Martin, I have just done my first leading edge and have experienced
exactly the problems you have highlighted. Rather than bond the slots
with 5 minute, I go straight for the micro as it saves time latter
during the major layup.
I noticed several things, firstly the blocks appeared bowed, secondly
the twist did not appear to be correct, thirdly the sections where the
cores join are not identical. Having made these comments they need
some qualification.
Where the cores join there where differences in section which varied
from 10 to 20 thou (0.25-0.5mm) per side. The amount depends on where
you take you datuum, flat TE side, LE, LE flashing strip?
The bow in the sections was very misleading. I rechecked the table on
which they were jigged when the slots were filled, and this indeed was
flat. I eventually decided that the actual LE was straight (where the
flashing was) in the horizontal plane, but not the vertical plane
(when viewed as jigged). This was due to the sag of the hot wire when
it was cut. The surfaces were equally bowed as you move aft of the
LE.
Having decided on the above two effects, and spent some time jigging I
found that the twist approached the right sort of value, and the LE
was straight, if not dead flat.
Having bonded the blocks in place I lightly fettled the LE and the
joints with a long (1.25m) sanding block, only taking off 0.5mm max
here and there.
The end result is a LE that is pretty straight in the grand scale of
things. Any non flatness is probably less than thickness of glass
going on, especially when you consider that the root and tip all have
overlaps that are going to create bumps.
In summary, jigging the LE is not a totally precise science and can be
frustrating if not decidedly nerve wracking when you finally commit to
the sticky stuff. However take it little by little with plenty of
good straight edges for guides (a length of dark cotton stretched
along the LE) and it should come true.
Cheers Carl
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