Can I make a rudder using Aluminum?

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Red5
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Can I make a rudder using Aluminum?

Postby Red5 » Thu May 10, 2018 11:54 am

My 1975 37' Sedan has steel rudders. They are pitted badly and need to be replaced.

Some of the newer Marinettes had a stainless steel rod that was welded to a steel rudder. Some have 100% stainless steel rudders.

Can I make mine out of aluminum?
37 Sedan Twin CAT 3208's "Under Way is the Only Way".

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Busia
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Re: Can I make a rudder using Aluminum?

Postby Busia » Thu May 10, 2018 2:41 pm

I have an older boat ( late 70's ) and it has all stainless shafts and I think rudders. In theory you could make new rudders out of aluminum or wood or titanium or whatever. Stainless is much easier to weld, stronger, less likely to corrode, and cheaper than aluminum. Also you say aluminum, but what alloy are you talking about? For fresh or salt water? Stainless is the way to go. You could build them with a hacksaw, file, and stick welder.
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EWRice
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Re: Can I make a rudder using Aluminum?

Postby EWRice » Thu May 10, 2018 9:03 pm

The only boats I have ever seen with aluminum rudders are sailboats and kayaks. I would be willing to bet that a powerboat would bend the rudder stock over time from the prop wash if it was sized the same as a steel rudder. When I made my SS rudders, I used pieces from my old prop shafts for the stock and cut out some 1/4" thick plate for the blade. One of my customers is a fab shop and they welded the whole mess together for me. Best upgrade to the boat. What size rudder stock do you need? I know I have a few 1" shafts laying around and I have either a 1 1/4" or 1 3/8" shaft on the shelf.
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Rockit
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Re: Can I make a rudder using Aluminum?

Postby Rockit » Fri May 11, 2018 12:35 am

I'd think it would take more engineering to make aluminum rudders. The boat's hull strength comes in part from the frames and cross members and there must be some reason why the rudders weren't made from aluminum in the first place. Not like there wasn't plenty lying around the shop! You could theoretically make them out of kevlar or carbon fiber reinforced plastic too.

I'd stick with stainless, you know that works and it's a minor hassle to haul a 37 as opposed to a 28 or even a 32.

Good luck.
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Re: Can I make a rudder using Aluminum?

Postby Fastjeff » Sat May 12, 2018 4:53 am

Hard to weld aluminum to the stainless round stock going up through the stuffing box (though Eutectic Corp actually came up with a way to do it).

I'd think aluminum would be too weak in bending for the rudder unless it was really thick--like 3/8 inch. And the round stock woul have to be several inches in diameter to be strong enough.

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Red5
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Re: Can I make a rudder using Aluminum?

Postby Red5 » Wed May 16, 2018 9:48 am

EWRice wrote:The only boats I have ever seen with aluminum rudders are sailboats and kayaks. I would be willing to bet that a powerboat would bend the rudder stock over time from the prop wash if it was sized the same as a steel rudder. When I made my SS rudders, I used pieces from my old prop shafts for the stock and cut out some 1/4" thick plate for the blade. One of my customers is a fab shop and they welded the whole mess together for me. Best upgrade to the boat. What size rudder stock do you need? I know I have a few 1" shafts laying around and I have either a 1 1/4" or 1 3/8" shaft on the shelf.



OK, I'll go with SS.

EWRice, are you in Louisville? I could use some 1" shafts. Or any SS that you have. I need to do this pretty soon. I can be reached at 502-8zero7-six837.

Thanks,

Matt
37 Sedan Twin CAT 3208's "Under Way is the Only Way".