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"Carbon" Dragon? 10 Dec 2013 23:36 #580

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.



On Fri, Feb 3, 2012 at 3:29 AM, Philip Lardner <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:



Hi Kenny,

You'll find a copy of your spreadsheet in the last tab/worksheet of my own spreadsheet of calculations, which is in the files section of this group - link below. I've updated my spreadsheet to tidy it up a little and to add my load/stress analysis of the ribs. I'm not sure how to do a load/stress analysis of the H-Stab and V-tail/rudder... but I have a feeling the loads are not big. Any advice would be appreciated!

I am planning to eliminate all the wood from my build and fabricate purely out of carbon fiber and foam. I successfully completed a load test of a root rib constructed out of 5mm foam (to 8g / 32kg) and am just starting to build a second root rib out of 10mm foam (with narrower caps and internal struts than the 5mm one) for a weight/strength comparison. I'll post the results shortly - I got a bit delayed while I got myself set up for using the resin infusion method rather than the wet hand lay-up I used on the first test piece.

Phil.

groups.yahoo.com/group/Carbondragonbuild...iles/Phil%20Lardner/

Direct link to file: f1.grp.yahoofs.com/v1/ALMqT3nGUcpm3vTxJR...201%20Feb%202012.xls

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