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moderate?
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Ran across this on Nigel Calder's Blog and was pretty amazed at the numbers.
Hey FastBttms...you might wanna distribute this around the docks!

"In the meantime, we discovered something really noteworthy with this summer’s limited test program. We had a propeller with just a few barnacles on it. As compared to a polished propeller, it increased the fuel consumption for a given boat speed by up to 50%, and dropped the boat speed for a given shaft speed by up to 30%. At the moment, the most cost effective way to improve efficiency under power is to regularly clean the propeller!"
 

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good thing I have a sailboat.....

you know...move by the force of wind....wind creating lift...ahh I quit...you've allways been a motor boy anyway...
 

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Ignoring Trolls in 2009
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Cam,
I heard somewhere that a magnet made by Algae-X can save you even more fuel than some "test" by Nigel Calder whoever he is. :D :D :D :D
 

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1977 Morgan OI 30
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[QUOTE

"In the meantime, we discovered something really noteworthy with this summer’s limited test program. We had a propeller with just a few barnacles on it. As compared to a polished propeller, it increased the fuel consumption for a given boat speed by up to 50%, and dropped the boat speed for a given shaft speed by up to 30%.[/QUOTE]

If I read that correctly, leaving a 'few' barnicles on my prop will make my Morgan slug go twice as fast :D Then I'm not going to clean it off, I have exactly 3 good size barnicles...;)
 

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"A few barnacles"?
"50%"?

It would need more tha a few to do that, methinks.
Actually I could believe that. Last year I before dunking my boat for the season, I forgot to paint my prop with any type of anti-fouling paint or spray. Once the water got warm about 2 months into the season I went for a swim to clean the prop...it was nasty with 3 inch long strands of growth and barnacles. Once it was polished clean I noticed the boat seemed to jump out of the hole when put in forward. I couldn't believe how much just cleaning the prop did as I could be doing the same speed at 1100 rpms as I was previosuly doing at 1900.
 

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Telstar 28
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Just a few would really cause a lot more cavitation, and the increased turbulence would greatly affect the prop's ability to push water... :)
"A few barnacles"?
"50%"?

It would need more tha a few to do that, methinks.
 

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It's better smooth, yes. I wonder would a "few" barnacles do it though?

Maybe. I know not.
I'll scrape mine clean, next tide, but there are no tides in Loch Ness.
 

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Midwest Puddle Pirate
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"A few barnacles"?
"50%"?

It would need more than a few to do that, methinks.
You should try sewing a couple of small kites (sticking straight out of course) to your sails and see how much it affects your sailing performance. It's the same thing.
 

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"In the meantime, we discovered something really noteworthy with this summer’s limited test program. We had a propeller with just a few barnacles on it. As compared to a polished propeller, it increased the fuel consumption for a given boat speed by up to 50%, and dropped the boat speed for a given shaft speed by up to 30%. At the moment, the most cost effective way to improve efficiency under power is to regularly clean the

I'm not sure it would have that great of an impact I can see it having some, not that high though.

 

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Prop-Speed, fellers.
It really works if you put it on EXACTLY per the instructions--and then keep your diver from scraping it off.
 

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Actually those barnacles are doing the same to power boating as the thread I started here about Botanical Gardens... Marine growth of any kind does slow you down.
 

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The fluid dynamics of a prop spinning in water is quite complex, but like SD mentioned cavitation will occur when the surface of a prop has growth on it. The change in surface condition caused by barnacle growth has a dramatic effect on the ability of the prop to produce a driving force i.e. Thrust.

Propeller polishing increases propeller efficiency by reducing turbulence and cavitation so that less power is required to maintain speed. I have not seen conclusive evidence that the drop in efficience would be as much as 50% but I am sure it would be significant.

Another serious issue with having barnacles on the prop is damage to the prop and drive system caused by vibration and cavitation.
 
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