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Post by maddog on Jan 11, 2012 22:49:51 GMT -5
Thank you for your time on this Jeff.
Looking forward to trying to see this video.
Mike
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peterzabriskie
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"Did I make that part the best I possibly could have?" Unknown
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Post by peterzabriskie on Jan 13, 2012 8:29:45 GMT -5
Jeff, because I missed the end of you presentation I have one more question. Once the foam core is made you covered it in fibreglass? Could it be covered in carbon-fiber or kevlar that Oahupilot is always talking about? Then too is the foam core removed or left in? Guess that's two questions. -Pete
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Post by Schmleff on Jan 13, 2012 11:07:18 GMT -5
Yes, the can be covered with whatever cloth you would like.
I left part of the cores in for impact resistance.
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hans
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Post by hans on Jan 13, 2012 14:16:58 GMT -5
Jeff, because I missed the end of you presentation I have one more question. Once the foam core is made you covered it in fibreglass? Could it be covered in carbon-fiber or kevlar that Oahupilot is always talking about? Then too is the foam core removed or left in? Guess that's two questions. -Pete rivetting carbon to alu is something you might want to reconsider... cheers Hans
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peterzabriskie
Junior Member
"Did I make that part the best I possibly could have?" Unknown
Posts: 99
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Post by peterzabriskie on Jan 13, 2012 16:00:46 GMT -5
Hans what is the issue with riveting carbon-fiber vs. fiberglass -Pete Also Jeff is the foam core a plug to make a female mold or is the covered core the final part. Sorry I am very new to this art. Thanks again. ;D
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hans
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Post by hans on Jan 13, 2012 16:24:32 GMT -5
Pete,
carbon is a conductor that, as a conductor, is dissimilar enough with alu that it could cause electrolytic corrosion. Better not use them together - this includes not using alu screws or rivets to fasten something made out of carbon. In that case use stainless or monel fasteners.
Hans
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peterzabriskie
Junior Member
"Did I make that part the best I possibly could have?" Unknown
Posts: 99
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Post by peterzabriskie on Jan 13, 2012 16:39:47 GMT -5
Thank you Hans......my panel is carbon and that will be good to remember. This would preclude using carbon for the tips then just insuring that the correct fasteners are used. The way costs of many things comes down with higher demand this may too. I shipped thru work two rolls of Carbon-fiber packed with dry ice in December that were 50" wide and perhaps 200 meters in length each. If the Dreamliner 787 becomes popular the producers will be increasing their line dramatically.
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hans
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Post by hans on Jan 13, 2012 16:42:14 GMT -5
that must have been carbon pre-pregs...
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Post by oahupilot on Jan 13, 2012 16:49:12 GMT -5
Pete, carbon is a conductor that, as a conductor, is dissimilar enough with alu that it could cause electrolytic corrosion. Better not use them together - this includes not using alu screws or rivets to fasten something made out of carbon. In that case use stainless or monel fasteners. Hans This is not as big as an issue as some people make it out to be. The thing to remember is that the fibers are in a matrix of non conductive polymer, epoxy. So their is no path of conduction between the carbon and the aluminum, in most carbon fiber bicycle frames have aluminum inserts bonded permanently inside the frame in areas of mechanical interface: head tubes, seat tube, axle points, crank case. Some military aircraft have an aluminum honeycomb sandwiched between sheets of carbon fiber. As long as you put some epoxy primer on your rivets and holes before final installation you will be fine.
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Post by n3480h on Jan 13, 2012 17:38:57 GMT -5
Hans, do you have data or pictures depicting the electrolytic corrosion you mentioned? Medical technology has made use of aluminum/carbon fiber bonded parts for years, as well as aluminum and stainless mechanically attached to carbon fiber with screws and bolts. Working in the field of medical accessory manufacturing for the last 8 years, I have yet to see a failure, nor have I seen dissimilar materials corrosion or even electrolytic deposition. Good advice from oahupilot.
Tom
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Post by mayday on Jan 13, 2012 17:44:14 GMT -5
I see some nasty corrosion on the aluminum inserts in carbon fiber floorboards used in the aircraft I work on. Sometimes the inserts are corroded so bad, the carbon fiber seems to "wick" it up and the carbon fiber itself turns green immediately around the insert. I would at least make sure the aluminum and carbon fiber mating surfaces have a decent layer of primer on them.
Edit: I should mention that I really only see this in the Galley or Lav areas where liquids get spilled, but if its on the tip of a wing I would be willing to bet it will be getting wet every now and then.
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hans
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Post by hans on Jan 13, 2012 18:15:31 GMT -5
my concerns for this combination of materials originates from my yachting years (I used to be delivery skipper) during which I have seen a number of failures of alu fasteners that clamped carbon fiber parts, like roller reef profiles and the like. Admittedly, salt water ingress in this environment speeds up this process considerably.
Laminates are at risk when you start to drill holes in it and put in fasteners without any extra protection. That way, you create a conductive path between the bare carbon fibers, the fastener and the material the carbon is fastened to.
Oahupilot is right with his recommendation on how some extra care can go a long way to prevent or postpone such issues. Alternatively, you can use fasteners that don't cause such issues in the first place.
Hans
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Post by n3480h on Jan 13, 2012 19:48:21 GMT -5
Yes, a salt water environment is about the worst for many metals. Its recommended to use faying compound or at least a good primer even between like materials, i.e. aluminum to aluminum joints, in aircraft. Seems we are in agreement.
Skipper Eh? That's pretty interesting work, Hans. Bet you have a story or two.
Tom
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peterzabriskie
Junior Member
"Did I make that part the best I possibly could have?" Unknown
Posts: 99
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Post by peterzabriskie on Jan 13, 2012 22:22:59 GMT -5
Good thread this one goes into the "future construction" file folder. Thanks folks. -Pete FYI...if you use Google Chrome like I do when you hit "print" and get a printable copy then right click the copy ..... the google chome makes a very nice PDF file vs other sloppier files.
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Post by Schmleff on Jan 14, 2012 6:42:46 GMT -5
Hans what is the issue with riveting carbon-fiber vs. fiberglass -Pete Also Jeff is the foam core a plug to make a female mold or is the covered core the final part. Sorry I am very new to this art. Thanks again. ;D These will not be glassed. The will be plugs for molds.
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