Fiberglass Surface Prep

[tx_jayhawk]

Hi All,

As I have nearly finished my cowling (and most of my canopy) and hated every minute of the fiberglass work, I am curious on guidelines for prepping the surface.

Some questions:

1) Appliying additional fiberglass
- Can it be applied over epoxy/micro or epoxy/flox (I don't think so?)
- If applying over a "finished" piece of fiberglass, how should it be prepared? Epoxy surface scuffed down to glass layer? Light sanding to roughen surface? Etc.
- How do gel coated items (wingtips, etc.) appy? Same rules?

2) Priming/painting fiberglass
- Must Smooth Prime or equivalent be applied first?
- Lightly scuff surface of epoxy?

Thanks,
Scott
7A Forever Finishing

[DanH]

<<1) Appliying additional fiberglass
- Can it be applied over epoxy/micro or epoxy/flox (I don't think so?)>>

Epoxy/micro: no if structural, yes if not structural or if merely used as a small core filet joining two right angle structural parts, epoxy/flox: yes for anything.

<<If applying over a "finished" piece of fiberglass, how should it be prepared? Epoxy surface scuffed down to glass layer?>>

Yes, 36 to 80 grit. Don't cut into the glass; the glass skin on a honeycomb core is pretty thin. Kill all signs of gloss and you're good to go.

I dunno about bonding to gel coat. I'd probably remove it.

<<2) Priming/painting fiberglass
- Must Smooth Prime or equivalent be applied first?>>

Gotta do something to fill the pinholes and scratches. Best is a pure epoxy wipe, squeegee it on, squeegee off all you can get, repeat in a few hours when the first coat tacks up. Harder to sand than Smooth Prime, K36 or whatever, but I'm finding it less overall work than sanding the SM and K36 multiple times following multiple coats. I've been experimenting with Clear Coat from System Three, a water-viscosity epoxy. The experiment parts had zero pinholes when I sprayed the first primer coat. Yessss!

<<Lightly scuff surface of epoxy?>>

Always before applying anything else. Kill the gloss.

[KTM520guy]

For pinhole filling try Evercoat Glazecoat. Works great, dries fast.