Rhino Rhino Rhino (hull thickness, offset surface, and unrolldvp for cnc cutting)

[metin_mehel]

Hi Guys,
I have an external hull surface of a hard chine boat. I want it to offset through inside and model the bulkheads. Also I will make unrolldvp surface for cnc cuttings. However when I did offset 10mm. then all the surface are getting smaller but some extensions intersects to each other. I tried to trim them inorder to get final inside surface but it is not possible to trim it...
How can I assign a inside thickness to a hull?

[DCockey]

Sounds like you have two separate questions: one about unrolling developable surfaces and the other about creating interior surfaces.

Originally Posted by metin_mehel

Hi Guys,
I have an external hull surface of a hard chine boat. I want it to offset through inside and model the bulkheads. Also I will make unrolldvp surface for cnc cuttings.

Is the surface developable? Not all hard chine boats have developable surfaces. How was the surface created?

Check for twist using CurvatureAnalysis and look at Guassian curvature. The Guassian curvature of a developable surface will be zero or very close to zero.

Developable surfaces can be unrolled using UnrollSrf. If the surface is not developable it can flattened using Squish. Squish is an add-in for version 4 which can be downloaded from the Rhino3D website, and I believe it is included in version 5. Be aware that when a non-developable surface is flattened using squish there will be some stretching or compression introduced into the flattened surface. Various options allow some control over how the distortion occurs.

However when I did offset 10mm. then all the surface are getting smaller but some extensions intersects to each other.

If the outer surface is convex then the offset inner surface will be smaller. That's basic geometry.

I tried to trim them inorder to get final inside surface but it is not possible to trim it...

First, the usual cause of the problem. Look carefully at the intersections of the inner surfaces you created. Depending on the angles of the surfaces the intersections may not extend to the edges of the surfaces. If so Trim won't work. Trim requires the intersection of the cutting object with the object to be trimmed to extend to the edges of the object to be trimmed.

Next, a simple method to deal with the problem.
1) Create a new layer and call it something like Temp Inner Srf, or anything else you want.
2) Copy the inner surfaces to the new layer. Make sure to create copies and not change the layers. These copies will become the cutting surfaces used to trim the inner surfaces.
3) Use ExtendSrf to extend the edges of the copies of the surfaces. Make sure you extend them far enough that they will complete intersect the iinner surfaces to be trimmed.
4) Use the cutting surfaces with Trim to trim the inner surfaces.

How can I assign a inside thickness to a hull?

See above.

[DCockey]

Attached is a simple example of a chine hull with outer and trimmed inner surfaces.

Since this is only a half model of the hull I also needed to create a surface on the center plane to use for trimming.

[metin_mehel]

hi,
this is my file. I modelled exteriour by delftship and now I want to assign a thickness to model bulkheads and I need to flatten inside surfaces.
Thanks

[DCockey]

Here it is with the surfaces unrolled. I put them in new layer.

[DCockey]

You should be able to create and trim the inner surfaces using the instructions above.

[metin_mehel]

Thank you very much David. First I should create inside surface then unroll.
Do you think the hull seems bad or not aesthetic?

[metin_mehel]

David I did not understand how I trim the inner shell

[DCockey]

What to unroll depends in part on the building methods used. If you unroll the simple outside surfaces then the resulting expansions will be slightly too large in some cases and the joints will require some fitting.

Unrolling the simple inside surfaces will result in expansions which are generally too small.

If you want to be very accurate you need to decide how the joints will be made. Will both edges be beveled so that they meet at the bevels? Or will one part be lapped over the other? Or ???

Spend a little while designing a simple box. Create the outer surface, then think about the different ways to actually build the box. Then create the parts actually needed to build the box.

It's simple using some software to create an outer surface and some pictures. But there is much more to designing a boat, even a simple boat.

[metin_mehel]

I will not use overlapped plywoods. Just beveled stringers. For the edges where two adjacent pw meets to eachother I will make a fillet with thickened epoxy. What is your opinion? Do you prefer overlaped pw? So I should offset 10mm inside and trim extensions but unfortunately I could not understand the trimming

[DCockey]

If you plan to fill the gaps between the plywood edges with thickened epoxy then the inner surfaces should be expanded.

Some questions:

What is your major goal?
1) Build a boat?
2) Design a boat?
3) Learn about boat design?
4) Learn how to use software such as Delftship and Rhino?

What is you experience in boatbuilding?

What else have you built?

What is your engineering or other technical background or experience?

How much experience do you have looking at boat plans?

[metin_mehel]

this is my catamaran