welding on a steel yacht hull

Discussion in 'Metal Boat Building' started by Andyman, Sep 21, 2010.

  1. Andyman
    Joined: Sep 2010
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    Andyman Junior Member

    i got job welding some patches in a friends yacht. It got passed on to me since the guy has become way to busy with work other wise he was gonna give it a shot and as far as i know he knows nothing about welding.

    I'm still fairly new to welding, only been into it for about a year or so. Had some people on another forum express concern that I may not be experienced enough for the task at hand.

    Just wondering some thoughts from people on here. The guy I'm doing it for is gonna cut all the spots out that he wants patched out then I'll come along and fit patches and weld it up. I plan on butt welding the patches with maybe 1/16th gap all around. was thinking about TIGing the root the MIGing over it. was looking around this forum for awhile and seems like everyone is either stick welding or MIGing. I don't feel all entirely to comfortable MIGing it which was why i was thinking of TIGing the root which i feel more comfortable with then filling the rest of any groove with MIG. most of the material I'll be dealing with is 3/16.

    the only machines i have are a Diversion 165 and recently purchased a MillerMatic 211

    let me know me know watcha think or if you got any tips

    Andy
     
  2. TwoByFour
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    TwoByFour Junior Member

    Hello Andyman,

    Hopefully you'll get plenty of response for your questions.

    To begin with, I am going to tell you to not take on this project unless you are certain that you can do it properly. As it is not your own boat, it would be quite bad if the welds didn't hold up. I assume that since you were offered the project, you have at least some welding experience. If you're not a qualified welder, I would recommend that you go and take a course so that you become qualified.

    How many feet of welds do you think you're facing?

    Are you able to weld from both sides on all of the patches?

    Personally I would do it with the MIG machine, but that is because I am more proficient with MIG than I am with the stick. MIG is also faster and you can generally weld longer welds than with stick or TIG, as the thermal input with MIG is lower.

    You need to make sure you are using the right technique and that your welds are good. The methods you describe sound OK. TIG is good for root passes to ensure good penetration, but personally I would not bother with TIG. unless the only machine I had was TIG, I might even fully weld it with TIG. It is slower, more expensive and more likely to cause distortion.

    Start by browsing the web for information and then go and practice to make sure that you know what you're doing before you start welding on the hull.

    Wikipedia is a good start to read up on the welding processes.

    Most of the welding equipment and filler material manufacturers have useful papers and documents on their sites, you should take a look at those.

    I would also recommend http://www.weldingtipsandtricks.com, the guy there has some nice videos and practical information on welding in general. I believe he is trying to make an income from the site, but it does not seem to affect the reliability of the advice and information he is giving out.

    Wynand Nortje, a boilermaker who has professionally built quite a few boats, has a web with plenty of information on boatbuilding and pictures that might be of use to you. I think the web is in development and he is adding information most days now. http://www.5psi.net

    There is plenty of information out there, you just need to search for it.

    Amateur steel boat building websites might also be of interest and use to you. Sometimes the amateurs share their failures on their websites, which then gives you an idea of what to avoid. An example are the Canadian ladies who built their own boat, they documented it very well and did a very good job at sharing information on what they realized they could have done better. http://www.thebigsailboatproject.com/


    Finally, a few tips from myself.

    • Make sure to grind out all rust and paint and clean off any potential contaminants before you start welding.
    • Make sure that the patches are of the desired shape before you start welding and that they are correctly aligned with the surrounding plates.
    • Tack the patches thoroughly before starting the welding.
    • Weld with back-step technique. If you're welding with MIG, for 3/16" plate, weld 4" long welds at a time, with 20" between welds. If you're welding with stick or TIG, shorten the individual welds down to 3". Let the welds cool down completely before you do another weld within the 20" radius of the previous one. Unless you're using TIG, grind out the start of the previous weld before welding the next one. Finish one side first and then move to the other side and grind the back of the welds clean before you start welding on that side. Grind the outside welds flush with a fine (80) flap disc but leave the inside welds untouched.
    • It does matter that the welds / repairs look good, but it matters more that the welds are good.
    • If you're not sure about the quality of a weld, grind it out and re-weld it.

    Again, I recommend that you do a lot of investigating and reading, and practicing, before you start the job. You will most certainly learn a lot from it all.

    Carl
     
  3. Andyman
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    Andyman Junior Member

    Carl

    I do have some welding experience. Probably enough you could say to get me in trouble lol I have some working in a shop. I've been working at a metal fab shop for the last 2 years and with in the last year decided to pick up welding. The guys i work with were a great help with learning how to weld.

    I'm roughing it out to maybe about 10ft of weld. there are going to be 2 good sized patches that look to be roughly 2-3square feet. then just some rust spots here and there.

    It seems like the guy would rather not go through the trouble of getting me access to the inside of the haul. If i do take the job welding both sides would probably be the best thing to do in my situation of not have a lot of experience huh?

    Also how do you recommend practicing? I know welding plate together is what you mean, but how should i test the strength of a test plate?
     
  4. gonzo
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    gonzo Senior Member

    If you are working outside, TIG is very difficult to use. The gas will dissipate and you will have a lot of slag. MIG, with flux wire, works fine. At 3/16 arc welding becomes a good option, cheaper too. Remember to back weld or the patch will have too much tension and deform. Also, all the corners should be radiused. If you are learning to weld, this is not the job for you. There will be corrosion and contamination which makes welding really difficult.
     
  5. peter radclyffe
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    peter radclyffe Senior Member

    you have to access the inside
     
  6. TwoByFour
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    TwoByFour Junior Member

    Hello again Andy,

    So far, what sort of welding have you been doing?

    All welding brings some experience, but not all welding is as crucial in terms of quality. Welds on boat hulls are very crucial and in my opinion you should have a similar respect for them as you would have for welds in pressure vessels, where you definitely do not want the welds to fail.

    A concern is that on a boat you are often welding in awkward positions, which can make the welding difficult. Regarding practice you need to take this into account and in order to understand how you need to carry out the welds, you need to weld your test pieces in a similar position as the welds you need to perform on the hull are in. In order perform destructive tests on your practice welds, you need to try and break them. If they do not break - you will be able to bend the plate 180°. For shorter welds you can use a vise and a lever or a hammer, for something longer you might need a hydraulic press. Another way to do it would be to have your welds x-ray tested, I don't know how difficult or expensive that would be though. This is something you would go through if you went to get certified.

    It is best practice to weld the plates on both sides where ever it is possible. In professional ship-building, all welds have to be welded on both sides where ever it is possible.

    I do not have much experience in repair of rusty boats, but as peter radclyffe pointed out in his post, you have to get to the inside of hull plating. Not only to be able to weld the inside, but to be able to see what else corrosion is going on as there might be some severe corrosion going on on the inside that you cannot see from the outside. A lot of hulls rust from the inside out. It is also feasible that if there are stringers or frames that are attached to the plating you need to replace, you need to be able to weld those back to the patches. Usually the frames and stringers are welded to the hull plating with intermittent staggered welds. In cases where you would not be able to access the plating from the inside, one could cut slots in the plate on the frames, and then fill up the slot with welds, joining the framing to the plating in the process (slot welding). I would not be surprised that the job would end up being much bigger than it seems to you or the boat owner, especially if the owner hasn't looked at the inside. If there is insulation on the inside you will need to remove that too, before welding.

    I second everything that Gonzo mentioned in his post. It is a messy job and not ideally suited for someone with limited experience. It could become something you wished you didn't get yourself into.

    Carl.
     
  7. Andyman
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    Andyman Junior Member

    Carl

    A list of everything I have done so far.

    AL mig
    -robot frame for a local high school

    steel mig(did all this at my job)
    -kick plates on the bottom of turn styles
    -capped the ends of bent steel for top mounting plates/covers for turn styles (covers were galvanized)
    -welded some hand guards on the cage part of turn styles
    -did about 5 or 6 guard rails
    -trailer repair
    -stair rail repair (did with flux-core)

    AL tig
    ---did at work
    -welded some small brackets together
    -put together one rail

    ---did at home
    -made i pretty cool looking coffee table for sis in-law
    -did another robot frame
    -recently patched some small holes in a boat for a friend of mine
    -welding screen shower curtain
    -working on a cool looking desk like the coffee table
    -made some trim for a guy's fire place.
    -shower bench for my aunt

    steel tig (all at home)
    -made a trailer for a friend
    -did my welding table
    -made a wheel stand for my milling machine
    -some shelf brackets
    -wall mount tool box stand
    -fish tank stand
    -small table

    I think that's about everything I have done so far.

    Don't you mean i should be able to bend my test pieces 90 degrees or more? At the moment it looks like all my welds will be flat to begin with and i don't think you can bend something 180 degrees if it is already there.

    just thinking out loud but i wonder if I'll be able to hammer over a piece i weld that's 9 or ten inches since i would wanna see how well tying the beads together works .i could probably see if my work would let me use a break to test the pieces or find a shop with a good press to test them for me. how big of a press do you think I would need? would 20 tons be enough? I have an 8 ton bottle jack i could probably rig something up for.

    in your first reply you talked about having to grind the start of mig welds out. i was wondering how much would i need to grind out? and I'm grinding it out so that when i pass over it with the next bead it makes a good seal against leaks that might be there because of a cold start/tying the welds together or something like that?
     
  8. TwoByFour
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    TwoByFour Junior Member

    Hello Andy,

    Nice list of projects you've done so far. It is of course hard for me to judge something I have not seen. All of it is useful for basic practice, but again, it's very different from the hull repair you're considering and not as crucial in terms of weld quality.

    I'm not a welding instructor so don't take what I am writing here as if it was the holy truth, just as something to give you an idea about it all. I won't be there to tell you whether you're doing it right or wrong. :)

    If you have a flat plate to begin with and you bend it 90° it will be at a 90° angle, if you bend it 90° further, the plates on each side of the weld will end up touching each other, having been bent 180°. It's not essential to reach the full 180° but do as you can. This is just a crude way of testing whether the welds are any good at all, they might not break but still not be perfect. Do what you can to try and break them.

    An 8 ton jack will probably be enough for a 2-3 foot long weld on a 3/16 plate, if you want to test a weld that long.

    In professional weld testing, they have all sorts of equipment for different methods of testing. The test weld is usually cut up in a couple inch wide strips across the weld (so that each strip contains a part of the weld and the plates it joins) and then you have multiple test pieces for conducting either the same test or different tests on.

    Here you have a link to an explanatory list of material and weld tests that are commonly used, both destructive and non-destructive: http://www.weldguru.com/weld-quality-testing.html

    You are correct on the part of grinding out the 'cold' part of the weld to remove weld bead that isn't fully fused to the base material and contaminants, to ensure that the next weld gets full penetration. With back-step welding you start the next weld 4" (for MIG on 3/16" plate) from the previous one and weld over where you ground out the start of the previous one and so forth.

    Click the http://www.boatdesign.net/forums/metal-boat-building/back-step-welding-17155.html link for clarification. It is best if you mark up the welds to the appropriate length with a marker pen before you start welding and keep yourself from welding more than you're supposed to :).

    Carl.
     
  9. Andyman
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    Andyman Junior Member

    Carl

    Now I understand about bending the plate. thank you

    I even found plans in a welding book that i have for the bending jig and much more about bend tests. how many test would you say i should pass before I'm "ready"? i was thinking maybe 3 or 4.

    I made up some test pieces today. did a good bevel on them with like 1/16th landing, 1/16th gap, and ground the mill scale back bout half an inch (made sure to use new grinding discs so i didn't contaminate anything), wiped it down with some paint reducer(all i had, need to buy a lot of stuff if i decide to do this) just to clean some cutting oil off, then i tacked the pieces up then clamped either in a horizontal or vertical position, and welded did about 3 inches let it cool enough to not be red hot and welded to rest. test strips were 1.5" wide 6 inches long 3/16 thick. then i put them in the vice and bent them up pretty good got the pieces bent 90 degrees with out any noticeable cracks or signs of breaking.

    I welded all my test pieces with solid wire. should I use flux-core if i weld on the haul??

    thank you for all your help and information so far i appreciate it. I'll probably meet up with the owner this weekend if he spends some time working on the yacht. I'll have a talk with him about the concerns that have been brought to light by everyone I've been talking to. If he still seems interested in letting me work on it then I'll work something out with him. I know i haven't done anything like this before but that's why I'm drawn to it i like challenge and the learning experience. Plus my work doesn't need me all that much any more so i got a lot of free time right now.

    Andy
     
  10. pdwiley
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    pdwiley Senior Member

    Some things that come to mind for you to think about:

    1. You ( really the owner) needs to have access to the inside of the plate to do a proper welding job. Not only for the reasons already listed but also there is a very real risk of starting a fire inside that will destroy the boat. I've seen the aftermath of this and it isn't pretty. We always used to have someone as fire guard with an extinguisher. If you can't see the weld area then you can't have a proper fire guard so you need to clear the interior to get access. If you do this then really there's no reason not to weld both sides (unless it's inside a tank or something).

    2. There's no reason not to use TIG if that's what you're confident with. It'll work fine, just be slower.

    3. Mill scale - it ALL has to go. Every bit of it. Do not weld any plate to the hull unless it's de-scaled first on BOTH sides or you plan on blasting it when finished. Frankly with small pieces for repairs blasting it first and then priming it is simpler.

    4. The patches need a good radius on the corners - somewhere else on this site there's recommended radii for patches.

    5. What is the life expectancy of the hull and where are the patches to go? It's not good practice but you CAN weld patches over weak spots and extend the life of the hull quite considerably. I wouldn't do it if I could avoid it but if it was a short-term fix to extend a hull life another 5 years or so, it's an option.

    6. If you are welding undercover or can set up wind shields then using solid wire and shielding gas is better than using flux-cored. If not then flux cored will work fine. So will a stick welder in the open, about the same amount of slag etc if you use E4111 rods as flux cored wire in a MIG. Having used both I think I'd go for the flux cored wire due to the smaller amount of heat going into the plate. 5mm plate is pretty forgiving with regard to staying fair as compared to 3mm which I hate working with.

    I don't recall if you said whether this is a round bilge design or a chine design. If round bilge then making the plate lay nicely might be more difficult. I've never done round bilge so I have no more to say than I'd do it in strips that can be formed to the curvature if I couldn't get a single piece of plate to lay nicely.

    Cutting the old plate out - use the thin cutoff discs in an angle grinder if you can't get at the inside of the plate but as I've said, you really NEED to get to the inside of the plate. If you can expose the inside then a couple of drilled holes as a start point for the cut and a cutting template from 3mm ply, MDF or similar, then use a plasma cutter if available. My plasma cutter has a drag tip and it doesn't burn the template at all because the kerf is so narrow and the HAZ is so small. I just allow for a 4mm offset from template to cut. Then you can use the template to cut the new bit of steel and there's a good chance it'll fit properly.

    As long as you're careful about your welding sequence and plate fit-up, and you're confident in your weld technique, it'll go fine. Just don't rush it.

    PDW
     
  11. TwoByFour
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    TwoByFour Junior Member

    Hello Andy,

    Regarding the tests, if your welds all come out good through the bending I don't know a reason to keep doing them.

    Yes, I think it's a good idea to have a conversation with the owner about the hull repair. Both regarding whether you are both confident in you taking on the job and also how things have to be carried out...whether he will let you get to the inside of the plating.

    Very nice post from pdwiley with excellent advice, as usual. I think he answered the rest of the questions you had :).

    Carl
     
  12. Andyman
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    Andyman Junior Member

    finally got around to doing a bend test. In my book i read you can have a total of a 1/8th inch of imperfections think this would pass? I know a guy that's a weld inspector out at the space center I'll have to show him maybe.

    Also just found out that i can use my mom's chiropractor's x-ray machine for just the cost of film which is really cheap he says. I'm suppose to find out what settings to use the x-ray machine on. I have no idea what he means by settings maybe if someone can't help me here the weld inspector i know should know about that. also do i wanna x-ray my pieces before i bend, after, or both?

    Andy

    oh ya forgot to mention i did this piece horizontal figured I'd have the most trouble with voids in the weld like in this sample so there for might be weaker than my vertical pieces.
     

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  13. TwoByFour
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    TwoByFour Junior Member

    Hello Andy,

    I'm afraid I don't know much about X-ray settings :). Hopefully someone else on here can answer that, or if your friend at the space center knows. You live close to Cape Canaveral?

    Depending on how expensive it is to have the test pieces x-rayed, I guess it would be ok to have a couple of bent ones done along with a couple of straight ones. I do not think that it is common to x-ray welds that been bent, though. But it might be interesting for you to see how it comes out anyway.

    Well done with the testing. I don't actually know if the "no cracks greater than 1/8 in" is entirely correct, but I don't have the standards here to refer to and can't find them online with a quick search. I imagine that the crack width allowed depends on the material thickness. A 1/8" crack in a 3/8" thick plate butt joint seems extreme to me, while it would be less extreme if it was for example a 1/2" thick test piece.

    There is some undercut in the weld on the photos which you will want to eliminate as possible. It is better to have to grind a bit of excess material away than to have to fill the undercut afterwards with another weld.

    It would be excellent if you could show your test pieces and the results from x-ray to your friend the weld-inspector. He should be able to tell you what to be concerned about, judging from what he sees.

    Keep going - good luck :)

    Carl
     
  14. Andyman
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    Andyman Junior Member

    Carl

    I live about 10-15 minutes away from Cape Canaveral.

    also as i edited my last post i mentioned i did this piece horizontal since i knew i might have some trouble with undercutting/voids in my weld bead. Should be able to fix that by slowing down, decreasing my bevel angle, or making a weaving motion right?

    Andy
     

  15. welder/fitter
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    welder/fitter Senior Member

    Andy,
    Sorry, I don't mean to offend, but that coupon is a definite failure. From the photos I see much evidence of lack of fusion with base material. As you didn't mention the process & other parameters you used, it is impossible to give much advice. You should perform both face & root bends, 1.5" to 2" coupon width is sufficient. One star of less than 0.125" per coupon is considered acceptable.

    In terms of performing repairs to your friend's boat, let me add a few thoughts to what others have said:

    1) Peter(PDW) has mentioned that access to the interior is required to avoid fire. This should be first and foremost on your mind & that of the boat owner, and is not the place to try to save time/work, as not clearing the surrounding interior area could easily cause the destruction of the boat.

    2) It is difficult to advise on something you haven't shown photos of, so I suggest that you or your buddy snap some photos & publish them to this thread.

    3) Normal practice is to remove compromised plate to two inches of the outside of each adjacent frame. You can usually find the frame edges from the outside by holding a piece of soapstone on it's side edge & running it back & forth across the plate(like a windshield wiper). Trying to replace plate within the area between frames will make for a real mess, as the insert is welded.

    4) Fit-up is very important; you'll want to make up dogs & wedges out of scrap to ensure insert is flush with existing plate. you can weld plate from outside(single-side) by using a ceramic backing strip or a backing ring, or double-side weld it. If double-sided welding, don't forget to properly back-grind root.

    5) Most important - Don't overweld it! Remember it's not 0.5" plate! (I'd suggest zip-cutting the old plate out, though you'll need a jigsaw for the radiused corners so you may just want to jigsaw the entire cut-out, unless you have plasma. Oxy-fuel is a last resort, due to obvious warpage. If you do use oxy-fuel, cut reliefs on scrap side every couple of/few inches, so you don't warp retained edge. you can also strongback edge you want to retain(0.5" to 0.75" from edge).

    I'd recommend replacing areas above waterline first. When you're satisfied that they're good, do the below-waterline sections. If there is anything else I can help with, feel free to message me.

    Mike
     
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