marine growth on propellers

Discussion in 'Boat Design' started by CDK, Aug 19, 2008.

  1. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Because of performance issues with my experimental tunnel drives and proposed solutions I went in the water yesterday to take some measurements.
    It had been some time since I saw the propellers from nearby....
    They had the texture of an old oak tree: lots of marine growth on both sides of the blades, almost doubling their thickness. Some of it could be removed with a wire brush, but what remains are warts and worm-like shapes that need a chisel or screwdriver to come off. In fact the props should be removed to clean them properly with chloric acid.

    The boat is in the water for nearly 7 months now and used at least once a week.
    I have two questions:

    1. There are numerous prop designs with different shapes, cupped blades, sharp leading edges etc. What good are these if after half a year oysters have grown on them?

    2. The props and rudders are the only part of the hull not covered with anti-fouling paint, so it is obvious that all sorts of sea creatures settle down on them. Is there any proven treatment to prevent or at least reduce that?
     
  2. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    I spoke to an owner of a commercial boat some years ago who had quite good results from coating the props with Plastibond. Thats a polyester filler material that you would use to repair plastic, wood, steel damage. Probably an upmarket 'car repair bog'

    He smoothed it all over the props, and because it was a 'filler', he could sand the surface quite smooth so as not to lose efficiency.

    The marine growth tended to fall off because the stuff was a lot softer than bronze and couldnt hold on in the prop wash, and any persistant stuff could be knocked of easily, and the hole refilled and sanded smooth.

    He reckoned that it cut the work down enormously.

    Might be worth a try
     
  3. bntii
    Joined: Jun 2006
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    Location: MD

    bntii Senior Member

    We have been using the newish product call 'Prop-Speed' on clients boats for a couple of years now. It has proved to very effective and the props show absolutely no marine growth when pulled after a season. As you say, a propellers effectiveness is wrecked by fouling. Only downside I see is the cost. Prop-Speed is a pricey product but is a bargain for owners who otherwise are sending divers down to clean the running gear a couple times a season.
     
  4. kenJ
    Joined: Jul 2005
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    Location: Williamsburg, VA

    kenJ Senior Member

    Haven't tried it yet but I was told soaking the props in a heavy oil or the oil treatment STP for a couple days will also keep the props clear. The bronze "absorbs" the oil making the blades too slick for growth to stick. There are also a couple commercial products, think they are epoxy based. Etch the blades, prime the blades, then coat. A popular product is http://www.getaprop.com/content-product_info/product_id-6149/prop_speed_running_gear_coating.html

    I have not yet tried it.
     
  5. juiceclark

    juiceclark Previous Member

    bntii,
    Is that the bright green/yellow stuff the marina painted my Nibral props with? Is has worked gloriously for nearly 3 years now.
     
  6. bntii
    Joined: Jun 2006
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    Location: MD

    bntii Senior Member

    Yes- thats the stuff.

    Three years if FL is saying allot. We are seeing it effective out to two years and think it can go longer if not chipped
     
  7. juiceclark

    juiceclark Previous Member

    good stuff

    Yes...proven to be very good despite the claim that it's environmentally friendly. My bottom paint is going on nearly four years as well - twice as long as I've had it last before. It's because I made one of these "barnacle barriers" and slide it under the boat when tied at the dock. I think the lack of moving water under the boat not only denies barnacles of any nutrition but prevents the erosion of bottom paint to some degree. How much...will find out when it's worn out. It's $3K for a bottom job and the barnacle thingy costs me about $100. It's a no-brainer.
    [​IMG]

    [​IMG]

    [​IMG]
     
  8. bntii
    Joined: Jun 2006
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    Location: MD

    bntii Senior Member

    Tony-

    From what I am seeing is the water captive in the barrier and much less saline due to the accumulation of rain water?

    Is this perhaps the manner by which it suppresses marine growth?
     
  9. juiceclark

    juiceclark Previous Member

    I've been brewing on an answer to that question since I made it. From what I can surmise, it's working so well (and it really has) because:
    --barnacles are filter feeders, with no new water movement their food source is cut off.
    --as you say, the water becomes quite fresh in the rainy summer down here and changes the whole equation for marine life
    --the captive water gets a bit warmer than that surrounding
    --the boat moves just a bit on top of the vinyl fabric. that movement may brush away tiny buggers before they are strongly attached. but this wouldn't help the props and they've stayed clear

    I have been getting some of the green, scummy growth along the waterline on the sunny side of the boat. It the kind you can just brush off but I still hate it. So, it hasn't prevented, at least, some plant growth...only the little barnacle buggers that cost us all serious money and performance. The bottom paint lasting longer has been a nice side effect.
     
  10. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Beautiful pictures and an idyllic spot Tony.

    My boat is moored head-on to a concrete jetty, two large concrete slabs and 3/4"ropes at the stern to hold her in position. Yet a couple of times each year I have to reposition the slabs after storms and waves have played with the boat, sometimes even overturning one. Our bay has a shallow lagoon about half a mile long, so even a normal tide causes lots of water movement twice a day.
    Your barnacle barrier would have an extremely short life here.

    I will check with a large marina nearby if they have something like "prop-speed" but I doubt it. Thusfar, when I walked between the boats after the summer season, the landscape is filled with ruined or missing stern drives, overgrown props and rudders and lots of people from all over Europe spending their weekends blasting, scraping and painting.
    And I've also seen marina employees quickly painting over the barnacles and lifting the ships back into the water when the owners aren't around.
     
  11. Guillermo
    Joined: Mar 2005
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    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    Keeping propeller clean is a summer diving 'job' for my 14 year old twins: makes them stronger, enjoys them and keeps them busy, and saves me money (if I don't account into the equation what they yearly cost to me, absolutely!) :D

    Cheers.
     
  12. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Good for you Guillermo, but I'm not that lucky. One son in Norway, the other one in Holland, both over 40 years and not really interested in the condition of dad's props. But in a couple of years I will try my luck with my grandsons. Also twins, but at the present more interested in their Sony Playstations or whatever it is they are staring at the whole day.
     

  13. kenJ
    Joined: Jul 2005
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    Location: Williamsburg, VA

    kenJ Senior Member

    swimming

    Over here in the land of "stinging nettles" the local name for a type of jelly fish, going over the side to scrub the prop isn't always an option. Don't mind doing it if the water is clear and free of the critters.
     
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