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Thread: Galvanic mess?

  1. #1
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    Default Galvanic mess?

    I need to brace the mount for an electric deck capstan which will only be removable for service from above. I imagine the machine will go on a plank that needs to drop into / onto some framework in the deck that I need to invent. I have some angle-iron for the strain-bearing frame and don't want to buy bronze. The heads of the bolts that will fasten the plank down will be visible and exposed to weather, but will need to go thru the plank and thread into the iron. These bolts will be removed at least yearly to grease the winch, so can I get away with bronze threaded thru wood into mild steel when it is inspected often?

    (the boat will mostly be in fresh water)

    Second question: The angle iron frame must be screwed into structural members under the deck, they hopefully won't ever get water, except for humidity, but I hope to not have to remove these in my lifetime, (I'm 68 :-) Do you recommend bronze or SS for these screws going thru mild steel into ash?

    fwiw, the winch itself is already a galvanic question: It's basically like a series-wound car-starter-type motor (but sealed) bolted to a cast iron worm-gear housing with a bronze shaft coming out of it to the bronze thru-deck plate and bronze capstan.

    Ken

  2. #2
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    Default Re: Galvanic mess?

    Have the angle iron hot dip galvanised and paint the hell out of it. You will have to clean the zinc out of the tapped threads, but if you put zinc rich paint in the tapped holes as a lubricant you will provide some protection for the bare steel.
    Angler iron will not provide many turns of thread, why not a clear hole and nuts on the hold down bolts?
    It really is quite difficult to build an ugly wooden boat.

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  3. #3
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    Default Re: Galvanic mess?

    Quote Originally Posted by Peerie Maa View Post
    Have the angle iron hot dip galvanised and paint the hell out of it. You will have to clean the zinc out of the tapped threads, but if you put zinc rich paint in the tapped holes as a lubricant you will provide some protection for the bare steel.
    Angler iron will not provide many turns of thread, why not a clear hole and nuts on the hold down bolts?
    If the alternative is to hot dip, galvanize, etc, etc, I wonder if I might as well cringe and buy some bronze angle?? Price is shocking plus delivery. The steel angle I have is 1.25 x 1.25 x 1/4" so threading it is decent, and the force will all be in sheer, but I can't thru-bolt because I won't be able to get to the back of it when it is in place. The winch rated pull is 350# at 25 ft per minute, it's not like I am heaving tons....

    This is the stuff that sucks days out of what one would think it takes to build a boat.....

    Ken

  4. #4
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    Default Re: Galvanic mess?

    Quote Originally Posted by kbowen View Post
    If the alternative is to hot dip, galvanize, etc, etc, I wonder if I might as well cringe and buy some bronze angle?? Price is shocking plus delivery. The steel angle I have is 1.25 x 1.25 x 1/4" so threading it is decent, and the force will all be in sheer, but I can't thru-bolt because I won't be able to get to the back of it when it is in place. The winch rated pull is 350# at 25 ft per minute, it's not like I am heaving tons....

    This is the stuff that sucks days out of what one would think it takes to build a boat.....

    Ken
    Are there no fab shops that send stuff for hot dipping near you?
    Our nearest galvanisers are about 2 1/2 hours away down the motorway, so they do a pick up and drop off service for our local fab shops. I would ask around if I were you. See if anyone will add your stuff to their consignment.
    It really is quite difficult to build an ugly wooden boat.

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  5. #5
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    Default Re: Galvanic mess?

    What size bolts do you plan to use? - would Riv-Nuts suit? - or "T-Nuts" set into the back-side of the timber......

    It is quite practical to weld a nut to either side of the angle iron.....
    Creationists aren't mad - they're possessed of demons.

  6. #6
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    Default Re: Galvanic mess?

    Stainless bar stock .25 ins. thick ( thick enough for tapping) would be less than $20. A backing plate would seem appropriate.

  7. #7
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    Default Re: Galvanic mess?

    Both my windlass's are bolted to my (strong) strip plank deck.
    Perhaps, re enforce a bit of deck with strip planking rather than a bunch of cobbled together metal bits, if corrosion is your concern?

  8. #8
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    Default Re: Galvanic mess?

    When it comes down to it solid deck beams and carlins under the windlass and some big tapped plates inlet into them would suffice.
    There would be less chance of leaks and other problems if the heads were down and the nuts were on the windlass bolting feet. That way where the bolts go through the deck need never be disturbed.
    It really is quite difficult to build an ugly wooden boat.

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  9. #9
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    Default Re: Galvanic mess?

    Would glass composite (aka FRP) sheet or angle serve as suitable backing? I can be bonded and tapped.
    https://www.mcmaster.com/8537k26
    Last edited by JimConlin; 11-18-2018 at 05:37 PM.

  10. #10
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    Default Re: Galvanic mess?

    If you dont want to go to hot-dipped, consider several coats of zinc rich primer. CRC sells it in spray cans. I think it would work OK in a freshwater environment.
    Have another think about the forces that will be exerted on your tapped holes through the thin section of the angle-iron.
    There is nothing quite as permanent as a good temporary repair.

  11. #11
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    Default Re: Galvanic mess?

    They do make 1/32" oversize taps for hot dipped parts. I have a few of them from jobs past.

  12. #12
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    Default Re: Galvanic mess?

    Ok, what I think I am getting here is that no one wants to see me tap bronze bolts into mild steel no matter what. Is that a fair summary?

    Following are some of my thoughts to individual responses above:

    Strength: this winch is designed for mounting with 3 bolts @ 3/8" diameter (about 9.5 mm) , so I guess I don't need much more than that to fasten it's mounting plank to the rest of the boat. If I wasn't worrying about galvanic, I would be comfortable tapping 3/8 x 16tpi bolts into 1/4" steel.
    Re: Stainless, I have had very bad experiences with work-hardening when trying to drill and tap stainless steel. I have used Cobalt drills, cobalt taps, lots of oil, and I still never know how the stuff will behave from one alloy to the next.
    Re: deck beams and carlins: if I could get to the back of the installation under the deck for service, I would have a hunch what to do, and wouldn't be bothering all you fine folks :-)
    Re: fiberglass angles from McMaster, etc. Thanks for the link, but what I have found there so-far has half the psi strength of mild steel and I would need to get a huge angle and cut it down to get the 1/4" thickness that I have on-hand in stupid generic angle iron. I haven't found thick angles with small legs 1.25 x 1.25"

    but keep those cards and letters coming :-) and thanks for all the help!

    Ken

  13. #13
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    Default Re: Galvanic mess?

    If it only needs three 3/8 bolts oak carlins let into the deck beams will be adequate with the bolts set in epoxy from below and the nuts on top where you can lubricate them to unwind them Any backing under the deck is over kill.
    You could even use hanger bolts https://www.amazon.co.uk/100pcs-8-16.../dp/B00TFZ5C6I
    It really is quite difficult to build an ugly wooden boat.

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  14. #14
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    Default Re: Galvanic mess?

    I'd send it out for Galvanizing. Since they charge by the pound with minimum weights, grab all the old anchors and old steel gear you can find or go in half-sies with someone.

  15. #15
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    Default Re: Galvanic mess?

    Whether or not I can get it galvanized, what do you folks think about the anti-corrosion stuff that electricians use when connecting copper and aluminum? I remember that one brand was something like Noalox.

    Ken

  16. #16
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    Default Re: Galvanic mess?

    Ok, here's another tack: The framework under the deck is welded + Rustoleum mild steel, hopefully not seeing liquid water. the bolts will go thru 2 1/4" wood to get there, but the heads would be exposed to weather and slop. Is it better to use iron, galvanized, or bronze, threaded into steel? The iron frame down under will be fastened to the surrounding wood, but (hopefully) will never see liquid water, just humidity. Fasten that to the wood structure with bronze, Iron, or galvanized?

    Ken

  17. #17
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    Default Re: Galvanic mess?

    I'm no engineer, but the strength increase over wood of 1/4" angle seems too small for the effort. I would be inclined to use 1/2". That would give you meat for tapping, and plenty of "sacrificial" material.
    The hot dip places, I'm told do stuff like bridge girders, so your assembly should be easy.
    If you make the whole thing out of wood, it should automatically be large enough to spread the stresses of rode handling over a sufficient amount of structure.
    Good luck

  18. #18
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    Default Re: Galvanic mess?

    Quote Originally Posted by David W Pratt View Post
    I'm no engineer, but the strength increase over wood of 1/4" angle seems too small for the effort. I would be inclined to use 1/2". That would give you meat for tapping, and plenty of "sacrificial" material.
    The hot dip places, I'm told do stuff like bridge girders, so your assembly should be easy.
    If you make the whole thing out of wood, it should automatically be large enough to spread the stresses of rode handling over a sufficient amount of structure.
    Good luck
    Wood blocking won't fit. :-( The winch is rated #350 at 25 feet per minute, it's not a monster, it would seem that 1/2" iron is overkill. The fasteners will mostly be in sheer load rather than pull-out. 4 x 3/8" bolts plus a bunch of #12 screws to fasten the iron to the boat, 6 x 5/16" plus 2 x 3/8" bolts to fasten the drop-in deck piece to the iron, , and 3 x 3/8" to fasten the winch to the deck piece (plus the shaft collar going thru the wood). I continue to think that my biggest possible issue might be electrolysis, not initial strength. What do you think?

    Ken

  19. #19
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    Default Re: Galvanic mess?

    Quote Originally Posted by kbowen View Post
    Wood blocking won't fit. :-( The winch is rated #350 at 25 feet per minute, it's not a monster, it would seem that 1/2" iron is overkill. The fasteners will mostly be in sheer load rather than pull-out. 4 x 3/8" bolts plus a bunch of #12 screws to fasten the iron to the boat, 6 x 5/16" plus 2 x 3/8" bolts to fasten the drop-in deck piece to the iron, , and 3 x 3/8" to fasten the winch to the deck piece (plus the shaft collar going thru the wood). I continue to think that my biggest possible issue might be electrolysis, not initial strength. What do you think?

    Ken
    I think that your biggest problem is a hugely over complicated design.
    K. I. S. S.

    Can you post photos of the top and underside of the deck so we can see how hard this installation really is?
    It really is quite difficult to build an ugly wooden boat.

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