Fabricate new rudder post and fingers, what material?

[lost soul]

I am back at it again. Finally took my rudder completely apart. The post is shot. The post is 1 7/8 inch OD and about .15 wall thickness. 49 inches long and made of stainless. Welded to the post are three 1 1/2 wide fingers made of plain steel. (as I hear, this was common).

I am seeking advise on what alloy to use for the assembly. I have no way of knowing what the original alloy was, but that does not really matter. Rudders like this are ubiquitous.

I know that SS can suffer crevice corrosion when in a low oxygen environment, so this is my main concern. The post has some deep pitting at the point where it exited the rudder and this is the reason I need to replace it.

I also have to decide on whether to copy the original design and use fingers or to come up with a new design. For instance, rather then use 3 fingers I could use a single plate, (like a mini rudder).

I did a quick search of the online metal suppliers and found 316 tube, welded and seamless.

There are a few decisions to make:

what material 316, 316L, 2250 Duplex SS, or something else
what wall thickness
welded, seamless...
where to get the materials from.

HELP! (lol)

Thanks guys...
Hopefully there are 2 pictures attached..I have no idea how to add a photo. There is nothing that says photo in the choices.....

 

[dlochner]

Since the rudder post failure is due to crevice corrosion and not stress, then pipe of the original dimensions is probably adequate. Or, maybe go up one size in wall thickness. If the pipe diameter is increased, the rudder bearings and all the fittings will need to be changed. That's a lot of work and expense.

For the relatively small cost, changing the fingers to SS is probably a good idea. Going with a plate instead of fingers doesn't add much except expense and weight.

In your area there will be a someone who supplies SS pipe or can get it for you. Google "Shop Stainless Steel Pipe My Town" or "Shop Stainless Steel Pipe South West Florida" Talk to the pipe supplier about the various options for type and seamless vs welded.

To up load a photo, click on "Upload a File" button. Then click on "Choose a File" and select the file to up load. jpg files are accepted. There is a size limit and hi res photos can exceed that limit.

 

[kloudie1]

Same thoughts here.. assuming it is original, it lasted a pretty good while.. I'd use seamless 316 L of the same outer diameter and one or so steps thicker in wall.. same with the fingers use 316L same diameter and wall thickness as was the carbon steel.. The "L" after 316 in the grade is very important because it is less susceptible to welding and corrosion problems.

 

[FastOlson]

I would talk to your local rudder builder... Foss Foam.
http://www.newrudders.com

If you've ever hankered for a more 'modern' rudder shape, this is the opportunity for that improvement as well.

 

[lost soul]

Thanks guys. Let me try that picture post again.
BTW a new rudder runs 2500 to 3000 plus shipping. Think I will fix mine.

I agree that the original worked and will duplicate that, most likely. The wall thickness that I measure is close to .15 and the thickest that I can find online is .12. Probably close enough for me.

Wow pretty easy for the upload. Right there in the buttons...duh, lol

 

[dlochner]

Did you see these videos from Boatworks Today?
https://www.youtube.com/playlist?list=PLV97GZkHhpHMfaW24ZBR-xitL-TN2si9A

 

[hutch5151]

I would upgrade the post to "Aquamet 22" This seems to be the alloy of choice for new shafts and posts.

 

[kloudie1]

Here is a stronger option.. sched 80 1.5" pipe .. OD can be turned polished to 1.875 (only in the piece that goes through the bushings) leaving ya with a thicker wall.. is welded, but I can't seem to find seamless in that size..
https://www.onlinemetals.com/merchant.cfm?pid=13007&step=4&showunits=inches&id=314&top_cat=0

 

[walmsleyc]

Thanks guys. Let me try that picture post again.
BTW a new rudder runs 2500 to 3000 plus shipping. Think I will fix mine.
...

I was just about to repair my rudder, and spoke to "Al" at Foss foam. He offered my a price that was significantly less that what you note. It's done and shipped, and expect to pick it up in a few days. He reused my shaft, but everything else is new, including the replacement of any non-stainless in metalwork embedded in the foam with stainless (was a mild steel "wing" welded to the SS shaft). Shipping is a little expensive, but all in, it's still much less that your $2500.

Chris

 

[lost soul]

I would upgrade the post to "Aquamet 22" This seems to be the alloy of choice for new shafts and posts.

Yes I agree. There is also 2250 called duplex SS. I am searching and seeing what I can find. Of course, it is about dollars too. SS pipe in 316L would be about 90 for the 4 foot I need. The batter alloys are over 300, from what I have found.
Funny thing is that the rudder inside should be water proof. So it would not matter what alloy was used. In fact the original rudder had ribs of plain steel. Funny thing with SS is that in low oxygen environments it suffers crevice corrosion. The post had some deep pitting right at the top of the inside of the rudder. The rest of it was in good shape. Inside the post, where water flows, it was in great shape.

I will use ss for the new ribs. Probably will make a one piece plate, like a mini rudder.

thanks!

 

[lost soul]

I was just about to repair my rudder, and spoke to "Al" at Foss foam. He offered my a price that was significantly less that what you note. It's done and shipped, and expect to pick it up in a few days. He reused my shaft, but everything else is new, including the replacement of any non-stainless in metalwork embedded in the foam with stainless (was a mild steel "wing" welded to the SS shaft). Shipping is a little expensive, but all in, it's still much less that your $2500.

Chris

Thanks Chris. I am a real do it yourself guy. I define myself by that.
My quote is a few years old. I will email them just so I can be more accurate.
Thanks!
BTW what was your cost?

 

[lost soul]

Here is a stronger option.. sched 80 1.5" pipe .. OD can be turned polished to 1.875 (only in the piece that goes through the bushings) leaving ya with a thicker wall.. is welded, but I can't seem to find seamless in that size..
https://www.onlinemetals.com/merchant.cfm?pid=13007&step=4&showunits=inches&id=314&top_cat=0

You really have me on the right track now, I think. I got out my caliper and measured the tube. It measures 1.9 OD, so that is the same as inch and a half pipe. Seems that is probably what was used originally. My wall thickness is .15 and schedule 80 is .2 , which would be srtonger. Then they also have schedule 160 which is .28 wall thickness.

At this point I am looking favorably at schedule 160 1.5 inch 316L pipe.....
Thanks a lot!!

 

[lost soul]

Thanks guys. This is time consuming on the computer, LOL,
Well worth the effort with this great advice!!
I will keep you updated,,
thanks again

 

[dlochner]

Y
Funny thing is that the rudder inside should be water proof. So it would not matter what alloy was used. In fact the original rudder had ribs of plain steel. Funny thing with SS is that in low oxygen environments it suffers crevice corrosion. The post had some deep pitting right at the top of the inside of the rudder. The rest of it was in good shape. Inside the post, where water flows, it was in great shape.
thanks!

The problem with rudder posts is that fiberglass and SS have different rates of thermal expansion. This causes the seal between the fiberglass and rudder post to fail, which allows water to enter. The water stagnates, becomes oxygen deprived and the SS post can no longer maintain a protective coating of oxidation. This is particularly problematic in northern climates where seasonal temperature variations are large.

The solution is to make sure the joint where the post enters the rudder is properly sealed with a flexible sealant. Carve a little valley around the post, fill with liquid Life Caulk and then seal with regular LifeCaulk. This will also prevent the rudder from filling with water which, at least in the north freezes and splits the rudder open.

Been there, done that, can't find the photos.

 

[lost soul]

Did you see these videos from Boatworks Today?
https://www.youtube.com/playlist?list=PLV97GZkHhpHMfaW24ZBR-xitL-TN2si9A

Yes I have seen many of his videos. The rudder one is ok, but he does not address the post. If I remember correctly, he does not want to change the original fabrication because that was the original design.
I am glad he posts videos, but the stuff I really want to know he leaves out, LOL. Things like what product he uses, and let me see the tapered joint for deck repair.
I have this perfectionist tendency and it drives my nuts!

 

[lost soul]

The problem with rudder posts is that fiberglass and SS have different rates of thermal expansion. This causes the seal between the fiberglass and rudder post to fail, which allows water to enter. The water stagnates, becomes oxygen deprived and the SS post can no longer maintain a protective coating of oxidation. This is particularly problematic in northern climates where seasonal temperature variations are large.

The solution is to make sure the joint where the post enters the rudder is properly sealed with a flexible sealant. Carve a little valley around the post, fill with liquid Life Caulk and then seal with regular LifeCaulk. This will also prevent the rudder from filling with water which, at least in the north freezes and splits the rudder open.

Been there, done that, can't find the photos.

Dave,
I am from NY, and spent years in Buffalo, so I know. Now I am in florida, and it is too hot.
I agree with what you said. How to keep water out of something that is made of different materials and submersed in salt water for years? (fresh water in your case)
Have a friend with an island in the thousand islands. Miss seeing the lights!!

 

[lost soul]

I measured a bit better. Finally got my good caliper out.
The od is 1.90. Wall is .15 or maybe .145. This does correspond with 1 1/2 pipe. I can feel a bit of a flat spot inside the pipe.

I looked around at metal suppliers. Interesting stuff out there.
There is inch and a half 316/316L pipe available for a lot less then the tube. Without shipping, it prices at just under 100 dollars for 4 feet.

TW metals had a choice of welded and seamless and schedule 40, 60 and 160.
80 is .20 thick and 160 is .28 thick.

Other alloys are available, like aquamet 22 and 2250 duplex, but only by email quote. I sent a few emails, but I doubt it is worth the extra expense.

At this point, I will most likely go with the pipe, probably schedule 160. My bottom bearing (pintle) needs to fit inside the pipe. I need to do some machining and checking for this. Schedule 80 would be fine too.


Then there is the ribs or plate decision. Ever price 316 SS plate? For about $250 I can get a nice 1/4 inch plate, wow. 3/16 is about 175. If I go with 1/4 inch ribs it is about half that price. I can make 3 ribs with a piece welded across the aft ends.

Next is deciding whether to weld center line or edge (tangent). If I weld it center line it is easier for my to rebuild the rudder. I do wonder if it would be strong enough, especially if using the 1/4 by 1 1/2 ribs.

With all my research I am going further down this rabbit hole. I am learning about what happens when SS is welded and how the welds are not corrosion resistant. Apparently pickling has nothing to do with spices. I have done a little bit of brazing and welding but not for years, so I will be having a shop do this work.

 

[jibes138]

Rudders are made to be neutrally bouyant. If you change the weight with heavier wall and more metal it will lose this characteristic. Just something to consider. Will put more load on whatever they use to retain your rudder and make it easy to turn.

 

[lost soul]

Rudders are made to be neutrally bouyant. If you change the weight with heavier wall and more metal it will lose this characteristic. Just something to consider. Will put more load on whatever they use to retain your rudder and make it easy to turn.

I brought this concept up in one thread about my rudder. It did not go over well, lol.

 

[jibes138]

Instead of butt welding the fingers to the post cut slots for the fingers to slide inside the pipe This may give a little more strength to the assembly if you are worried