Hi, I just wanted to try making a quick propeller in OpenSCAD, and thought I
had a brilliant idea, but it's not turning out exactly like I pictured it.

My plan was to do this:
//hull() {
cylinder(d=20, h=10, center=true);
for (x = [-100:2:100]) {
translate([x, 0, 0]) rotate([x,0,0]) cylinder(10, center=true);
}
//}

to create this, and then do a hull() on it to smooth out the edges.

http://forum.openscad.org/file/n10550/Propeller.png

But when I do a hull() on the entire thing it doesn't really look like a
propeller, but more like a treetrunk :/

Is there any way to make the hull "tighter", if you know what I mean?

--
View this message in context: http://forum.openscad.org/Smoothing-with-hull-tp10550.html
Sent from the OpenSCAD mailing list archive at Nabble.com.

Good question, I had to think about since yesterday. :)

Create each cylinder twice and hull each pair:

cylinder(d=20, h=10, center=true);

for (x = [-100:2:100]) {
hull() {
translate([x, 0, 0]) rotate([x,0,0]) cylinder(10, center=true,
$fn=4);
translate([x+2, 0, 0]) rotate([x+2,0,0]) cylinder(10, center=true,
$fn=4);
}
}

Best wishes,
Bananapeel :)

--
View this message in context: http://forum.openscad.org/Smoothing-with-hull-tp10550p10562.html
Sent from the OpenSCAD mailing list archive at Nabble.com.

Good solution Bananapeel. That is what I pictured in my head as well. Had to
get out of bed yesterday to try my "brilliant" idea, which didn't turn out
so good as yours did.

I'd like to research the sweep(), loft() and skin() functions as well. Those
sounds more like the proper way to create a organic surface.

--
View this message in context: http://forum.openscad.org/Smoothing-with-hull-tp10550p10563.html
Sent from the OpenSCAD mailing list archive at Nabble.com.

------------->8-----------
module Blatt(H=10, D=2, L=100, W=45)

{
translate([0, 0, L/2])
linear_extrude(height = L, center = true, convexity = 10, twist = W,
slices=50)
translate([-H/2, -D/2, 0])
scale([H,D,1])
polygon(
points=[
[ 0, 0],
[ 1, 0],
[ 1, 1],
[ 0, 1]
]
);
}

module Rotor(Hight=10, Size=100, NarbeR=10, Winkel=90)
{
cylinder(r=NarbeR, h=Hight, center=true);
translate([+NarbeR,0,0]) rotate([0,+90,0]) Blatt(H=Hight, D=2,
L=Size-NarbeR, W=Winkel);
translate([-NarbeR,0,0]) rotate([0,-90,0]) Blatt(H=Hight, D=2,
L=Size-NarbeR, W=Winkel);
}

Rotor(Hight=10, Size=100, NarbeR=10, Winkel=-90);
------------->8-----------

http://forum.openscad.org/file/n10564/propeller.png

--
View this message in context: http://forum.openscad.org/Smoothing-with-hull-tp10550p10564.html
Sent from the OpenSCAD mailing list archive at Nabble.com.

Thanks Koenig!

The result looks similar to Bananapeels, but this is very nice with the
parameterized setup. I see that you choose to start out with a 2D object,
which is extruded with a twist. Nice.

--
View this message in context: http://forum.openscad.org/Smoothing-with-hull-tp10550p10565.html
Sent from the OpenSCAD mailing list archive at Nabble.com.

You can change the polygon to a contour of a wing. But put it in a box 1x1

--
View this message in context: http://forum.openscad.org/Smoothing-with-hull-tp10550p10566.html
Sent from the OpenSCAD mailing list archive at Nabble.com.

I'm running OpenSCAD version 2014.03 on Windows from the pre-built
executable.  From time to time I hit MinGW assertion failures.  For example,

/home/don/openscad_deps/mxe-w64/usr/x86_64-w64-mingw32/include/boost/smart_ptr/shared_ptr.hpp,
Line 653

Expression: px!=0

which would seem to be a null pointer fault.  I'm wondering if handling such
things a little more helpfully might contribute to usability and acceptance.
I can certainly dig into source and find Line 653 to see what's going on but
an error message (however cryptic) with a return to the top of the
interpreter loop might be a little more graceful.

IMHO, as always.

Cheers, Scott