Screws??

Outboard designs up to 14'

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gfunk
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Joined: Sat Apr 18, 2009 2:55 am

Screws??

Postby gfunk » Sun Apr 19, 2009 10:13 am

Why bronze instead of stainless steel? I would think SS would be better. Of course i know nothing of boat building.

Warren

Nova SS
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Location: Calgary, AB

Re: Screws??

Postby Nova SS » Sun Apr 19, 2009 10:36 am

my understanding is that stainless steel cannot be used in an airtight situation IE epoxy encapsilated, under fiberglass etc. They will rott.

gfunk
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Joined: Sat Apr 18, 2009 2:55 am

Re: Screws??

Postby gfunk » Thu Apr 23, 2009 11:52 am

thanks i just needed to clear that up... my dad always used stainless steel on his boat but now that i think about it none of them were incased.

Warren aka gfunk

Lost Again
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Location: Lawtey, Florida

Re: Screws??

Postby Lost Again » Thu Apr 23, 2009 5:24 pm

I know the tugboats use bronse but the line boats use stainless to deal with the riprap and lines they hit the line boat will stall and not even chaif a plasma line the aluminum and bbronz (in the smaller thinner props) bend and worp but are cheaper. On the tug's they are so thick that they will shatter befor they bend. I worked the line boat for 3 years and now im an engeneer on the tug I still do the maintnance on the lineboat and have not seen a bent prop in 2 years. the stainless steel with knockout hub works grate in low water jobs.

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thudpucker
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Location: Cullman AL

Re: Screws??

Postby thudpucker » Fri May 08, 2009 10:41 pm

The anchient rule has always been; "Bronze below the water line, and Stainless above!"
But I dont know if encapsulating a Stainless screw would make a difference or not.
ALso there are many differnt grades of Stainless Screws.

John K
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Location: AL

Re: Screws??

Postby John K » Sat May 09, 2009 4:50 am

316 stainless is what you want to use in boats. I never heard about the encapsulation and "rotting" of stainless.

316 ss holds up to salt water. There are other types of stainless you can use if you are not in salt water, but cost is almost the same.

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BruceDow
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Re: Screws??

Postby BruceDow » Sat May 09, 2009 4:52 am

It took me a couple of readings to figure out that "Lost Again" is talking about propellers (screws) versus fasteners (screws). Serious. Cool.
Bruce.

~~ Do what you love, and love what you do. ~~
~~ To me - only my boat is not yet perfect. Everybody else's is to be admired for I know the path they have walked (Dave Lott, 2010) ~~
Dow's Monaco Project

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Fifty Plus
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Location: Thumbpit,Michigan

Re: Screws??

Postby Fifty Plus » Sat May 09, 2009 6:26 am

I used 316L SS when needed.
The encapsulate and rot goes like this:
Encapsulation is never 100% and if some dampness gets to the SS it will quickly rust.
The nickel in SS needs oxygen to form it's protective oxide to prevent the rust.
Encapsulation is better at excluding oxygen than water.
So without oxygen and with water, the SS "rots"

Carl
Last edited by Fifty Plus on Sun May 10, 2009 6:41 am, edited 1 time in total.

Nova SS
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Re: Screws??

Postby Nova SS » Sat May 09, 2009 5:14 pm

Fifty Plus wrote:I used 316L SS when needed.
The encapsulate and rot goes like this:
Encapsulation is never 100% and if some dampness gets to the SS it will quickly rust.
The nickle in SS needs oxygen to form it's protective oxide to prevent the rust.
Encapsulation is better at excluding oxygen than water.
So without oxygen and with water, the SS "rots"

Carl



Thank you, that is exatly what I had heard. Glad it wasnt my imagination :oops:

John K
Posts: 1538
Joined: Thu May 18, 2006 5:19 am
Location: AL

Re: Screws??

Postby John K » Sun May 10, 2009 5:14 am

Fifty Plus wrote:I used 316L SS when needed.
The encapsulate and rot goes like this:
Encapsulation is never 100% and if some dampness gets to the SS it will quickly rust.
The nickle in SS needs oxygen to form it's protective oxide to prevent the rust.
Encapsulation is better at excluding oxygen than water.
So without oxygen and with water, the SS "rots"

Carl


Now I know. Thanks


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