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Old Nov 01, 2009, 03:27 AM
Stranger in a land
Haole's Avatar
Hawaii
Joined Dec 2007
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Thanks very much, I'll have a look at your motor in a minute. Here, this is my current project; a 14' quad. I'm prepping my file to output contours in order to build the 8'+long fuselage plug.

The saddle was an area of focus during development of the airframe since I designed the wing section (it has a fair amount of undercamber at the root) and the bird has a T-Tail, so layup needs to be very accurate. I sorta used the techniques mentioned above to get these perfect tangential fillets--variable filleting, then manual splitting and joining of curves to create the finished contours.

Hope to see your propellers fair in!

Carl
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Old Nov 01, 2009, 03:32 AM
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I hadn't noticed the command 'curve network' at all. One more arrow in the quiver: Yes that will be very useful to play with.

That's why this thread is SO useful. Many many thanks.

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Old Nov 01, 2009, 03:36 AM
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Quote:
Originally Posted by Haole View Post
Thanks very much, I'll have a look at your motor in a minute. Here, this is my current project; a 14' quad. I'm prepping my file to output contours in order to build the 8'+long fuselage plug.

The saddle was an area of focus during development of the airframe since I designed the wing section (it has a fair amount of undercamber at the root) and the bird has a T-Tail, so layup needs to be very accurate. I sorta used the techniques mentioned above to get these perfect tangential fillets--variable filleting, then manual splitting and joining of curves to create the finished contours.

Hope to see your propellers fair in!

Carl

TBH the props are finally sanded to shape by eye, so any extra wood is easily rounded off..I would say the same with a mould plug: finally I suspect you will just add filler or scrape and polish a bit to get it right.
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Old Nov 01, 2009, 03:38 AM
Stranger in a land
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Hawaii
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Yeah, you're correct of course--those are 2" intervals so there is still some art of sculpting the final result, which I like. The nice thing is that I know I will be very close to the computer model for the product.

Give the curve network command a whirl, it's very powerful and glad I could help out. I'm still figuring this software out if you couldn't tell, so don't be shy regarding sharing more tips. This is rapidly becoming my favorite thread on RCG thanks to you guys.

Carl
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Old Nov 01, 2009, 04:02 AM
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I already did..created some random curves and made a random surface. It looks pretty useful. I'm still at the stage of " I know what I want to do: Now which commands get me closest, the quickest?'

By the way beware of just using cross -sections of a solid when laminating: That caught me out with the first prop. A given lamination needs to be the greatest of two curves at any given point, as defined by the cross sections at each side. I create solids and take a mesh outline, or do a curve boolean on the silhouette.

AS an aside, I don't suppose anyone has a true vector font that comes up as just curves rather than filled outlines?
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Old Nov 01, 2009, 04:43 AM
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These are ugly but are somewhat legible. Just install it to your Windows font directory and they'll show up in Rhino.

C

Edit: whoops, these two are better.

Edit2: Machine Tool Gothic wins hands-down.
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Old Nov 01, 2009, 04:58 AM
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My Hero <swoon>

You have just saved me about 4 hours per model work..
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Old Nov 01, 2009, 05:14 AM
Stranger in a land
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Hawaii
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That's great. Your turn now! I've gotta hit the sack but perhaps you or our German friend will have some helpful tips posted by morning

The biggest command that I'd like better understanding and control of is editing meshes, such as refining a surface from a lofted network. Ex: adjusting protrusions from a fair fuselage surface. I can see how it works but it is ungainly and/or I'm doing something wrong (maybe not pulling on enough handles or something). There's gotta be a better way to manipulate a NURBS surface and have the software automatically fair the adjustments, like you'd adjust a bezier curve in Illustrator, Photoshop or Corel.

Signing off for now.

Carl
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Old Nov 01, 2009, 06:36 AM
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Wish I knew the answer.
I have the same question.

Maybe I need the T-splines package?
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Old Nov 01, 2009, 01:36 PM
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problems with complex nose surfaces

OK,

I have one for you guys. The fuselage nose that is shown below, I had to create in a number of sections to allow the program to calculate the surfaces as close as I could for shape. They are now far from perfect and I was wondering if there would be a better way to to do this. I had to use 9 different surface sections to get the curves that I wanted and I wonder if there is an easier way. most were done through Curve networks, but I find that the edges between two surfaces don't reflect perfectly when shown as rendered. This is good enough for modelling, but it bugs me because it is not right!!!

Question, is there a function that allows one to smooth between to butted surfaces?

Float Flyer
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Old Nov 01, 2009, 01:53 PM
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you could but this would take horrible calculation efforts to you pc...

the following analogon in 2d

A SPLINE is a line ( similar to a polynome) , defined by order / ~the amount of its control points.... as a line which is smooth and fluent can be defined by little amount of control points , has a sharp kink in this line to be defined by a very large amount of control points .. .and the order of the formula is also defining the calculation effort ... so sometimes breaking such a one spline definition into two straight parts reduces the efforts drastically ( balancing or weightening of the control points could also help a bit) ... so as you have done by using multimesh surface in 3D ( you can unify them using the puzzle button!!! or stitch them toghther as you have isues as the seams do not fit...)

your chosen strategy is probably one of the best for "normal PCs"
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Old Nov 01, 2009, 02:00 PM
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for smoothing joined surfaces try blend edges

But its best not to join except where there is an edge - i.e. round the cocpkit front.

I would probably have done that in three part - aft fuselage, forward fuselage and cockpit, using probably sweep1, sweep2 or loft for the fuselage halves and a loft of some sort for the cockpit canopy area. I find these utter swine to do usually. If you want to extend a surface you can extract a cross section curve and extrude that along a bit.
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Old Nov 01, 2009, 04:15 PM
mcg
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fairing, curvature analysis

This might or might not apply. It shows how to fair surfaces using curvature analysis tools, using the example of a boat hull.

http://www.rhino3d.com/tutorials/fairing.pdf

Surfaces can be sometimes improved by experimenting with rebuilding and fitting to reduce the number of points.

As the tutorial remarks, and as a first principle, fewer curves work (much) better than many. In the shop, we can get a smoother curve on a fuselage by using many formers, because more formers integrate the curve better than fewer formers. In NURBS curves, for some reason, fewer is better. So it is counter intuitive.

In this example I think I would try to see if maybe there were some way to create the same surface using fewer curves.

mcg
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Last edited by mcg; Nov 01, 2009 at 04:30 PM.
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Old Nov 01, 2009, 04:43 PM
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very good article. Food for thought there.
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Old Nov 01, 2009, 06:00 PM
Stranger in a land
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Hawaii
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Got my contours of the T-Tail all pretty-like. Still undecided if I'll be building the plug in lateral or plumb split halves, but probably plumb since a horizontal rhumb line passes out of the center axis on one end or the other, depending on where I place it.

mcg, thanks very much for the article. I'll be studying up this evening. My goal in modifying surfaces is create simple protrusions or indentations such as venturis and instrument nacelles. Building the original surface with as few cross sections as possible definitely works best for creating a fair object to start with.

In my (limited) experience, if there is a large deviation however, careful placement of additional curves in that area lets Rhino interpolate with better results when using the Sweep2 command.

Carl
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