Yet another epoxy vs vinylester ...

Discussion in 'Fiberglass and Composite Boat Building' started by fcfc, Nov 3, 2011.

  1. Herman
    Joined: Oct 2004
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    Herman Senior Member

    OK, you want a carbon rudder. Keep in mind that there indeed are some pitfalls.

    In tension, there usually is no problem. In compression, the strength is about half of the strength in tension. This is true for both glass and carbon, so "no big deal" you would think. Then again, the carbon you plan to use will be less than the amount of glass, so your laminate will be thinner. Your thin laminate will be more prone to "skin buckling" which you could prevent in all sorts of smart ways, like making a "mini sandwich" of the skin, or just use a higher density foam sandwich, which will support the thin laminate more.

    What do your rudder pintles look like? I built lightweight carbon rudders long time ago, and at one point I reversed the pintles, as the rudder pushed upwards considerably.

    All in all, at this moment I feel that the most effective way to build a rudder, is to mimic the design of an aircraft wing, or a windmill blade. Which basicly means a sturdy spar, which can handle the bending load, and a fairly lightweight "fairing" around it, strong enough for local loads from steering.
    That is, if weight is the critical factor, not labour...

    About the vinylester / epoxy / infusion epoxy comparison: do not stare blind on their properties, and do not get trapped into the pitfall of always aiming for the technological optimal solution. There is no use spending 20% more to increase properties 1%, especially if you do not need that 1%.

    Look at all the crap that is floating around, mostly 30+ years, with constructions and materials that give you a terrible headache. Your product is already so much more advanced. Make it work, produce it in larger quantities, and sell it. If you are not a sales-person, get someone else to sell it for you.
  2. jim lee
    Joined: Feb 2007
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    jim lee Senior Member

    Hmm.. ok, now how about spars & tubes?

    With these its all about weight/strength.

    -jim lee
  3. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    There were some ISO-ORTHO blends around, but they were phased out even in the low cost interior parts.

    At one time the marine market was about 30% of my sales, but in recent times the economy has taken its toll on that market and it's been reduced a great deal.

  4. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Spars and high-tech tubes (there are plenty of low-tech ones) in general are made with carbon and epoxy. Which epoxy? Depends on the process used.

    There are very nice prepreg resins, very nice infusion resins, but also very nice pultrusion resins. In a price range from some 6 euro / kg up to 30 euro / kg.

    It is all about not over-specifying, and choosing what fits your production systems.

    ondarvr. About same here. Although the iso-ortho blends are still big here, for various (non marine) parts. Our biggest sales come from the infrastructure and building industry, pipes and silos, and all kind of general purpose stuff.
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