looking for some scale of things like water clearance. The target style of fishing for my would be boat will be an efficient fishing platform at no more then 1m above water as otherwise the lure worked back to the boat will tumble frequently. Around 70cm is great as windage is another problem when idling near a reef and throwing poppers
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Do those mad tourists still want to catch GT's ? Wean them onto 'Hoo ! :D
     
  5. Turnpoint
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    Location: Port Townsend

    Turnpoint Junior Member

  6. Saqa
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    Saqa Senior Member

    Wahoo are great fun too, should have heard the drag on the old B series baitrunner scream! But seriously my hopes are on this boat to be my "working retirement" plan
     
  7. Saqa
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    Saqa Senior Member

  8. Saqa
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    Saqa Senior Member

    Lol is that a pumpkin under the bit!!
     
  9. Turnpoint
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    Turnpoint Junior Member

    Yep that's a pumpkin... Halloween party a 10 years back. Fixturing the pumpkin on the machine was tricky .... but the eyes came out as perfect circles.
     
  10. Saqa
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    Saqa Senior Member

    I came across this 6.5m design. Seems to meet a bit of my requirements
    http://www.spiriteddesigns.com.au/stowaway

    Would appreciate some thots on this if was modified to build without the sailing features. Availability of precut foam core kit is also attractive
     
  11. groper
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    groper Senior Member

    Got a couple last week :) [​IMG]

    That design is restricted by its ability to be trailered. Are you looking for the same ability?

    The other thing is that, with the full CNC cut kit, you will fall off your chair when you ask the price of it...
     
  12. Saqa
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    Saqa Senior Member

    Nice lil hoo mate, well done

    I agree it could be wider but one advantage being trailable is getting it out for cyclones and such. So the design as is, the speed is in the performance window I am after and with some added railings the all around walkability and standup castability seems will be good

    Its the bits like the 450mm bridge deck clearance that I don't know about. 350kg payload is only 3 guys and some gear, after the fuel and water capacity I suppose
     
  13. groper
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    groper Senior Member

    Standard convention would mean that it's bridge deck clearance is 450mm when it's sitting on its design displacement waterline. This includes its payload, which is said to be 350kg etc. it doesn't mean that you can't put more weight or people in it, ifs just that it will sit lower than it's designed waterline. Stability will not be a problem with a catamaran, so it still should be safe if carrying more weight within reason of course.

    As to its performance. I doubt one of these designs has been built yet, it's a paper design only at this point. So the numbers quoted are only an estimate, and probably an optimistic one at that. With close spacing of the demi hulls, there is a large interference wave drag problem. This will create a very large resistance hump, and I seriously doubt it will get to 20kts with a 40hp.

    Spirited designs came to be, when one of Jeff schionnings sons, a boat builder, not a naval architect, decided to go out on his own. I believe he employs naval architect design services through a 3rd party, but perhaps not on this rather small design. This is pure speculation on my behalf. However the performance numbers just don't add up based on the specifications shown on the website.

    In addition, if you intent on building this design from the kit, were you not concerned with the price? Building in foam or balsa sandwich is about the most expensive road you can go down.... Without this type of lightweight materials and construction, the performance will only get worse... Although thin ply will be close in a boat this size, but at a fraction of the price...
     
  14. Saqa
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    Location: Hervey Bay

    Saqa Senior Member

    Again, many thanks for helping understand some of these aspects mate. The cost of the project is definitely a concern. At the moment I am only checking out the potential in these designs. I do like the idea of not using ply. I also like the idea of an aluminium bridge deck
     

  15. Saqa
    Joined: Oct 2013
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    Saqa Senior Member

    I am not locked into the long wide displacement type either. Something like this open centre console might get two anglers plus skipper out over the chop to the fringing reefs and back in comfort with twin 40s with good mileage. Seems no one has plans for an open boat like this

    http://www.multimarine.co.uk/powercat-525.html
     
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