Vac Infused Carbon / Nomex Core / Carbon Tender

Discussion in 'Fiberglass and Composite Boat Building' started by variverrunner, Dec 21, 2009.

  1. variverrunner
    Joined: Dec 2009
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    Location: New York, USA

    variverrunner Junior Member

    I recently came across Burt Ruton's website for Scaled.com and looked at his description of the construction of the Voyager. It is a airplane that he built to fly around around the world non-stop, non-refueled. The site notes that the craft was built of .010 graphite tape skins with a 1/4" nomex core.

    I am interested in building an ultra light lawley tender using the same structure. I have built a few vac infused canoes but I have never workd by nomex or any other honeycomb. In a perfect world I would like to produce the hull in one step. I have tried to locate a few books about modern composte engineering without much luck. Does any one have any recommendations? I would really like to learn how to calculate lam schedules.

    What is double bagging? Bagging a hull twice?

    Thanks
     
  2. Jimbo1490
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    Jimbo1490 Senior Member

    Building such a tender from the materials you described is a bit like building a mower deck from titanium: very expensive and in the end probably not as good.

    Thin skinned carbon/nomex structures are not in the least bit 'damage tolerant'. These structures don't like impacts, including wave impacts, and should never be 'beached'. Dropping an anchor inside the boat, from even a modest height might prove interesting as well.

    Of course you could make the skins thick enough to make them more damage tolerant, but then you really would not save much, if any, weight as you'd wind up with a VOLUME of reinforcing fiber similar to that of a structure in glass fiber instead of carbon, which is really no less dense. Yes, such a boat would be VERY strong and stiff, in fact far more so than needed for a rowboat.

    The 'next step upward' in strength and stiffness/weight from 'conventional' fiberglass is actually a good wood structure which is in turn bested by high-strength aluminum with carbon/epoxy/nomex at the very top. Cored structures are always less damage tolerant. Reducing the skin thickness (as is done with carbon skinned sandwich) just makes this worse.

    If you wanted to reduce weight and improve stiffness/weight in such a craft, you might consider using a more advanced construction in either wood of fiberglass, such as fiberglass skins over either a foam or end-grain balsa core. This will result in a sensible incremental improvement, without too great a sacrifice in utility because of damage intolerance.

    A well-designed/executed wood hull will be the benchmark for this kind of boat, in the end.

    Jimbo
     
  3. variverrunner
    Joined: Dec 2009
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    variverrunner Junior Member

    Jimbo, Thanks for your response.

    Is the lack of " damage tolerance" caused by the brittleness of the carbon or the lack of compressive strenght of the honeycomb? A rough calc of the Ruton schedule used on the Voyager would yield a 8.5 foot tender at +- 35 lbs which would be handy for older boat folks trying to get thier tender on board.

    Would it help if I switched to carbon/kevlar hybrid reinf. or maybe just kevlar?

    Does anyone have experience infusing a composite honeycomb hull in one step?

    Does anyone have any books suggestions that would help me learn more ?

    Thanks.

    This is an incredible site.
     
  4. apex1

    apex1 Guest

    Vari,

    the lack of damage tolerance is just due to the extremely thin skin!

    The voyager skin would have been destroyed immediately in a heavy rain sqall with some high speed impacts of drops, I´m sure.

    Regards
    Richard
     
  5. variverrunner
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    variverrunner Junior Member

    Thanks Richard,

    I am a new be to this and trying to learn. Are there sources where I can learn how to design a thick enough comp. hull that is thick enough?

    Does anyone have any idea of how a " typical america's cup racer or other race boats are built? c/nomex/c? Vac infused or vac bagged?

    Thanks again
     
  6. Herman
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    Herman Senior Member

    Honeycomb and infusion is not possible. The resin infusion process will fill every void in the laminate, including the honeycomb cells.

    Besides that, UD carbon can be tough to infuse.

    The AC boats are prepreg, bagged and baked, and this at least 3 times: Inner skin, honeycomb, outer skin. On top of that, thicker laminates are debulked every couple of layers. (putting vacuum on, but no cure cycle)
     
  7. Jimbo1490
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    Jimbo1490 Senior Member

    Recall that it was even damaged on takeoff for the circumnav trip. Inspection by chaser aircraft concluded that the damage (a destroyed wingtip) was not great enough to warrant an abort, and the mission was completed as planned.
     
  8. simon
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    simon Senior Member

  9. variverrunner
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    variverrunner Junior Member

    Herman,

    What is UD carbon?
     
  10. apex1

    apex1 Guest

    U ni D irectional.
     

  11. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

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