So after slathering on the "dry micro" and then taking a lot of it off again with the surform file, i have the following observations:
1. The surform file is a great bit of kit. "Cheese grating" took off 80% of the extra micro and the rest was easy to sand off. In fact, i missed some places and used it after a week or so to see if it still worked on cured expoy - no problems at all.
2. Once i started sanding, i used 80 grit on a long flat sanding block i have from my model aircraft days - this worked really well and i was able to cut the micro fast back to being flush with the aluminium skin. I was also able to contour the tip to a good shape, taking off almost all of the micro, but leaving the low spots filled. Sands a lot easier than car body filler in my opinion.
Having said this, there were a lot of holes which i would call bigger than just "pinholes" (there were a lot of those). I think the large holes were from voids when i trowelled on the micro - i am thinking it was too thick (you could definitely notice it getting thicker as i worked).
Is it better to make it a little runnier, or try a heat gun to thin it out? Would this "avoid the voids"?
Holes in the counterbalance end skin:
Holes near the trailing edges of the tips
I think these are just normal pinholes???
What is the best way to fill the larger holes? I am aware that adding more micro is a bad idea - polyester body filler from the car shop? Will the "skim coat" of neat epoxy fill these?
3. I am not a fan of the packing tape. I had 2 layers on the skin and in some spots sanded through either the top or both layers. I used a brand name tape, not cheap stuff, but this still sands through very quickly using 60 grit. This was fine, but meant the stuff was a real pain to remove (kept splitting). I am thinking of going back to the electrical tape.
Next up is the skin coats of epoxy. I plan on the following - with the part off the aircraft:
- Bush some on so that it it all glossy.
- Leave for 30 mins
- Squeegee it all off again with a rubber squeegee
- Leave for 30 mins
- Repeat until it looks like i have built up enough resin to fill the holes that exist.
- hope. pray. et al.
Here is an overall picutre of what it looks like. I was really happy with the hard sharp edge this process had created and a very even gap. I ended up sanding the edge very slightly lower than the skin, to allow for the thickness of the epoxy skim coats to come.
Thanks all for following - if anyone has any further advice i would really appreciate it. The shed looked like a Dean Martin song this arvo - snow everywhere.