I wasn't clear enough. The problem I thought would be eased was the
ultrasonic inspection problem. So, is the spar cap attached to the
outer wing skin, or is there actually foam between the outer skin and
the spar cap?

In article ,
ess says...
On Thu, 16 Oct 2003 08:00:49 -0700, Eric Greenwell
wrote:

In article ,
says...
I understand your point about ultrasonic testing. The sound wave
would have to go through the outer skin, foam, inner skin, carbon
fibre rovings spar cap, bonding paste, shear web of differing
compositions.

Is the spar cap on the Duo Discus bonded to the inner skin or the
outer skin? If it is bonded to the outer skin, it would not have the
foam to go through, which should ease the problem considerably.

The problem is that the bond in question attaches the top spar to the
web. Any problems with this bond will drastically affect the spar
strength by allowing the top spar to peel off the web. In the DG-style
of assembly with carbon cloth between the spar and the web the bond
between the spar and the cloth is equally as critical as that between
the web and the cloth.

In the model world we prevent spar peel failures by assembling both
spars to the web and then wrapping to lot with Kevlar thread or an
epozy-wetted woven carbon tube before building the wing round the
complete spar. This gives a 30G wing. I accept that this is overkill
for full size, but my teeth still itch a bit at the lack of any
binding round both the spars except on the protruding stubs at the
root.

I flat out would not fly a glider with foam between the web and the
top spar and would hope that such a structure has never been made or
flown.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :



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Eric Greenwell
Richland, WA (USA)