Makes me wonder... for those of us who have molded wing skins, Dan Diehl
style, how much weaker would our KR2s be as compared to the original Rand
Robinson foam core design, and what would the failure mode be? High Gs?
Nearing the VNE?
Serge Vidal
KR2 "Kilimanjaro Cloud"
Paris, France
<nght...@bellsouth.net>
Envoyé par : krnet-boun...@mylist.net
28/05/2006 17:13
Veuillez répondre à KRnet
Remis le : 28/05/2006 17:14
Pour : KRnet <kr...@mylist.net>
cc : (ccc : Serge VIDAL/DNSA/SAGEM)
Objet : Re: Re: KR> removing the foam after glassing as wing.
To put the engineering in perspective, the foam controls two very specific
and important structural concerns - first, the pure moment of inertia of
the structure; the larger the moment of inertia, the easier it becomes to
make a structure stiff for the amount of material needed- here in lies the
secret to building superior composite structures. Second, the foam nearly
eliminates the composite lamina critical local buckling stress (the
critical local buckling stress is primarily in reference to the side of
fiberglass/carbon/kevlar that is in compression, which in most cases, is a
composite structure's failure mode). To complete Steve's reasoning
(below), a cored composite maintains its structural integrity so long as
the skins *stay* apart.
Cedric Gould
>
> From: "3343V" <33...@swbell.net>
> Date: 2006/05/27 Sat AM 02:25:59 EDT
> To: "KRnet" <kr...@mylist.net>
> Subject: Re: KR> removing the foam after glassing as wing.
>
> Harold Woods wrote:
> > Hi Netters.
> > The answer to the subject of this question becomes readily available
> > if the person involved will do the following experiment:
> > Take a piece of the blue styrofoam that is used for home insulation.
> > Cut it 1 foot wide, 1 foot long and use the type that is 1 inch
> > thick. Cover it with fibreglass cloth as you would your wing. Epoxy
> > the glass to the foam. After curing, place one end on the edge of one
> > chair and the other end on the edge of another chair. Sit in the
> > middle! It should take it. Now pour gasoline onto the blue foam to
> > dissolve it. Now it is gone. Repeat the experiment but this time
> > press down in the middle with your finger. You now have the answer to
> > your problem. The foam may be light , it may be frail but it servers
> > a very important purpose.
>
> In other words, a cored composite structure's strength increases as the
> glass gets farther apart.
> --
> Steve
> 33...@swbell.net
> N3343V- '75 C150M
> N205FT- KR1 #6170
> He who seeks will find, and he who knocks will be let in.
>
>
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