Backyard Space Program

(image wikipedia)

Here is my attempt to print out the code for a 2 litre Morrisons (UK supermarket) water bottle, others may vary. I had to extend the overhang and I elongated the cone keeping angles at 45 degrees or lower for my printer (0 is vertical 90 is flat).

Make sure in slicer you use the Spiral vase mode and say 'yes' to the warning. I still haven't worked out how to 'switch off' the base, but i will update as soon as I know.

spiral mode printing

Final print came out with a thick base, but looked good.....

This was overall quite strong, except for the 45 degree upper cone which was too thin, and split slightly. This could be solved by varnishing, by using a thicker extruder nozzle or by simply making the upper cone a sharper angle.

Here is the edited code for MY bottle, it may not fit any others! Slight glitch in the angle calculations for the upper cone, which ill fix on the next update.

overhang =50;//to secure to bottle
bottleradius=98/2; //width of bottle/2
lowerconeheight=60;
sideanglelower=20;
sideanglehigher=45;

cylinder (overhang,r=bottleradius);
translate ([0,0,overhang]){
    cylinder (lowerconeheight,bottleradius,upperconeradius);
}
upperconeradius=bottleradius-(tan(sideanglelower)*lowerconeheight);
upperconeheight=tan(sideanglehigher)*upperconeradius;
translate ([0,0,overhang+lowerconeheight]){
    cylinder(upperconeheight,upperconeradius,0);
}

Bonus, don't have a 3d printer or want to choose a better material. Here is pepakura, a papercraft software. It would need a bit of fiddling, but could be worth it....

I have made a parametric nose cone generator in openscad to be used in conjunction with Slic3r spiral vase mode for thin walls and light weight. This is a Bi-conic design and is meant to be permanent, it provides the (currently) lowest drag while being FDM printable. A flat base may need to be carefully removed depending on your print settings, and if you have measured properly it should just slide over and all you will need to do is duct tape or glue in place.

For more info on bi-conic nose cones. https://en.wikipedia.org/wiki/Nose_cone_design#Bi-conic

overhang =30;//to secure to bottle
bottleradius=60;
lowerconeheight=40;
sideanglelower=30;
sideanglehigher=45;


cylinder (overhang,r=bottleradius);
translate ([0,0,overhang]){
    cylinder (lowerconeheight,bottleradius,upperconeradius);
}
upperconeradius=bottleradius-(tan(sideanglelower)*lowerconeheight);
upperconeheight=tan(sideanglehigher)*upperconeradius;
translate ([0,0,overhang+lowerconeheight]){
    cylinder(upperconeheight,upperconeradius,0);
}