Advanced Commercial Aluminum Catamaran

Discussion in 'Multihulls' started by anthonydimare, Aug 7, 2015.

  1. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    I think you need to recheck the rules.
     
  2. TANSL
    Joined: Sep 2011
    Posts: 5,805
    Likes: 204, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    SOLAS?, I dont think so.
    In any case, an explanation of why you consider it necessary to be very interesting and very formative.
    I sure am able to recognize my mistakes, if any.
    Thanks.
     
  3. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Tansl

    It is not the matrix of boundaries to look at, it is the understanding of what SOLAS defines as "non-combustible"....i.e place the material into an oven at 750deg C and must not burn or give off vapours.

    The only way we have been able to satisfy this (remember both sides for internals) is with an A60 boundary to satisfy the time v temp requirement when exposed to 945deg. C.
    We did an half composite and half ally boat..all the composite has A60 boundaries.

    We even had to do an ally boat like this about 10years ago.
     
  4. TANSL
    Joined: Sep 2011
    Posts: 5,805
    Likes: 204, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Ad Hoc,
    You probably know that a structural element A-60 should be made of steel (among other requirements) and stand the test of fire for 60 minutes. Probably you know that there are elements type A-30 or A-0 and even "B" and "C".
    Nowhere that I know (that's why I tell you to explain) it is said that the whole hull must be A-60.
    A boat of aluminum or GRP has very difficult (impossible) to meet the "A" class fire because, as I explained above, the Class "A" means that the structure is "steel". So speaking of class "A" or "equivalent".
    I think it's very commendable the work (unnecessary) you did with that ship but that has nothing to do with the claim, which is what I question, that the whole hull should be A-60
    Happy to help others.
     
  5. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,916
    Likes: 339, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Amazing how Aluminium burns once it gets started, and with tremendous heat......it is a solid rocket fuel after all ! And it is claimed the Twin Towers only collapsed because of the fierce heat of the burning aircraft aluminium that weakened the steel structures sufficientlt. The other combustibles would not have burned hot enough to do it.
     
  6. hump101
    Joined: Oct 2004
    Posts: 261
    Likes: 14, Points: 18, Legacy Rep: 58
    Location: Brittany, France

    hump101 Senior Member

    Most grades of marine aluminium are alloys, not pure aluminium, which is very flexible and weak. 6000 series is alloyed with magnesium and silicon, 5000 series just with magnesium.
     
  7. hump101
    Joined: Oct 2004
    Posts: 261
    Likes: 14, Points: 18, Legacy Rep: 58
    Location: Brittany, France

    hump101 Senior Member

    The RNLI lifeboats in the UK are sandwich throughout the hulls, as are quite a few others. Most displacement hulls are single skin, but sandwich is used more for higher speed planing hulls as it reduces issues around panel stiffeners on a single skin subjected to high pressure. Improvements in resins has greatly reduced delamination issues.

    Around here we're seeing more GRP fishing boats now in the 10-20m range, mostly steel above that, and rarely an alloy boat. I can't recall seeing a pilot boat that wasn't grp for a long time now (80's, maybe?). I do remember seeing a lot of alloy boats when I was in Australia, but that is also many years ago. The big difference is the commercial boats here are slow, due to the North Atlantic weather, so little benefit in moving away from steel.
     
  8. Jetboy
    Joined: Feb 2012
    Posts: 278
    Likes: 6, Points: 0, Legacy Rep: 65
    Location: USA

    Jetboy Senior Member

    Isn't there a study group at IMO working on a new set of guidelines for allowing the use of FRP in commercial ship structure? Obviously there are many 20m size FRP commercial use vessels, but I assume this would allow for use in the full range of size.

    The calculated payback for a commercial cruise liner was calculated to be only 2.5 years based on the lower fuel use and additional cabins that could be added due to the reduced weight. Lots of military ships use composite super structures now. It would seem that it's just a matter of time before the money pushes policy into allowing composite structures on the full range of commercial ships. I suspect hulls will follow.
     
  9. Leo Lazauskas
    Joined: Jan 2002
    Posts: 2,696
    Likes: 146, Points: 63, Legacy Rep: 2229
    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    Thanks for clarifying that. I wasn't sure if you were referring to aluminium, alloyed or not.
     
  10. brian eiland
    Joined: Jun 2002
    Posts: 4,788
    Likes: 157, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    This is a prototype Trimaran warship (Independence-class littoral combat ship) for the Navy that experienced quite a number of problems with galvanic corrosion,...and this from a builder who had considerable experience with alum construction.
    https://en.wikipedia.org/wiki/USS_Independence_%28LCS-2%29

    Mixing alum boats with electric propulsion as the OP wants would have me thinking twice.
     
  11. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Well, they must have changed the design then. Since we used to build them at my previous yard for the RNLI. All single skin, solid very thick indeed.

    But I still do not know of any commercial operator that would want sandwich construction on the hull bottom. Not saying others wont, but my none of my clients do.
     
  12. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Leo

    All aluminium in commercial usage is alloyed. Only the aluminium foil used for cooking is as close to pure aluminium that you'll get.

    Aluminium whether it is 5000 or 6000 series is always called aluminium, or ally for short. Only in design when specifying the type of alloy and temper does it become important. Since on the shopfloor when being fabricated, it is clear which alloy and temper must be used by the plater/welder and thus colloquially it is simply referred to as ally. The shiny light stuff! :D
     
  13. Leo Lazauskas
    Joined: Jan 2002
    Posts: 2,696
    Likes: 146, Points: 63, Legacy Rep: 2229
    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    I was simply wondering if the other poster was using "alloy" to mean something other than "ally". In reality, it's all just plumber's jargon to me :)
     
  14. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Indeed it is...see, it's simple, even a dumby like me can understand it too :p
     

  15. upchurchmr
    Joined: Feb 2011
    Posts: 2,874
    Likes: 89, Points: 48, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Well, we only use alloy at work, if we use that at all.
    Basically its aluminum or 7050 or 2024/6.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.