welding on a steel yacht hull

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

  1. tugboat

    tugboat Previous Member

    Thanks PDW--that exactly the advice ill take--i got a good buzzbox--its brand new and a lincoln ac 225- im told its a great little welder. although it wieghs 108 pounds!! im gonna need long leads cuz I dont want to be dragging that thing all over hells half acre trying to weld tight areas and do taks here and there and all the sequencing--its gonna break my already broken back more...the hull is 3/16th frames and plating. 1/8th inch deck.
    25 000 lbs displ. the engine weighs 4000.00 with the gear. 3:1 trans. i did the prop calcs today--turns a 34.39'' x 32.3p wheel. but ill go with a 32" wheel. or maybe a 34 x 30. not bad for a 25 ft tug.

    so am i able to splice in longer wire for my clamp and electrode?
     
  2. tugboat

    tugboat Previous Member

    Richard--nice post!
    before i comment-
    I am sorry to Darr-- since I had to change my design to a smaller one i wont be doing it in FAL. I regret this because Darr has been a great help to me and I have nothing bad to say about the man. he's been professional to me in his dealings. yes Richard you helped convince me about steel...i admit it. i think i knew it was always going to be steel but being the stubborn rebel....FAL I still think is a good way to go for a round bilge hull especially if you want alight hull--it is almost the same as c-flex.

    --i guess im not so stubborn anymore--(laugh) just more practical. and with a smaller design -richer too!!
    also thats really interesting--i agree with you in the order you placed materials other than fiberglass--the costs of the resin if using epoxy is out of this world. and for a one-off its very expensive.
    I always thought fiberglass could make a good commercial tug hull but so bloody expensive- Jay benford has a 38 foot tug design in airex! and plans alone are 3000.00!! i paid 17.00 for mine...and good lord--thats gonna cost a fortune to build(Benfords 38 airex deisgn)..out of the scope of most pocket books for certain.
    haha "fc doesnt exist"--your funny Richard. kudo's im starting to like your sense of humour.
    yo are so right about the costs--and time as well--probably half the time to weld up a 25 ft tug too??!
    ill be keeping in touch with you--thanks
     
  3. pdwiley
    Joined: Jun 2008
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    pdwiley Senior Member

    My stick welder is over 40 years old, I inherited it from my father. It weighs well over 50 kg, it's on a trolley to move it about.

    Sure, you can increase the length of your leads, mine are a bit over 10m long. Just make sure you increase the cable diameter as you'll get increased resistance and heat in the longer cables. I have 400A rated cables and the handpiece gets quite hot when I'm running 4mm iron powder rods one after the other. I rarely need to move the buzz box itself.

    You don't need a long ground lead either, just keep the welding machine near something that's grounded and attach to that.

    Be careful welding the 3mm plate. It distorts if you give it a dirty look in my experience. Some of my keel tanks are 3mm and I did not enjoy welding them. I found that I had to weld in very short runs of no more than 25mm at a time doing vertical-up welds with 2.5mm E6011 rods.

    Think on how you're going to move the boat when you're finished. I built a grid from heavy channel and then I'm building the boat on top of the grid. The whole assembly will slide out of my shed and onto a truck.

    PDW
     
  4. tugboat

    tugboat Previous Member

    I had thought about moving it--i have a guy with a hydraulic trailer- he moves boats failry cheap-he just drives the trailer under the boats and pulls it up with the hydraulic trailer...but--your idea makes me think of the same thing--did you install the keel first as outlined in colvins book?? he has a shed- a loftng floor - platens for bending and a tool shed--it seems ike thats about the costs of a boat right there..ok not quite but its a chunk of it...did you sink concrete piers into the ground to level up the keel? I had thought this the best way--dig a few holes -fill with concrete and add steel protrusion set in concrete to weld the keel to??? i dont know about the ladders...and do i really need all those water lines?? shouldnt a baseline and a waterline be ok? im off to check out Colvins site---again...how far along are you into the build?
     
  5. tugboat

    tugboat Previous Member

    for anyone curious--my NA designed 25 ft tug--i did lower the bulwarks about a foot. low bulwarks for easy alighting to and from the vessl to shore to dock etc. no awkward climbing over large bulwarks and yes it decreases freeboard --but they are wet decks anyway. the larger one is scaled to 90% of the orignal 45 ft'er its 40.5 ft in this pic with the robaxacet guy on deck.
     

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  6. CDK
    Joined: Aug 2007
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    CDK retired engineer

    A welding related question:

    I am in the process of welding a mild steel construction that should be watertight. So I use stainless electrodes because the material flows better and the seams are easy to clean. But to my surprise some welds of 2 inches long split right through the middle from thermal stress in this 25 ft long construction, so the welds are brittle.

    Is this because too much iron migrates into the weld?
     
  7. tazmann
    Joined: Aug 2005
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    tazmann Senior Member

    stainless rods

    the stainless is britle, it's not the way to go. I would recomend grinding it all back out and rewelding with 7018 or 6011.
    Tom
     
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  8. pdwiley
    Joined: Jun 2008
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    pdwiley Senior Member

    What designation were the rods (assuming you used a stick welder)? They should have been E308 or E309 rods IIRC as these ones are designated as suitable for welding stainless to carbon steel.

    I have used stainless electrodes to re-weld a linkage arm on a tractor and that arm was a high tensile heat treated forging. It's still intact 15+ years later and has seen considerable use. I can't remember what rod I used now but it was selected due to its high ductility characteristics. In theory there's nothing wrong with what you did but we all know about the difference between theory & practice....

    I'd use E6011 rods too but then I use them for almost everything.

    PDW
     
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  9. pdwiley
    Joined: Jun 2008
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    pdwiley Senior Member

    With the shape of that tug hull you might get away with winching it up onto a hydraulic trailer truck. Not practical for a sailboat with keel in my case.

    Yes I built the keel first as Tom specified, then erected/plumbed frames etc.

    Yes there are a lot of infrastructure costs for building a boat. I did it my way for reasons that suit me, I'm not holding my way up as the only way by any means. How Tom describes doing things in his book is pretty minimalistic for steel boat building really. Caveat - if you get CNC cut plates & frames then a lot of the lofting etc issues go away - in theory.

    I'm building inside a barn I designed & built first, with a full concrete floor. I did this because I own the land and I live on site, and the weather can be difficult. This way I can walk off for months and not worry about anything. For me it was worth it as I figure I'll save more in time (though not money) in building the boat inside the barn than it cost me to build the barn itself. For you, probably not.

    Sinking piers is a good idea. Check Murielle's web site, there's a ton of good information there. She used piers without sufficient support, over the years they sank and the boat no longer has a horizontal DWL. You can work around this but it's a lot easier to work with it.

    Ladders - I made all my frames with an angle iron support vertical on the centre line and horizontal on the DWL. This made it easy to level them in. I also used a tight wire strung over the top of the keel above the highest frame and EXACTLY on the keel centre line. I could then drop a plumb bob off this to the C/L of the keel and ensure that my frames were vertical and on centre. This is a lot more accurate than relying on a carpenter's level and not much slower. I also used a laser level to cross-check and string lines 50mm above the level of the horizontal frame braces to pick up any frame tilt in case my vertical had shifted or I'd welded it wrong.

    Yes you end up using a ton of bracing material but your frames don't distort and they end up how you want them.

    So basically I did follow how Tom recommends doing it with variations based on having a barn with solid concrete floor to work off.

    My steel grid support isn't essential either, it's just convenient. The boat had to have some sort of cradle to get to the water eventually and I could get the steel cheaper than big timbers (from a steel broker who buys scrap & surplus stock) so I used steel. It was easier to build the grid then the boat on top than assemble a cradle around a finished hull for me, so I did. It's not the only way to do it.

    I'm plating out the hull now. If I apply myself (ie, I don't spend a lot of time interstate like now) I'll have most or all of the plating finished in 4 weeks, possibly all of it if I don't run out of blasted & primed steel (which I have done ATM and is one reason why I scheduled this trip now, while more plate is off at the blasters....). The bow section from the chine down to the keel on a Witch has compound curvature and has to be strip plated until you get aft of frame 3. I had to be a purist and butt weld the strips not lapstrake them as recommended which meant I needed damn near perfect fits and more plate edge support, all of which took a lot more time. With your hull it seems unlikely you'll have issues like that.

    Re-read Tom's book as a lot of the materials he recommends you need to build end up in the finished boat. The plywood for the lofting goes into the interior, the timber bracing you rip up for nailers etc, the piece of steel you use for a platen when making the frames ends up part of the hull plate etc. There's not a lot of scrap.

    I used a platen made from 3600 x 900 sheets of chipboard flooring material 19mm thick rather than a chunk of hull plate. I painted it white and laid out a grid on it with a base line, a DWL and a C/L plus exactly vertical side lines. I used this to make all my frames, repainting it as I needed to. I only really had to do this once as I made the aft most frame first then worked my way forward to the largest frame, then painted the platen and did the frames as they got smaller. It was a lot easier to follow the lines this way.

    I'd pre-drilled my frame sections on 100mm centres so fastening the interior later would be pretty simple. It's fast & easy to drill holes with a drill press when you're dealing with a piece of flat bar only maybe 3000mm long at most compared to drilling a frame with a hand drill after the stringers & hull plate are in the way. The pre-drilled holes meant I could screw the sections to the platen prior to welding and they'd stay put. I didn't get any frame distortion to speak of though I was careful with my weld sequences anyway. There are a lot of holes in my frames that I'll never use but so what.

    If I was doing it again I'd do the platen & frames my way again as it worked fine.

    PDW
     
  10. CDK
    Joined: Aug 2007
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    CDK retired engineer

    The stainless electrodes are marked E308-R16.
    Once I discovered the brittleness of the welds I continued with E6013 because that's what I have plenty of, then welded it over with stainless.
    When I was younger, welding without gaps never was a problem, now it seems impossible.

    Nearly everything I welded in the past 10 years has been stainless and I never noticed that the welds weren't strong. I first contemplated tig welding for this project but feared the gas would quickly blow away in the wind.
     
  11. tazmann
    Joined: Aug 2005
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    tazmann Senior Member

    I carry sanvick brand on truck 308/308L we use for welding 304 grades, 309/309L we use for welding mild steel to stainless and 316/316L to 316 grades. Stainless does not take kindly to vibration or flexing. Another thing that would make me a bit nervice there is the stainless under water line, dissimular metals under water = electralises.
    Tom
     
  12. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Thank you Tom.
    The project is a very large trailer that gets deep into the sea because of the local situation. To avoid the hollow tubes from filling with seawater and rusting from the inside, I do everything within my power to make the construction waterproof.
    That includes spraying the whole trailer with zinc, sealing some joints with Sikaflex and finally applying two coats of the best polyurethane paint I can find.

    The immersion itself will not take longer than half an hour, it is the standing near the sea for 5 months I want it to survive with minimal damage.
     
  13. tazmann
    Joined: Aug 2005
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    tazmann Senior Member

    Yep on a trailer there shouldn't be a chance for electrolisis. One thing that you could do there to add more life to it is weld in small pipe plugs or simular top and bottom of the hollow sections, then you can pressure check them for leaks and allso put in a little oil when finished.
    Tom
     
  14. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Great idea, I will certainly do that. A useful destination for some used engine oil.
     

  15. tugboat

    tugboat Previous Member

    PDw- thanks- yes I just recieved an email from the NA who did the 25 ft boat- and he is going to supply me with the cnc files inexpensively. There are 10 frames of 3/16th frames. It costs 100.00 per hour to cut the frames, im guess this could be done for around 500.00 much less than if i lofted it out - built sheds, platens etc. -true the platen gets used as hull plating. However my boat has no accomodations. The inside of the pilot house might have some plywood but not much...maybe 3 sheets or so. Yesterday I was travelling for the weekend and saw a 25 ft single chined tug VERY similar to mine-having almost the same proportions and the same bow style. she had plywood doors. the owner uses her to puch barges on a large freshwater lake here. There was a steering wheel., a door a seat some guages/controls/lights and that was it...
    I think in todays world- cnc is the way to go. It cuts my construcitons times down and I believe its less expensive overall to go this route.

    What about using a level I-beam/s as a jig? then weld tabs on to hold the frames, then brace them in a similar fashion as you did?

    Murielle 's concrete probably moved because of the frost line. (my guess)
    so ill have to mke sure i foot the sonotubes about four feet in the ground below the frost line. if i go that route..
    I think everyone has a different way of erecting the frames. as long as they are erected to the centerline and plumbed they should be good to go...
    ill move my posts to my other thread-- so as not to hijack it by accident..

    ill start a new thread about building a 25 ft tug...
    see you there hopefully...
     
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