Re: [balloon-makers] envelope shape

[Arnaud Deramecourt <private e-mail address>]

The software calculates the following shapes :
* sky, like sky balloons
* smalley (using the datum from the BBJ)
* Rolland, Sébastien Rolland is a french homebuilder of balloons. He did
this design for himself and some friends.

The calculations only provide gores that are not bulbous. In fact, the
gores are slightly bulbous.
The first balloon I calculated 3 years ago has only 16 gores which were
a bit "flat", despite the fact that I used curved top and bottom. I have
now changed the value (I double it, see after) of the height of the
curve at the bottom and the top.

              W
        ******************
       *        ^         *
      *         |          *
     *          |           * l
    *           |h           *
   *            |             *
  *             |              *
 ********************************
               W'

Assuming a trapezium (without curves) :
h : the height of panel
W and W' the widths
l the length of the titled sides

To have a good shape, you must increase h by a value that is :
eps = sqrt (h*h + ((0.5)(w-w'))*((0.5)(w-w'))) - h

In fact, this value is to small. I personnally double the value. This
give a slightly bulbous balloon. I did not though about really bulbous
gores.

You can see the result of such balloons:
www.dynafly.com
aerostation.free.fr/mfr/images/jpg/p181_13z.jpg (a bit dark)

In the near, I shall probably update my software in english/french. 
If you get trouble with the present release, do not hesitate to send me
an email with the exact parameters.

Arnaud

Tom Deering a écrit :
> 
> On 4/4/01, Tom Deering wrote:
> 
> >Arnaud Deramecourt wrote a piece of software that can calculate three
> >balloon shapes: "sky, smalley, rolland".  I haven't quite gotten it to
> >work, although I speak no French.  It's at
> >http://aerostation.free.fr/mfr/panel.zip
> 
> I still get errors, but it turns out the "Sky" and "Rolland" are both
> bulbous gore balloons.
> 
> I can see the shape of the individual panels as DXF files.  Curved on
> the top and bottom.  But I get errors when I run the program.
> 
> Tom
> ---
> tmd@deering.org    http://www.deering.org
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-- 
Arnaud Deramecourt, Toulouse, France

Tout savoir sur l'aerostation : vols en ballon, manifestations, ... ?
http://aerostation.free.fr
La construction amateur de ballons : http://aerostation.free.fr/mfr
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