Greg ,
# 3 is a simplified version of the SH approach. The web has a pocket
along the spar
in which the web slides upon closure.The total amount of epoxy is
reduced,
and the shrinking acts in a different direction, hence less shrinking
in the vertical.
In any case that is my take on it.
http://www.alexander-schleicher.de/englisch/e_main.htm
Udo

Greg Arnold wrote:
Udo:

The DG website has a diagram of 4 different spar construction methods:

http://www.dg-flugzeugbau.de/holm-aufbau-e.html

Do I understand you to say that SH uses #3, and AS uses #1? DG says
that they use #4, so that would mean that each of the major
manufacturers uses a different method.



Udo wrote:
Here is my hypothesis.
The SH lays up there spar cap into the wing skin, versus the
AS factory, which built there spar complete and separate from
the wing structure.
This requires a different joining technique and application
of epoxy slurry. In the later case the spar is set into the lower wing
skin in a controlled fashion, hence using less epoxy.
Before the top skin is set into place,
dams out of beaded foam are built, they are a bid higher then the
insight
of the skin when joint. The spar cap with the dams in place is now
filled
with an epoxy mixture. The shape of the mixture has a little inverted
V shape like a roof but shallower. This allows for the epoxy to make
contact in the centre first and pushes it out ward. At the same time
the foam dam gets pushed out of the way to allow for a bead to be form.
Due to the tolerances between the height of the spar cap and
the inner wing skin, there is more epoxy used then at the bottom joint,

hence more shrinking of the top skin occurs.