The Controllable Pitch Propeller, a summary.

Discussion in 'Props' started by apex1, Dec 26, 2009.

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  1. SeaJay
    Joined: Jun 2007
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    SeaJay Senior Member

    Richard,

    Thanks for posting the links at the beginning of this thread. I knew of several of them, but most were new to me. However you mentioned that the WestMekan site was the worst of the bunch (or you may have meant that the particular example was the worst on thw WM site?). In any case, when I investigated this option some time ago, WestMekan was the only manufacturer that seemed to have a unit appropriate to my small (75 hp) application. I took a quick look at all of the links you mentioned but didn't see everything seemed to be designed for much larger vessels. Is there one other than WestMekan that you think I should invetigate further?

    Regards,

    SeaJay
     
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  2. apex1

    apex1 Guest

    Frydensbo does smaller ones too.
    http://www.frydenbosabb.no/index.php?mapping=16

    No, Westmekan is a good quality, just the hand operated hydraulic is´nt the best choice. The same arrangement is available with a power operated prop adjustment.

    You are right, below 100hp the market is narrow.

    The quality of the systems is almost equal btw. And most of the props are cast and milled in the same factory in Germany.

    Regards
    Richard
     
  3. baeckmo
    Joined: Jun 2009
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    baeckmo Hydrodynamics

    Please note that the Sabb/Frydenboe unit comes complete with reduction gear, while the WestMekan produce only the propeller and shaft unit. The latter will probably need a reduction gear unless you use a low rpm stomper engine.

    BTW, the engine development towards higher rpms for higher power densities is probably the main reason for the demise of the small scale CPP. If we go back 50 to 100 years here in Scandinavia, there were small semidiesels produced by every second village blacksmith, practically none of them had a reduction gear. The shaft speed was low enough to suit propeller demands.

    The only remaining engine, specially designed for marine use today is the small Sabb diesel. Its output shaft is actually the camshaft, making an extra reduction unnecessary!

    So if we want a revival of the CPP for the 20 to 100 hp range, it must come with an integrated solution to the demand for a rpm reduction, otherwise it won't happen.

    And please Moderator, could you get that frog Kistinie off our backs before every sensible person in this forum has left!!!!!!!!!!!
     
  4. thudpucker
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    thudpucker Senior Member

    When I said 30 Kts I was thinking like a 16 Yr old at the helm of a rocket ship in Lake Washingon (Seattle) going toward the floating bridge at an astounding rate.
    Actually all we had on board that worked was the Engine guages.
    So it was only 20 eh? :) I might have called it 50 at the time.
    I wonder what duty might have been like, especially if we thought we had a Sub? Gimmee some!:D
     
  5. narwhal
    Joined: Aug 2009
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    narwhal Junior Member

    Dad's diary recorded a lot of boredom. Almost as many days spent on maintenance and repair as on patrol. When called to investigate a reported sub contact, invariably the bogey had departed the area. SCs, especially those with a 15 knot top speed, had little chance of catching a sub if it took them two hours to reach the area of reported contact. Duty at sea was about equally split between guarding the entrance to a base's harbor, delivering or retreiving a pilot from a larger vessel, or convoy duty between remote islands far from the active combat zones.

    But SCs operated in groups. There were spirited ball games ashore between crews, with a few cases of beer changing hands on the outcome.
     
  6. apex1

    apex1 Guest

    Thats all nice telltales mates, but what has it to do with the topic please?

    When the lunatics drivel down a thread one can understand it. (not enjoy but understand)
    But why can the interested part of the Forum not withstand either?

    Could we come back to topic please?
     
  7. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    Hi Richard,
    This would be really learnfull... thanks.
     
  8. apex1

    apex1 Guest

    No offense meant Thuddy, but is really impressive to see how widely misunderstood such a simple thing can be!

    But to the first argue first:

    You can skimp on those enquiries. I made it very clear, that only Frydensbo and westmekan provide smaller systems!
    Smaller means they make sense from about 50hp onwards!

    The US market does´nt exist for all of these manufacturers, there is definetively no need for them to "convert" any currency. What a bold idea. (and the Euro is a world leading currency and can be converted by every other schoolboy if need be)

    The rest was commented in your text above.

    Regards
    Richard
     
  9. TollyWally
    Joined: Mar 2005
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    TollyWally Senior Member

    There is no doubt in my mind that a CCP is the way to go to optimise a propulsion system. If it doesn't break what could be better than tuning your wheel on the fly? So what's it going to cost?


    What's a ballpark number for a replacement set up to handle 300 horsepower and 400 footpounds of torque, currently running 1.25" shaft aft of a 1.5:1 gear to a 17" x 15" wheel?



    If I remember right KW is about 75% of horsepower. Different places have different customs, I prefer horsepower having grown up with it. We associate kilowatt with electricity and hardly ever think of electricity in horsepower terms. Probably an illogical disconnect but what the hell.

    All that aside, it's a shame for us that the US market doesn't exist for the europeans. I'm not sure what that means exactly. It seems like our boating market both pleasure and commercial is big enough to be worth while but perhaps not. Maybe we won't be seeing these set ups till the chinese steal the design and sell it to us already converted into a dollar price.

    You'd think it would be handy for a manufactor to have the first hull of a series being trialed to have been fit with one of these. They could do the testing and come up with an optimised conventional wheel for average conditions with out all the hassle of changing props.
     
  10. apex1

    apex1 Guest

    What should brake? If a prop blade brakes it is only one to replace. All the rest is as simple, or simpler than a conventional setup.

    The KW is worldwide the standard measurement since I left school! That is a pretty long time. And although everybody talks hp when we discuss cars or engines, the interested amateur knows pretty well what a Kw is. A shame if not.

    There have been several years (in the 50ies and 60ies) when the CPP was offered in the US. But it was (as it still is) a high quality system. The US market was much more interested in el cheapo crap. Accordingly the manufacturers stopped their engagement. Only Sabb survived for a bit longer.
    In Europe quality always sold well.

    But it is arrogant and bold to try blaming the European manufacturers for the ignorance of the US customers and yards.

    On top of that, the far too low fuel prices did´nt force average Joe to save some fuel. The more he could waste, the luckier he was.
    Times changed, now some have to pay the price for their dumb thinking.
    The poor man pays twice.

    On the low power question:

    we cannot blame the industry for our own idioty.
    When it comes to engine and prop requirements, the average sailboat customer becomes a penny shitter. The stinky is not a welcome crew member but a "pita". So, the cheapest has to do it.
    Look in any sailboats engine room and you see what I mean.
    Who would be dumb enough to provide engineering and marketing cost to conquer such market.

    Regards
    Richard

    PS I do´nt bother the manufacturers with empty enquiries for the amusement of a few (and footpounds do´nt exist in SI). I am a boatbuilder, serious business is what counts. Mark will get his quotation, sure.
     
  11. FAST FRED
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    FAST FRED Senior Member

    Is this right ?

    In the case of a diesel motor you would have 2 settings, one for idle and one for where the motor makes the optimum torque, say in this case 2000 rpm.

    You'd start the motor at idle and probably allow it time to heat up a bit.

    Then set the revs to 2000 and use the CPP from there on to adjust speed.


    NO ,

    Diesel engines are only efficient when LOADED.

    The CPP technique to cruise would be to set the engine RPM desired and then load the engine at that RPM till the egt gets high and stop at the engine MFG 24/7 loading..

    No EGT (not reccommended) the drill would be to load the engine , then advance the throttle , looking for at least a 10% rpm rise being available.

    Then back down IF there was the ability to increase the RPM at least 10%.(15% safer)

    The engine might smoke black when advanced , a temporary overload , that is cured with the RPM reduction.

    If the desired speed is not made at the selected rpm, step up another 100 and try again.

    If the engine is well loaded it will last longer and burn far less fuel than a FP simply backed off.

    FF
     
  12. apex1

    apex1 Guest

    Thanks Fred,

    now it gets serious again, nice.

    Yes you are much better away with a EGT gauge.

    The first days one needs a lot of guessing to find the proper setting.

    I´ll go deeper into it as promised.
     
  13. powerabout
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    powerabout Senior Member

    I'm on a vessel at the moment where the engines and thrusters all operate at constant speed and the power is the CP and there's hundreds of them in the offshore industry
     
  14. fcfc
    Joined: Feb 2005
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    fcfc Senior Member


  15. apex1

    apex1 Guest

    Yeah

    nice paper, well known, and completely off topic! There is no CPP in that comparison mate.

    And hybrid was not our topic anyway.

    Is it really impossible here to have, at least for some days, a thread which is not hijacked or drivelled to death?

    It is a burden, really.............
     
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