Not another one!!

Discussion in 'Metal Boat Building' started by Welder4956, Dec 28, 2008.

  1. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect


    Firstly I should point out that if you try and weld and fabricate aluminium the same way you do a steel structure, you’ll make a pigs ear of it. The two are chalk and cheese. Steel being bash bash bash all is ok, whereas as ally is to be treated with kid gloves. It is like comparing a formula 1 racing car to a day to day saloon car.

    1) Work hardens. This only occurs during manufacture, not welding. The work hardening is simply using mechanical means, by the use of slip planes within the alloy to dislocate and move the crystalline structure closer together. In other words it makes the movement of the crystal matrix under strain more difficult, thus increasing the properties. An “O” temper for example has minimal work hardening and as such is easy to fabricate, roll, bend etc. This is reflected in its “yield” strength of around 120/5MPa. Whereas “H2” temper for example, is heavily strain hardened. As such is much more difficult to bend and fabricate under the same conditions as O-temper, has a “yield” of around 240MPa. Only when you weld H2 temper, locally, will it revert back to O temper.

    2) Yes it does distort more. This is where one must exercise caution and balance the welding. However you can weld 2 identical structures under same conditions and each will distort slightly differently. Good practice and procedures minimise this to be just a minor inconvenience.

    3) Welding controls. This is really down to the skill of the welder, if I understand what you are saying correctly. Not everyone can weld ally very well, it is an acquired skill. Also, the new range of sets such as those from Fronius are serious sophisticated, these help lots too.

    4) Electrolysis. This only occurs if there bimetallic corrosion can take place. Such as bare copper pipes allowed to drip condensation onto the plate etc. This is generally poor design or incorrect procedures during production.

    5) Stainless fittings. If they are high quality stainless, and the fittings are not constantly being scratched, there should not be a problem. I’ve used SS fitting for many years on ally, with no serious problems. Usually basic maintenance will prevent any occurrence of corrosion. SS has a tough oxide layer, rather like Ally.

    6) I’ve been all over the world overseeing repairs. Oddly enough the worse place I ever came across for getting qualified coded welders was in Barcelona. Had to train up 2 local guys to assist on a job. However if you are talking about actual repair of the job...again, this is a specialised skill. Being a good ally welder in shipyard is not the same as being a good ally welder on repairs in ports or elsewhere. Not everyone can do it.

    Maybe this will give you some thoughts?

    As for Cor-ten, it has better corrosion performance compared to other high-strength steels. However, when left unprotected it rusts uniformly until the action stops after 1~2 years. After which no maintenance is required. It is slightly more nobel than mild steel so being slightly better protected underwater. For example, if the shaft is a low alloy steel on a mild steel boat, the difference in potential is not enough to prevent rusting though. Its prime attraction is slightly higher strength and a lower rate of rusting, but of course at a cost…so is it really worth it. Better to put the money into blast cleaning and epoxy painting.
  2. Welder4956
    Joined: Dec 2008
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    Location: Tauranga

    Welder4956 Junior Member


    It has been a little while since i last thanked you for your valuable input and offered some insight into how my quest is going.

    I recived my study plans from a handful of designers and have looked long and hard at these.

    From talking to various individuals and reading material we have shortened the the length of the vessel and lightened it by going with Aluminum.

    I am now getting my suppliers to give me quotes on materials and profile cutting services.

    I must add that the VDS study pack was exceptional and was most insightful. compared with a couple of the other i received which were paled somewhat in comparison. Not to say there were not sufficient information but when placed next to the VDS set well....the bar was set high by these gentlemen.

    Now that i have reduced the size of the vessel it has opened up a couple of designers that i could not use for the larger size so i will need to look more at the available shapes and configurations.

    My welding plant has been ordered for the end of the month and once i get plans and material should be looking to start construction August.

    But as they say anything could happen in the next half hour.
  3. Guest62110524

    Guest62110524 Previous Member

    congrats my boy!! a wise decision, and VDS always sell well Mico Metals have keen prices and branch in your town
    Always get you mill cert. and keep the cert numbers against where you place the plate on the boat
    Will follow with interest
    to those who posted strange things of myself, I start to put my gallery together
  4. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    then wait until you get the complete set of plans with booklet and literature that goes with it - you even get a metal plague with your design number (making your plans legitimate) and other data left open such as builder, date etc. This you can mount at a convenient place in the boat. I usually mounted the plague at the nav station...

    I said it before - vd Stadt is my favorite plans to work from:cool:
  5. Ilan Voyager
    Joined: May 2004
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    I agree totally with you, Wynand.

    Van de Stadt is Dutch high quality: that means all...Some of my acquaintances built VDS boats with always the same results; very good boats, cleverly engineered, built by the simplest ways with so outstanding plans that you want to put them under glass in your living room. It's money well spent.

    For those interested I give some links;
    Two methods of boat building used by VDS
    wood core
    quick assembly steel or alloy
    Very good method for metal boats. Fast and simple. I have used a similar method for patrol and fishing boats. A similar method can be used with polyester boats.

    A digression: when it's possible the use of good prepainted steel plates saves a lot of money of sand blasting and finishing. In France I've used prepainted Marinor (a steel with exceptionally easiness to form and weld). It's worth the extra cost of material because you save more while finishing the boat.

    Out of this thread but interesting; (in dutch)

    About the freestanding mast promoted by VDS.
  6. Guest62110524

    Guest62110524 Previous Member

    AD HOC

    If you have to bash bash bash either, you are doing something very wrong, you should be able to stretch and form so that the plates fit with no struggle at all Good steel building requires I would say more skill, even though I build in. The welding requires more skill
    I have no idea where you got the idea alloy distorts more than steel, it is in fact quite the opposite, the reason being it soaks up heat faster
    having built many of both and 32 aluminium vessels myself, I assure you this is not the case.
  7. Guest62110524

    Guest62110524 Previous Member

    you have to remember Island voyager that ALL the knockers of al al, have never used it
    I wonder why the worlds billionairs get their vessels done in Al Al?
    I know of one yacht in perfect condition, MORAG MHOR, built 1959 in UK saw here in St Maartin not so long ago
  8. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Well, clearly you have been using a very different form aluminium than everyone else when welding boats together.

    The coefficient of linear expansion of aluminium is 24 x10-6 C-1
    for steel it is 11 x 10-6 C-1

    In other words aluminium expands more than twice than of steel in one direction.

    When talking about thermal expansion, ie volumetric, the ratio is still approx 2:1, that being 69 x10-6/K to 32 x10-6/K.

    So when you heat up aluminium, the heat travels faster and the alloy expands and moves to accommodate the increase in volume owing to the heat much more than steel.

    As for the bash bash comment, you clearly didn't read the whole text and its meaning.
  9. Guest62110524

    Guest62110524 Previous Member

    to dix
    the boat here nimbus 2 has a below wl pl of 8mm, that is equiv of 2.5mm steel so strong is not necessarily heavy
    the weight of this 54 footer 19tonne at departure
    to ad hoc, can you post what YOU HAVE BUILT, i SEE NOTHING, in your gallery
    I know Wnyard is real, but as for some of you that have knocked me?
    ad hoc, you are totally and absolutely wrong to demonstrate simply lay 2 plates on ground make a 12 foot long butt, in steel without peining first, in 4mm plate, watch the spagetti mess you arrive at
    now take two alloy and do same, backstepping , just the speed alone which is many times faster, in the weld, ensure far less buckling
    Until you prove who you are then why should we listen? I have given you positive pts for some of the things you wrote, others like your post on 6061 was totally wrong
    I can tell by the way you write, yours is a paper theory, lets see what you did please and tell me who do you work for and do you have welds tickets?
    Last edited: Jun 21, 2010
  10. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect


    So are you saying that aluminium does not have 2 times the coefficient of linear and thermal expansion of steel?

    Since you feel you know more than the known laws of physics. Here is one in your "language": so perhaps you may like to read:

    Simple quote
    "..Aluminum expands more than steel as it heats up.."
  11. Guest62110524

    Guest62110524 Previous Member

    ad hoc, I notice you have not answered my questions
    I no bugger all abt science, all I know is from 35 years HANDS ON is that when youi weld a piece of alloy the area all becomes warm quickly, that is because it conducts heat, therefoire local HOT spots are coolwd evenly and quickly, in realtionship to steel , where you weld and the area around stays cool, the weld is hot, the area that is hot shrinks down, far more than in alloy, so welding flat plates as per a b/h you would either pein the seam area first or after
    Are you a student, a new grad? because youa re talking like someone who is all theory, , and thsi is NOT meant to insult, its just that I have worked with so many people with bits of paper to their name who quite frankly know zilch
    It would be good if you could answer the questions, tell us what YOU have built, and who you have worked for. Put a name to your posts, mine is Stuart
  12. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect


    Clearly you prefer the "mine dog is bigger than you dog" discussion. Since showing pictures of boats does not convey the quality of the fabrication, only that a boat has been built, nor does it convey any understanding.

    The position you take that you dispute the fact that aluminium expands and moves more than steel, despite the known laws of physics to the contrary, highlights this point. As such our foundations for a discussion are no longer valid, as your points of reference are diametrically opposite to that which is well established by many independetly.
  13. Guest62110524

    Guest62110524 Previous Member

    well that says it all,
    you have not backed your considerable words with any proof, clearly IMO you have just copied stuff from a book, a pic is worth a 100o words. And really what a person has done is what counts, words mean very little
    Your profile is empty, you know nothing and it shows, never mind, you are keen perhaps one of us builders may give you work, and teach you to weld, form stretch , and in general build a BOAT, but you really should stop giving bad info as people who know little will believe you
  14. Welder4956
    Joined: Dec 2008
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    Welder4956 Junior Member

    Trying not to add fuel to the flame but to answer the question posted to me by whoosh.

    I have been welding for the past 18 years and i have welded all manner of materials. I have fabricated from a many different items from Exhausts to missile parts and the odd ship or 2. I shall endeavor to explain what i believe through a 5 year craft apprenticeship rather than a university paper.

    When you weld a material you create a HAZ(Heat affected zone). Now with steel this remains relatively small because the heat conductivity of the material is lower. This means the steel will distort only about the HAZ thus your comment on hammering and peining. With Alloy the conductivity is far greater and the heat dissipates throughout the entire part (soaks up as you put it). In fact the furthest point will heat faster than the welding area. As this is the case more heat is required to maintain a weld pool and in some cases a pre-heat. The other issue with alloy is that it has 2 melting points in the same plate. That of the Aluminum and that of the Aluminum oxide which forms on the outer 2 microns (about 1/50 of a thou for all you USA types out there) of the plate. Because the core of the material melts at around 800Deg and the oxide at around 1300Deg the core will expand faster than the oxide. This causes the dendrite crystal formation to become restricted and begin to distort the structure of the oxide layer. For material to normalize it is best to cool naturally and return to an equiax crystal formation. I beleive these properties are what leads to work hardening and a lack of elastic property in the material. Try welding up a box made from steel and then the same from ally you will see what i mean.

    Now as a famous engineer once said "You canny change the laws of physics captain"

    Boffins feel free to add the science bit to that.

    Now that was what i remember from 15 years ago studying city and guilds in weld metallurgy. I have not looked in a book. But i can if we need to.

    If you recall this was not a thread about welding the boat. It was about which designs to look at. Not arguing with any of you as it is pointless and time consuming. Have asked for quotes on materials from MICO and Ullrich.

    Should this thread be later read by someone wishing to know the properties of the materials and their weld ability i would suggest they visit either the TWI web site or both of which are frequented by the best in the industry of welding. Not necessarily people who have only ever welded boats.

    Whoosh your input has been thought inspiring to say the least but not always all together correct but not without substance. But without you this thread may have only been 2 pages long and where would the fun in that be:p

  15. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect


    Not bad :)
    Only 2 main comments.
    The oxide layer must always be buffed off when welding ally, which i'm sure you know...for said reasons as well as inclusions etc.
    "..For material to normalize it is best to cool naturally and return to an equiax crystal formation. I beleive these properties are what leads to work hardening and a lack of elastic property in the material..."
    Work hardening is by mechanical means not by heat. Mills roll the plate which become more and more flat, as well as increasing the mechanical properties. That is why rolling H116 plate for shell plate is so much more difficult than O temper. H116 is work hardened, O-temper is not. (well just minimal for straightness etc). Rolling, bending forming bashing with a hammer etc when fabricating increase the work hardening further. The heat affects the working hardening, ie it releases the 'locked in strain' created by the mechanical process.
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