Jabiru J450 Constructors Manual
Paint>Surface preparation
Tuesday, April 6, 2010
198 of 343
Paint>Surface preparation
It is true that any paint job is only as good as the preparation – shiny paint will most definitely
not
hide anything, and in fact shiny paint will only magnify any lack of preparation so surface
preparation will be the most time-consuming (and ultimately rewarding) part of the painting
process. If you want a slick-looking finish this is how to get it: prepare carefully!
The surface preparation process is: sand everything with 180 grit paper; fill where required
(Q-Cell for larger areas and lightweight body filler for smaller areas, nicks etc); sand the filler
smooth with 80 and then 120 grit paper; apply undercoat; fill pinholes and small nicks with
spot putty; sand spot putty with 240 grit paper; touch up with undercoat; final sand with 240
grit paper; wash with wax and grease remover, dry off and wipe over with a tack cloth.
Wear your half face respirator all the time during the sanding and painting process – there will
be a lot of fine dust generated and your lungs will thank you for it.
Lets get started!
Sand the entire surface of the aircraft and all parts to be painted with 180-grit sandpaper – we
use a random orbital sander for this task and for most of the sanding in the factory. This will
provide a key for filler and undercoat to bond to. Be careful not to sand through the gelcoat
and into the structural glass fibre – if you do go through the gelcoat do
not
sand any deeper.
Filler is used to fill imperfections in the surface to be painted, so you will use filler for things
such as filling in ripples or dents. When filling large areas we have found that the use of a
very wide (~9”) spatula (make your own from plastic) provides a good finish with little waste.
Mix up a large batch of Q-Cell and polyester resin to a creamy consistency and keep it in a
sealed tin: this mix will last about 5 days. Stir the Q-Cell mix thoroughly before each use and
then scoop out one hand-sized amount at a time onto a flat mixing board, add 3% of M.E.K.P.
catalyst/hardener and mix it in thoroughly - this will give you about 15 minutes working time
- and apply with a wide spatula. Allow to cure for a few hours until it cannot be scratched
with your fingernail and then sand back to a smooth finish with 80 and 120 grit paper.
Smaller areas can be filled with lightweight body filler and sanded back in the same manner.
You might find it easier to work on one area at a time when applying filler so that you don‟t
loose track of where you are. If you decide that this way or working appeals to you, you might
want to consider working on a specific area until you are happy with the finish and then
undercoating that area before moving on to the next area. Working in this manner means that
you are less likely to miss anything and the undercoat allows you to see where you have been.
Metal surfaces such as the noseleg must be cleaned and primed with an etching primer.
Now spot putty can be used to fill smaller imperfections such as pinholes and the like. Spot
putty is applied with a spatula, left to dry and sanded back with 240-grit paper. Work your
way around all surfaces in this manner and then apply undercoat to all spot puttied areas.
By now many days will have passed and all surfaces should be smooth and undercoated.
All surfaces can now be hand-sanded with 240-grit paper as the final stage in surface
preparation, then all dust can be blown away and everything can be wiped down with a clean
cotton cloth. Wash everything with warm water and detergent and then with automotive wax
and grease remover and then allow all surfaces to dry off completely.
At this point the entire work area must be thoroughly cleaned and the floor and walls washed
with water to wash away and damp down any dust.