Question for Rhino users

**murphyaa** · #1 09-17-2011, 02:29 AM

I've got a question for Rhino users:

Sometimes when I try to unroll a curved part, Rhino will take a long time, then the result will be a tangled mess, rather than the part I intended. Unfortunately I don't have any pictures to demonstrate yet, so I'll have to wait until I get home to get some screen grabs. Sometimes it happens when I try to unroll canopies as well.

My question is, what am I doing wrong? Usually it's a smaller cone, or short rolled section (nose endcap, or usually nose gear strut).

Here's what I do. When I start off, I always set the measurements to small measurements equal inches. Then when I lay down the 3 view background bitmap, I usually set it 6 squares to each side of the green line. When I get to lofting, I usually set the redraw points to 50 or 100 so it's smoother.

Am I designing too small?

**goodduck** · #2 09-17-2011, 07:34 AM

how big is per squares? inch? mm? try scale up 2~400% unroll then scale back down.

**Willja67** · #3 09-17-2011, 07:55 PM

I really don't know about size issues and can only give you some generic advice. Hopefully it will be useful.

Sometimes if you trimmed a surface and then used that trimmed edge to loft the surface you are unrolling that can make Rhino hiccup. Also look for darkness in the corners of the surfaces (have to have shaded display on for that) which means that there is a gap in the edges used to create the loft.

Usually if I have the problem I go recreate all the edges used to make the loft and rebuild the curves.

Overall just dot all your i's and cross all your t's.

And there are still times that I can't figure out why rhino won't unroll something or does it really goofy.

ps do you have the most current updates for your version of Rhino? When i first got my copy it required one of the service updates before it would unroll anything.

Zathros · #4 09-17-2011, 08:48 PM

If you make any curves and connect them with a straight line, they will unroll. If you make a fuselage, use the side profile to draw a curve, and then use that curve to cut out the windows, windshield, etc, by extruding the curve, and then using the extrusion as a cutting tool. This never fails.

The first picture is the fuselage using the curves of the windows extruded and used as cutting tools. The second shows the parts unfolded. The 3rd picture shows straight lines (cross section profiles) connected to former in preparation for "Running 2 Rails". The 4th picture shows the "Surfaces" formed. The 5th shows the surfaces colored in, as a visual aide. If you run rails with curves for profiles, they will not unfold. it is best to split the parts using extrusions as shown, as the parts will then unfold as they exist, and the cut out pieces serve as templates for, in this case, the windshield, and windows.

**Gil** · #5 09-17-2011, 09:20 PM

Hi Murph,

I second what Will said. You also might try increasing the absolute tolerance to 0.0001 or even lower.

+Gil

**murphyaa** · #6 09-17-2011, 09:28 PM

Where do I do that?

Zathros · #7 09-17-2011, 10:34 PM

This is a simple hypothetical bubble cockpit. No curved lines, all parts unfold. Made only by running 2 rails. Rhino allows you to make things many ways, it especially allows for over complication. Since we are dealing with paper, this is one of the better ways. If you are going to make a plastic canopy, I know an even simpler way. The cut outs were to demonstrate that "Splitting" parts while before the are unfolded allows for easy unfolds. This also works of you project a line to the surface, which may be used later in Paint of Photoshop for graphics, or numbers, etc. location or reference

**murphyaa** · #8 09-17-2011, 10:56 PM

The way I make a bubble cockpit it to project the curves of the canopy shape onto the fuselage, then make arches wherever it changes direction. Then I loft between the arches.

I've noticed with all the design threads I see on here, that I seem to design a different way than other people. When they post their CAD drawings, either in Rhino or whatever software they use, they have smooth flowing curves and look almost like an actual representation of the plane. Half the time I look at the picture and think "How the heck are they gonna put that on paper with all those compound curves?"

Me, on the other hand (I know, bad grammar. Saying "I, on the other hand" sounded like I should be running for president), the first thing I look at when I get the 3 view imported is where to put the part breaks. I force the model to fit into a paper design before I even put mouse pointer to pixel. I do everything in my power to avoid compound curves and double curved objects. Sweeping rails is not my friend.

That's just how I am.

**looker** · #9 09-18-2011, 05:48 AM

How are you generating your surfaces? It's generally best to generate them by using the sweep 2 rails command otherwise Rhino can get confused about which directions the sweeps are travelling.

**murphyaa** · #10 09-18-2011, 08:50 AM

I loft between curves. I try to avoid sweeping rails because that generates double curved objects that have to be butchered to be unrolled or smashed.

Take the F3D canopy. For 3 days I fought with it, because I wanted to model the overall sideview curve. I did the sides by sweeping. It finally ended up with about 30 tiny petals per side to get that graceful curve. Then I tried smashing it. This is where I encountered the problem that generated this thread. I finally gave up and treated it like an extra wide normal bubble canopy with the flat sections.