Your views on this comparison table...

Discussion in 'Materials' started by Mick@itc, Sep 11, 2011.

  1. Mick@itc
    Joined: Jan 2011
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    Mick@itc Junior Member

    Hi all

    I love finding comparison tables of material suitability for boat building. Found this one reciently and would like to hear your observations and opinions of the content...

    See attachment below...I cant seem to get it to show in the post...
    Mick
     

    Attached Files:

  2. SheetWise
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    SheetWise All Beach -- No Water.

    Notice the final row -- it is the total of values -- values from an unidentified range of unidentified properties. I wonder what the total would be used for?
     
  3. Mick@itc
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    Mick@itc Junior Member

    Ahhh...bad cropping on my part....the site says ...Scale 1-10 ,10 being the best, 1 the worst. So its an opinion piece of good and bad...not very scientific is it. But still interested on opinions on the relative numbers

    Mick
     
  4. Submarine Tom

    Submarine Tom Previous Member

    I think it pretty general.

    It does show the total scores as not that dissimilar, highlighting there are pro's and con's to different materials.

    Like boat design, material choice is a compromise.

    -Tom
     
  5. PAR
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    PAR Yacht Designer/Builder

    There are some rater important omissions, such as cost, cost per pound, cost per preformance potential (bank for the buck) an example would be SAN foams having half the compressive strength at several times the cost of balsa, etc., etc., etc. The numbers might be useful in an overview on the subject.
     
  6. daiquiri
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    daiquiri Engineering and Design

    Looks like an excerpt from a technical report where the use of honeycomb polypropylene had to be justified as a core material. Could have been compiled by a producer of the HC PP core, since the table apparently aims to demonstrate how much this material (according to the author of the comparison) excels over other core materials in comparison.

    But... There's one column missing in that table - "bonding properties and cost". It would imho be just 2 or 3 for honeycomb PP, as PP in general is a very difficult plastics to bond. And that characteristics should also lower its scores for "closed cell structure" (in case of local de-bonding) and "versatility in boatbuilding" (cost and availability of bonding equipment) columns.

    So, imho, a more objective scoring would see the gap between H-C PP and the rest of materials in the list shrink significantly, or possibly vanish.

    Cheers
     
  7. DCockey
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    DCockey Senior Member

    In addition to the missing criteria, there is no weighting of the different criteria which would be application dependent. For example price, weight, flexural modulus and shear strength would be weighted differently for a high performance racing boat and a cruising boat. Also there is no indication of the relative magnitudes of the difference between a 1 and a 10 for the various criteria.
     
  8. gonzo
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    gonzo Senior Member

    It could be useful. However, often one of the requirements, like heat resistance, may weigh more in the decision.
     
  9. Mick@itc
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    Mick@itc Junior Member

    Yes I agree with most of the comments above. It is interesting that the internet is littered with comparison tables that push cetain viewpoints. It's actually very hard to find an objective comparison which is a pity as it would be most useful to all/most of the visitors to this and many other forums.

    Weighting is an interesting question and I think it is a bridge too far for this type of comparison. most weightings are directly related to a specific application of a material and is a vialid selection criteria rather than a comparitive characteristic.

    This is good input from everyone, I encourage debate in material comparison as I think it helps everyone.

    Regards
    Mick
     

  10. Herman
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    Herman Senior Member

    Comparisons like these are basicly non-sense, from a technical point of view. Although they show very roughly what you are dealing with, the sums are useless anyhow, and the rest of the numbers are not backed up by numbers.

    It is already a lot better to compare technical datasheets, but even then one must be aware of the different testing methods, giving different results. Besides that, bending the numbers seems to be the favorite passtime of core manufacturers.

    To select a core for a given purpose, is still a matter of experience, and can be based on different criteria, availability being one of the most important.

    Unfortunately this overview does not include other useful cores.

    Oh, this one comes from Nidacore if I recall correctly. In the past the Core-Cell Design Manual (by ATC Core-Cell) was available (out of print now, but I have it available still) which had a similar table. Guess what? Core-Cell (SAN Core) came out best....
     
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