Brett - Guess I'm still old school... interior fillets wise anyways. Using a monojet syringe really helps... you can make them very small and precise. Coming from ST60's and 46's, it took a while for Randy to beat me about the head and ears until I stopped using 1/2x1/2 motor mounts and 6/32's... LOL!
As to superfil vs/aeropoxy, I'll suggest a counter point or two for your consideration. Superfil is extremely ridged, and much lighter than Aeropoxy. I have been using it for years, since I stopped using Aeropoxy, and have yet to have a fillet crack or pull away, even post-mortem after a fatal crash. Not sure if the added strength is needed? So, if you can do a fillet nearly twice the size thats just as light and easier to sand, wouldn't that spread the load better? Plus, one major drawback I see with some uses is that when the fillet is hard to sand on a foam wing, some people have been known to sand into the sheeting and that's right where the wing is going to fold like a cheap tent. With Superfil, a finger whetted with alcohol slipped over the fillet at about half cure time almost eliminates the need for any sanding at all...
I'm genuinely interested in your thoughts on this, since I was pretty sure I was on the right track, you have me wondering what aspect I might have missed?
EricV
Super Fil sands a lot easier than AeroPoxy, and it works better as a filler. For fillets I use AeroPoxy because it's much tougher. Particularly on the tail, it spreads the load to the fuse sides much better and results in a much stiffer attachment. It's just enough easier to sand than Epoxolite than you can touch it up slightly if necessary.
Back in the ST46 days one of the tricks was to use Epoxolite fillets around the wing on the inside AND outside to keep the front end attached and stiff. That's arguably not necessary for TP motors, but we have certainly found that sometimes you still have issues with engine runs from vibration on the bigger engines. The airplanes will stay together and not have much problem with stress cracking but the engine run can be affected. One of the reasons I think I have more consistent runs than most people is that I still build the front ends about as stiff as I used to. Not to the Big Jim ST60 degree but aside from the internal fillets no changes.
Brett