Hi jiro, it really helps if you can post a .3dm model file that has the objects in it that you are having problems with.

Otherwise it can be difficult to guess what you might be running into just with a description.

> 1) I must be missing something. Is there a reason why when i model a
> 'wing' that has 3 equal parts then extrude it on the Z-plane that a couple
> of the parts are hollow and 1 is filled? (The 2 just extrude
> the outer points but not filled.

When you extrude a shape, it will only get automatically capped into a solid if it is both a closed and planar shape.

It's likely that your outlines either have a gap in them somewhere where 2 endpoints are not meeting up, or they could have a point moved up in z so that they are not planar. Probably something like that. If you post the .3dm file I can give you some more precise information.


> 2) When i try to combine the parts using the boolean>union, it doesn't work?

Tough to say without seeing the model... But from your first question above it sounds like you may have some pieces that are not fully closed solids, that can create some difficulties when you try to union them.

- Michael