scrollF4

scrollF4

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I'm getting ready to form the front edge of my canopy/skin junction. I've been presented two great options for epoxy fill material--SuperFil and Aeropoxy Light. I dove into the VAF search engine and read everything that bubbles up. Now, I'd love to hear from my fellow offenders and repeat offenders about the pros and cons of each product. Both appear to be easily formed and sanded, with low levels of pin-holes, etc.

Any really good reasons to (or to not) use one over the other?
 
Super-Fil is super easy to work but super expensive. Aeropoxy is almost as easy and a little cheaper. Micro and epoxy are a fraction of the cost which lets you be a little more flexible in making up multiple batches. The right mix will work almost as easy as Super-Fil and you can vary your mix as desired.
 
Go with Micro...

I tried the Superfil and it works fine. Easy to sand, not difficult to get ready. It's not much easier than Epoxy/Micro though and it's much more expensive. I also like the ability to tailor the Epoxy/micro to the consistency that I need.

I'm currently working on my canopy fairing and using West system and Micro. The superfil is sitting on the shelf so that should tell you something. The Superfil would be a good option if you just had a small area to fill quickly and don't want to buy all the epoxy and micro. That's generally not the case on the RV's.
 
I have used both. I prefer Aeropoxy light, it is easier to get to lay out the way you want.

The issue with those is the resin settles in the bottom of the cans and it iss a pain to get each thoroughly mixed before you use it.

There is another option in that US Composites sells a filler (called SM Fairing compound) to add to your own epoxy. I like it because it is relatively cheap ($12 for 5 qts) and no can mixing, plus it is red/maroon so it is easy to see contrast when applying. I found the white micro hard to see how it was filling, when spreading thin and then sanding. But, your milage may vary.
 
West systems has several different fillers available to be added to their epoxy resins. The Fairing Filler is the easiest to sand, but structurally the least. I used each of their products as required for the various levels starting with the structural fillers and finishing with the fairing filler. As you progress away from the structural additives the epoxy becomes easier to sand. I believe this provides more flexibility for finishing than using a fixed viscosity product.
 
scrollF4 said:
Any really good reasons to (or to not) use one over the other?
Click to expand...

Tried SuperFil back in the 90's. Never tried Aeropoxy Light.

Nothing wrong with pre-mixed filler....it works, within its narrow spectrum of intended use.

The claims of "easier sanding" and "less pinholes" are very subjective.

Sanding ease is mostly a function of epoxy/microballoon ratio. A dry mix sands easier. I'm told adding talc is another approach, and some recipes seem to include ground plastics. The base material in all lightweight filler is microballooons. I use glass micro only, and I'm as lazy as the next guy. Some builders are real cheapskates about sandpaper. Buy good stuff and replace it often.

Voids and bubbles are due to air entrainment during mixing. Mixing thick pastes like SuperFil in a cup will entrain lots of air. For premix use a mixing board just like bondo.

I realize the price of composite filler is not a big deal in the context of an RV. Still, you can buy a pound of glass micro, a pound of flox, and a pound of cabo for the same total price as one single quart of SuperFil. With these base ingredients in hand you can do anything. It's a lot like prepared food from the freezer case vs fresh ingredients.

My task this AM was to pot some phenolic hinge material in a glass flange. Mix 20 grams of a high Tg epoxy with 6.6 grams of hardener (see why I don't use pumps?), toss in some flox and a pinch of cabo, and I have exactly what I need for this particular task, without waste. Tomorrow I can mix a lightweight filler, or a structural filler, or a casting material, or......well, you get the idea. The blue stuff would still be on the shelf.

Anyway, you want comparison opinions? Go to any RV fly-in and look for the unpainted birds just out of Phase 1. Sure as sunshine there will be at least one party-colored airplane....blue here, red there, gray, beige, black, every filler color in the spectrum. The builder tried 'em all, looking for the "easy" one. ;)
 
Thanks, Everybody

Lot's to think about, and I'm sure I'm overthinking it, but you've all given me great insights.
 
I agree, roll your own, cheeper, easer sanding, better, go West Systems an all will be compatible.
 
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