Hi,

When I went through this not long ago I tried Autodesk 123D and it doesn't import or export 3dm. Maybe someone knows if I'm wrong about that now. MoI can easily do this fillet task though. It's just of matter of figuring it out. It took me awhile too but what Burrman is showing is essentially the same thing I arrived at.

Make your wing a solid, make your plane a solid. Union them. Then fillet will work fine on the intersecting curve it makes. The reason I make the wing and plane a solid first is that sometimes there can be issues with either one. So this way you find which is messed up. But burrman did it all in one op which is fine too if you have good geometry.

What I do and what could work for you is make a leading edge (le) and trailing edge (te) curve. Then make an airfoil cross section out of two curves. A pressure side (bottom) and suction side (top). Sweep the airfoil curves along the two rails. Then see if it will union into a solid. If it does you should be good to go. I found lofting like burrman was doing can create some problem areas. Sweep gives you a very smooth surface. But lofting could work for you. You don't have as much twist as a propeller has. It looked like the lofting was working fine in burrmans video. I've never experimented with sweep when you have a non-constant chord like you do. You might need a height rail too. Michael or burrman would probably know. Bascially you would have to make sure the airfoil is scaling appropriately. I don't have that problem because I have a constant chord distribution.

Autodesk 123d is a bear to download and install. Also the interface is redonkulous. I think they were hitting the c-pipe when they came up with that. I prefer MoI. The other thing I liked about MoI was that it forces you to model more like you would build. Yes other software may work in more situations but thinking about how its made and modelling it that way seems like a good idea to me. My experience was all the failures I would have with MoI were in situations were you couldn't make it anyway. If you can make it MoI can model it.

I did have the issue with tolerancing however. That required an unintuitive switch to the mm unit system then back to the meter system I was actually using. Other than that MoI gets an A+ from me. Your fillet is way bigger than mine though, so this probablly won't affect you.

Just my two cent, I can see you're already well on your way to success.