Strut alloy

[ABoatGuy]

Anyone know what alloy the mil-spec is for boat struts. Also open for suggestions. Lot of zinc in mag bronze, but it seems to be used succesfully. How about aluminimum bronze or Nibral. Good? Bad?

Thanks

[plowanchor]

Best that I have been able to come up with is the 5083 alloy. It seems to postpone oxidation. Two, the alloy Al. needs oxygen to be able to prevent oxidation and corrosion from salt water. So beneath the deck with out a lot of oxygen and with out a lot of raw water wash down creates the ideal place for breakdown. By default this would be my choice. But with some of the other alloys that mills are playing with now adays you may find something like what you are talking about. Try looking a " JORGENSONS" They are a pretty popular distributer of alloys in the U.S.

[bananas]

Hi aboatguy

The strongest and most fatigue resistent alloy in salt water is Nickel Aluminum Bronze C95800. It is substantially better than stainless steel in those conditions. I make large propellers from it and they have proved to be very durable under the most adverse conditions.

When you consider wash conditions, the tip a a large (40-inches+) propeller running near 150-MPH is about as severe possible.

Some manufacturers adulterate the alloy with zinc (permissable under ABS rules) but I find that is not a good practice.

C95800 can be cast, but the mold must be bottom filled without significant turbulence. It can be done, it is not easy.