<<I don't think you've shown any evidence that excess vacuum causes surface
defects. You should at least have a theory as to how that happens.>>
The idea was that the lower compression strength foam has a higher
displacement response. While testing the foam, it's very obvious that the
compressive
displacement is a continuous (and apparently non-linear) function of applied
weight. So as more pressure is exerted on the more compressible foam, it
should displace inward more than the lower compliance foam. At some point, the
path length around the core surface shrinks enough (while the skin does not)
that the skin should buckle inward somewhat, perhaps leaving indentations.
At least for the most recent samples, that was not a significant response.
<<If you mean a longer cure time for the wax then I can tell you that that is
not an issue.>>
No, I meant for the epoxy. I'm waiting ~ 24 hours before opening the bag.
Until recently, the basement ran ~ 80F but the temperature is dropping slowly
so, in the absence of a heater, I should probably leave them bagged ~ 48 hours
and then check the release quality. Or get a heater. The comments on the
ease with which the mylars should come off is very helpful. That's about the
way
the Turtle Wax is working but it is a soft wax and leaves a residue.
<<At what point does the carbon become fuzzed up?>>
While rolling it out on the beds. It's a uni sheet with cross stitches. I'm
changing to uniweb and the fabrics you recommended in a recent post - thank
you very much for that summary,
I pick up a few loose hairs on the roller and wind up dropping them nearby.
It's not very much but black shows up real well against a pink background.
This is purely a technique thing but as these wings get closer to emerging
from
the bowels of the workshop, appearance starts to be an issue. I'll work on
that.
***
Guys, every time you view Phil's video, you learn something new. The DVD
format is great for going over a particular step in detail. After adding up the
templates and leftovers in the shop, I've probably bagged over 100 wings over
the past 7 years - mostly HLG/DLG for myself. So when this latest problem
showed up, it was a real surprise. Both the videos and the comments here have
been very helpful - in some cases for identifying what is not the problem.
I still suspect pressure may be a variable for this light foam and layup.
However, if I had to blame one thing, the most likely culprit is handling the
cores while peeling the mylars. If you have to slide your finger under the
mylar to get it off, you may have a problem. If you have to tug real hard to
pull
it off, you may get a small delam somewhere (at least for this very light
layup). Experience seems to suggest the 25psi foam is a bit more robust than
the 15.
Although there's been a hiatus from bagging for ~ 2 yrs, my notes from
earlier indicate Foamular 250 with CSTs Partall (Green) never had this problem.
Cheap is never obsolete - but it can be costly in the long run.
Thanks for all the input,
- Dave R
PS - In the previous post I mentioned ACS as a supplier - sorry, that should
be ACP (as in Phil's note).
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