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Thread: Stainless Steel / Steel / Bronze

  1. #1
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    Default Stainless Steel / Steel / Bronze

    Hi one and all.

    I have galvanised steel floors in my 34ft wooden boat. Questions......

    Can I replace them with stainless steel ones? (I know that bronze is preferable but expensive)

    Do I need to use stainless steel fixings or can I use Bronze for the through hull fixings?

    Can also use copper nails and roves with them.

    Any help appreciated or if you can point me to a good source of information.

    Thanks in advance

  2. #2
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    Default Re: Stainless Steel / Steel / Bronze

    How long did the original galvy floor timbers last?

    Got any photos?


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  3. #3
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    Default Re: Stainless Steel / Steel / Bronze

    Unless the galvanized floors are so wasted due to corrosion so as to have lost a lot of strength I would simply send them for re galvanizing and re fit as built using the same material fastenings.
    It really is quite difficult to build an ugly wooden boat.

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  4. #4
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    Default Re: Stainless Steel / Steel / Bronze

    Hi, welcome to the forum.

    Try not to mix metals... so don't fasten galve with stainless, or stainless with copper etc.

    Don't put stainless under the water line, even fastenings.

    I would re-use what you have, and if the floors are not useable, make up similar from the same original metal type and get them galved.

    Galvanic corrosion is a bastard to understand fully, but go with what has been working before and you won't go far wrong.

    Pics would be welcome... it would be useful to know why the existing floors have corroded, unless they are just very old.

  5. #5
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    Default Re: Stainless Steel / Steel / Bronze


  6. #6
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    Default Re: Stainless Steel / Steel / Bronze

    What do you think is wrong with those? ^^

  7. #7
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    Default Re: Stainless Steel / Steel / Bronze

    Quote Originally Posted by Faykee360 View Post
    They look OK. Have them shot blasted and send for galvanizing.
    It really is quite difficult to build an ugly wooden boat.

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  8. #8
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    Default Re: Stainless Steel / Steel / Bronze

    They look ok I agree

    I just wanted shiny ones

    What fastenings should I use?

  9. #9
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    Default Re: Stainless Steel / Steel / Bronze

    Quote Originally Posted by Faykee360 View Post
    They look ok I agree

    I just wanted shiny ones

    What fastenings should I use?
    The same as you took out. Following the principle "If it ain't broke don't fix it". After all the Yacht Architect does know best.
    It really is quite difficult to build an ugly wooden boat.

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  10. #10
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    Default Re: Stainless Steel / Steel / Bronze

    They look ok to me too. Galvanized steel bolts are the best way to go in this case. If you want to go all out, get a lab to test the composition of the floors and try to match the bolts to it. Also, trust in Nick's opinions.
    Jay
    Last edited by Jay Greer; 02-11-2019 at 03:38 PM.

  11. #11
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    Default Re: Stainless Steel / Steel / Bronze

    so i can use bronze bolts again to the keel

    and copper nails and roves thought the frames

    What I think I am trying to get at is there is not a better way of doing this?

    I think you answered it mainly by saying that no stainless steel below the water line

  12. #12
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    Default Re: Stainless Steel / Steel / Bronze

    Quote Originally Posted by Faykee360 View Post
    so i can use bronze bolts again to the keel

    and copper nails and roves thought the frames

    What I think I am trying to get at is there is not a better way of doing this?

    I think you answered it mainly by saying that no stainless steel below the water line
    Copper through plank and frame is excellent practice. The bolt holes in those floors do not look as though they had boat nails and roves. Were they not bolted through plank and frame?
    It really is quite difficult to build an ugly wooden boat.

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  13. #13
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    Default Re: Stainless Steel / Steel / Bronze

    Sorry these are the new ones that I got with the boat.

    The originals in the boat are well past their best.

    The ones in the boat currently had a bronze bolt though the steel floor and then through the wooden keel .

    Then where the floor met the frames they were nailed and roved

  14. #14
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    Default Re: Stainless Steel / Steel / Bronze

    Is the rest of your boat bronze/copper fastened? What is the ballast material?

    If you have iron ballast and steel/galv fastenings, stick with galv floors. I would never put a bronze or copper fastening through an iron fitting. If you have bronze/copper fastenings and lead ballast, I would try to cast your own bronze floors. In your cold water, you could use stainless in either situation as its between iron and bronze on the scale, but I would fasten them with stainless not bronze. The floors will not last as long as bronze, but will last for several decades, at which time you will need new frame heels and maybe a keel.

    If your boat is already a mashup of materials, try to make the situation better, not worse.

  15. #15
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    Default Re: Stainless Steel / Steel / Bronze

    A lot depends on how much seawater is in the bilge and how saturated the wood tends to be. It would be interesting to know how badly the bolt holes in the old floors were corroded. The bronze bolts are likely to cause the zinc in the immediate area to go very quickly and the steel to rust faster close to the bolts. If the bilge stays mostly dry, there will be a lot less corrosion. Stainless corrosion is temperature sensitive. Boats in cold water seem to have a lot less problems with stainless than boats in warm waters.

    The new ones are mostly black with some light spots. Are they painted and is the paint chipped? Pettit sells a zinc filled PU called Rustlok 6980 Product Data Sheet. It is also sold as Trailercoat (I asked Pettit and yes, same paint, different label) that would be a good belt and suspenders coating here. Nice hard, tenacious paint, you open the can once, use some, and next time you try to open it you have to cut the lid off.

    Sources of information: Corrosion and metals:

    Before you add anodes to stop galvanic corrosion on a wooden boat,
    https://waitematawoodys.com/2015/05/...f-leaky-homes/
    https://www.fpl.fs.fed.us/documnts/fplrp/fplrp229.pdf

    There may be an anode that is safer for wood, Maddox, but This is the first I have seen, so I would like to know if anyone else knows about them before recommending any more than looking into the possibility: https://www.bbsc.org.au/resources/Do...e-Easy-SYC.pdf

    Good general information:
    metals http://www.kastenmarine.com/_pdf/mbqMetRef.pdf

    Maybe:
    https://www.yachtsurvey.com/corrosion.htm
    http://www.terryking.us/boatbuilding...nance-USCG.pdf

    Galvanic series chart:
    https://structx.com/Material_Properties_001.html
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  16. #16
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    Default Re: Stainless Steel / Steel / Bronze

    I do believe some pictures of the boat itself, especially the floors and keel, would be very beneficial.
    There's the plan, then there's what actually happens.

    Ben Sebens, RN

    15' Welsford Navigator Inconceivable
    16' W. Simmons Mattinicus double ender ​Matty

  17. #17
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    Default Re: Stainless Steel / Steel / Bronze

    Morning

    Originally....

    Ballast Keel = Lead

    Floors = Galvanised iron/steel

    Other fastenings = copper nails/roves and bronze screws and bolts

    To make the floors from stainless is cheaper and easier as I know someone who will do it for me.

    New bronze floors are expensive as I am sure you are aware, if Bronze is the way then so be it.

    I appreciate that mixing metals is best avoided.

    When the boat was built it had copper nails through the galvanised iron/steel floors and frames, would you stay away from this practice if......

    A) The new floors were made of bronze

    or

    B) The new floors were made of Stainless steel

    It is the different opinions that is the reason for my initial question.

  18. #18
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    Default

    My boat has galvanised steel ring frames, which I think are fastened to the hull etc with stainless bolts. Could be Monel I suppose. Hmmmm, might even be copper? Been OK for 45 years or so anyway.

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  19. #19
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    Default Re: Stainless Steel / Steel / Bronze

    It may be that the original floors were corroded away because of galvanic corrosion. If you won't post pictures of them and the boat you will continue to obtain only educated guesses about what the problem is, and hence a way forward.

  20. #20
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    Default Re: Stainless Steel / Steel / Bronze

    Monel is pretty much inert when it comes to mixing metals. Stainless below the water line is not your friend!
    Jay

  21. #21
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    Default Re: Stainless Steel / Steel / Bronze

    Bronze is best, to be sure. That said, stainless will be better than the galvanized floors. Not better in terms of strength or longevity really, but it will react with the bronze fasteners less and cause less damage to the wood.

    Bronze would be good for the next 100 years, stainless will only be good for 10-20 years. That's a big difference, but I can appreciate that the boat might only have 15 years left anyway and SS can be fabricated by many more existing tradespeople.

    I think you need to weigh the specific heritage/value of the boat against your own pocket book and make your decision. If you go stainless, it would be worthwhile to use thin plastic under them to isolate them from the wood as much as possible.

  22. #22
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    Default Re: Stainless Steel / Steel / Bronze

    Quote Originally Posted by J.Madison View Post
    Bronze is best, to be sure. That said, stainless will be better than the galvanized floors. Not better in terms of strength or longevity really, but it will react with the bronze fasteners less and cause less damage to the wood.

    Bronze would be good for the next 100 years, stainless will only be good for 10-20 years. That's a big difference, but I can appreciate that the boat might only have 15 years left anyway and SS can be fabricated by many more existing tradespeople.

    I think you need to weigh the specific heritage/value of the boat against your own pocket book and make your decision. If you go stainless, it would be worthwhile to use thin plastic under them to isolate them from the wood as much as possible.
    All true except perhaps for the plastic strip. A butyl rubber caulk would be better than plastic. It will seal in addition to isolating, and will not promote crevice corrosion. Plastic is used to test for crevice corrosion. It doesn't react with stainless, but does make for nice tight crevices.
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  23. #23
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    Default Re: Stainless Steel / Steel / Bronze

    Quote Originally Posted by Jay Greer View Post
    Monel is pretty much inert when it comes to mixing metals. Stainless below the water line is not your friend!
    Jay
    I'm ignorant on metals, but why is stainless no good below the waterline? Just curious.
    I was born on a wooden boat that I built myself.

  24. #24
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    Default Re: Stainless Steel / Steel / Bronze

    Quote Originally Posted by Rich Jones View Post
    I'm ignorant on metals, but why is stainless no good below the waterline? Just curious.
    Most stainless relies on an impervious coating of chromium oxide to keep the iron and oxygen apart. A ready supply of oxygen is required to maintain the chromium oxide layer. Bury the fastening in wet anaerobic wood and the oxide layer can break down allowing corrosion to start.
    It really is quite difficult to build an ugly wooden boat.

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