Date:	Mon, 11 Apr 1994 23:54:33 -1000
From:	Simo.Salanne@bofnet.mailnet.fi
Message-Id: <2DAA6FD9.
	55801*_G=Simo_S=Salanne_UA-ID=000000001_PRMD=BOFNET_ADMD=MAILNET_C=FI_@
	MHS>
Organization: Division of Applied Sciences, Harvard University
Subject: Re: Recent experiences with spars... - Vastaus



Marty wites:

>One things that I have noticed with the new SkySharks versus the old
>ones is their failure mode. The old spars would break very cleanly,
>much like short grained wood. The new rods splinter like pultruded
>rods. The new rods are much stiffer and stronger, but I found the
>difference interesting.

Not only "interesting" but also more hazardous (sp?). I have heard
Flexifoil changed their spar material because they were concerned
about the responsibility in case of splintered spar causing injuries.

>The new round of ultra-light kites are relatively easy to fly in no
>wind. Do we really need an even lighter spar for stunt kite flying?

If the development continues, we soon need weight classes like in
boxing... not for flyers :-), but for kites.

I have updated "my" spar stiffness table (more European stuff in it)
with Dave's new measurements, but I would like to have the outer
diameter of the following U.S. made spars:

SkyShark IIIP (<1994)           
SkyShark VP (<1994)             
SkyShark IIIP (1994)            
SkyShark VIIP (<1994)           
SkyShark VP (1994)              
SkyShark VIIP (1994)            
Clearwater 187-2                
Clearwater 202-2                
Clearwater 283                  
Clearwater 254                  
Clearwater 315-3                
Clearwater 385-2                

Dave, or somebody else?, could you supply ODs?

I have generated a "radar" chart from the updated table, for scaling
reasons it contains spars with relative stiffness between 0.5
and 2.5. I'll send a GIF and postscript version of it to
rec.kites archive.

Smooth Winds
Simo




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Date:	Tue, 12 Apr 1994 09:30:58 -1000
From:	lord@eskimo.com (David Lord)
Message-Id: <Co5vJo.89v@eskimo.com>
Organization: Eskimo North (206) For-Ever
Subject: Re: Recent experiences with spars... - Vastaus

<2DAA6FD9.55801*_G=Simo_S=Salanne_UA-ID=000000001_PRMD=BOFNET_ADMD=MAILN
ET_C=FI_@MHS>
 
In article
<2DAA6FD9.55801*_G=Simo_S=Salanne_UA-ID=000000001_PRMD=BOFNET_ADMD=MAILN
ET_C=FI_@MHS>, Simo.Salanne@bofnet.mailnet.fi writes:
> 
> 
> Marty wites:
> 
> >One things that I have noticed with the new SkySharks versus the old
> >ones is their failure mode. The old spars would break very cleanly,
> >much like short grained wood. The new rods splinter like pultruded
> >rods. The new rods are much stiffer and stronger, but I found the
> >difference interesting.
> 
> Not only "interesting" but also more hazardous (sp?). I have heard
> Flexifoil changed their spar material because they were concerned
> about the responsibility in case of splintered spar causing injuries.
> 
> >The new round of ultra-light kites are relatively easy to fly in no
> >wind. Do we really need an even lighter spar for stunt kite flying?
> 
> If the development continues, we soon need weight classes like in
> boxing... not for flyers :-), but for kites.
> 
> I have updated "my" spar stiffness table (more European stuff in it)
> with Dave's new measurements, but I would like to have the outer
> diameter of the following U.S. made spars:
> 
> SkyShark IIIP (<1994)           
> SkyShark VP (<1994)             
> SkyShark IIIP (1994)            
> SkyShark VIIP (<1994)           
> SkyShark VP (1994)              
> SkyShark VIIP (1994)            
> Clearwater 187-2                
> Clearwater 202-2                
> Clearwater 283                  
> Clearwater 254                  
> Clearwater 315-3                
> Clearwater 385-2                
> 
> Dave, or somebody else?, could you supply ODs?
> 
> I have generated a "radar" chart from the updated table, for scaling
> reasons it contains spars with relative stiffness between 0.5
> and 2.5. I'll send a GIF and postscript version of it to
> rec.kites archive.
> 
> Smooth Winds
> Simo
> 
> 
 
 
Hi Simo
The o.d. of wrapped spars is rarely provided. When you cut the graphite
wraps thay almost always have a very small overlap that can thwart your
attempt to measure it accurately, also there are some variations in the
process. They are by and large hand made. However most manufacturers
make up some test articles generally of several layers thickness to
determine there cured per ply thickness. The only one I know is the
Clearwater standard graphite wrapped spars. For these spars the per ply
cured thickness is 0.007 in. None of the other manufacturers has said
what their values are.
                                 Dave Lord


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