[balloon-makers] Panel Curvature

Mon Nov 13 21:35:22 CST 2006

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

I have drawn out the word picture and
think that I now understand how to arrive at the shape for a bulbous gore.

It wasnâ€™t exactly an answer to the
question that I asked but very close to an answer to the question that I was
about to ask. Isnâ€™t ESP wonderful!

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

<span style='font-size:
10.0pt;font-family:Arial;color:navy'>Thanks for taking the time to share your
knowledge

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

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

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

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

<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> Don Piccard
[mailto:private e-mail address] 
Sent: Monday, 13 November 2006
12:35 PM
To: private e-mail address; <st1:PersonName
w:st="on">private e-mail address; private e-mail address
Subject: RE: [balloon-makers]
Panel Curvature

<span style='font-size:
12.0pt'>Â 

Hey I passed differential.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 

I did not use calculations to make the
bulbous gore balloon.Â 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 

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.Â  I had seen several balloons split
due to circumferential stress caused by the aerodynamic load from rapid
ascent.Â  Just adding extra fabric in the circumference beyond the natural shape
just makes vertical wrinkles.Â  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 

When I saw the spinnakers being made at
Hanna Sailmakers in Costa MesaÂ  I realized that if I sewed eight spinnakers
together it would make a balloon with a great deal of extra looseness in the
circumference.Â  It worked.Â  Later I went to twelve gores to give better
flexibility and shorten each panel seam.Â  The sailmakers lofted the sail shape
on the shop floor.Â  They fold the material with a fold at the center of the
sailÂ  (one gore for me) and place that fold line along the line of the curve of
the pattern.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.Â  If you just
cut off the over lap, you would have a pointed nose on the sail.Â  Each panel
would haveÂ  obtuse angles at the center line.Â  So when you have the panels laid
out you loft the edges starting at the fold at right angle to the fold.Â  Note
that the folds of the upper and lower panels are at an angle to each other.Â  So
you are lofting the two panels separately.Â  The other end of the horizontal
seam is at the center of the overlap of the two panels.Â  The radius of the
curve is then defined by three points:Â  The two ends and the center.Â  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 

Donâ€™t forget to add the seam
allowance each way from the lofted lines.Â  Note that half way from the center
fold to the edges there is considerable overlap.Â Â  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 

A convenient empirical way to loft these
curves is to use a Â¾ x Â¾ inch plaster ground.Â  (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.Â Â  Near the
bottom of the balloon where the fold is a straight line, the ground will not be
bent,Â  At the equator where the curve is pronounced the ground will be bent.Â 
Once up and once down at each panel.

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

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 

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:0cm 0cm 0cm 4.0pt;
margin-left:3.75pt;margin-top:5.0pt;margin-bottom:5.0pt'>

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

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

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 

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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