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Posted by anotherid on July 29, 2008, 6:01 pm
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I confess I'd overlooked the possibility of soldering (though I'm not
very good at it). I might go that route, else it'll be an epoxy.
Thanks.
Brendan
--
anotherid
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Posted by Stephen Howard on July 29, 2008, 7:42 pm
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On Tue, 29 Jul 2008 17:01:21 -0500, anotherid
>
>I confess I'd overlooked the possibility of soldering (though I'm not
>very good at it). I might go that route, else it'll be an epoxy.
>
If you gave us some idea of the application/dimensions we might
collectively be able to come up with some additional pointers.
Regards,
--
Stephen Howard - Woodwind repairs & period restorations
http://www.shwoodwind.co.uk
Emails to: showard{who is at}shwoodwindcouk
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Posted by Tony Jeffree on July 30, 2008, 3:46 am
Please log in for more thread options On Tue, 29 Jul 2008 23:24:22 GMT, etpm@whidbey.com wrote:
>From my friends who work at Boeing the
>word is that the new composite wings have far exceeded the calculated
>maximum stress where failure should occur. So far the wings have not
>been destroyed because the flexing has so far exceeded the design and
>calculated failure point. Word is that some folks think it's not
>needed but I bet that they will ultimately be stressed to the breaking
>point if only to see where they really fail and for bragging rights.
If that is really the case, then they've over-engineered them & they
will probably be looking into reducing the weight.
Regards,
Tony
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Posted by Tim Leech on July 30, 2008, 4:46 am
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>On Tue, 29 Jul 2008 23:24:22 GMT, etpm@whidbey.com wrote:
>
>>From my friends who work at Boeing the
>>word is that the new composite wings have far exceeded the calculated
>>maximum stress where failure should occur. So far the wings have not
>>been destroyed because the flexing has so far exceeded the design and
>>calculated failure point. Word is that some folks think it's not
>>needed but I bet that they will ultimately be stressed to the breaking
>>point if only to see where they really fail and for bragging rights.
>
>If that is really the case, then they've over-engineered them & they
>will probably be looking into reducing the weight.
>
....except that, if it's 'new technology', they'll perhaps be anxious
to keep it a bit on the over-engineered side until it's been proved in
service. They wouldn't want a Comet-style series of failures.
I thought I had read somewhere, a few months ago, that the project was
a bit behind schedule because they were having to sort out issues with
the attachment of wings to fuselage.
Tim
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Posted by rsss on July 31, 2008, 9:56 am
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Tony Jeffree Wrote:
> On Tue, 29 Jul 2008 23:24:22 GMT, etpm@whidbey.com wrote:
>
> >From my friends who work at Boeing the
> >word is that the new composite wings have far exceeded the calculated
> >maximum stress where failure should occur. So far the wings have not
> >been destroyed because the flexing has so far exceeded the design and
> >calculated failure point. Word is that some folks think it's not
> >needed but I bet that they will ultimately be stressed to the
> breaking
> >point if only to see where they really fail and for bragging rights.
>
> If that is really the case, then they've over-engineered them & they
> will probably be looking into reducing the weight.
>
> Regards,
> Tony
It's a little more complicated than that.
Both the Boeing and the Airbus wings have been tested far beyond the
maximum
stress expected on the wings, more or less the point where
either the wing, the
fuselage or the passengers would have failed.
If I remember correctly the safety factor is Maximum *1.5. The Airbus
designs
failed at around the critical point (actually slightly below it
but within 3%)
The Airbus wing flexed 7.4 metres before rupturing.
http://www.cs.york.ac.uk/hise/safety-critical-archive/2006/0031.html
I remember reading somewhere (High Performance Composites?) that a
Boeing design
had had a similar failure.
The design problem is enormous, whereas one can look as a piece of
aluminium as
a single piece, the equivalent composite part may be
mutiple layer of a material
in a matrix . Each layer may be laid at a
different angle and where the material
is woven, there is a stress point
whereever one thread crosses another.
So instead of the fairly precise data that is available to the metal
engineer,
one has to work with approximations of behaviour.
Another problem is that effectively you 'create' the material every
time you
make a component part. Imagine if you had to mix, melt, roll
and treat and test
every piece of aluminium instead of relying on the
manufacturer to do so. Indeed
the Americans have the AGATE database
which defines how to put the various
materials and resins together to
make a standard material and the various
figures that one can use for
that material to avoid some of the problems.
So 'overengineered' is a relative term, given the large variables
possible and
the many modes of failure that have been identified.
--
rsss
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>I confess I'd overlooked the possibility of soldering (though I'm not
>very good at it). I might go that route, else it'll be an epoxy.
>