weight aluminium vs GRP yacht

Discussion in 'Materials' started by innomare, May 6, 2005.

  1. Herman
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    Herman Senior Member

    I can only add one thing: It is "tot ziens" if you want to be 100% correct... :)
     
  2. mydauphin
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    mydauphin Senior Member

    Rock - Paper - Scissor ... Steel - Aluminum - Fiberglass... Except Aluminum will cut thru a fiberglass boat like nothing. Aluminum best if you can afford it. Steel good for displacement boats over 20 meters. Wood good if you feel good about having to maintain something.
     
  3. truecougarblue
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    truecougarblue Junior Member

    Thanks Eric.
     
  4. TomE
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    TomE Junior Member

    I'm seeing that new commercial catamaran ferries (20-40m) are moving to carbon fibre construction. Has there been improvements in price of the fabrics or construction methods lately that have brought this change? Or is phenomenon local to Norway?

    Does anyone have anyone have comparable figures for carbon similar to Sponbergs?

    My interest is triggered by playing with the thought of having built an 35-50 ft catamaran for semi-pro fishing (line, nets and pods) and excursions of a few weeks at a time. Keeping fuel and other running/maintenance costs as low as possible while maintaining cruising speed of 15-20 knots (disp/semidisp hull). Any input to set me off researching it the right directions will be greatly appreciated. Both with regards to materials, size, propulsion systems and designers.
     
  5. Ad Hoc
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    Ad Hoc Naval Architect

    Local to Norway/Scandinavia.

    Rest of the world opts for Aluminium.
     
  6. Eric Sponberg
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    Eric Sponberg Senior Member

    There are not enough carbon fiber catamarans or boats built yet to get a full comparison or analysis on costs. Carbon fiber composite hulls are going to be lighter than regular composite hulls, but the cost for construction is going to be much higher. There is nothing really new in the molding of carbon fiber that is a break-through that will shift the industry. It is more of a matter of different people pursuing their own specific interests, just like you. Remember, too, that when considering the whole package of everything in the boat, the hulls and deck are but a part--the rest is the equipment and the systems, which are going to be pretty much the same from boat to boat, no matter what the boat is built out of.

    You may want to consult with a designer sooner rather than later--he can help you sort out what your requirements are and where you should look for construction. A lot of things are intertwined, and some features may be more important than others. For example, if this boat is going to be used commercially, then generally the more commercial you are, the more you want to tend toward metal construction, probably aluminum. The more yacht like that it is, the more you will tend toward composite or wood construction because it holds a better finish at a lower cost. Those are just some thoughts.

    Eric
     
  7. MikeJohns
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    MikeJohns Senior Member

    That sounds like a 'set up' to market a construction material rather than any valid test.

    For a proper comparison you'd design to the same structural criteria and then compare weights rather than building to the same weight and using buckling as a comparison.

    It's not an indication of which material can "Take a beating" neither a light weight foam core nor it's equivalent weight in any material could stand up to abuse.

    Foam cores are much less able to absorb impacts without damage than other forms of construction it's simply a function of the shear strength of the outer laminate.
     
  8. watchkeeper

    watchkeeper Previous Member

    We have looked at Sealium products and research showed that for scantling the strength/size ratio to be so small a gain that it didn't justify the additional expense.
    As to the increase corrossion resistance I saw no real documented evidence and again the additional expense didn't justify the material when the same precautions or lack of - stray current, incorrectly calculated anode protection and lack of maintence would have the same effect on either materials.
     
  9. watchkeeper

    watchkeeper Previous Member

    Re. selection of construction materials for yachts, commercial or govt service craft.

    I agree with Eric, its really common sense/experience of the owner and horses for courses.
    I've built 30m to 40m steel, steel and aluminium, or aluminium sail yachts (ketch rig or schooner rig) and 20m to 32m timber (carvel plank) sail yachts, 20m to 47m aluminum yachts mono and CAT hulls, numerous commercial aluminium CAT work boats, pilots, patrol craft and LC.

    I see GRP construction as ideal medium for any production boat, yacht or work boat where the hull is not excessively abused - banging up against pillings or docks such as ferries do on a daily bases.

    I like the use of GRP for superstructures styling that requires compound curves mounted on an aluminium hull, providing the owner the best of both materials technical advantages.

    CF hulls I think are a trend that some manufacturers want to promote as replacement for aluminium. Its fine for recreational hulls but results so far are not in its favour for commercial applications.
    Several windfarm CAT crew/service boats built with CF hulls have not deliver ed the same operations hrs as aluminium hulls without serious repair work for impact damage.

    Marine CF is ideal for certain craft such as very high speed 50knot-60knot enforcement & interdict fitted with ballistic shielding or navy missle boat high speed craft with stealth requirement to be used in actions with a basic fire & forget life cycle.
     
  10. susho
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    susho Composite builder

    But, foamcored sandwich laminates are better in absorbing impact with damage!

    When you puncture a single skin laminate, you have a hole. A (corecell especially)foamcore can absorb a lot of energy, leaving the inner skin in tact. For safety a foam core is better.
     

  11. MikeJohns
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    MikeJohns Senior Member

    Sure in small light boats boats you might make a case for foam absorbing impact energy without fully rupturing. But once the crafts displacement is a few Tonnes it’s not feasible to expect the foam to absorb collision energy . The skins are too thin and the core is too weak and too elastic to absorb the realistic levels of impact energy.

    Experience shows foam core below the waterline to be a poor choice in larger displacement craft subject to grounding. Underwater reef Collision damage for example is often extensive and catastrophic. Similar impacts that a solid laminate equivalent would have survived .
     
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