Rudder shaft

[Adodero]

We dropped our rudder today.

This is a 5 y/o shaft with that had no zinc attached. The pitting extends around most of that same part of the shaft.

Pretty scary.

[Cheechako]

Is that where the bearing is or a close fitting Fiberglass tube? There are ways to ground the shaft inside of the boat to external zincs. However, that may be SS corrosion caused from low oxygen environment.
My guess is that can be found on many rudders .
A prop shaft sitting unused will do a similar thing inside the Cutlass bearing.

[Adodero]

Originally Posted by Cheechako

Is that where the bearing is or a close fitting Fiberglass tube? There are ways to ground the shaft inside of the boat to external zincs. However, that may be SS corrosion caused from low oxygen environment.
My guess is that can be found on many rudders .
A prop shaft sitting unused will do a similar thing inside the Cutlass bearing.

I think you are right about the corrosion. Either way, the shaft is also bent and will be replaced with a proper fitting shaft, I thought the amount of corrosion on such a new shaft was scary, though.

[Cheechako]

Yeah, it is a bit. Better if the shaft is solid rather than thick wall tube like some. Too bad Monel pretty much went away....

[wingless]

My rudder is bonded to the rest of the underwater metal by a wire at the rudder arm.

[Adodero]

Thanks for the info.

We are going to cut open the rudder and replace the shaft completely. We were on the fence about doing it, because the shaft is stepped down from 1 1/2'' down to 1'' using welds along the rudder shaft. While that's not an ideal construction means, it's "functional" and works, but the fact it was bent during the welding process and displays corrosion (things we only saw after removal) leads me to believe we should replace it all together.

Another item on the seemingly never ending list

[bizzy]

I had a 2'' one the same looking . i cut it off only to find it would of lasted for thousands more miles . but i felt better.

[Lepke]

The wrong stainless alloy in contact with salt water will corrode quickly in the absence of air. A marine alloy will not. My guess is a home built rudder shaft with some off the shelf stainless shafting meant for industrial use.

Lepke

[Jim Cate]

If you are building up a whole new shaft, consider using 2205 Duplex stainless instead of 316. Stronger and far more corrosion resistant, not so much more expensive these days. Good stuff!

Jim

[crazyoldboatguy]

I am not sure this would be the proper place to post my question but this stream is recent enough and some thoughtful folks responded so I will proceed.

I am restoring an Alden auxiliary ketch, 47' long. It was originally constructed just after WW2 in Chile. The rudder is a traditionally hung unbalanced type using a thick 2 1/2" bronze shaft. Unsure what type of bronze involved - I could assume silicone as it is fairly common but have no way of knowing without testing. And this brings me to the point of my post.

I don't want to have to replace this huge heavy thing if I don't have to. However, I will not use it until I am comfortable that I have ascertained the integrity of the shaft. It has a bend in it and this will be a source of concern. I know metals can be x-rayed and subjected to other forms of non-destructive testing like magna-fluxing and the like. Can anyone steer me to the proper technique to check for flaws, cracks and the like? This boat hasn't been in the water for nearly 30 years and spent much of her life in fresh water. There are no obvious signs of any flaws but obviously I would want to be sure of the piece before hanging my rudder on it.

Any suggestions are appreciated.

[Adodero]

Originally Posted by crazyoldboatguy

I am not sure this would be the proper place to post my question but this stream is recent enough and some thoughtful folks responded so I will proceed.

I am restoring an Alden auxiliary ketch, 47' long. It was originally constructed just after WW2 in Chile. The rudder is a traditionally hung unbalanced type using a thick 2 1/2" bronze shaft. Unsure what type of bronze involved - I could assume silicone as it is fairly common but have no way of knowing without testing. And this brings me to the point of my post.

I don't want to have to replace this huge heavy thing if I don't have to. However, I will not use it until I am comfortable that I have ascertained the integrity of the shaft. It has a bend in it and this will be a source of concern. I know metals can be x-rayed and subjected to other forms of non-destructive testing like magna-fluxing and the like. Can anyone steer me to the proper technique to check for flaws, cracks and the like? This boat hasn't been in the water for nearly 30 years and spent much of her life in fresh water. There are no obvious signs of any flaws but obviously I would want to be sure of the piece before hanging my rudder on it.

Any suggestions are appreciated.

how bad is the bend?

The issue for us with the bent shaft was the impact it had on steering of the boat, it made the helm heavy and awkward, for lack of a better phrase. The bend was not visually noticeable with the rudder in, but was visible when it was removed.

Maybe post some pictures?

[neilpride]

Originally Posted by crazyoldboatguy

I am not sure this would be the proper place to post my question but this stream is recent enough and some thoughtful folks responded so I will proceed.

I am restoring an Alden auxiliary ketch, 47' long. It was originally constructed just after WW2 in Chile. The rudder is a traditionally hung unbalanced type using a thick 2 1/2" bronze shaft. Unsure what type of bronze involved - I could assume silicone as it is fairly common but have no way of knowing without testing. And this brings me to the point of my post.

I don't want to have to replace this huge heavy thing if I don't have to. However, I will not use it until I am comfortable that I have ascertained the integrity of the shaft. It has a bend in it and this will be a source of concern. I know metals can be x-rayed and subjected to other forms of non-destructive testing like magna-fluxing and the like. Can anyone steer me to the proper technique to check for flaws, cracks and the like? This boat hasn't been in the water for nearly 30 years and spent much of her life in fresh water. There are no obvious signs of any flaws but obviously I would want to be sure of the piece before hanging my rudder on it.

Any suggestions are appreciated.

My rudder is similar as yours, naval bronze called in the past i think, last time we drop the rudder we check the bronze for corrosion, found nothing, green patina sanded to bare metal and found a golden bronze original color, now if you found pitting or pink spots around its time to consider a replacement, i suggest sand the whole shaft with a fine sandpaper and see if there is signs of corrosion or cracks or whatever.....

[crazyoldboatguy]

The bend is deliberate - part of the shape of the shaft where it enters the prop aperture. I should have described it better. There is no way to know what technique was used to create the bend. I highly doubt it is 2 pieces brazed together. Probably was heated and then bent in a hydraulic brake press of some type. If not heated properly and bent too quickly, the internal structure at the bend could be too weak.

Naval bronze. That's the name. Probably what it was made of. I may rely on a surface test using penetrant and developer - I used enough of it as a welder in the ship yard I worked at in the 70s. I may remove some material and have it tested to see what alloy it is just to make sure it ain't brass. I had a prop shaft for my Pearson Triton made by a machinist. He wasn't familiar with nautical materials and decided I should have brass, not bronze. It was too close to launch time so I went with it. Replaced it the next year. Even in fresh water I would not want to depend on that soft material for long. I will definitely sand and check for the pink spots. That is certainly the easiest thing to do right off.

Thanks to both of you for responding.

[Adodero]

The shaft was cut today and found to be full of seawater, corroding from the inside out! We hazarded a guess than less than 50% of the material remained.

[Cheechako]

Originally Posted by Adodero

The shaft was cut today and found to be full of seawater, corroding from the inside out! We hazarded a guess than less than 50% of the material remained.

Yeah, never been a fan of hollow shafts.