Re: carbon

Jeffrey Bevilacqua <jlbevila@...>

Very well said and thanks for keeping us safe.

--- On Sat, 12/19/09, rick_nordgarden <grnordgarden@...> wrote:

From: rick_nordgarden <grnordgarden@...>
Subject: [Q-LIST] Re: carbon
To: Q-LIST@...
Date: Saturday, December 19, 2009, 10:50 AM


--- In Q-LIST@yahoogroups. com, "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS Q1.
This is an example of how risky an untutored "common-sense" approach to engineering can be. Make two identical foam wing cores, then skin one with fiberglass and the other with carbon fiber. With the same number of layers of cloth of the same weight per square yard the carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly stiffening a wing's skin alters its spanwise load distribution, shifting load away from the tips and toward the centerline; the wing's load-carrying capacity and its g-limit at a given load are both thereby reduced. Stiffness and strength are not necessarily complementary properties; to a great degree they're antagonistic. This problem can be overcome by altering the number and/or weight of the plies when switching materials, but that means re-engineering the structure -- the fuselage and bulkheads as well as the wing-skins and spar layups. Before you can build a *safe* all-CF Quickie you'll have to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction

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