In the attached file I am trying to trim a surface of a propeller blade to the propeller hub. In the attach image you can see that the blade extends way into the hub. BUT, when I try do to a split Rhino tells me they do not intersect.
If I do an intersection, I get a curve partially along the intersection. However, it fades out even in places where the two surfaces intersection.
How might i correct this?
Hello - it looks like you created the red surface using what amounts to the intersection curve - you can split the surface, using the Isocurve option and Int osnap to hit the iso that is the expected curve of intersection.
You can also tryInsertKnot > Automatic maybe 3 times on the revolved surface in the V direction, then Intersect.
-Pascal
using a MakeUniform on the red surface keeps the topography in this case and lets you split as expected. i believe it does not work because the isocurve is very very close to the intersection line.
You are correct the base of the surface was created at the intersection points. I extended the surface when that would not intersect. The plans show this intersection.
As you found out that’s a good way to make intersect fail
Why do you need to split or intersect? If you want this to look realistic there will need to be a large fillet around the base of the blade so that part of the surface is going to be cut off anyway .
Another thing that is designed to cause you grief down the road is making the blade with a singularity. You will be less likelly to have trouble if you make the blade surface as a trimmed surface like this Prop.3dm (653.1 KB)
Unfortunately, the intersection at the hub is what is shown in the plans. It seems the solution that problem is to split the hub using the intersection curves rather than the surface.
No fillet is shown in the plans but pictures of the props appear to show a very slight one.
The singularity has bothered me. Fortunately, that’s the end step so it does not appear to cause down the road problems (yet anyway). The problem is how to go from the blade cross sections from the plans to a trim-able surface. I’ve had to go to extremes to eliminate singularities in other places that did cause problems.
Anybody involved in the manufacturing of props knows there has to be fillet there. Which means the intersection doesn’t exist on the casting. It is just a theoretical construct used by the pattern-maker to develop the shape of the vanes. Typically the fillet would be defined in the notes in the drawing used by the pattern maker.
A propeller blade would have thickness so making that surface is hardly the end step if you want a realistic model.
