----- Original Message -----
From: "Garry Copeland" .
> Is there an optimum time between filling and sanding back?
Garry and all
FWIW I do not yet have first hand experience with filling and sanding
but I was present at a demonstration given by another builder some time ago
for the benefit of about 7 or 8 other Europa builders. The man who gave the
demo is very experienced with fibreglass work having designed and built
glass yachts as a profession and has also built a Europa of course. Whilst
everyone might not agree with the technique, thought I would share it
anyway.
When using the Expancel, it was applied fairly dry (to make it as light as
possible) consistent with still being able to adhere Ok.
It was applied quite thickly with the intention that extra filling later
should not be necessary. No thickness gauges of any kind were used, just
plastered on with a painters scaper which was about 4" (100mm) wide from
memory.
On the day after application, especially if slow hardener has been used, the
epoxy is not fully cured and the majority of the filler can then be removed
very quickly using a carpenters plane, the technique being to take it down
until one can see it starting to get thin. During the planing operation,
shavings were flying as if the tailplane was made of wood. This can only be
done on flat surfaces or simple curved surfaces of course like the wings and
tailplanes and I assume ailerons and flaps etc.
The rest of the material is then taken down to the final profile with
standard torture boards with varying grit sizes as normal.
I wish I had been able to take a video of the faces of all those present
that day (including mine) when we all saw one surface of a tailplane
prepared ready for painting in 30 minutes. Some present had already spent
days doing the same job and they were simply amazed and rather disappointed
I might add that their knowledge had been gained a bit too late.
How long to leave before sanding back? At the demo, the sanding was done
immediately after the planing but I think I might leave mine go for a week
or so to more fully cure after planing it down hopefully to help alleviate
further shrinkage after sanding. In fact, I may prepare everything up to
the ready to sand stage and then put it all in my closed in (and insulated)
trailer for the heat curing which I have not yet done.
Kingsley Hurst
Mono Classic 281 in Oz
|