Brainstorming Retractable Drives

Discussion in 'Propulsion' started by CatBuilder, Sep 29, 2011.

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  1. CatBuilder

    CatBuilder Previous Member

    Injuneer, there are a lot of problems with the outboards you are talking about.

    A displacement boat needs large, slow turning props. These are all for power boats, Boston Whalers and the like.

    Wrong gear ratios and wrong props.
     
  2. Injuneer
    Joined: Sep 2011
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    Injuneer Junior Member

    Hmmm... according to Aquawatt, their 13 kW is suited for displacement as well as planing hulls.

    But let's look at some numbers. Quite a few catamarans use the Yamaha 9.9 High Thrust. The Yamaha HT uses something like a 12 or 13 inch prop. The Aquawatt 13 kW comes with a 9.25 inch prop, but since it uses standard props, you could specify it with the largest prop that will fit, maybe a 12 or 13 incher. You could also specify a very high pitch prop - basically, try to overprop it.

    The Yamaha's gear ratio turns the prop at around 2,100 RPM at top engine RPM. The Aquawatt runs up 3,250. So a couple of choices here - you could ask Aquawatt to give you a higher gear ratio, which should be relatively easy on an electric outboard. Or you could simply run it slower, say up to the 2,100 RPM of a Yamaha prop (assuming you were overpropped). This is not an ICE, so the torque will be more or less independent of the actual motor RPM and will be available throughout the motor RPM range. The worst that could happen is that you might get some higher motor heating at the reduced RPM, but since this is a water-cooled electric motor, there should be some buffer in the system to take care of the extra heat (larger water pump?). It's not ideal, but I suspect it can be made to work.

    And lastly, if you don't like any of those suggestions, as I mentioned in my previous post, you could "get a couple of blown outboards, rip out the engines and install electric motors of your choice - DC, BLDC, PMCT, brushed Lynch, or 'industrial-quality' AC motors. That way you could select your own gearing and modify the length of the lower unit leg to exactly match your installation." Frankly, that's exactly what I would do, it's not that complicated.

    Unless you are willing to explore some of the above suggestions, my guess would be you will not find anything on the market that fits your ideal configuration.
     
    Last edited: Oct 6, 2011
  3. tunnels

    tunnels Previous Member

    what about doing all your drives with hydraulics ? altenater , 2 props and what ever else you want to drive . could all work at the same time or just one at a time or not at all just the motor running with no drives working !!
    just means running pipes or hoses here and there . :?:
     
  4. masalai
    Joined: Oct 2007
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    masalai masalai

    www.mastervolt.com/e-propulsion - Have you seen this? or is it too small/expensive? - - A pair as a minimum may get 6 knots and maybe even 2 pairs? :eek: but that would mean mini-keels, just sufficient to protect the propeller.... Gensets forward for hull-balance and making mains-voltage-house-AC, battery-charger, (mains-voltage to 48VDC), aft with 48VDC LiFePO4 batteries near each engine (aft) and inverters there to take care of silent living when desired... An aft mast and Hitch-hiker-dual-genoa, one to each bow will leave the coach-house roof clear for solar panels

    On CNO, I can carry 13 panels 800mm x 1600mm for 2275W nominal output when at anchor in the tropics... My Nanni321SD engines burn about 3 litres/hour at 3000rpm and deliver around 10hp/11Kw each so those electric drives are about on a par with the Nanni321SD at Au16,500 each including OEM installation package... A Nanni mains generator in Australia is about http://seawasp.com.au/docs/6.5 KVA.pdf I feel more comfortable/secure with fixed blade propellers for long range efficiency and confined quarters manoeuvring...
     

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    Last edited: Oct 12, 2011
  5. masalai
    Joined: Oct 2007
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    masalai masalai

    hehehe

    Do you want to buy my cold-fusion-energy package for cats? I need Au$40K for incidental materials... - - and then research access to CERN...
     
  6. keysdisease
    Joined: Mar 2006
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    keysdisease Senior Member

    Cold fusion, how yesterday. Fund me for dilithium crystal mining and I'll produce a matter / anti-matter drive.

    Steve:p


     
  7. Wingandaprayer
    Joined: Oct 2011
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    Wingandaprayer Junior Member

    Catbuilder, I am in a similar situation as yourself, building a 19m cat and playing with various propulsion options, with similar limitations/requirements as you have mentioned. By the way, I know the owners of ZeeVonk and can put you in touch with them if you like. I would like to discuss propulsion issues with you offline, if you are willing. Email me yours and maybe we can invent/discover something.
     
  8. CatBuilder

    CatBuilder Previous Member

    I would love to speak with the owners of Zeevonk. I contacted them once, but all they did was give me the hard sell on buying a charter from them. I was trying to ask details bout the boat and the reply was, "we are very happy with the boat, you should buy a charter."

    Maybe a warm introduction would make a difference.

    I'd be quite happy to discuss propulsion issues offline. I will send you my email after I finish typing this. Thank you for reaching out.
     
  9. masalai
    Joined: Oct 2007
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    masalai masalai

  10. keysdisease
    Joined: Mar 2006
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    keysdisease Senior Member

    Was setting up at IBEX today and saw the Mastervolt display. Pretty extensive hybrid stuff. Sure there is more, but the place is a mess during setup and I have a mission.

    Steve
     
  11. brian eiland
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    brian eiland Senior Member

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  12. brian eiland
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    brian eiland Senior Member

  13. michael pierzga
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    michael pierzga Senior Member

    Looks nice but what is the advantage over the present designs like the one from Boatspeed Australia ? The unit from the Netherlands looks to consume too much interior space and presents substantial lateral resistance.
     
  14. brian eiland
    Joined: Jun 2002
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    brian eiland Senior Member

    over here we had this discussion...
    http://www.boatdesign.net/forums/hybrid/diesel-electric-propulsion-system-design-have-your-say-39662-10.html#post490628
    ...to which I replied...
    Why add in the complicated retraction system if you are going to make use of a folding prop?


    I don't see this as a problem when you are under power. In fact it could be advantagous in preventing your being blown sideways.

    And I don't think it consumes that much more interior space when you look at the total cavity allowed for the non-folding prop verse the stretched out cavity for the folded one? We would have to look at this more closely.

    I also would want to look at the servicability of the two in comparison.
     
    Last edited: Feb 9, 2012

  15. Boatguy30
    Joined: Dec 2011
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    Boatguy30 Senior Member

    Update

    Kind of an old thread, but wanted to see if there was an update. I think you are the guy in Green Cove?
    I am building a woods Vardo in St Aug. Pretty sure I am going to have a diesel with shaft drive in starboard hull and then some type of electric in port hull either outboard, DIY Glen L sail drive, for maneuvering.

    I was planning to come out to Toms in the next few weeks to have a look at some gear he has. I was out there in Nov getting a mast and had a peek in your shed.

    Give me a call 904.436.5174
     
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