Excellent discussion. Either building new or fabricating a new do-dad for the
plane I do the following:
After layup, I fill the surface with microballoons to fill the gaps.
This leaves a filled weave (sort of) that can be easily scuffed for filler.
Clean
and wipe with acetone to get your dust and paw prints off.
If not, I use 80-150 grit for a light scratch then use red or green Scotch-Brite
to rough up the dimples in the surface to a sort of dull state. Clean.
If using expand cell as a filler, I use a slightly wet fill then even out to a
very thin layer. The extra epoxy is heavy but it sticks for sure. Allow to
cure
and sand with 80-150 grit and my DA sander to get back to near the glass.
Refill one more time with a drier filler. The vibration of the pneumatic DA
is higher than a hand sand, but it is faster and will tell you if you have an
area that is not sticking well as you feel it and see the dry or not attached
area to crumble away.
At Scaled Composites in the dry heat of the dessert, once cleaned up, one worker
would lay on a thin clear epoxy coat and allow it to tack, then put on their
filler which was normally micro and epoxy as a paste (witch is really itchy and
irritating when sanding) but I used Poly-Fiber SuperFil which is expensive,
but nice to use and easy on the lungs and eyes. The reason the worker used for
the clear epoxy was assured bonding in a dusty environment of the micro and
the sticky epoxy allowed him to use a drier filler and get a smooth pull of the
filler to a consistent, flat spread.
Ideas are like butt holes, everybody's got one. That's mine.
I did an article some time ago on finishing and painting, it is on my website
https://www.customflightcreations.com.
Bud Yerly
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