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Thread: Prop Shaft Lock

  1. #11
    Join Date
    Dec 2008
    Location
    Near Glasgow
    Posts
    382

    Default Re: Prop Shaft Lock

    Quote Originally Posted by duncan99210 View Post
    The problem with either a folding or a feathering prop is that you need to stop the shaft turning to get them to fold/feather. Thatís why you have to engage a gear on a mechanical box and use a shaft brake of some sort on a hydraulic box.
    I have a feathering prop with a hydraulic gearbox and no shaft brake. You just switch off the engine in fwd gear and the prop stops quicker than the hydraulic pressure can dissipate so the propellor feathers without any problem. This is the recommended method by the prop manufacturer.

  2. #12
    Join Date
    Feb 2010
    Location
    Bristol
    Posts
    2,067

    Default Re: Prop Shaft Lock

    Quote Originally Posted by captainboo View Post
    I have a feathering prop with a hydraulic gearbox and no shaft brake. You just switch off the engine in fwd gear and the prop stops quicker than the hydraulic pressure can dissipate so the propellor feathers without any problem. This is the recommended method by the prop manufacturer.
    That's right and that's how we all do it with hydraulic gearboxes. Common practice and that's what Varifprop says.

    Turn engine off in gear and it folds instantly before the hydraulic pressure is lost.
    www.Chasing-Contours.com - A circumnavigation by boat, bikes, climbing & paragliding

  3. #13
    Join Date
    May 2004
    Location
    Plymouth, Devon
    Posts
    265

    Default Re: Prop Shaft Lock

    Oops. Previous message deleted in error.

    Thanks for all your comments. It looks as though it's a choice between leather or string or else splashing out on a feathering prop. Just returned from an expensive day at the boat show so the final decision will be deferred for a bit but I now have all the information I need.

    Thanks again.

    J

  4. #14
    Join Date
    Nov 2001
    Location
    Me: Johannesburg South Africa Yacht: Richards Bay East Coast Africa
    Posts
    6,895

    Default Re: Prop Shaft Lock

    Quote Originally Posted by Petronella View Post
    Oops. Previous message deleted in error.

    Thanks for all your comments. It looks as though it's a choice between leather or string or else splashing out on a feathering prop. Just returned from an expensive day at the boat show so the final decision will be deferred for a bit but I now have all the information I need.

    Thanks again.

    J
    Could something like this be adapted.

    https://www.banggood.com/BIKIGHT-160...iABEgIc4PD_BwE
    Life is too short not to have a sea view
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  5. #15
    Join Date
    Aug 2004
    Location
    Home East Lancashire boat Spain
    Posts
    4,570

    Default Re: Prop Shaft Lock

    Considered a ( cheaper) bike disk brake but didn't want to disconnect prop again to fit. used a cantilever bike brake but it and the cable went rusty! I can stop the prop by hand and will look for a useful point/nut to try the string solution! I Or leather belt with mole grips sounds my style as well!

  6. #16
    Join Date
    May 2004
    Location
    Plymouth, Devon
    Posts
    265

    Default Re: Prop Shaft Lock

    It's been a few months since I first asked this question and during that time I've tried a few things.

    Mark 1: Two semi circles of stainless clamped to the shaft coupling with an electronic Quashai handbrake caliper. It might well have worked but was too complicated and we feared for a situation where it 'failed on'. (PIC 1).

    Mark 2: An anode bolted to the prop shaft in a more accessible position with one of those large wide band jubilee clip type things on a bracket that could be meachanically tightened around the anode. Too fiddly.

    Mark 3: A piece of household string looped around the threads of one of the shaft coupling bolts and led to a substantial engine bracket. Result? Success up to 4.8 knots. Then the string snapped!

    Next I set up a little 'string lab' to identify a cord stronger than the string but weaker than a piece of 2mm rope. (PIC 2).

    Mark 4: Potentially the final solution. A piece of thin orange crabbing line of which I have many metres. I've been surprised at just how much torque is generated by the rotating prop and I wanted a string that would snap if we needed to start the engine suddenly or simply forgot but would remain intact otherwise up to say 10 knots. Hopefully I now have that. We will have a routine whereby another piece of crabbing line is hung next to the ignition key whenever the 'brake' is applied. (PIC 3).

    So, it's thanks to RobbieW for his suggestion, forever remembered when we say "Shall I connect the Robbie?" or "Is the Robbie still connected?"

    Thanks guys.

    J

    Screenshot_20190610-152153.jpgScreenshot_20190610-151614.jpgScreenshot_20190610-152425.jpg
    Last edited by Petronella; 10-06-19 at 15:12. Reason: Added PIC Refs.

  7. #17
    Join Date
    Jun 2007
    Location
    On board
    Posts
    2,748

    Default Re: Prop Shaft Lock

    Quote Originally Posted by Petronella View Post
    ...
    So, it's thanks to RobbieW for his suggestion, forever remembered when we say "Shall I connect the Robbie?" or "Is the Robbie still connected?"
    ...
    Fame at last ! I'm deeply honoured thank you
    If you're not confused, you're probably misinformed

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