topic Re: Create Surface edge offset in Fusion Design, Validate & Document Forum

Create Surface edge offset

gixxerrider73 — Fri, 15 Apr 2022 21:42:59 GMT

I have this top surface of this boat hull. I'm trying to offset the perimeter of it so that I make it overhang the hull by 15mm. My thought was kind of light when you use the offset tool in a sketch but I know it doesn't work that way. I'm stuck on the workflow approach to this.

The red line is to show how it want it to overhang all the way around.

Re: Create Surface edge offset

hamid.sh. — Sat, 16 Apr 2022 00:16:50 GMT

To get that edge you can first offset the surface (or Ruled Surface if you want more control), then make a new sketch (on any plane) and use Project/Include > Include 3D Geometry and select edges of the offset surface.

Re: Create Surface edge offset

jhackney1972 — Sat, 16 Apr 2022 00:16:46 GMT

I used surface planes to form the outside railing cavity and then filled it with a Boundary Fill command. You mentioned you want the railing to be 15 mm from the side of the hull but did not mention the deep. I used 15 mm for that as well but it can be edited is desired. The railing, right now, is a separate body but can be combined with the hull if desired. Model is attached. It is a rather long process but if need, I will be happy to capture it in a video. I colored the rail to make it stand out.

Re: Create Surface edge offset

gixxerrider73 — Sat, 16 Apr 2022 00:44:29 GMT

John,

Thank you, That isn't exactly what what I'm trying to do. I'll try to explain it better. I want to keep the top surface and thicken it to 5mm. This is a top deck and will be separate from the lower hull. Here is a view from the stern, hopefully this shows it better. I need this overhang to be part of the top deck, 15mm overhang and turn down 10mm.

Re: Create Surface edge offset

jhackney1972 — Sat, 16 Apr 2022 00:53:57 GMT

Do you want the railing to go around the stern also?

Edit: Will the railing be measured from the top of the deck or from the top of the side?

Re: Create Surface edge offset

gixxerrider73 — Sat, 16 Apr 2022 00:53:35 GMT

yes sir

Re: Create Surface edge offset

jhackney1972 — Sat, 16 Apr 2022 00:55:31 GMT

Does the top deck thicken into the hull sides or above the sides?

Re: Create Surface edge offset

jhackney1972 — Sat, 16 Apr 2022 01:39:59 GMT

Since your top deck surface is "inside"the hull sides, the top railing, as you describe it interferes with the hull sides. You probably will come back and tell me you do not want that so I did it twice. Once with the top surface as you have it and once where the top surface is even with the outside of the hull. The process is the same for all of these iterations.

Re: Create Surface edge offset

gixxerrider73 — Sat, 16 Apr 2022 11:17:40 GMT

wow!, that looks great. The outside version is ideal. a lot of steps, I follow most of what you did.

I attempted to combine the new body with the top deck and it errors about no overlap or possible coincidence?

Re: Create Surface edge offset

jhackney1972 — Sat, 16 Apr 2022 13:24:25 GMT

Two versions of your model are now attached. One is a complete Combine of the hull, top deck and railing and the other is a Combine of the hull and top deck with the railing as a separate body. I named the railing body in this one.

Re: Create Surface edge offset

gixxerrider73 — Sat, 16 Apr 2022 14:42:32 GMT

that's awesome. I see the offset face is what fixed it.

Re: Create Surface edge offset

TrippyLighting — Sun, 17 Apr 2022 13:24:52 GMT

I've seen your boat posts before, but did not have time to dig deeper into into it.

I am assuming the reason that you thickened the boat halves separately is because the usual shell command, or thickening a complete hull did not work ?

If there is still interest on why that is and how to fix it I can provide some pointers.

This is a shelled boat hull that addresses the issues.

Re: Create Surface edge offset

gixxerrider73 — Mon, 18 Apr 2022 22:29:40 GMT

I would be interested in your pointers as well. thanks

Re: Create Surface edge offset

johnsonshiue — Wed, 20 Apr 2022 01:25:45 GMT

Hi! Another approach is to leverage Ruled Surface feature. The ruled surface can be normal to the hull faces (at an angle). Then you can thicken the surface as a solid joining the hull body.

Many thanks!

Re: Create Surface edge offset

TrippyLighting — Thu, 21 Apr 2022 10:52:09 GMT

You sketching needs to be more precise. For example, in Sketch 9 you create a tangency condition by snapping the handle to the line. However, I personally don't usually use that "feature" and prefer to see the tangency or "smooth" constraint symbol. That way I can see directly when editing a sketch whether I missed a constraint or not.

I sketch 11 for example, you forgot one such tangency constraint.

also, usually I for curvature continuity (G2), not just for tangency (G1), although for many 3D printed projects, more than tangency is often not needed.

In sketch 13 (1) you use too many fit points. 2 is all that's needed, and you also forgot two tangency conditions. those can create near tangency conditions, which Fusion 360 is very sensitive to.

Last, but not least, at the bottom of the boat, you are lofting into a singularity. NURBS surfaces prefer to be 4-sided.
So one way to battle this is to trim out the offending area and re-loft it with a 4-sided patch.

I projected the edge of the boat to use it as an extrusion profile for capping off the boat so it could be shelled.

Usually I avoid projecting curved edges into sketches, because Fusion 360 has a strong tendency to create horrible curvature. So as a general rule, if you do project curved edges or curves from other sketches, always us the curvature comb to check the curvature for discontinuities.

It's OK in this case:

If all goes well, than the surfaces can be mirrored and stitched and the geometry shells just fine: