Aluminum Welding Cost

Discussion in 'Boat Design' started by APP, May 28, 2012.

  1. APP
    Joined: Nov 2010
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    APP Junior Member

    Hi

    I am searching some general info for boat alluminum alloy welding cost, expressed in welded feet (or meters) within an 8 hours working day, in a specific country e.g in America, Australia or Europe. The relative overall welding length of a boat is known from the design, in each case.

    Practically, I seek the average number of welded feet/hour. It refers to skilled workers (or semiskilled if you have data) including the preparation time, smoking cigarette as said, etc. It can be given separately for plates and scantlings (if for scantlings it could take longer to weld them).
    Otherwise, how designers calculate the welding cost?
    Thanks for any reply,
    Regards
    APP
     
  2. Stumble
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    Stumble Senior Member

    APP,

    This is typically measurd in lbs/hr or kg/hr. The leingth of weld applied over that time will depend on the size and depth of the weld. Generally a good welder will apply around 2.8lbs/hr, but this can be greatly increased by automating the process to some extant, and it changes based upon the gun, the efficiency of the welder, ect.
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    The problem with that image is the usage of the kg/hour.

    2 identical plates butt welded together shall have the same amount of time to weld. Here we are talking only about the function of the weld.

    If you now make one of the plate half its size, like "B", yet the long length the same dimension for both (that is welded), then the amount of time taken shall be the same. There is no difference.

    The difference comes in how you wrap up the whole function of fabrication.

    Most yards use man hours per tonne (ie hours/weight), as the image indicates. However, welding is just one function. Thus, if those 2 plates were in the store, as virgin plate uncut, then the hours required to lift, mark, cut and position the plate would be different between the 2, but the edge prep and clean would be the same.

    Since the size (hence its weight) has a direct influence on how many man hours are required to get the plate(s) into position prior to welding.

    A 10 x 5m sheet of 5mm plate that comes into the yard shall have totally different handling in terms of man hours to that of a 1 x 0.5m sheet of 5mm. Especially if the yard has no moving equipment. Yet both are 5mm sheets of plate. So when welding the 5mm sheet, just the welding length in meters is required.

    The welding time is governed by length, metre.

    Yet the whole function of fabrication is related to the weight, since the weight of material affects the time required to fabricate from taking the metal from stores to the jig to welding.

    That is why there is a difference and you need to understand the difference. And thus, each has a different time and cost attributed to it. Which is more often than not, yard/experience related. Which makes it harder to use one yard's values as a "norm" for all, you can't.
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    Says who??..where dopes this figure come from...what does it include, what does it not include...what is the experience of the yard etc etc. Is this for a monohull or for a catamaran, simple structure etc etc...???

    You can make up what ever values you like....but you need to be able to justify that 1.27kg/hour....i have no idea where that comes from nor what it relates to either.
     
  5. APP
    Joined: Nov 2010
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    APP Junior Member

    It comes from the above reply of Stumble (2.8lbs/hr=1.27kg/hour). He should probably clarify better this value.

    Thanks. Regards
    APP
     
  6. mariablack
    Joined: May 2012
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    mariablack New Member

    I agree with stumble.measured in lbs/hr or kg/hr. The length of weld will depend on the size and depth of the weld.
     
  7. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    I find most welders charge by the job... not the foot or the hour. Unless you hire one full time and just pay by the hour. Speed of production depends on thickness, conditions, equipment and type of welding.

    Then you also have cost of fitting pieces, prepping and grinding.
    I figure it differently, measure by days of work. It doesn't matter if welder can weld a foot or a mile but how much can you have ready for him to weld. Most welders can go faster than you can get materials ready for him to weld. So if it takes you five days to fit
    the piece up, and he is welding along those 5 days then it take 5 days of welding.
     
  8. Stumble
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    Stumble Senior Member

    I am sorry if it wasn't clear. 2.8lbs/hr is the amount of weld material a average welder should be abe to apply. This is just the welding industry standard, not specific to boat building. NOT the weight in metal a welder can weld up in an hour.
     

  9. messabout
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    messabout Senior Member

    OK you asked about downtime for cigarettes and such. That depends on how tight a shop you are running. It has a lot to do with the quality and skill of leadership as well.

    Manufacturing engineers in the US often use a factor they call PF&D. That is personal, fatigue, and delay. The personal part is for cigarettes, bathroom breaks, getting a drink of water and so on. The fatigue part is based on the reality that a worker will not move as quickly in the sixth hour as he might have in the second hour. He may rest for a minute or more several times a day. Delay part addresses the probability that a part will have to be fetched, a machine may break down, or precut parts do not fit and repair will be needed and a whole lot of small things that cause delay.

    A PF&D rate of 17% is used in many well organized industries. That means that you will get 83% of actual production but you will be paying for 100%. Obviously you have to fiddle these numbers to suit your own application. I would not even think of bidding a job without adding the phantom seventeen percent or more.
     
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