I have been asked by Anthony van Eldik how I got on with pip pin alignment;
here is the answer.
The new bolts were easy to screw in by hand, using the pip pins to give a
little leverage; having screwed them in to the measurements I had taken, we
offered up the wings. The port wing required half a turn adjustment, the
starboard was correct, so we took the wings out again, and then unscrewed
the bolts, counting the turns - 21 for one, 20.5 for the other. We then
cleaned the threads, both of the new bolts and within the bonded-in plates,
to remove old Loctite. We then screwed the new bolts in for 10 turns,
applied Loctite to the remaining 10 turns still exposed, and screwed in to
the agreed position. We then refitted the wings, and (because I was away the
following day), left the Loctite to set for 36 hours; that was Tuesday.
On Thursday morning I made the flox fillet; I was very concerned that, if I
used the Nyloc nut to position the washer such that it flattened the flox,
it might cause the new bolts to break away from the Loctite, thereby ruining
all the setting up; I therefore obtained 2 nuts without Nyloc heads, and
screwed them, with grease inside, up against the washers - finger tight was
enough to flatten the washer.
On Thursday evening we re-fitted the wings, fitted the Nyloc nuts, and
tightened them up with a standard ratchet; we then removed the wings again
ready for the lay-ups.
That all sounds simple; however, we had very great difficulty last night
getting the port pip pin in - it is definitely now a 2 man job, because the
wing needs to be tweaked forward (as the Mod instructions said might
happen), and quite a bit of pressure applied to the pin itself, both to get
it in and to get it out again. Before starting this, and in anticipation of
a possible problem, I got the pip pin rings welded so that they would not
just pull open under strong pressure. The starboard pip pin now goes in more
easily than before - and it was never difficult (neither of them were).
Today I have inserted the foam plugs, and laid up the 5 layers of BID, as
instructed - and the job is signed off by my Inspector, although all the
filling is still to be started - and as there was well over 2 mm filler
ground away over the root of the wing, filling and sanding down will have to
be done in 2 or 3 stages.
On Tuesday, whilst getting the bolts correctly set up, we did damage the
head of one pip pin (where the ring goes through), and John Wheeler at the
factory tells me that they have no spare pip pins in stock - so be careful!
In summary, I asses that because of the need to let 4 stages cure before
moving on to the next step (before getting to the filling and finishing),
Mod 74 cannot realistically be done in less than a week - and I have the
hangar space and all the tools and materials, and have been able to work on
a pair of wings at the same time. You need two people for the wings in and
wings out operations, but otherwise it is a one man job - 2 together will
not speed it up.
Any questions??!!
David
G-BZAM
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