On 21/05/2017 16:29, MNLou wrote:

The resulting scratches under the nose seem to be in, not through, the polyurethane paint. There does seem to be some dirt embedded in the scratches that won't come out with soap and water.

I would welcome suggestions on what type of rubbing compound or correcting cream people with similar experiences have used to successfully remove the scratches.

I have owned and flown gliders with PU paint for many years and I would
never consider a refinishing a glider with gel coat. (Actually once you
have a decent PU paint job, you wont ever need to refinish it).

But PU has its weaknesses. The colour layer is very thin. If the
scratches penetrate the paint you cannot polish them out, you have to do
a touch up.

My approach to this:

Wash, then polish as best you can, then leave the scratches till the end
of the season. I normally accumulate scratches for two or three seasons
before touching them all up.


For an "airfield" repair. This is not a 100% invisible repair like a
professional job but it can still be pretty neat and you can DIY over a
weekend or two:

- Sand out scratches completely.
- Clean area with acetone to remove all traces of polish etc (or you
will get "brown stains").
- Brush on several thick layers of 2 part PU primer (You can mix up a
batch of 2 part primer and it will have a pot life of a few hours. But
once it is painted on the glider, it will harden within say an hour.
Thus you can use one mix to apply 2 or 3 coats to build up the thickness
without it running). It must be thick enough to allow final finishing in
one step, or you waste another day.
- Allow the primer to dry completely ( 24 hours). This is at least a
two day procedure.
- Sand carefully to restore contour and a smooth finish.
- Touch up the colour with two or three coats from a spray can. Thin
coats, do not let it run. Mask surrounding areas to protect them from
over-spray. Masking before is quicker than cleaning up afterwards. I see
you can now get PU touch up spray but I have never tried it, maybe next
time. Otherwise hardware store "fridge white" normally works.
- Finish with very light 800 to 1500 grit wet sanding, then polish. Be
very careful that you do not go through the top colour layer.


For a "workshop" repair:

- Do the same as above. But use a spray gun and matching PU paint
instead of the spray can for the final layer.


There is some skill required in the above. But if you own the glider it
is one worth learning. Each season you will get better and learn new
tricks. Alternately get a contractor with sailplane experience to touch
it up every few years.


Ian