DIAB Foam

Discussion in 'Materials' started by MarineSurvey, Sep 23, 2009.

  1. MarineSurvey
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    MarineSurvey New Member

    I wanted to share an experience I had with DIAB foam and their processes: I am an old boat builder in China at present. I was called and asked to survey a non complete sailing vessel in China. The vessel is a 50' catamaran. The process used for construction was and is infusion. Please look at the pictures posted and you will noticed many areas of dry-glass indicating a failed infusion. The builder has given permission to use the pictures. The builder contracted DIAB to come and give training and instruct workers on the infusion process. DIAB set up and ran this class and actually did the infusion on this deck (noted in the pictures). The builder contacted me as they were apprehensive as to the end product. According to DIAB this is a easy fix. When I contacted them ask for help no call back from them. I had the gel-coat sanded off most of the deck and that is when you see most of the problem. Has anyone had similar experiences?
     

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  2. Landlubber
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    Landlubber Senior Member

    I have had dealings with DIAB in China (Shanghai specifically), yes they do come and do in house training and instruction, and yes there are stuff ups, but that is not the fault of the DIAB crew, it is rather the standard Chinese way of doing things "Their way"...they have some sort of desire to show us all how wrong we are and how right they are....this is typical of the results....I personally can only thank DIAB for all the help and genuine support that they have offered my work collegues and myself whilst "trying" to teach locals the way it is.
     
  3. rwatson
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    rwatson Senior Member

    If this was a DIAB demonstration, and they got it wrong - what are the chances a new user would get it right ?

    I have selected the DIAB products for my next project, and they state in their literature that I can expect a good result even by hand layup using their cores.

    If this happens during infusion, I am a bit worried about my first effort of using core material with hand layup methods.
     
  4. Alik
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    Alik Senior Member

    Was it Prout catamaran?
     
  5. MarineSurvey
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    MarineSurvey New Member

    Clarifications

    Thank you to those who have replied so far. To clarify, it was actually DIAB who conducted the actual infusion, not the workers at the plant. I have seen Chinese workers who are unwilling to change their ways as well, but that wasn't the case this time unless it was DIAB's employees (including their technical director in Asia) who were unwilling to follow DIAB's plan.

    Rwatson, I can understand your apprehension, which is why I posted this message.

    As a further note, DIAB's Asia office contacted Winfair last Friday and said that a DIAB manager from Sweden would contact Winfair and then fly to Winfair in China to resolve the matter. In what seems to be a pattern, they have not done so.
     
  6. Alik
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    Alik Senior Member

  7. themanshed
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    themanshed Senior Member

    This is why I like Bagging better on a hand layup. I know it is more work but it's not hidden.
     
  8. rwatson
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    rwatson Senior Member

    I am confused - "what is "bagging better on a hand layup" ?

    Can you explain a bit more please ?
     
  9. Landlubber
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    Landlubber Senior Member

    rwatson,

    I do not agree entirely with that statement, but I do understand what he means.

    Vacuum bagging is done with the resin already rolled (or in th ecloth in the state of prepreg), so there is no risk of voids as the resin is done by hand and eye manually. Resin infusion is done after set up, any faults along the process from the start are not all that simple to either see or fix as you go.

    However, like all building processes and techniques, it is all up to the operator....even ferro built boats are exceptionally well done if exceptionally well done......
     
  10. rwatson
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    rwatson Senior Member

    Thanks for that landlubber - it just needed translating.

    Time and efficiency permitting, doing the hand impregnation, and then vacuum bagging *has* to be more reliable. Look at all the shenaningans you have to do with extra taps, inlet hoses etc to control the infusion on a dry stack of materials.

    You cant always see what is going on under all the layers during infusion, so if you have done a pre-impregnation, there is a lot of worry removed.

    To quote Mr Roger MacGregor when asked why he doesnt use foam core on his boats
    "Foam cores are also widely used for stiffening hulls, however, they offer less than 200 pounds of adhesion per square inch. That is not much better than rubber cement. "

    And thats a *good* layup.

    I will be starting some test panels with foam soon - it will be interesting.
     
  11. Alik
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    Alik Senior Member

    I don't see much advantages of infusion in Asia where labor is still cheep. Yes, some boats are built here with infusion (including some our designs), but this requires more expensive resins and fabrics, but still depends on human factor and staff training. I have seen few unsuccessful infusions here, however the customer will never know what the builder did with unsaturated areas. I won't buy a 50' 'hi-tech' cat with such 'surprises' in the structure.

    For my new cat (that is in construction now) we use DIAB H130 foam, but builder just vacuums it to the bottom, so all process is under control. Rest of hull and deck areas are in HexaCor that is also vacuumed. All lamination is done in by hand lay-up, in multiaxial fabrics.

    In Asia, ‘infusion’ sometimes if is a kind of fashionable marketing trick, often not justified to the purposes and realities of build.
     
  12. Landlubber
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    Landlubber Senior Member

    Alik,

    All very true, the Asian example of anything high tech is in many cases " just a cardboard cutout of the real thing".....I have seen it so many times, looks real, smells real, tastes real (did you know that the Chinese can make eggs), but it is not real, caveat emptor.
     
  13. themanshed
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    themanshed Senior Member

    Resin Infusion is where you have your dry laminated in place in a vacuum bag. Then from the vacuum you draw the resin from one end through your lay-up to the other end into a run-off pot. It is the vogue way to do the wet out. I’ve seen it work and I’ve seen it with disastrous results. The problem is that you cannot “see it” so you hope that Murphy does not bear his ugly head. The problems that I’ve seen are dry spots as with this post or pooling of resin, which causes a brittle or heavy spot. If done correctly - without any problems they say it is fast and good.

    What I’ve found is a good glass man can work himself out of the corner with problems. But with this technique you do not see the problems they show up later. Prepreg is nice but who has the ovens, and in a tropical climate Prepreg needs to be frozen. For the price I can get Carbon Fiber at $18 / yard and do a hand wet-out with West Systems then Vacuum Bag it. At least I know the glass is wetted out and the extra resin is sucked out into the bleeder cloth in the vacuum bag process and tossed out with trash.
     
  14. themanshed
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    themanshed Senior Member

    "Foam cores are also widely used for stiffening hulls, however, they offer less than 200 pounds of adhesion per square inch. That is not much better than rubber cement" Quote

    Not sure what adhesion quality he speaking of but the foam core is used to physical separate strong laminated skins and transmit shearing forces across the sandwich. It has an I-beam effect usually measured in Tensile strength, Tensile Modulus, Ultimate Elongation, and Shear Strength.

    An example if you took a solid glass skin and called that "T"

    Then make a composite cored lay-up twice as thick as "T" and split the glass layup half on top and half on the bottom with a "T" thickness of a core in the middle. It would be 700 times stiffer, 350 times stronger and only weight 3% more.
     

  15. rwatson
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    rwatson Senior Member

    "Foam cores are also widely used for stiffening hulls, however, they offer less than 200 pounds of adhesion per square inch. That is not much better than rubber cement" Quote

    "It has an I-beam effect usually measured in Tensile strength"

    Yes, that is a good explanation.

    I think what he is getting at is that if either skin separates from the foam, the I- beam is considerably weaker.

    The propensity for the gap to be filled with water, (especially of the break is caused by violence), cant be good either.
     
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