Ever been in a boat and have a prop lose an ear? I used to have an 18 ft pickle fork hydro with an 11"" 2 blade cleaver that passed mag the year before. Cruise speed close to 90 @ 6000 rpm, about 8400 prop shaft rpm one ear broke off right at the hub. Unbelievable amount of vibration..if I didnt have the kill switch next to my thumb on the wheel I would have been done..my hands on the wheel is the only reason I was still in the boat. it bent the end of the prop shaft enough that it wouldn't rotate witbout the motor running, that turned the other prop blade into a rudder..good thing it wasnt a flat bottom..hydros slide sideways pretty easy..new prop and shaft, and strut,new rudder and a full day inspecting every square Inch of the boat and back on the water...shit happens and I love to tell the story
What he's calling "demetalization" is actually Galvanic Corrosion. Galvanic Corrosion is an electrochemical process in which one metal corrodes preferentially to another when both metals are in electrical contact and immersed in an electrolyte. The same galvanic reaction is exploited in primary batteries to generate a voltage. Zinc has a greater potential to galvanic process because of its outer shell electrons and is used on vessels for sacrificial anodes to protect other metals on boats.
Cathodic Protection should stop this. The passive method is to fit sacrificial anodes made from zinc. One can also have an active system. For example the Kiekhafer Corporation have marketed their active system "Mercathode" for several decades.
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Ever been in a boat and have a prop lose an ear? I used to have an 18 ft pickle fork hydro with an 11"" 2 blade cleaver that passed mag the year before. Cruise speed close to 90 @ 6000 rpm, about 8400 prop shaft rpm one ear broke off right at the hub. Unbelievable amount of vibration..if I didnt have the kill switch next to my thumb on the wheel I would have been done..my hands on the wheel is the only reason I was still in the boat. it bent the end of the prop shaft enough that it wouldn't rotate witbout the motor running, that turned the other prop blade into a rudder..good thing it wasnt a flat bottom..hydros slide sideways pretty easy..new prop and shaft, and strut,new rudder and a full day inspecting every square Inch of the boat and back on the water...shit happens and I love to tell the story
What he's calling "demetalization" is actually Galvanic Corrosion. Galvanic Corrosion is an electrochemical process in which one metal corrodes preferentially to another when both metals are in electrical contact and immersed in an electrolyte. The same galvanic reaction is exploited in primary batteries to generate a voltage. Zinc has a greater potential to galvanic process because of its outer shell electrons and is used on vessels for sacrificial anodes to protect other metals on boats.
Nautical PappyStu is Veri good
this is dezincification and selective leaching of Zinc.
Cathodic Protection should stop this. The passive method is to fit sacrificial anodes made from zinc. One can also have an active system. For example the Kiekhafer Corporation have marketed their active system "Mercathode" for several decades.
Nice.to.see.someone.who.is.a.craftsman.will.shaft.anodes.slow.the.process.and.what.are.ship.propellors.made.of.i.cant.see.them.being.changed.like.your.underpants.they.would.cost.thousands.and.shipping.companys.dont.like.spending.money.remember.the.exxon.valdez......??????????
What?