Date: Wed, 13 Jan 1999 07:53:45 +0200
From: Rego Burger <BurgerR@telkom.co.za>
Subject: COZY: Static Loading?

Does anybody have some experience with this subject to add or subtract
from....

I have a problem with folks static loading wings and canards to extremes
and then saying they're O.K. fitting them on aircraft and flying them.
If you stretch material to it's limits it has been exposed to STRESS...
this is not wise as I feel it now reduces it's servicability life-span.
If an aircraft has DESIGN limits of +6g and -4g this does not mean your
static load must be pushed to these limits prior to flight of those
components. If the craft has these DESIGN limits it should only operate
between +4,5g and -3g. So then, limit static loads to the OPERATIONAL
levels... this will not over stress a usable component.

Destructive testing will determine a break point, therefore the part
will be out of action.  I recall Burt pushing a L.E. canard to about
+14g before it bust..... imagine someone static loading a canard to +10g
and sticking it on to fly, he has possibly put 500000hrs of stress into
the part in one day...ouch!

R.B.
RSA
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                          

From: lschuler@cellular.uscc.com
Date: Wed, 13 Jan 1999 09:40:16 -0600
Subject: Re: COZY: Static Loading? 

Rego wrote:

>Does anybody have some experience with this subject to add or subtract 
>from....

>I have a problem with folks static loading wings and canards to 
>extremes and then saying they're O.K. fitting them on aircraft and 
>flying them.


I'm not a structural engineer, but I do tend to agree; particularly if the 
parts are metal.  Glass is different.

My layman's understanding is that glass doesn't deform like metal; it just 
breaks when over stressed.

If, in your 14G canard test, nothing (as in not a single strand of glass), 
is broken then the part is probably usable and it's life expectancy will 
continue as if new.

'Ultimate' loads in metals (I think) is the point at which permanent 
molecular deformation occurs causing the part to take a new set (shape 
etc).

Glass failures are more catastrophic, where glass simply snaps.  Metal 
failures are a bit more benign and the part just takes on a new shape (bend 
etc) unless the load continues over time.  Thus the life-cycle or life 
expectancy relative to stresses in metal.  Metal spars, for example, can be 
subjected to ultimate or near-ultimate loads and bend permanently, yet 
still remain attached to the fuselage (unless the load continues).  Doing 
the same with a glass spar would ensure that it departs the fuselage at the 
instant of ultimate load application.  The flight safety factor differences 
between these materials may be why 'ultimate' load is normally 1.5 times 
design load in metal planes and 2 times design load for glass.  

Kicker for loading a glass part is "knowing" if any of the glass strands 
broke or not; not easily determined.  On the other hand, over-stressing is 
readily evident in metal; the part looks different (stays bent) when you 
take the sand bags off.

Great item for discussion and further understanding of all (especially for 
us amateur 'experimenters'.

Larry

From: Epplin John A <EpplinJohnA@jdcorp.deere.com>
Subject: RE: COZY: Static Loading? 
Date: Wed, 13 Jan 1999 10:14:04 -0600



> -----Original Message-----
> From:	lschuler@cellular.uscc.com [SMTP:lschuler@cellular.uscc.com]
> >Does anybody have some experience with this subject to add or subtract 
> >from....
> 
> >I have a problem with folks static loading wings and canards to 
> >extremes and then saying they're O.K. fitting them on aircraft and 
> >flying them.
> 
> 
> Kicker for loading a glass part is "knowing" if any of the glass strands 
> broke or not; not easily determined.  On the other hand, over-stressing is
> 
> readily evident in metal; the part looks different (stays bent) when you 
> take the sand bags off.
> 
> Great item for discussion and further understanding of all (especially for
> 
> us amateur 'experimenters'.
> 
> 
	[Epplin John A]  
	I usually don't get into these things, way over my flat head.  But I
have an idea here.  First, load the structure to some point considerably
less than the damage point and measure the deflection, could be simply
measured with good instrumentation such as a machinists dial indicator or
even with strain gages.  Record these readings then load to the limits of
the test, but not to catastrophic destruction.  Unload and allow the system
go relax, then apply the first load again and note the deflection.  If you
have broken any significant number of strands you should notice greater
deflection.
	As I said, way over my knowledge and experience level, but how does
this sound to you structural gurus?

	John epplin   Mk4  #467,  installing engine.

From: cdenk@ix.netcom.com
Date: Wed, 13 Jan 1999 17:10:09 -0600 (CST)
Subject: RE: COZY: Static Loading?

Static loading of structures is a routine way of proof testing, remembering that this is a test of 
only one loading condition. For Structural Steel, wood , and reinforced concrete the test load is 
85% of the minimum failure load. For live loads typically the failure load is 1.7 times the maximum 
actual anticipated load. I have designed and supervised loads on precast concrete where the load was 
over 300 tons. Load bang when failure! 

From: cdenk@ix.netcom.com
Date: Thu, 14 Jan 1999 17:23:37 -0600 (CST)
Subject: Re: COZY: Static Loading?

When loading a structure in bending, the extreme fibers get the most strain (stretch), and should be 
the first to break, and that would be visible. If a significant percentage of fibers broke, the 
deflections would not go back to the original shape. Is important to measure accurately.

There have been more than a few full scale load tests on Ez's to satisfy foreign (to the USA) 
governments. I haven't heard of anything bad happening a a result.

