Brainstorming Retractable Drives

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

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  1. boat fan
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    boat fan Senior Member

    How much do you think this would cost Mas ?
    That swing out idea is good.Would have to be very strong because of that long lever arm .....
     
  2. masalai
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    masalai masalai

    "Schools Out" a 44C had something similar, but the electric drives in pods, from USA failed ........ and warranty not honoured... They tried another from Europe but electrical/electronic interference caused problems so he reverted to a 60hp outboard in a pod midships, under the aft end of the brid-gedeck... The arms seemed capable and robust with the pivot beam extending some 500mm either side and braced substantially into bulkheads, and lifted by hydraulic ram, not for the weight but difficulty to access whilst sailing... I would not like to run aground with the legs down :eek: (That is why I have mini-keels - - to protect my sail-drive legs :D )

    The owner of "Schools Out" made them - composites, - and maybe SS ties? - sort of wing-let shaped for minimal flow resistance...
     
  3. boat fan
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    boat fan Senior Member

    Good points ....I had considered the grounding issue...it seems it would require the main pivot bearing assembly to be protected by a shear pin or something similar.More complexity and cost ..soooo , how much $$$$...???
    ..
     
  4. Petros
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    Petros Senior Member

    what if you took your rudder and designed it to be driven back and fourth like those Hobie peddle yaks or whatever they call them. The rudders would have duel purposes, locked in place they are your rudders, but with the drive activated they occilate back and forth pushing the boat forward. They are actually fairly efficient if the blade is shaped properly. The mechanism is not that complicated, it would have to be made very durable and sized to the power input of course, but all of it can be contained in the hull. Than you do not have any extra drag when you are under sail. And there is nothing to retract out of the water, you would only have the one through hull point at the rudder, and it could likely save a lot of weight too.

    I can likely design such a drive for you, I am a mechanical engineer with many years experience.

    It would be an interesting concept to explore.
     
  5. boat fan
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    boat fan Senior Member


    Interesting...I am skeptical about it being able to produce enough
    "push "for such a large craft. Very interesting all the same tho`.....
    Do you mean a drive like this ?
    .
    [​IMG]Hobie MirageDrive
     
  6. masalai
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    masalai masalai

    I doubt that up-scaling would be an option as the ones I saw seemed almost at the limit of the available materials... Bigger would be unmanageable and they are extracted from above before beaching as damage may happen... What % of a horsepower can a pair of human legs produce continuously?
     
  7. waikikin
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    waikikin Senior Member

    "Monstrosity Drive System" or M.D.S.

    That would of coarse be up to Catbuilder where he puts the "monstrosity drive" Personally I would opt for outboards, IF I were to fit one or two monstrosity drives to a sailing/cruising cat, probably would adapt the "concept" to a degree & fit the small diesel engine/s fwd of the mast bulkhead, these could also be coupled to generators for house power needs & be well sound insulated & muffled. The monstrosity drive system could be something like but not limited to this, using off the shelf industrial & easy to fabricate weldments (engine maybe air/water/HE/radiator cooled + FNR gearbox + cv + intermediate shaft + cv joint then a thrust bearing that allows the "drive shaft & tube" to pivot down to opperating position, the monstrosity drive when in the opperating postion could be a suspended from a wire or solid bridle/track arrangment for geometry purposes, the prop could be large & efficient 2/3 blade within the draft constraints & also incorperate a cav plate to the prop area too, the final propeller postion would/could be sub cockpit area & be accessed through hatches or the lifted postion could also be adjacent to the rear of the aft connective beam structure where easily inspected. When underway the very discreet monstrosity drive system would be hardly noticable except for the smooth & efficient progress though the sparkling blue ocean, if the wind was right & the sleek catamaran sailing nicely the gensets could be clutched in & be contributing nice amounts of full fat electricy to desal some refreshing bathwater & also to heat same, also to cook a delicious lamb roast, with rosemary, baked spuds etc, to be consumed as the golden orb of sun sets behind the swaying palms at the next secluded island anchorage, Catbuilders charter guests could & would be enjoying the first of a few thirst quenching sundowners as they sit around relaxing, clean & fresh & happy & ready to tuck in to another grand meal as the balmy spice scented breeze cools the tropic heat whilst they discuss the days fun.................. All thanks to the wonderful catamaran that Catbuilder built, sporting the latest M.D.S.
    Regards from Jeff.
     
  8. waikikin
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    waikikin Senior Member

  9. yipster
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    yipster designer

    Kurt Hughes designs fine boats but underwater hullshapes and props are mostly cut off at the waterline so only a wild gues here
    never seen such but one idea might be to have the props also kick-up, perhaps somehow intergrated with the rudders
    looked at more of Kurt's designs and altho i dont really like that set-up pic below it does come close to that idea
    no better studyplans with underwater hull and propulsion drawings as KURT Hughes envisioned your 45?
    [​IMG]
     
  10. CatBuilder

    CatBuilder Previous Member

    Wow, Yipster. That's an interesting idea. I had never thought about having the drive system integrated with the rudders system in a larger kick up. You might just be on to something! That might be a very intelligent way to set up outboards.

    I would make one small alteration...

    Instead of having the props all the way aft, where they are likely to come out of the water, I could possibly move them just forward of the rudder, but have them as part of the kick up system, essentially kicking up on the same cassette as the rudders do.

    Question: What happens to an outboard when it's upside down like that? Won't all the fuel run out of the carb and leak everywhere?

    Very interesting idea though. Impressive.
     
  11. CatBuilder

    CatBuilder Previous Member

    Other ideas in this thread are great too.

    I have a couple follow on questions for some of the CV joint type ideas.

    1) Does anyone know where to get 316 Stainless Steel CV joints?

    2) If your engine looked like the following at the drive shaft (most do), how would you set up both a drive shaft *and* a generator head to run from this engine? Could anyone let me know how you would do that, normally? I'd like to be able to disengage the drive shaft and run the generator by itself, or be able to engage the drive shaft and disengage the generator head. I'm sure I'd never run both at the same time since there wouldn't be enough available power at the shaft. Thoughts?

    [​IMG]
     
  12. masalai
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    masalai masalai

    Check with nanni? on ss CV links, but as they are inboard and likely in an easily accessed service part, just carry one spare of the ordinary... Otherwise someone in Europe may offer a link, - or else, - the Phillipines - as there seemed to be quite a bit of SS work in the passenger Jeepneys? (sort of dolled up local taxis)

    The generator assembly goes between the engine and the bell-housing, before the gearbox, not after it... Switching off the 'exciter circuits' reduces the load from the generator I think?
     
  13. waikikin
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    waikikin Senior Member

    I'd invision the generator in front of the engine with an interconecting shaft & clutch- a pearling lugger I've been working on has such an arrangement for the dive air compressor running off the propulsion engine, alternatively a multiple vee belt could be arranged from the end you've pictured. I think maybe you start having to think "industrial/automotive" in terms of whats got to be acheived but with an eye on "weights" if you go down that path.
    Regards from Jeff.
     
  14. waikikin
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    waikikin Senior Member


  15. CatBuilder

    CatBuilder Previous Member

    Jeff, the terminology might be getting us. I don't want a 60 amp alternator, I need to attach a 10kw generator head to the drive shaft. The motor needs to do double duty as a genset.
     
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