Propulsion general questions for heavy use on 30ft power cat.

Discussion in 'Propulsion' started by xellz, Dec 29, 2018.

  1. xellz
    Joined: Jul 2017
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    Location: Japan

    xellz Junior Member

    Motors are in hulls, basic straight shaft setup. All monos here are straight shaft and well over 30 years in water, i'm using one myself. Hauling out for anodes not that big of a deal in return transom is clean. Marine growth is not an issue here. I'm not sure what exactly is leaking from volcano into port, but upper layer is orange most of the time and keeps barnacles away rather well. Oxidized iron probably. This is how it looks from above. There are also no owners of outboards around here that i could talk with or even mechanics that i could get advice. So i'm still torn between two choices.
     

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  2. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Metals in the water I'd say.

    I would want ob first, diesel ib next, electric last.

    Electric gonna change too much next 20 years.
     
  3. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    I sometimes wonder whether a single"longtail" drive might not work on this type of cat. Maybe Richard Woods can give you an opinion on that.
     
  4. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    That's a lot better view than Kobe harbour that i see daily! Wanna swap...? :D

    If it were me, and the issues you've noted. Just go for long slender (high length-displacement ratio) design with a small outboard on each and supplemented by small sails. Thus when the wind is in the right direction just sail to the site.
    And then use the motors when sailing is not an option. Best of both worlds.

    Plenty of decent J's outboards available here, as I'm sure you know.
     
  5. xellz
    Joined: Jul 2017
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    Location: Japan

    xellz Junior Member

    While island life can be difficult, i won't change this place for any other. Fishing paradise right beside us that i won't be able to find anywhere else :)

    I sure would love to have boat with purpose made design, use carbon fiber for everything, etc. But i'm on my own now, money situation doesn't allow it :) Richards design cost me under 1k usd, since i was one of first to buy it, so got a discount. In addition, design consists mostly of straight lines and a bit of slight curves that are easy to do. I did search for ready designs before settling with Richards Jazz 30, but light and long displacement cats just didn't come up. Racing sailboat minus rig only, but again it's not optimized for power and far more complicated to build. I asked before how much custom design could cost, but didn't get even example price. So it's probably way out of my price range.

    Back to the question, here i see everyone supports outboards as first choice. More points for outboards. I still need to learn more about maintenance though.


    What would be the point of longtail drive on cat over ready available outboards? How is steering from remote controller? Bare engine i see on photos is just too dangerous, need housing.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    They are a bit of a rough-and-ready 3rd World type of solution, but I am attracted to the idea of single engines for fuel economy, and especially with a prop working in water that has not been dragged along by a hull ahead of it. The fuel consumption can be reduced substantially. But it would be difficult to set up such a drive on a cat with a high tunnel. Just a thought.
     
  7. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I'm surprised the hull design would suit inboard or electric. The Skoota 32 has a lot of stuff aft, xtra bulkheads, knees and such. I have a feeling you are underestimating the importance of space to work. The Skoota 32 hull bottom is under 22" wide.

    For nearly any service on the inboard diesel; you will be cramped. Electric motor obviously smaller.

    Not saying impossible, but not easy.
     
  8. xellz
    Joined: Jul 2017
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    Location: Japan

    xellz Junior Member

    Before buying plans i did ask Richard about possibility of straight shaft electric version, he said it should be possible. Inboard diesel i discarded already, too much trouble even if it could be fitted.
     

  9. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    The Tesla electric engine is made a bit different. I suspect some of these engineering marvels will make their way to marine service, so perhaps you can plan to change it
     
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