Open a new document (Small Objects - Inches)
Keep all 4 viewports open but only work in the FRONT viewport.
Use the curve tool to create 1/2 of the profile shape of your balloon.
Select the Scale Tool
Select the Curve
Click on the Top then Bottom of Curve
For Second Scale Factor
Type in your desired distance (24" - 48")
Type Revolve and Select your curve to Revolve.
You must do this all in the FRONT viewport.
Select the Axis by dragging a straight line down from the top right corner of your line.
To create a straight line hold Shift and Click when the line is "OnOrtho".
Set start angle to 180 by typing 180.
Press Enter.
Set Revolution Angle to 360 by typing 360.
Press Enter.
To make the Balloon look Shaded.
Two Finger Click on the Perspective Viewport Label and select Shaded at the bottom of the drop down.
Select the Balloon in the Perspective Viewport.
Type Mesh and Press Enter. Then Slide the Bar to Fewest Polygons.
Press Enter
Drag the Mesh Balloon from under the previous Balloon.
The Mesh one will look less round and have segments.
Type MeshtoNURBS in the command bar.
Select the Mesh Balloon you just created then
Press Enter.
Separate your new Balloon from the Mesh Balloon.
Click the new Balloon type or press the Explode command.
Hold Shift and Select one sliver (Gore) of your balloon.
Once selected press the Join command or type it.
Type UnrollSrf in the command bar.
*Make sure the Explode check box is Unchecked.
Select the sliver (Gore) you just joined and press enter.
The unrolled piece will look like this.
Go back to all the 4 viewports and select the top viewport to see your sliver flat.
Use the tool DimAligned by typing it into the toolbar.
Click the edges of each section to add dimensions to your sliver (Gore).
Your final dimensions should look like this.
Once your have finished this you can start cutting out your template.