Another way to design & build in Aluminium boats

Discussion in 'Metal Boat Building' started by monomad, May 17, 2014.

  1. Webbey64
    Joined: Jul 2014
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    Location: Tasmania

    Webbey64 New Member

    Hey manomad and others, i am looking at building just one 19ft aluminium cuddy cab for myself as a tuna/all round boat. Just wondering how you come up with such great hull designs, i came across this

    http://youtu.be/_ff2f8s-Ou8

    I really like the design but am struggling to find any info regarding building something like this. Also what would the cost of aluminium be for a 5.7m boat with a 5mm bottom and 4mm sides.

    Cheers Web
     
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Webbey64, I recently projected a RIB 5.8 m in length, aluminum. The net weight of the aluminum structure was 430 kg. If you want, you can add 30% there for the gross weight of aluminum. Say, then, that to make a boat of this size, it takes 560 kg of aluminum.
    I hope this information will serve as guidance, not take it as absolute truth.
     
  3. rustybarge
    Joined: Oct 2013
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    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    Hey Monomad and Kevin,

    I'm just wondering what sort of welding equipment would be suitable for just 'tacking' together aluminium for a boat of about 30' length, using 6mm plate.

    I fully understand the welding is a highly specialised job not suitable for amateurs, so I want to cut out the alloy plates, assemble them with tack welds, and then get a pro to weld them.

    Approx What sort of prices/ ft would a coded welder charge?(only for private use)
    How many amps would a tack welding setup need?
    Any recommendations?

    Thanks,
    Peter.
     
  4. Webbey64
    Joined: Jul 2014
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    Webbey64 New Member

    Hey Tansl thanks for your reply! Silly me shouldhave realised just to estimate hull weight for aluminium pricing. Thanks for the help now to figure out some plans i am happy with.

    Cheers Web
     
  5. Kevin Morin
    Joined: May 2013
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    Location: Kenai, AK

    Kevin Morin Junior Member

    aluminum boat design and welding; one off

    web, the lines and designs come from two sources, the full time designer/marine engineer/naval architect who is not a builder, but may be affiliated with a yard or builder; OR, the builder who designs for themselves.

    I'm not making any case for either group, just noting these are the sources for metal boat designs/lines/plans.

    As to how people 'come up with' these designs(?) I'd say they combine imagination and practice; which seems to take some time to refine into a fully found plans package. Not sure what else could be said in reply?

    Rustyb', I'm at a loss to give a recommendation for other than US based welding power supplies and torches. I'm not familiar with the brands and models sold outside the US so I could only offer my advice by ratings. I'd suggest a power supply that can produce 300 A of welding current in both TIG and MIG for all work on 1/4" /6mm plate material.

    I won't go too far into the open circuit voltage issue implied by these power supplies except to note- tacks are of two general categories. Single dime or 'spot ' tacks and multiple dime or short welds. The term dime is used here to express a size of these welds; single dime, just pull the trigger and release, resulting in a dime sized spot of weld. Multiple dime or short weld is done by beginning a regular weld and stopping -soon, perhaps three or four dimes of weld puddle.

    The issue of effective tacking is related closely to a power supply's open circuit voltage that initiates the arc; higher is better for 1/4"/6mm material. Smaller, full ranges welding power supplies (I'm discussing MIG) may have open circuit voltages below 70-80 VDC so they could 'cold tack' this thickness material.

    As to tacking up yourself? There are potential flaws with this idea; one is the sequence of the welding done on boats. There are some locations where a fully formed permanent weld needs to be 'buried' or where access will be lost once the boat is further tacked up around this location.

    So while I can appreciate the idea of tacking yourself, then hiring the weld out from someone with fully developed skills? Care needs to be taken in understanding fully where and when every area of the hull needs to be welded; in sequence and with real world access.

    I have no idea of labor rates in other locations so I won't bother to guess. One aspect of the concept that may be critical path?

    Potential Flaw #2; If a person is able to do the type and quality of welding that you imply, then it's very possible that person is fully engaged doing that work for themselves or for an employer. If that is the case, then finding someone to handle just the welding and no other scope of work is often unappealing to welders and full time yards since they cannot control the joint prep or fitting and are being asked to accept whatever is delivered to them to be welded.

    I would personally only accept that offer from one of a very few fitters, and only those with whom I've had extensive experience- fearing, due to my experience, that I'd become involved in something that might reduce the reputation of my work that I've spent so long building up.

    The old saw in computer code is 'junk in junk out', the old saw in welding is that "bad fit and prep produces a bad weld". If I can't control or reject the fit and prep, I won't get involved so I can't have my work reduced in quality outside my control. No really good welder will agree to this unless they're pretty hungry.

    The idea that "I'll just hire out the welding" has showed up on other Forums I've read as a near disaster. First, the people 'open' to this idea are not full time, they have some spare time available. (Why aren't they full time if they're able and qualified?) Next, the owner is not able to fully judge good work and are often 'taken in' by the claims of these guys who're "The best in the area" as described by the local pub's patrons.

    Last, if the work is not up to par, what resources does this 'traveling' welder have to make them good? If they aren't with a full time shop, working full time building quality boats(?) is that someone you want to risk working on your boat?

    The entire concept may seem ideal or valid from a first time builders' point of view, but I'm not willing to accept such an offer, and I've built many skiffs. If I was asked to head up the build, supervise and agree and approve all the stages of construction and then accept the welding fits and prep, that's one thing but much, much more expensive.

    My 2 cents, not to denigrate your proposal, but a caution that you locate this 'phantom' welder first, before you buy metal and plans.

    Cheers,
    Kevin Morin
    Kenai, AK USA
     
  6. rustybarge
    Joined: Oct 2013
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    Location: Ireland

    rustybarge Cheetah 25' Powercat.


    Thanks Kevin for that advise, which I will take!

    Alloy seems like such a fantastic material, light, strong, corrosion resistance; but I now understand why a commercially fabricated alloy hull costs twice as much as a steel one! It's such a pity as aluminium seems like the perfect choice for home builders, just as steel is; but taking what you have said I now have much deeper understanding of the technical problems encountered with this material.

    So it's either take out the cheque book and get the design built in a commercial yard in alloy, or build in plywood/epoxy which is what the plans call for. Compromises, compromises......

    Plan B is too buy a GRP hull moulding and rework it to suit the lines of the boat design, might work out much faster and stronger than ply/epoxy which is very vulnerable to scraping damage and delamination.

    There is never an easy answer, that's boats for you!

    PS: plan B 1/2.... Get the hull built in alloy by a yard, and build the superstructure in plywood or GRP myself; should save a bit of cash.
     
  7. yofish

    yofish Previous Member

    ^^^

    What Kevin said.

    Not to in any way discourage creativity and the desire to have a boat that you had a hand in building - BUT - don't even think about it! And if you still want to do it, please do yourself a favor and first get a Glen-L or other plan for an 8' dingy and make it from aluminum before you enter an unknown parallel universe. There is soooo much that can go wrong........If ever there is a craft that compounding errors can become remarkable, it is building small metal boats. Welding a boat up bares almost no resemblance to what most people consider 'welding'. Not that it is magical or beyond the ken but only because it takes not only practice but a background of extensive and expensive screw-ups to get good at it.
     
  8. Kevin Morin
    Joined: May 2013
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    Location: Kenai, AK

    Kevin Morin Junior Member

    Starting Out; Building in Welded Aluminum

    rusty, Yofish and I have made more mistakes than either can count, and so we raise a voice of caution, not refusal, not "you can't do it"- instead a voice that advises to try walking before applying to your Olympic try-outs.

    There are a few major issues, welding being the biggest hurdle if you're not a welder yet. But like all problems to be solved, step at a time exercises exist all over the net to help you decide which steps to take and then will review with you visual images of your progress! (weldingweb, other welding sites, many building sites, AluminumAlloyBoat.com and others).

    Therefore- it is a fact you can learn to weld aluminum: here's an example in real life. I know of a poster on the Weldingweb who was just learning, and he posted and practiced and posted and practiced and now this man is one of THE most proficient TIG welders of light alloys I have seen. Took him a few years to be as good it gets. He is not a boat builder but has become widely recognized as a craftsman who produces fine vehicles of his own preference.

    Next is Yofish's idea for building a smaller, simpler shape. Just like welding, or drawing or being an Olympic athlete, step at a time. I constantly teach myself new stuff', and I use the reminder phrase "easy little steps for muddy little feet" to recall I'm not going to be the best I can be unless I do the exercises, learn my ABC's and work upward in complexity.

    I think skiff building (or >25' boatbuilding) can be described similarly? Ever notice the modeling step an experienced builder like Yofish used to confirm his panels and shapes? (they're at the beginning of this thread) Well, here's a long time builder, more hours starring at the blue light than we can count, and what did he do? he modeled the new hull in scale sheet material.

    There's a lot to be said for modeling as a contribution to your own build. I know that may sound trivial but I do it myself, and know what I've learned/confirmed/adjusted in the last few decades.

    rustyb; you can do it, it's not just for the yards and existing builders, yes you can resort plastics, goop and dead plants but you could also spend your effort to learn the skills to build in welded aluminum: its purely a matter of inclination.

    If you want to do it, you can; but its likely your first 30'er will be a better boat is you make it your 4th of 5th aluminum hull.

    Cheers,
    Kevin Morin
    Kenai, AK USA
     
  9. rustybarge
    Joined: Oct 2013
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    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    Thanks Yofish,
    I already have some experience in fabricating steel, I've built and welded a 60' by 13' steel barge; but I realise that alloy is a different ball game: easy mistake to make..and I've already heard about hairline cracks in alloy boats that weren't welded properly,which turn out to be impossible to fix because of the contamination of the weld area.

    Alloy welding IS rocket science!
     
  10. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Nothing is impossible to fix. Only limiting factor is cost.

    Cracks usually occur in aluminium owing to poor fabrication practices, i.e QA. As has been repeated like a mantra by several, practice practice and practice.....and oh, do not ever use steel work fabrication methods on aluminium.

    Steel is NOT aluminium.

    Sorry no. Like most skills that one acquires, it takes time to learn and fully understand. It is only rocket science to thsoe that assume building/wedling is like cut-n-paste of text, for an easy life. Qualit...there are no short cuts. Sloopy work...ahh..anyone can to that! ;)
     
  11. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    Nothing is impossible to fix. Only limiting factor is cost.

    Cracks usually occur in aluminium owing to poor fabrication practices, i.e QA. As has been repeated like a mantra by several, practice practice and practice.....and oh, do not ever use steel work fabrication methods on aluminium.

    Steel is NOT aluminium.

    Sorry no. Like most skills that one acquires, it takes time to learn and fully understand. It is only rocket science to those that assume building/welding is like cut-n-paste of text, for an easy life.

    Quality...there are no short cuts. Sloppy work...ahh..anyone can to that! ;)
     
  12. rustybarge
    Joined: Oct 2013
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    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    Spending a few years to learn to weld alloy on top of the build project would put the finish date years into the future; in a couple of years I'll be 60, and judging by the number of my relatives and friends that have died in the last few years it would be tempting fate to take on such a long protracted undertaking.:!:

    The steel boat I built was totally built by me, everything from the cleats to the engine bearers was home fabricated; so shopping out the hull build to a yard goes against my principles, it also makes the finished boat into a massive loss making project with the expense of the alloy fabrication.

    Life's like a box of chocolates, or more correctly like designing a boat: every choice you make comes with a massive compromise!

    Estimate: 33' alloy hull about £2k/ft plus 20% tax. I'll stop there, the cost can't be justified when you could buy a GRP moulding at half that cost.


    Thanks for the advice, better to find out the facts before wasting money on the plans.:)
     
  13. rustybarge
    Joined: Oct 2013
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    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    In the end it all comes down to €€€€... Or rather the lack of them!
     
  14. yofish

    yofish Previous Member

    "and oh, do not ever use steel work fabrication methods on aluminium." Yep, that's pretty much the case.

    "Steel is NOT aluminium." And THAT is always the case!
     

  15. monomad
    Joined: May 2014
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    monomad Junior Member

    Webbey 64
    Hi all my designs have been boats that I have built. Style , shape are things that I work on to improve build time and give the customer the boat he or she wants. Yes there is a cost to every thing. Having a hull that performs well with any power plant will give you a wider scope of customers.
    If I was give anyone advice on what hull to get, fist of all what do you won't mouse the boat for and how fast you won't to go.
    You won't a workbook so sea worthiness, load capacity, not so much speed.
    Go for a constant deadrise hull and don't get a fine entry bow. A constant deadrise with a bluffer bow will give you the best performing hull with any drive. All so if you have lifting or planning starkes have them put on so they run from the transom parallel to the keel right up to the chines at the bow.

    One other thing to add to if you are thinking of building a aluminium boat. Yes the welding can be problem but also the sheet aluminium by that I mean some sheets of aluminium have a grain andwhatI call pre bend. If you can stand the sheet 6m , 1.2m on edge you can some times see by looking down and a long the sheet a bow in the sheet so by using that bow will make it easier or harder to foam the bow.
     
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