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Re: "Carbon" Dragon? 10 Dec 2013 23:24 #572

Why all the experimentation with rib construction with cores? Jim Marske made the ribs for the Pioneer 3 from one laminate of7725 fabric with wood capstrips. This plane is a bit heavier than the Dragon and none has ever failed. The D-tube is also built without a core from three laminations of glass, again with no failures in a heavier, faster airplane. Why not use these proven techniques instead of getting wrapped up in one small aspect of design?

--- In This email address is being protected from spambots. You need JavaScript enabled to view it., Kenny Andersen wrote:
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> Once again Russ -- you aren't making any sense. If you are loading your core in compression, you are doing it wrong. If the sandwich skin is failing, it's too thin...
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> --- On Thu, 2/2/12, russell wilson <ruzty27@...> wrote:
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> From: russell wilson <ruzty27@...>Subject: Re: [Carbondragonbuildersandpilots] "Carbon" Dragon?
> To: This email address is being protected from spambots. You need JavaScript enabled to view it.
> Date: Thursday, February 2, 2012, 5:57 PM
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> hi phill.......a heads up on the pannels you are making...8g/32kg......your comparing to a standard rib...yer?........my test pices/tested to distruction and compared on a balance beam......showed that any core material under 200kg was a loser with thin laminates....in a 200 kg core i had to go down to 2 oz glass before the skin failed under tension.....all other failures were of the compression skin buckling in toward the centre of the pannel/core material failing under compression.
> you may have a winner when compared to a standard rib...but there are lighter stronger options.....try some samples of the cheepest crapiest ply you can find....find a thikness that will match the weight of your expensive foam...lay it up with your cf and test it to destruction....you will find it will absorb less resin than 32kg so the finished pannel will be lighter and it will be stronger and cheeper/free core if you scrounge........then do one with bolsa(not end grain as end grain has tiny holes that go from one side to the other and the resin will fill these.)
> my test showed that with thin laminates....do not use a core lighter than 200....even a thinner pannel of 200kg and above out performs thicker lighter cores with thin laminates....even though we know that dobling the thikness, much moor than dobles the
> strenth /stifness. hey while your testing...i never got oround to testing woven jute fibers/hesian...these fibers are round the same strenth as e glass and lighter than kevlar and cheep as chips.
> russ.

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