[balloon-makers] Panel Curvature

[Don Piccard]

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hey I passed differential.<span
style='mso-spacerun:yes'>Â  It was in integral that I had a world class mathematician
for a professor and he was higher over my head than my mother was on Oct 23,
1934.

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Â 

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>I did not use calculations to make the
bulbous gore balloon.  <span
style='mso-spacerun:yes'>Â The invention was inspired by an orthodox cut
spinnaker sail (as contrasted to a radial cut).

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Â 

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>I wanted to add fabric into the balloon
way beyond the natural shape developed for fully inflated stratosphere balloons
to enable it to deform under dynamic loads. 
I had seen several balloons split due to circumferential stress caused by
the aerodynamic load from rapid ascent. 
Just adding extra fabric in the circumference beyond the natural shape
just makes vertical wrinkles.  That is
O.K. in a stratosphere balloon at launch, but I felt that wrinkles in a hot air
balloon would cause hot spots by insulation the skin from external cooling.

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Â 

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>When I saw the spinnakers being made at
Hanna Sailmakers in Costa Mesa<span
style='mso-spacerun:yes'>Â  I realized that if I sewed eight spinnakers together
it would make a balloon with a great deal of extra looseness in the circumference.<span
style='mso-spacerun:yes'>  It worked. 
Later I went to twelve gores to give better flexibility and shorten each
panel seam.  The sailmakers
lofted the sail shape on the shop floor. 
They fold the material with a fold at the center of the <span
class=GramE>sail  (one gore for
me) and place that fold line along the line of the curve of the pattern. <span
style='mso-spacerun:yes'>Â Â (I used a sigma five gore pattern to make it
nice and fat.) Â Because that line is
curved, the other ends overlap each other. 
If you just cut off the over lap, you would have a pointed nose on the
sail. Â Each panel would <span
class=GramE>have  obtuse angles at
the center line.  So when you have the
panels laid out you loft the edges starting at the fold at right angle to the fold.<span
style='mso-spacerun:yes'>Â  Note that the folds of the upper and lower
panels are at an angle to each other.  So
you are lofting the two panels separately. 
The other end of the horizontal seam is at the center of the overlap of
the two panels.  The radius of the curve is
then defined by three points:Â  The two
ends and the center.  On the floor, just
the two end points and the angle from the centerfold point (90) describes it.

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Â 

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Don’t forget to add the seam
allowance each way from the lofted lines. 
Note that half way from the center fold to the edges there is
considerable overlap.   At the center
fold and at the edges, the overlap is just the amount needed for your seam
allowances.

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Â 

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>A convenient empirical way to loft these
curves is to use a ¾ x ¾ inch plaster ground. 
(For a 3/8 inch folder to get the right seam
allowance.)Â  Hold it at right
angles to each panel at the fold and bend it to the center of the overlap at
the edge of the panels.   Near the bottom
of the balloon where the fold is a straight line, the ground will not be
bent,  At the equator where the curve is
pronounced the ground will be bent.  Once
up and once down at each panel.

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Â 

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Now draw the above word picture on paper
and see if I have described it fairly.

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Â 

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Please let me know how you do so we can go
back and edit this ..

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Â 

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Don Piccard



<font size=3
face="Times New Roman">





<span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:<font size=2
face=Tahoma>
private e-mail address [mailto:private e-mail address] <span
style='font-weight:bold'>On Behalf Of private e-mail address
Sent: Sunday, November 12, 2006
6:33 PM
To: private e-mail address;
private e-mail address
Subject: Re: [balloon-makers]
Panel Curvature



<span style='font-size:
12.0pt'>Â 





<span style='font-size:10.0pt;
font-family:Arial'>In a message dated 11/12/2006 12:10:13 AM Pacific Standard
Time, private e-mail address writes:



<blockquote style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt;
margin-left:3.75pt;margin-top:5.0pt;margin-bottom:5.0pt'>

<font
size=2 face=Arial>Dear All,

<font
size=2 face=Arial>I am trying
to write some software to calculate panel sizes and have come to a grinding
halt when it comes to calculating the curvature on the top and bottom of panels
in a horizontal cut panel design. Is there anyone out there that can shed some
light on the mathematics behind this problem?

<font
size=2 face=Arial>Â 

<font
size=2 face=Arial>Steve







<span style='font-size:10.0pt;
font-family:Arial'>I don't know anyone that has built more horizontal panel
balloons than Don Piccard. I'd recommend him to you but he didn't do that well
in calculus class. Oh well, I'll recommend him anyway. 





<span style='font-size:10.0pt;
font-family:Arial'>Â 





<span style='font-size:10.0pt;
font-family:Arial'>Good luck on your project.





<span style='font-size:10.0pt;
font-family:Arial'>Â 





<span style='font-size:10.0pt;
font-family:Arial'>Richard Rapp












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