fiberglass help wanted

[E. D. Eliot]

Generally, I have found working with fiberglass and epoxy an enjoyable learning experience. Some of it, I actually enjoy - so here is where I need help - I am building an RV-12 which, as you all know has a tilt up canopy.

I want a good a crisp line across the canopy front where the fiberglass layup attaches to the plastic material at the front/bottom of the canopy. I don't want to give in and accept 'that's good enough'.

The edge of my epoxy layup has a few very small jagged edges where the fiberglass meets the canopy front no matter what I do. These measure maybe 1/64th inch or so.

I am using several layers of electrical tape and laying the fiberglass edges against it. Results are ok but I would like to make it as close to perfect as I can.

Should I lay in a small layer of flox against the electrical tape there or what - I'm afraid that that solution would chip off as my 12 ages. Please advise - what am I missing here or doing wrong? Thanks in advance, Ed

 

[snopercod]

You're on the right track. On my Lancair canopy, I used a single layer of black vinyl electrical tape to mask the canopy. Then I lightly sanded the plexiglass and the edge of the fiberglass. Next I used micro (not flox) to feather the edge. IIRC, I went through this process a couple of times, applying another piece of vinyl about 1/16" back from the previous one.

 

[Av8torTom]

Wait until the epoxy has started to cure then use an xacto knife and a straight edge. The epoxy should be cured enough so it?s dry to the touch, but not so cured that you can?t slice through the epoxy and fiberglass.

 

[E. D. Eliot]

Thank you

This detail has been a real learning experience. Thank you both for the info. I appreciate.

 

[DanH]

No flox or micro for edging.

If the edge is sawtoothed, you should be able to slick it out using a technique similar to no-ridge paint edges.

I assume you've blocked the edge down to a one or two tape thickness as John suggested.

Pull all that tape, as it's probably scruffy from sanding. Get some 3M 471+ or 218 fine line tape. Re-mask with 1/32" offset from your current edge. A little variation to attain clean, straight lines is fine. Mix some neat epoxy. With a fine brush, paint in enough epoxy to fill the gap, then pull the tape before it cures. The tape edge will "melt" to a rounded edge, rather than the sharp ridge expected if the epoxy (or paint) was allowed to cure before pulling the tape.

After cure, re-mask again for sanding protection, this time right on the edge. Block sand any excess epoxy thickness so it blends with the fiberglass layer.

If the finishing plan includes epoxy sealing of the entire fiberglass fairing and skirt prior to high build primer, the edging is incorporated into the larger application.

Here is an additional offset at the paint edge. The fineline tape was peeled while the paint was wet, just as described for the epoxy edge. This canopy frame is all glass, so the process is repeated both inside and outside, with matched edges.

 

[E. D. Eliot]

Beautiful - thanks, Dan

Many thanks to you all who contributed to my knowledge - I appreciate.