So we are now trying to build envelope coming with shape around something like this:

As you may see it is quite simple concept of joining two ellipsoids with interlaced cylinder reaching maximum diameter of 2m. So the front part is traditional ellipsoid with w=2.5 (A), followed by a central cylinder w=1 (B), closed by another ellipsoid of w=3 (C). The plan is to buckle in the ellipsoid A so it will all end up being ~6m long.
The idea is to do a 5:1 scaled model and send it to Windreiter guys for review and a quote. To be able to do so, we actually need to draw parts which we can glue together next. Here we’ll be using classical pie/rugby-ball seems method, hoping that it will all work out when inflated.

Having a radius of 1m, maximum circumference comes to 6.28.
C=2πr=2·π·1≈6.28319
Divided by 6 to get height of each part we are getting h=1m. Scaling down 5:1 this is 20cm + 2cm for seem we have the first parameter 22cm.
With the W – part A this is going to be half-ellipse of -> 52cm (scaled 2.5m/5 + 2cm for seems), part B is a simple cylinder of 20cm and part C is -> 62cm (scaled 3m/5 + 2cm for seems).
To get this transformed this onto a paper, I prepared myself a tiny Excell helper (with another help from here). Where X is calculated with =B$2*COS(RADIANS($A5)) and Y =B$1*SIN(RADIANS($A5)).
Ellipse A:
H | 22.00 | |
W | 52.00 | |
a | x | y |
0 | 52.00 | 0.00 |
10 | 51.21 | 3.82 |
20 | 48.86 | 7.52 |
30 | 45.03 | 11.00 |
40 | 39.83 | 14.14 |
50 | 33.42 | 16.85 |
60 | 26.00 | 19.05 |
70 | 17.79 | 20.67 |
80 | 9.03 | 21.67 |
90 | 0.00 | 22.00 |
100 | -9.03 | 21.67 |
110 | -17.79 | 20.67 |
120 | -26.00 | 19.05 |
130 | -33.42 | 16.85 |
140 | -39.83 | 14.14 |
150 | -45.03 | 11.00 |
160 | -48.86 | 7.52 |
170 | -51.21 | 3.82 |
180 | -52.00 | 0.00 |
190 | -51.21 | -3.82 |
200 | -48.86 | -7.52 |
210 | -45.03 | -11.00 |
220 | -39.83 | -14.14 |
230 | -33.42 | -16.85 |
240 | -26.00 | -19.05 |
250 | -17.79 | -20.67 |
260 | -9.03 | -21.67 |
270 | 0.00 | -22.00 |
280 | 9.03 | -21.67 |
290 | 17.79 | -20.67 |
300 | 26.00 | -19.05 |
310 | 33.42 | -16.85 |
320 | 39.83 | -14.14 |
330 | 45.03 | -11.00 |
340 | 48.86 | -7.52 |
350 | 51.21 | -3.82 |
360 | 52.00 | 0.00 |

Ellipse B:
H | 22.00 | |
W | 62.00 | |
a | x | y |
0 | 62.00 | 0.00 |
10 | 61.06 | 3.82 |
20 | 58.26 | 7.52 |
30 | 53.69 | 11.00 |
40 | 47.49 | 14.14 |
50 | 39.85 | 16.85 |
60 | 31.00 | 19.05 |
70 | 21.21 | 20.67 |
80 | 10.77 | 21.67 |
90 | 0.00 | 22.00 |
100 | -10.77 | 21.67 |
110 | -21.21 | 20.67 |
120 | -31.00 | 19.05 |
130 | -39.85 | 16.85 |
140 | -47.49 | 14.14 |
150 | -53.69 | 11.00 |
160 | -58.26 | 7.52 |
170 | -61.06 | 3.82 |
180 | -62.00 | 0.00 |
190 | -61.06 | -3.82 |
200 | -58.26 | -7.52 |
210 | -53.69 | -11.00 |
220 | -47.49 | -14.14 |
230 | -39.85 | -16.85 |
240 | -31.00 | -19.05 |
250 | -21.21 | -20.67 |
260 | -10.77 | -21.67 |
270 | 0.00 | -22.00 |
280 | 10.77 | -21.67 |
290 | 21.21 | -20.67 |
300 | 31.00 | -19.05 |
310 | 39.85 | -16.85 |
320 | 47.49 | -14.14 |
330 | 53.69 | -11.00 |
340 | 58.26 | -7.52 |
350 | 61.06 | -3.82 |
360 | 62.00 | 0.00 |
Of course we’ll use just a part of those ellipses getting:

And:

Now let’s get practical!
Sounds like the wrong approach. Why not a plain cylinder – vastly more volume, vastly less complicated, and since you’re not pushing through any air (rather – tunneling the air through it) a cyl would be more efficient as well, right?
Thanks Chris, well the aim of this exercise is to prepare “how to” for the Windreiter guys to get us a proper envelope. So while cylinder would probably do, I though that giving it bit more blimpy shape would be better. 🙂
FYI – That’s called the “sheet metal workspace” in Fusion360 – which also lets you do the overlapping seams, folds (which you can fold or unfold to work on in the software), and so forth and can output to a laser cutter when you’re ready to glue…
Yep! I saw something similar in Blender and it wasn’t good at all, but I assume that Fusion 360 will be much higher quality. Can’t wait to give it a go! 🙂
co zkusit kostku? 😁
😛