Boolean difference failed

[chetosmachine]

Hi all,
I'm pretty new to Rhino. In fact, i'm pretty new to everything that is 3D related...

I'm trying to make the design of a wing mold. What i've done is:
-draw the wing outline
-draw the airfoil (in fact, import it from a .dxf file)
-join the airfoil so it's a single curve
-"sweep 2 rails", being the airfoil the cross section and the wing curves the rails

Then, i want to make a cube, then substract the wing from it so i have a mold.

I draw the box, then try to make the "solid"-->"difference".
Then i have some troubles.
I have tried it 3 times. It only worked the first time. As it succeful, i tried to do some renders... while it was rendering, i tried to play some music and my pc freezed; i had to close everything.
when i reopen Rhino, the file had not been saved, so i had to do the "sweep 2 rails", then the cube and try to make the difference between wing and cube, BUT all i got is a message that claims "Boolean difference failed"

Any thoughts about what happens and how to solve it?
Kind regards,
Chets

[spoiledbrat]

Boolean operations work best when the object being union/subtracted is a SOLID. Solids are fully enclosed surfaces, with no holes. You can check if an object is a solid by selecting it, then using the ANALYZE_MASS PROPERTIES_VOLUME function. That will tel you if the surface is open or closed (surface or solid)
You should try to use the CAP PLANER HOLES function to close up the ends of that wings before trying to boolean, or (if the ends are not planar) split it with some rectangular surfaces, then cap the ends.
Also, without some kind of intersection between the objects (touching each other), the boolean operations will not work.


I would draw the "cube", and then BOOLEAN SUBTRACT the solid wing from it.

Rob

[HuFlungDung]

Rob's advice sounds good, not that I have used Rhino, but in general principle he is correct.

I would question exactly how you forced a sweep that included the wing tip. IMO, the wing tip does not likely share the airfoil shape in the sense that a profile could be swept around the end without creating a wrinkle in the resultant surface. Having worked on a few models of wings made by other people before I machined the molds, the wing tip detail was always a seperate set of surfaces, perhaps made by 3 edge surface construction. I do not know what this method would be called in Rhino.

Another option is to forget about doing the boolean operation, and simply use half the wing profile to create the airfoil surface, and then create a face frame around the countour, representing the surface of the block of stock. If necessary, the under side and the 4 outside edges can be constructed as individual surfaces (of a rectangular cube) and then merge everything, and voila, one half of the mold is complete.

[chetosmachine]

Thank you guys. I really apreciate your help and time.
So far, i've found that what i thought was a solid, it is not.
I still don't know how i can have achieved the boolean difference once, but now i think i know where the problem is.
By zooming a lot, i' ve found the cross section does not match the wing trailing edge (the "rear" curve).
What annoys me is that i cannot move the curves, nor the points, so they match
At the same level of zoom, i've found the airfoil that i thought was right, is not perfect. I think i must work on it a bit.

Any inputs are always welcomed.

As for the wing tip, first i would like to know the general how-to, then i will work on the small things that need some work.

Kind regards,
Chets

[spoiledbrat]

can you post your 3dm file? If you can just post the airfoil and the two rails (without your cube or 3d wing) the file will be very small. I would like to see what I can do with it.

[chetosmachine]

Sure, here it is.
Very kind from you
BTW don't worry if the the file is non-use and i have to start again. It just a matter of time, some practice and some questiosn well answered until i get it sorted.
As always, and since i'm a total newbie, any help is welcomed.

Kind regards,
Chets

[Dan B]

What annoys me is that i cannot move the curves, nor the points, so they match

Did you try manipulating the control points? Try the PointsOn command. This may be what need if your file is comprised of surfaces. If you have joined them into an open polysurface, you should explode it back to surfaces first.

Dan

[spoiledbrat]

your curves are probably exported from DesignFoil, a wing creation software. The problem with that is that the wing-curve is comprised of 257 control points. You should really think about re-drawing the curve with about 20 control points maximum. Your planform wing curve (the top view) is also made from a LOT of points. When you sweep curves like this, the resulting surface is so dense with isocurves (and control points) that it will be very hard to edit the surfaces.

I know that you do not want to deviate from your "perfect" wing curves, but if this is a flying toy, I would not worry about that.

I tried using the "rebuild" command to reduce the points, but that changed the shape of the wing in an unfavorable way. You will have to manually draw the curves to do it the way I would. I am only concerned about being able to edit the surface once you sweep the curves. 1000 control points is a lot easier to manage than 64,250 when dealing with a surface.

Do not be afraid to deviate, unless this is a Laminar airfoil that demands perfection. In that case, get a super computer and take a couple of weeks off work to work this wing out.

[chetosmachine]

Thank you guys ,
Dan, yes i tried to manipulate the control points with no effect.
spoiledbrat, thank you for your time. This is half a toy airplane, half a business so i need it to be the best i can do it. No access to super computers, though, so i will do it on my free time at home.

I've talking to a friend who has some experience doing this and first i will work on the airfoil (actually, made by "profili 2" software, exported to .dxf and imported in Rhino) to get a good one, then taking care of what i've been told here, start to really this look like a real wing.

I really appreciate your time & effort.
Kind regards,
Chets