Hi Michael, Hi Andrei

The seam occurred after I carried out the Loft command. Perhaps I forgot to carry out a Join on that rail? Am I correct in thinking that a Join will make all the curve segments into one curve? Or should I draw a curve (the rail) as Freeform > Control Points?

Sorry these are probably obvious questions. I will read the manual again!

I'm not sure what do you mean. Post a screen and mark there you problem. Also if you want you can upload you project it will be easier to solve your problem.

Hi Brendan,

> Am I correct in thinking that a Join will make all
> the curve segments into one curve? Or should
> I draw a curve (the rail) as Freeform > Control Points?

Yes definitely use Freeform > Control Points where you can to get a smooth curve, one thing about surfaces and modelling from curves is that your surface is going to be as good as your curves so, bad curves equal bad surfaces.

What Michael is assuming and the way most would do is use a curve to Boolean>Diff the shape out as long as your model is a solid, you don't have to use Loft for everything as some might think ;)

Here's a short video showing what I've just explained.



Cheers

Hi Brendan,

> The seam occurred after I carried out the Loft command. Perhaps I forgot to carry out
> a Join on that rail?

Every closed surface has a "seam edge" in it which is a normal part of the surface's structure and can't be deleted. Basically every NURBS surface has an inherent rectangular structure to it like a rubbery sheet of paper. With a closed surface it's like if you took a sheet of paper and rolled it into a tube with 2 opposite sides touching each other. There will be a "seam edge" in that closing spot.

I had thought you were referring to all the small edges running across this area here:




That area of your model looked to me like it came from a boolean cut from a side profile curve, and probably the side profile curve is made up of numerous segments in it. If you wanted to get rid of some of those edges you could run the Rebuild command on your cutting curve before doing the boolean with it.


> Am I correct in thinking that a Join will make all the curve segments into one curve?

It does make it into one curve but the curve is sort of like a group that retains the original segmentation. If you use Edit > Separate on the curve you can see that it breaks apart back into the original segments.

If you want to remove segmentation and fuse adjacent smooth segments into single segments, the Rebuild command can be used to do that.

- Michael

Thank you all for your informative posts!
Sorry for the delay in replying, part timezone (New Zealand) and part work getting in the way of a hobby :-[

Probably a newby mistake but I didn't stop to think past joined arcs for making the curves, a Freeform curve with control points is surely going to be a lot more 'Bezier' and smooth.

The lines under the fus would certainly be caused by the method I used to create that 'cutout'. What I did was import an airfoil closed curve (PW51 if anyone is interested) and extrude it. The problem is to import, I used a PDF print of a DXF airfoil-plot. This method I imagine created micro-steps in the foil surface which would have transferred to the fus during my Boolean>Merge. By the way, I take it a DXF Import is not currently possible?

So I shall start from scratch (want to change the shape a little anyway :-]), use Freeform curves and build the airfoil-solid by drawing a closed curve over a JPG image of the foil plot and extruding it.

Will also play with the Rebuild command.

Cheers and thanks again.

Moi3Beta does do DXF import...

You could also use import points for the airfoil:
http://www.rcsoaring.co.nz/viewtopic.php?f=22&t=138

How about a 2d version of import points which assumes a z value of zero, (or a constant.) ?


Import the PW51 dxf, if available, or convert dwg to dxf, or ...

or
For the 2d PW51 text file, the commas can be replaced with period in text editor, notpad++, and probably a macro could add the z values of zero.
Or excel could concatenate z values and save to a text file.

-Brian

Or you could just grab the edit frame and drag everything to "flat"...

Hi Brendan, yes like Brian mentions above the v3 beta has DXF import, you can get the v3 beta here: http://moi3d.com/beta.htm

But often times DXF plans may be made up of all line segments and not actual smooth curves, so if that's the case you will want to maybe use the import as a tracing guide or rebuild it or something like that instead of using it directly because you don't really want to have something that's a curved form to be made out of a whole lot of little plane fragments.

- Michael

Attached is a PW51 text file, from the download link, which may or may not be different from your file.
It is space delimited, modified with decimal points instead of commas, and with "space 0" added manually to each of
the 232 points. The MoI script ImportPointFile (existing revised version), was used to import the points into MoI2, as Control Points, and also as
Points. The Control Points curve looks fairly good. The trailing edge shows one point which is irregularly placed, which may be deliberate?
(The trailing edge comes out badly with through points.) There are fewer points on the top of the cross section, versus the bottom.

Made some good progress thanks to all the suggestions. Got the wing section sorted out by using the foil coordinates to create an image and then building a MoI section over the image using Freeform>Control Points.



Sorry, have more questions though!

I can't seem to shell out the attached solid? I've used Offset>Shell and also Offset>Inset and the function fails to make any changes. Any ideas?



I can carve out a piece using Boolean>Merge with a down-scaled copy of the model-solid, but would like to find out what I'm doing wrong with 'Shell'.



Also the Fillet>Fillet function does not seem to work for the junction of the fin and fuselage base (not that I'm too worried). I selected the seam and and started with a fillet of 0.1mm but no go, also any ideas on this?

Cheers.

Hi Brendan,

> I can't seem to shell out the attached solid? I've used Offset>Shell and also Offset>Inset and the
> function fails to make any changes. Any ideas?

Shell is easily confused by little perturbations in surfaces, part of how it works is by generating offset surfaces and an offset surface tracks along the surface normal of the original surface. If the surface has wrinkles in it or worse yet folds back over on top of itself those get magnified on the offset (think of the offset being like a stick on the surface, any little wiggle at the base of the stick is magnified at the tip of it).

In the back part of your model it looks like there is a self-intersecting or "folding over itself" part in these areas here:




> Also the Fillet>Fillet function does not seem to work for the junction of the fin and fuselage base (not
> that I'm too worried). I selected the seam and and started with a fillet of 0.1mm but no go, also
> any ideas on this?

Fillet also involves generating offset surfaces and then intersecting them with one another, that's part of how it forms the path for the fillets to follow. So anything that hoses out offsets will usually also break filleting in those same areas as well.

- Michael

Here's another zoom in to just the one surface:






That looks like the kind of fold over / self-intersection as described here:

http://moi3d.com/forum/index.php?webtag=MOI&msg=1127.4

- Michael

To get a better end shape there, you probably want to either have the end come to a single point like the front part, or maybe if you didn't want to do that because it's kind of flat you might want to make it come to a flat end shape initially and then put a planar cap on the end and then fillet where they connect.

For the latter one you'd want to have the long rails end without swooping downwards, more like so:


- Michael

Thanks very much for the tips Michael.

I'll clean up some of the geometry and see how that goes, makes sense that 'wrinkles' would cause problems, not sure how I ended with them though.

With the tail-end I tried to Loft the tail the same as the nose (to an end point) but the Loft function didn't want to play ball. Actually the Lofts (on the four curves) seemed to be governed a little by the general happiness in the universe (ie: random) with a view change (zoom out seemed to help) sometimes causing the loft to succeed or not, but perhaps my swooping long-curves caused problems? I'll try the plan-off the end and see if I can then fillet it back to a softer 'cap'.

Will report how I go. Thanks also for the fold-over link I'll read that as well.

Hello,

You could try a two rail sweep with some regularly spaced profiles. This seemed to result in smooth surfaces as opposed to some other methods I tried out.

Which program is doing the zebra striping?

argo, what is the purpose of such a large vertical stabilizer?

Hello,

It's generated by the Lightlines feature in the VSR Shape Modeling plugin for Rhino 5.

Thankyou.