On Sunday, November 4, 2018 at 12:00:05 AM UTC-7, Fraser Wilson wrote:
Last 2 coats of Vinyl ester primer sand with 180g next. The
reason for so many coats of fairing primer and primer is to sand to
make sure the surface is flat with no flaws. If you don't do this
the finish with not be good and all the defects will show at the
finish coat. Next sanding with P180.

http://www.craggyaero.com/ventus.htm

Richard

Richard
www.craggyaero.com
Last coat of JP202 Primer, tomorrow sand with P320, then
top coat with JAU Acrylic

I’m not saying the JP202 will be a problem but my experience of a
similar high build primer was that it suffered significant blistering
when only about 5 years old. It’s not really a problem for the auto
boys because who keeps a car that long?

The issue is the filling medium used in the primer;- Talc or chalk
are bad;- water enters the plastic due to fick’s diffusion where it
mixes with the chalk = carbolic acid which neutralises by drawing
in more water + generating pressure (osmosis) which pushes up a
blister.

As a result of this I currently would fill surface with chemically
inert filled (alumina/kaolin) epoxy or polyester, untill defect free
and then use a standard white 2 part primer.

Fraser

Fraser,

The last time I used this process was 17 years ago on my ventus wings. Since then the glider has been tied out in the sun and weather every summer April thru October. The wings except for some chips and dings are still in excellent shape.

Richard
www.craggyaero.com