Welding the skin to the frames demystified

Discussion in 'Metal Boat Building' started by M&M Ovenden, Aug 31, 2008.

  1. Guest62110524

    Guest62110524 Previous Member

    can not understand how someone could make such a mess as you have described .

    this was my first ever, in the middle of a field, I got those huge plates on in one on bottom without forming gear, hadda do lots shriking in places I hate long keeled boats, I sailed this all over the Pacific, in strong over 35 kts she sailed on her ear, steel, never ever again steel:)I made lots of mistakes, taught myself as i went, took seven years Frames at 400 centres angles, bent with truck screw jack The belting was ss faced 1/4 inch , she could(because of tumble home) grind away at concrete walls all day
     
    Last edited: Jun 21, 2010
  2. Ad Hoc
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    Ad Hoc Naval Architect

    "...How many light fibreglass boats have survived pounding across 300 yards of coral reef in a big swell , or collisions with freighters, steel barges at hull speed, etc?.."

    I'm with MikeJohns on this. Since your statement above I can easily counter.

    I designed a catamaran with waterjet duct which was made 100% out of GRP 10 years ago. It was just glued into the vessel. It was for a LIPS 90 jet. The vessel is a 50m ally HSC catamaran.

    During a typhoon she was moored up, but an incoming ocean going liner some 4000 tonnes but couldn't manoeuvre correctly in the high winds and swell. Consequently the liner rammed the stern of the catamaran. The ally all buckled and bent in, the GRP duct was intact not a crack, other than slight crack on a joint owing to the buckled ally pushed one of the frames which is was glued to!

    So, without real hard evidence one anecdote is as good as another. Since what ally scantlings did the vessel have, and what about the GRP ducting, what were they designed too etc??

    Without such facts, one story is as much as the other and about as helpful as a chocolate tea pot!
     
  3. tazmann
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    tazmann Senior Member

    I can Stu, I have had the misforune of working with a few so called welders. Perfectly capable of burning rod but cant read a tape,level or square. Dont seem to care and everything is close enough. Wont follow simple instructions or a plan let alone a welding sequence. Take someone like that building a boat and it will turn out a nightmere.
    Tom
     
  4. welder/fitter
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    welder/fitter Senior Member

    "can not understand how someone could make such a mess as you have described ."

    Though I know nothing of the original builder of the boat, I'd make an uneducated guess that it was someone who took a weekend welding course, bought a set of plans & went to work.

    Like Tazman says, there are some "professional" welders & fitters out there who seem to think that "eyeballing" and "close enough" are the mark of a "veteran tradesman". While some instances may call for a degree of eyeballing, whenever the opportunity exists to take accurate measurements or follow accepted procedures, why would anyone stray?

    The new owner of the boat is well-versed in joinery & has some experience working on ships, so there is a chance that he'll succeed. Then again, he did feel that I was being too picky with my frames alignment, so who knows. Yeah, I'm a perfectionist, which can piss some people off, but I always go back to the maxim that "it takes the same time to do something well, as it takes to screw it up."
     
  5. Guest62110524

    Guest62110524 Previous Member

    for as long as I have known you guys I have always said, boatbuilding is a trade, sure it is made up of other elements, but essentially is a trade,, where it all starts wrong is that no full size lofting is done, everything has to be PROVED on the loft, UNLESS , your cad designer is known to you , even then you must Make up all the frames on a full sized body plan, mark the wl ,s on the frames and buttocks on the beams, then you can keep a close check when setting up
    Ah well nuff of that:)
     
  6. Dudley Dix
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    Dudley Dix Designer

    This is a general response to various posts in this thread.

    1) When I use floating frames on a steel design it is for sides and most of the bottom. The centreline has integral tanks that form part of the keel support structure and the floating frames stop short of the tank sides, so the heavily loaded central area is solid to prevent buckling under ballast loads. I don't use floating frames on aluminium designs.

    2) I am with Brent on the issue of steel boats surviving groundings on reefs, rocks etc that no composite or wood boat will survive. Many of my steel boats have gone onto reefs or rocky shores in hurricanes or simply due to bad navigation. Not one of them has been lost nor had hull damage that needed more than straightening. One of my very solid sandwich GRP boats did the same thing and only survived because of lucky coincidence of low tide and available materials to repair her before the tide returned. Why should we consider a metal boat as being structurally unsound if it dents in a situation that destroys boats built from other materials?

    3) I quizzed someone (who shall remain nameless) who was onboard "Imagine" when she suffered her serious structural damage. My opinion is that there was considerable operator error involved in that incident. Conditions were such that she should not have continued sailing but should have hove to until the water or wind settled rather than sailing downwind at speed into big and very confused seas. Consider that the damage included slamming dents and collapsed frames at both bow and stern as well as compression wrinkling of the deck. She was slamming at both ends simultaneously and bent as a result. We all see photos of BOC and Volvo boats flying off waves, sailing to windward, which may give bow damage, not stern damage. This damage was done sailing downwind.

    I wonder if anyone on this thread has experienced slamming of any consequence under the stern of any boat on which they were sailing, even one that is light and fast. I have sailed light boats many thousands of miles and not felt more than an occasional small slap under the stern if a wave hits under the quarter when power-reaching. Here we have a boat that was slamming at both ends so badly that serious structural damage was the result, yet they were still sailing.

    Conditions were not normal, they were quite extraordinary. There has to be a time when any boat must be stopped for the sake of preservation of boat and crew. This was such a time. I would never sail a boat downwind into the conditions that were described to me.

    The "Imagine" damage was the prime reason why ABS stopped development of the rule. I guess that they did not want the hassle of it. It resulted in the rule coming under massive fire for being inadequate. My opinion is that the rule is really very good for the boats that most of us design but very fast flat boats like the BOC boats behave so differently at speed that they fall way outside of the forms used for the model tests on which the rule is based.
     
  7. Guest62110524

    Guest62110524 Previous Member

    no I have never sailed on a boat that slams at stern, however I believe boats, in the interest of SPACE AFT, have become too full, carry beam too far aft, , with result that quartering and stern seas seas push the boat around too much
    I remember being larfed at when I suggested in here, that a boat should be able stand a blow from a big hammer and suggest that those doing the larfing, had sailed very few or calm miles, this is essentially the test Greens did on the big Tripp design yacht, think was Shamon, cant be sure
     
  8. Dudley Dix
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    Dudley Dix Designer

    Wide sterned light boats are easier to sail downwind. A boat with narrow stern pulls up a quarter wave, which pushes on one side requiring a lot of helm to counteract. That results in over-steer then the quarter wave pushing on the other side and the process starts again in the other direction. A broad stern on a light boat makes very little quarter wave and helps the boat to have finger-light steering, going where the bow is pointed.

    This applies to to a hull with clean lines and an easy run-off of course. A fat stern is something else and neither fast nor nice on any boat. A broad stern is also slow on a heavy boat.

    The problem is not that the boat is given a wide stern for space but that the wide stern is designed in for performance but gives so much space aft that owners pile in heavy stuff into the worst position that it could be placed.
     
  9. tazmann
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    tazmann Senior Member

    Very nice transom Stu. Given me some ideas.
    Tom
     
  10. Ad Hoc
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    Ad Hoc Naval Architect

    whoosh
    I'm confused.

    You have cropped the picture, as you say you don't own the rights. Yet you say you put lots of thought into the transom.

    Which are you referring to when you say you put lots of thought into the transom, you designing the transom, or you building it?
     
  11. Guest62110524

    Guest62110524 Previous Member

    this is my last build, I had not really become accustomed to the pilot, B AND G when I delivered her across Tasman, the run aft was great, she is fast not heavy but seemed she screwed a bit
    I have cropped to protect rights, I do not own design
    I put lots of thought into transom, but as you know, it is very difficult sell expensive smaller yachts
    had to delete body plan sorry
     
    Last edited: Jun 21, 2010
  12. Ad Hoc
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    Ad Hoc Naval Architect

    whoosh

    still not clear...did you design the transom, or, build it, or both?
     
  13. Brent Swain
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    Brent Swain Member

    Welding skin to frames

    I tried grinding out a few of the longitudinal welds and they were full of slag. It would be a major job doing the whole hull , far more than doing it from scratch, as there was a lot of seam, being multichine with the chines running full length. I can't imagine how they could screw it up so badly.
    Brent
     
  14. tazmann
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    tazmann Senior Member

    Well I recieved one of the bonus Cd's today and it has some of the plans and patterns on it for the Roberts 345. Bit confusing but from what I can tell so far the frames are 2"x 1/4" flats and the stringer-chines are 1" x 1/4" flats with
    1/8" hull plating. stringers and chines setup proud of frames a bit and recomended only weld to frames where touching skin except for where internal tankage is then weld fully to make water tight.
    Working with this light of material I could see how it could be made a mess of pretty quick from an unskilled welder.
    Tom
     

  15. Ad Hoc
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    Ad Hoc Naval Architect

    3mm plate with frames/stringers at 6mm...if not done carefully the welder will just over cook it all too...he'll see 6mm, lots of 6mm in his mind....too much heat, too much weld bead etc too...
     
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