Welding Sequance

Discussion in 'Metal Boat Building' started by Katoh, Jun 5, 2010.

  1. Katoh
    Joined: May 2010
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    Katoh Senior Member

    Good Evening All
    I am currently endeavouring to build a 23' aluminium cruiser, inboard style of vessel. the boat contains a total of 11 frames spaced at 600mm centres bottom plate strings at 200 centres and 3 top plate stringers again at 200mm centres. the frames will be cnc cut from 6mm plate and all will be assembled on a inverted jig.
    Now come my questions, they may sound silly but please bare with me I am a first time builder.
    My first point of attack is attach all the stringers and keel bar to the frames, Do you tack weld or full fillet weld these components on all 4 sides?
    Ok I have all the frame and strings and keel together inverted on the jig, I then plan to weld on the Transom, again is this tack welded or fully welded to the stringers?
    After this I start with the bottom plate, I have read that I tack weld this to the frames and the stringers then start my full continuous welds from the centre of the keel only from the inside. does this mean you leave the vessel
    inverted on the jig and weld upside down inside the boat? Once finished with the bottom plate on both sides I am to repeat the process with the top plates. Ok as i understand this the boat is upside down the frame is either tack or fully welded the plates are just tacked to the frame but are continuously welded to the keel bar the chine bar the gunnel from inside only
    while the hull is inverted on the jig? Is this even possible as most welds will be upside down and wouldn't you have to raise the jig and hull so you can get under it without being a contortionist.
    Ok next step weld the outside of the hull using the same sequence as the inside, is it necessary to run a saw blade along the joints to leave a groove prior to welding were plates meet?
    Ok I have got to the point were the hull is welded inside and out but only tacked to the frame. the hull is now turned the right way up, do you go through and weld the frame to plates now? if so are they continuous welds on the stringers and frames or stitched, if stitched what are the specs on how much weld to have, ie. how much hit and miss, on both sides are alternately? I don't have this information with my plans but there must be a standard out there.
    Information or references to relative standards will be appreciated,
    as stated I'm new to this game.
  2. kmorin
    Joined: Apr 2005
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    kmorin Senior Member

    weld sequence in aluminum

    If you don't know the answer, that doesn't make your question 'silly', however most people consider it good form for web posters to search and read all they can before just asking a question.

    The simplest answer to your question is there is not a hard and fast weld sequence universally accepted by all builders. Instead there are, like most other facets of metal boat building, adherents to several different general ideas of weld sequence and countless variations mixing the main concepts.

    So, there is not single source, one size fits all answer. In general, there is one school of design/assembly who leave the entire frame and stringers/longerons tacked but not final welded together until the hull is welded at the plate edges. Another (general) method is to tack everything and begin a methodical weldout by performing the long hull welds, and slowly contracting the hull with short welds on both hull and frame placed in a pattern symmetrical about the keel and amidships.

    If you have Steve Pollard's book Boatbuilding with Aluminum, there is a chapter on sequence of assembly with welding notes. Dave Gerr's The Elements of Boat Strength is also a known reference for welding sequence, timing in the build and locations of welds. I'm not saying either book teaches boat building, but they are good references for the types of questions you're asking.

    If you were to read the many posts on this site regarding various aspects of assembly and weldout- I think you'd find a very wide spectrum of opinion and experiences reported about this matter.

    One thing I did notice in your post was about overhead welding. Aluminum MIG is so rapidly deposited that overhead MIG is one of the best positions in boat welding. The reason is that while the hull is inverted you can stand (depending on elevation) under the hull, on your feet, balanced, and with a very clear gun/torch access to the weld. If the hull is keel down, ('right side up) many welds are below your kneeling position and therefore much more difficult to perform.

    I have built a few welded aluminum boats in the last 40 yr, and have built a skiff jig (Davis Jig) rotisserie to roll skiffs (my term for almost any boat shorter than 26') inverted to allow overhead welding instead of welding inside in a kneeling or other more cramped position. Yes you have to raise the jig or boat up to get under, but the improved weld access will be worth that effort.

    Also regarding seams, I'd recommend a tool by ArborTech of Austrialia http://www.arbortech.com.au/view/woodworking-information/mini-grinder_20070202100615/ down this page is a two tooth carbide blade that will back gouge weld seams with great control and is better than using a larger format circular saw. I have several of the cutters and touch up/re-sharpen the cutting edges with a diamond hone and they do the best most controllable job of hand back chipping a weld seam.

    more important than an exact weld sequence or location is weld proportion to the parent metal. I'd spend time reading the power supply mfg's sites 'knowledge base' posts to make sure your welds are in proportion and fused correctly to the hull and frame.

    The most common weld problem I've seen in first time builders is lack of fusion compensated for with oversized, too-slowly deposited, overly heated welds. Practice each of the four of five basic welds, inside fillet, outside fillet, thin to thick T butt fillet and thick to thin T butt fillet until the toe and top of each of your beads fuses into the parent metal cleanly. It is most advisable to practice until your break bend tests will show you are ready to weld on your boat- and not until.

    Kevin Morin
    2 people like this.
  3. Katoh
    Joined: May 2010
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    Katoh Senior Member

    Hi Kevin
    Thanks for the feedback, I have bought Steve Pollards book and am using that as my reference material I also have some literature on aluminium welding from a local tafe, I have gone through the forums and found what others do but all different as you stated, at least now I know that there is no real sequence written in stone that is correct. I will have to redesign my jig so I can move it up and down ect, might use 4 wind up dolly wheels from trailers to do the job, also they will act like casters.
    I will stick to Steve Pollards sequence I have it here and its not that difficult to understand, and in the mean time try to contact the designer to see if he has any information that can assist me. ( if he ever gets back to me). I will also set up some scrap practice pieces in an overhead position and see how I go.
    Many thanks again.
  4. Guest62110524

    Guest62110524 Previous Member

    good post Kevin
    I used to build all my small boats to 9m, upsides down on a frame on wheels . I wont add much to Kevins post, except to say if you build each frame with a T or angle at a high waterline and weld that to your frame jig, which will be abt a metre high, then you can comfortably work under it, then you can simply roll it after plating with a rope or wire that wraps around it, and using two chain blocks roll it If you search there are many posts abt turning a boat
    If you get stuck pm cheers Stuart
    as he says overhead is a very easy position, you just need plenty of leather, on body and head, hair on head does not seen to grow back:))
  5. alidesigner
    Joined: Nov 2006
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    alidesigner Senior Member

    Let me preface this by saying that we dont build upside down using jigs but if I was going to here's what I would do.
    1. Tack everything first. Much easier to break a tack if you have to adjust something later.
    2. Then once the boat is tacked and locked up I would weld the outer seams.
    3. Then I would turn the boat over and weld out the inside down hand. Kevin is right about overhead welding but for a newbie it would be easy to get poor penetration, plus sore neck, burnt etc. Downhand is much easier to start with. I just bought a cig auto darkening hemet off ebay for $100. Its awesome so would recommend one of them.

    For stringers and frames we use 75mm long stitches on the bottom, down to 50mm on the sides. You dont want too much heat in the sides or you will buckle it and your paint costs will go sky high. Bottom frames are floating to the side, ie not welded to the side at all, not even touching (10mm clearance).

    Use plenty of bracing on flat panels to minimise buckling, eg transom.

    If you can press a seam then press it rather than welding it, gunwales, seat boxes, dash etc.

    Consider back stepping to stop heat build up.

    For non structural areas consider gluing with sikaflex or riveting (alloy rivets only)

    Keep it uniform. Ie dont just weld one side then the other. Weld a bit on port then the same area on stbd etc. For frames, dont weld front and then back. Weld all the fronts, then go back and weld all the backs. This reduces buckling.

    I'm sure there will be those that disagree with some of the above but that's how our builders do it.
  6. Katoh
    Joined: May 2010
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    Katoh Senior Member

    Thanks for the heads up on wearing plenty of leather, I have not tried overhand welding yet in ally, I'm waiting for some parts to arrive to get the big Mig up and running, many thanks to Kevin Morin for his assistance and direction in that department. I have welded overhand before with a stick on MS and I know I don't like doing that, but until I try with a mig I'm not really sure what I'm up against.

    I agree a 1000% I bought an auto darking helmet about 6 years ago, they were bloody expensive then but the best money I ever spent on welding gear.
    You wrote. Bottom frames are floating to the side, ie not welded to the side at all, not even touching (10mm clearance).
    Sorry this has totally lost me!
    With the welding sequence, I have read that after say you have your frame all tacked together and you start your final welds, you weld one side then the the opposite, then you weld the same part on the opposite side of the boat in the same sequence. What I might have to do is drawing of the total parts, and maybe you could give me sequence on them.

    I am slowly drawing the plans in digital format so I can cut the frames on my CNC from plate material, I am drawing the last two frames at the moment frame 10 and 11 being the last frame before the transom. My plans show the transom as meeting level with the bottom of the last frame. To me this causes a problem as there is no way of welding the inner joint at the bottom of the transom plate. Would it be advisable to move the last frame in 20-30mm so you would have access to weld this joint, this would mean instead of having frames at 600mm centres the last one would be 570mm, but the bottom of the transom will be at 600.
    Thanks for all the advice
  7. alidesigner
    Joined: Nov 2006
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    alidesigner Senior Member

    Sounds like you are drawing your frames from a lines plan that shows the last section and also the transom at the angle and they meet at the bottom. Normally you just ignore the last section so you have your angled transom then your first frame 600mm further forward.

    Here's a photo showing floating side frames. See how they stop short of the side plate by 10mm so they cant be welded to it.

    With welding secquence I meant port then stbd when welding longitudial seams (eg chines) and stringers. Eg weld 600mm of port chine then weld 600mm of stbd chine. Dont weld the whole port side then move to stbd. This can twist a boat.

    For front then back I meant weld the front of fr1, then the front of fr2, then front of fr3 etc, then go back and weld back of fr1, back of fr2 etc.

    Attached Files:

  8. Katoh
    Joined: May 2010
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    Katoh Senior Member

    Hi alidesigner
    Many Thanks for the photo I can see what you mean now, My plans are different from this, thus the confusion. I think You are dead on the money with frames, I am working with a line drawing but still it says frame 11, I will PM you regarding this.
  9. alidesigner
    Joined: Nov 2006
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    alidesigner Senior Member

    I have seen boats with much less structure. No one can deny the success of trailcraft and you can have a look at whats inside their boats here http://www.trailcraft.com.au/tough/tough.aspx Compared to them my boats are way over designed.

    4 full length girders without any stringers can give a larger unsupported plate panel, more deflection, and lower fatigue life so could be worse.

    To put it into perspective a 50m, 40 knot ferry is built with 6mm bottom and stringers at 220mm. Our 6m boats have 5mm bottom and 220mm spacing. That's more than strong enough.

    Given the choice of 4 girders or 8 stringers I will take 8 stringers any day. Each to his own though.

    By the way the boat in the picture is 5 years old and no warranty claim yet.
  10. Guest62110524

    Guest62110524 Previous Member

    the girders are just the start, the floors are same depth at 500 centres, the inner Girders 600 apart( with a proper t keel bar--for engine beds and outer ones 3 hundred outside of that again The panel size is tiny But wait and see, I had a number of failures in the early 80,s then I soon changed to deeper vee and the above system People demand and are entitled to 5 years warranty on a pleasure boat and I would happily give 10 years So these must be flat water boats surely? you see that section by the gun cable, it looks like those stringers are intercostal by way of that shallow frame, that whole area would flex and those short vertical welds would break Can you post a body plan scan
    May I ASK how many of these you have in service? and what sort of hours have they run Some boats can do a,lifetime hard work in a very short time, others, do nothing much in 20 years That red boat in the gallery clocked 3500 hrs in 5 years sportfishing up to 40 miles off NZ coast
    best rgdsStu
  11. Guest62110524

    Guest62110524 Previous Member

    this is the deadrise that worked in rough conditions just leaping from wave to wave Before this we had round low vee entrys, landing so hard you had to slow Anything that rattles your teeth is not right for a boat offshore If it feels wrong it is wrong
    Mate bought a bayliner , in the lowest of swell we actually have to go at walking speed, it is not fun and mostly has to be left on the front lawn
    All o these I built upside down, the girders made it easy to set up the whole thing
    These days with computerset weld settings you are safer from burns , if you used a straight unprogrammed mig as we did, leather was essential especially if you got into the bad habit of stirring the pool
    Last edited: Jun 21, 2010
  12. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    What is this then, Scotch mist?

    I don't to see how you feel knowledgeable enough to know when something is going to fail, when you can't even recognise poor quality joints on your own boat. As you show here:


    And as for:

    Alidesigner had it spot on:

    And again with:

  13. Guest62110524

    Guest62110524 Previous Member

    yes we know you hate me and that is only YOUR opinion, that joint is perfect and you know it
    As I have said many times , you hide, nobody know syou, your face is invisable
    But I knew that you would pop up here again, you have nothing better to do, so back on Iggy for you my son:) we have seen nothing you have produced, ever? have we Because you are just an academic nerdle, who has scoffed at my welding ickets, by references and everyother piece of proof Get a life Ad Hoc
    The brains of this forum do not bother with you, do they? No I can not argue math with you, but I do know what works
  14. alidesigner
    Joined: Nov 2006
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    alidesigner Senior Member

    All I was trying to point out is that different construction methods can be equally as good. I wasnt meaning to critisise yours. That structure in the photo was designed to class rules and checked with FEA, professionally built and hasnt failed in 5 years. So intercostal connections can be fine if done right.

    I always welcome constructive critisim, that's how we all learn, and if you had of said that frame should be Xmm deep, or the welds should be Xmm long, or something specific then no probs, but to just say that it will fail without any specifics isnt really fair. Especially considering it hasnt failed.

    I did 4 years at uni but learnt more during my 10 years working in a shipyard talking to the guys on the floor. So I place a high value on practical experience, so much so that I just spent 2 weeks as a TA to one of my builders while he assembled a kit. So yes I do value the opinion and recognise the experience of the builders.

    I agree. I'm not here to argue to create problems, just to help out where I can. All I was trying to show with the photo is what I meant by floating frames, not how he should make the frames (thats the job of whoever sold him the plans)

    Let's hope at 73 youre still working or happily retired, not dead :) .
    1 person likes this.

  15. Guest62110524

    Guest62110524 Previous Member

    you like me are honest, I,ve been trying to ring you
    take some points and I wish you every success
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