I am working on a small skiff that will be built from aluminum.
The bottom surface was created with DevSrf in V4.
The file was brought into V5 and Unroll Developable Surface was used but the unrolled surface has a wrinkle. The wrinkle is outlined by the red torus in the attached drawing.
V4 unrolls the surface without a wrinkle.
Further this if either the V4 or V5 surfaces are offset (6.34 mm) and the offset surfaced unrolled things get worse.
So what am I messing up :)
That doesn't sound good.
Is it possible you can give me some curves so I can see what's going on in that case?
It sounds likely that its because of some other difference that you get different answers, but the only way to know is to look at the example.
I think I see what's going on.
The bottom is pretty flat so the rulings can go pretty much anywhere.
With the flat area, the locations are probably being influenced by numerical noise in the calculations. There may be a difference between v4 and v5 as far as choosing between very low twist locations. I'll look at that.
This is a good example to see what's going on.
Run DevSrf and pick the centerline then the inside chine.
Set Ruling density to 1 and Twist tolerance to 0.7
With Least twist selected, all of the rulings are green, meaning that they have less than 0.7 deg twist.
Check Show ranges and you'll see that the fans between the blue lines for the rulings on the flat part are very wide. Those are the limits of where the twist is under 0.7 degrees.
Change Twist to 0.6 and the ranges get smaller at the curved part but don't change visibly at the flat part.
Change to 0.5 and one of the rulings in the middle of the curved part turns red, meaning it's twisted more than 0.5 deg.
Change from Least twist to Shortest and see that the rulings in the flat part go straight across between the rails and stay green, which means that they are able to achieve 0.5 deg twist at the shortest distance between the rails. The rulings in the curved part all move as far as they can within the range fan to try to get to the shortest distance between rails. They can't get to that and still maintain 0.5 deg twist so they turn red.
So for that surface, with Shortest selected, you can get all of the rulings to under 0.7 deg twist. If you choose Shortest, you get the complete bottom surface. When you make that surface, you get the folded over part that got us here in the first place. I'll work on that.
Here's a description of what Twist means in the DevSrf dialog
When you nudge control points until an acceptable surface appears, how do you evaluate when the surface is acceptable?
I like the idea of using history with loft I'll give that a try.
I'll use both loft and DevSrf depending on the amount of curvature and what needs to be done with the surface.
The issue I've have with loft is the poly surfaces created. Often hull surfaces we work with are offset, trimmed or split to fit the plates together with the desired thickness.
This is the original set of 3D Curves in V5 for the skiff, before the sheer line was lifted 50mm.
The back (stern) of the surfaces would be trimmed off afterwards