Having had the internals of my starboard wing successfully inspected,
I'm getting ready to close it up. I offered up the upper rear wing
skin and noticed a few oddities.
First, the skin appears to be longer than required and it seems that
the tip end should be trimmed - there is a 5mm gap between it and the
tip moulding at the spar, if the TE is butted up. Also, in that
position the brown foam doubler doesn't clear the root rib. Thus it
seems pretty clear that the skin should be fitted with the root end
flush with the root rib flange, and the tip end trimmed to fit the
tip moulding.
I had to remove a small area of brown foam on the bottom skin, and
add a BID patch over the area, to accomodate my outboard horn box
(the aileron horn positions didn't quite match the wing mouldings)
and I will have to do the same with the upper skin, so it's not
sitting quite right yet. However, I noticed another reason for the
poor fit at the TE.
When looking at the underside of the top skin in the horn box
regions, I noticed artifacts that look like lines of resin proud of
the skin surface. They are about 1mm thick and run along close to the
TE, symmetrically disposed about each cutaway in the brown foam for
the horn-box, for about 130mm (inner) or 150mm (outer) with, at each
end, a line at right-angles forward towards the brown foam.
It almost looks as though something rectangular was pressed against
the undersurface of the skin during cure, forcing excess resin out to
its edges. Might even have been a T-shaped thing fitting into the
horn-box cutaways.
Questions:
(1) Are these excresences supposed to be there? (And if so what
purpose do they serve?)
(2) If they shouldn't be there, is it OK just to rub them down flush
with the surrounding area? (If I don't rub them down, it'll be hard
to abrade the area within the lines for the Redux bond.)
If no-one here has any prior art on this problem (I suspect not, as a
search of my archives failed to bring up anything drectly relevant)
I'll call Roger at the factory after the weekend.
(3) An additional query - my manual says the top skin is to be glued
on with a Redux-flox mixture, but I can find no suggestions about
what proportion of flox to add.
(4) And a final, possibly related thought. My inspector has suggested
bonding on the top wing skin upside-down (with appropriate jigging to
apply pressure to the joint areas) so that any Redux that squidges
out under pressure cannot fall onto the aileron controls, etc, but
instead forms a fillet at the edge of all the joints. I had forgotten
when discussing this with him about the flox - maybe that would make
it thick enough to avoid any tendency to drip?
regards
Rowland
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