Should stainless steel inside a rudder be coated for corrosion inhibiting?

[Wind River]

Originally Posted by Copacabana

Have a look at this video (and the others on his rudder rebuild). I think the expanding epoxy foam looks a great solution for rudders and I imagine it will result in a dry rudder core.

I look forward to Mad's videos every week.

[Wind River]

Originally Posted by robwilk37

built mine using 2205 duplex SS. the entire assembly (shaft and frame) that is embedded inside the rudder itself was scuffed and coated in epoxy. the only likely place for water ingress is the top if the rudder where the shaft exits so i relieved a 1/4" channel about 1" deep and filled with polysulfide on the assumption it will be a bit flexible over time and maintain a watertight seal. should out-last me i think...

I was planning a similar process for mine.

I considered the 2205 duplex also but decided to go with 316L.
Where did you get your 2205 material from? I had a hard time getting anyone that says they carried it to talk to me.

[Cheechako]

If I'm seeing your rudder properly, why glass in the SS? leave it exposed where it has fresh water flow.... If any of that rudder is hollow, fill it with epoxy foam or similar. NOT expanding foam.

[jharding]

I am with robwilk37, when I rebuilt my rudder 8 years ago I read a good article about epoxy not sticking to stainless around where it meets the shaft, twisting and flexing crack the glass there, and water gets in. I ground a bevel in around all three places that my shaft was exposed(partial skeg hung rudder) and filled in with 5200 which adheres to both and flexes. Just hauled my boat and drilled holes in bottom of rudder and no water came out.

[sailah]

Originally Posted by Wind River

I was planning a similar process for mine.

I considered the 2205 duplex also but decided to go with 316L.
Where did you get your 2205 material from? I had a hard time getting anyone that says they carried it to talk to me.

McMaster has everything. Probably not the best price but since they deliver next day to me I often buy metals I need for my home machine shop. Looks like it's about 2x the price of 316 comparing 1.5" rods.


https://www.mcmaster.com/9079k15

When I built my spinnaker crane and bobstay fittings from 316, I sent them out to be electroplated. This process also passivates (I am pretty sure) so it's a nice step to do to make parts shiny and also very corrosion resistant. After 3 years being splashed constantly they still look great.

I would def passivate the rudder due to welds. Keith Fenner built 2 SS rudders for a cat and walks thru the process. Was a cool video series. This is the video about passivating SS at home with a spray.

https://www.youtube.com/watch?v=bBVn...dex=21&t=1899s

[Cpt Pat]

Originally Posted by pcmm

Other factors often come into play when choosing between 304 and 316L where I am (Canada) just finding 316L is a massive challenge. No one stocks it and when you find someone that does the cost is a small fortune! I can replace 304 fittings (often) twice for the cost of one 316L fitting. Have to factor in the age of the boat too. If the boat made it 40 years on a 304 rudder, do you think it has another 40 years left in the boat? 30? 304 will likely be fine, but like everything else keep an eye on it. I see this a lot with the current fascination with using titanium for chainplates. Really is the boat going to last another 40 years? does it really make sense to go to that extreme?

I got my rudder post from online metals: https://www.onlinemetals.com/

[blubaju]

I made my ones of carbon fiber/epoxy, since 10 years no problem ;-) For my cat I thought, better a broken rudder and I can still use the other one than a bend stock that jams anyway.

[robwilk37]

as to sourcing... i stumbled on an ad for two 1.5" x 99" aquamet22 shafts on seattle craigs list. after verifying the chemistry (spectrographically) i paid more for oversize shipping than i did for the shafts. more than enough for my rudder, propshaft and spare.

and now vaguely remembering that aquamet22 is nitronic50 and not purely duplex? not clear on this - someone is slipping me decaf...

[Chotu]

You really should use 316 L from a quality stores. That’s the best material for any part of a rudder.

This is not the place to save money.

[Wind River]

Originally Posted by Cheechako

If I'm seeing your rudder properly, why glass in the SS? leave it exposed where it has fresh water flow.... If any of that rudder is hollow, fill it with epoxy foam or similar. NOT expanding foam.

I have seen rudder on other Fore 50's that have these parts exposed but they still are painted with antifoul so they are sill not exposed to clean water. I'm not sure if the original design of my rudder has been modified since the original build, but it doesn't look like it. The upper tabs have been replaced. This was an obvious repair, but the rest of the fiberglass looks original and the lower tabs were actually just covered with fairing compound and not glass.

There is wood inside the the rudder and between that and the outside fiber glass there is some kind of foam.

Pictures show a rudder with the tabs exposed , my rudder after a previous bottom paint job and after a peel of the antifoul and CSM layer of glass

[Wind River]

Originally Posted by Cpt Pat

I got my rudder post from online metals: https://www.onlinemetals.com/

+1

That is who I used also. Once you get on their list they usually send out discount codes every other month or so. I got 20% off from a one day only sale. Timing is everything!

My original rudder stock was 60mm so I was able to use 2-3/8" and it still fit fine. The only thing I was concerned with was the rudder arm, but it fits even better than it did on the old one.

[JDanielBryant]

Do not coat it. All coatings will have pores and nicks, each of which will become a site for crevice corrosion compared to its coated neighbor. Dr. J Daniel Bryant, PhD in Metallurgy

[Wind River]

Originally Posted by JDanielBryant

Do not coat it. All coatings will have pores and nicks, each of which will become a site for crevice corrosion compared to its coated neighbor. Dr. J Daniel Bryant, PhD in Metallurgy

It will be covered with something, be it fiberglass or antifoul. Are you saying don't coat it before the glass or antifoul? Or don't coat it at all, period?

[hellosailor]

Beneteau's solution to rudder metal corroding, since the 1980's, has been to shift to composite rudder stocks. Currently carbon fibre, IIRC. They can be stronger than stainless, and they are apparently impervious to corrosion.

Apparently there simply are no permanent ways to seal stainless going into a rudder, including the heavy rings of 5200 or polysulfide. They only delay the inevitable.

[deblen]

I don't believe SS needs to be be "enclosed" in anything,including paint,that will starve it of oxygen. To work as a "stainless(non-"rusting") type of steel,it needs exposure to oxygen,in order to let it's chromium content oxidize. The oxidized chromium is what inhibits the steel component from corroding(rusting). https://www.stainless-structurals.co...ainless-steel/


Why put foam,or anything else,inside a fiberglass rudder,if it has a structurally strong "rib" system & SS components?
Why not just a drain hole(s) to prevent freeze splitting?


Len