Adding vee to cat hulls

Discussion in 'Multihulls' started by mikereed100, May 22, 2011.

  1. sabahcat
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    sabahcat Senior Member

    Agreed
    this would probably be easier
     
  2. Alik
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    Alik Senior Member

    Guys, what You suggest is secondary bonding in slamming area, with possible loss of watertight integrity. I won't do that.
     
  3. sabahcat
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    sabahcat Senior Member

    So if one of your vessels sustained damage in a slamming area you would throw that vessel in the bin because it cant have secondary bonding in that area, even though it probably be getting done with epoxy, which will in some cases be superior to the original polyester build?

    Crowther has been doing major cuts for many years on many vessels with no issue.
    The southern ocean 50's (now 58) had several feet added in the center of the hull length and the underwater shape removed from bow and stern with new section's added in to improve performance

    I have seen power cats have 20 feet of the underwater area removed and replaced with improved sections

    I have seen 60 ft sailing cats have entire bows removed back to mast b/h and new more buoyant, longer sections added.

    None of these vessels have had any secondary bonding issues to my knowledge.
     
  4. Alik
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    Alik Senior Member

    Damage is another story. I would not cut it for purpose.

    It is easy the design properly from beginning, and not to involve in amateurish modifications later.
     
  5. HakimKlunker
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    HakimKlunker Andreas der Juengere

    I see your point, Alik. What would be your opinion of bridging the connective laminate with a wide overlap and clearly more laminate than required in theory ( to build-in a safety factor) Even when doing so, the extra weight cannot be as much as leaving the former structure inside? I mean: More weight will lead to more draft. That will cause higher bottom pressures and also increase stresses on the upper girder (hull/deck joint)
    One other option is maybe to carry the replacement up; far enough to be away from the high bottom pressure area?
    When you say 'I won't do that': Does that mean that you would favour a new skin over the old skin?
     
  6. HakimKlunker
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    HakimKlunker Andreas der Juengere

    There you are perfectly right. But unfortunately, the baby was born already. The concept of 'unworthy life' cannot be applied here...
    Mike: Would you scrap your boat? It is indeed one logic option
     
  7. Alik
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    Alik Senior Member

    German Lloyd requires 115% of laminate for secondary bonding.
    Lloyds accepts secondary laminate with epoxy resin.

    But the quality of joint depends greatly on builder and climate conditions. In Thailand, it won't be dry enough and filler would be used as major material for such work :)
     
  8. HakimKlunker
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    HakimKlunker Andreas der Juengere

    Such as TALCUM oder COTTON SHRED :D
    And I am sure that we both think of the same persons now :p

    At 'dk compostites' (Malacca, Malaysia) the entire laminating section is separated and has a climate control (temperature, humidity). I would say that conditions there are reasonable.
    Would you know if someone tried similar on a smaller scale? Like: laminating in a sort of 'tent' with a de-humidifier?
    I only saw the opposite solutions: the extreme has been a canvas sunshade on bare sand ground.

    I presently work in a somewhat open shed, but entirely wind- sun- and weather- proof. There is an electronic hygrometer and humidity often drops as far as 50-55%. Above 65% we never touch resin jobs and the drums remain closed, the same when clouds promise rain later. Temperature sometimes causes issues when areas to work on are big enough. Still, a 3 men team can easily handle two (relatively simple) layers of 10m2 plus a vacuum. Provided, one plans the workday properly, everything is so far cured before humidity rises again during the night. We also produce identical small sample laminates each time and inspect them on a regular base.
    If this is not enough, the conclusion must be: do not build boats in tropic regions.
     
  9. Alik
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    Alik Senior Member

    Of those we work with here AusThai, SEAT have fully air-conditioned lamination rooms. Some others just cover mould with film and install air-conditioner inside.

    I wonder if it can be done in Satun; I don't know any reasonable FRP builder there. Of course, many would claim they are 'builders' :D Also consider that average Thai lamination team is not skilld to work with epoxy.
     
  10. HakimKlunker
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    HakimKlunker Andreas der Juengere

    My 'neighbours' in Satun work in relatively open conditions. But my information so far is that in GRP they only offer repairs. I met a few owners who had repairs done there and they were basically happy. However: I'll be there next week anyway. Perhaps there is something to report then. If you need a REAL Pro, you need to look in Langkawi: His name is Hakim.
    Heh heh heh
     
  11. sabahcat
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    sabahcat Senior Member

    Still, its a secondary bond in a slamming area
    damage must be cut out and repaired properly, not just filled up with snot and glassed over

    Some of these vessels I talk of were 32 footers and then after a few decades of hard sailing turned into 37 footer.

    Others were 35. stretched later as above

    Others started out as motor-sailors and again after many years were modified into longer passagemaking powercats.


    All were designed properly at the beginning for their intended purpose and did it very well.
    But then their intended purpose changed.

    Amateurish?

    Designs done by some of the worlds most respected multihull designers and modified by some of Australia's most respected multihull builders?

    And your claim to fame is ...........
     
  12. Alik
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    Alik Senior Member

    Hmm, sorry to say, but most of Australian pleasure multihull builders and designers never desigend boats to class/certification. If You extend boat by 3-4' and increase its weight, the scantlings should change requiring heavier laminates and stiffeners everywhere. This would be a substandard boat once modified.
     
  13. sabahcat
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    sabahcat Senior Member

    Of course they dont
    To do so makes them overly heavy and makes them sail like pigs

    Look at the charter-boat industry for proof of this


    And yet they are out there working just fine, winning races and logging up countless sea miles with happy owners on board.

    Proof is in the pudding me thinks.
     
  14. HakimKlunker
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    HakimKlunker Andreas der Juengere

    Sabahcat: You will not believe what sort of gangsters are freely walking around and claim to be boat builders. Here; there; and also in your country (in my original country as well of course);
    If you want some names: ok via e-mail or pm, because they are mostly violent persons at the same time...

    Certainly there are also serious players; but everyone is only as smart as of today. Tomorrow, something new may turn up.
    Some of my (our) customers put their life into my hand's quality. That is quite a responsibility if one takes his job for serious.
    But to discuss that further, we better open a new thread.
     

  15. sabahcat
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    sabahcat Senior Member

    I agree
    But I did qualify my comment with
    But allas, even they were described as amateurish
     
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