This is a description of a successful "classic" wing filling technique.
For those not affected, I will not feel offended if you delete this
posting here :-) NG
Hi Troy,
You're not alone, I'm plodding along at the back of the pack with you!
One advantage is that it gives us the opportunity to learn from the
others.
Over the years, I have seen some pretty clever suggestions.....and some
less so.
One of the early better suggestions was to use fishing line, but the
problem here is that is only follows the underlying surface - troughs
and peaks will be faithfully replicated, whereas the real intention is
to create an known profile.
Here is a trick that guarantees you the thinnest covering necessary to
fill the troughs, without risk of shaving through the glass peaks and
results in a dead flat surface with the minimum of filler, the minimum
of sanding, and can replicate any desired profile.
This works on any flying surface with a flat, or single curvature
profile (i.e. everything on the Europa "Classic").
The technique is to think big, filling 40 inch wide strips from leading
to trailing edge in one go. Each wing can be filled in six operations
(evenings) after preparation.
Tools.
I first created a filling/sanding spline from extruded aluminium (mine
came from an old double glazed door frame) 2.5 x 1 x 80 inches. This
stuff is dead flat and straight.
On the broad, flat side, I attached (using double sided tape) a
continuous strip of 3M Aluminium Oxide 120 grit paper, sold in rolls for
belt sanders.
The reverse side (long edge) is used as the filling tool.
This technique is a development of the fishing line method, without the
pitfalls.
The first step is to lay four 1-1.5 inch wide "master profile" strips of
filler (I used SuperFill) from LE to TE, starting at the wing tip,
spaced every 40 inches to the wing root. Note, leave a 4 inch space at
the extreme root to which the root fillet will be bonded later on. A
large syringe or caulking gun works well as an applicator.
When cured, the strips are now profiled. Make up templates if you want a
perfect profile. If you can get hold of the factory profiles - so much
the better.
You need to carefully sand these strips, using the spline spanning any
three at the same time to ensure all four align spanwise. This is where
the attention should go. By shining a strong light behind the spline,
you can gently reduce the height of these strips to the point that the
highest part of the glass only just touches the spline. This will
guarantee the thinnest possible filling later on.
Time spent here will save tens (hundreds?) of hours later.
When all four strips (per side) are the right profile and as low as you
can get
them and aligned spanwise, you can start the real filling.
Since the volume to be filled is now relatively small and reasonably
estimable, you will find that you don't need much filler to complete
each 40 inch wide section.
Pile a reservoir of filler along the LE between any two strips,
carefully place the spline behind the filler and slowly drag the spline
towards the TE.
Moving slowly, keep a steady pressure to ensure the spline remains in
contact with the
profile strips and aim to complete the entire action in one go. Don't
attempt to back-fill, it won't work.
When the speed is right, filler will not curl up behind the spline and
will "glaze" over behind. DON'T touch anything! leave it to cure.
When all three sections have been filled and cured, turn the wing over
and do the other side.
After cure, use the spline's abrasive side to level the surface using
alternate 45
degree diagonal stroke with spline aligned spanwise.
You will be amazed how little material needs to be removed and how soon
the finish is achieved.
The last tip concerns eliminating "sinking"
All filler continues to shrink for some months after initial cure. I
have seen some beautifully finished wings where the spar and ribs show
through after six months to a year.
To prevent this, fill the wings six to twelve months before you begin
final sanding/finishing. This way, the filler has shrunk as much as it
is going to BEFORE you finish it.
I did all of this and it worked superbly.
Hope this helps.
Nigel
----- Original Message -----
From: <TroyMaynor@aol.com>
Subject: Wing Filling
> Hi All You Classic Builders
>
> I am in the middle of filling the classic wing. I know, I'm probably
the last
> one in the field that still hasn't done this. But never the less I
have some
> questions for those of you that have done this. It seems the more low
areas I
> fill in the more others show up. I am using a drywall knife of about
12
> inches wide to spread the Superfil. (The widest one I could find.) I
used the
> fishing line method. The sanding splines are 42 ", 24", and a short
12" one.
> All are 4" wide. On one surface I tried using some black paint to
reveal low
> areas but these still are visible after more filler has been applied
over
> them, confusing the next sanding/filling phase. How did some of you
guys get
> those perfect finishes? How much of a mistake can be hidden with the
Smooth
> Prime filler? It's too late when you have the paint on it. (I'm still
"gun
> shy" after trying to prep a car for paint a few years ago.)
> HELP
> Frustrated in NC
>
> Troy 120
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