Envelope Rip Panel

Many gas balloons still utilize a rip panel.  Most modern balloons use deflation ports or an oversized valve so the gas can be vented quickly without tearing the envelope.

The rip-panel is located inside the envelope near the top of the balloon, with its upper end about 3 ft from the valve.  It is commonly made in the form of a narrow slit with a length equal to about 1/5 of the balloon's circumference.  More positive discharge areas and minimum length of seam for reinsertion can be made by using a triangular or quadrilateral opening.

A rip-panel consists of a reinforced opening in the balloon covered by a reinforced piece of fabric.  There three types of construction commonly used for rip panels.

1.     The panel is cemented in place (not sewed), and when being ripped the cemented seam is pulled apart.  The lap of the seam should be 1 inch to 1 ½ inches.  This type has the advantage that the same rip panel can be repeatedly reinserted.  However it rather heavier to pull then either of the two other and unless inserted within a few weeks of the flight may be impossible to pull by hand.

2.     The panel is sewn, and taped; when the panel is pulled out the stitches are torn.  This type is easy to pull, and the same panel can be used several times provided care is taken that the stitches are slightly off the line of the previous row of sewing.  This type should, however be used only on net balloons.

3.     The fabric is torn.  To enable this to be done the panel must be made in such a manner that the warp of the fabric is paralle to the side of the triangle.  When 2-ply fabric is used, it must be of parallel construction.  This type of panel pulls easily, but is difficult to replace.

If a sewing machine is available for repairs, construction (2) is to be preferred.  Otherwise, if simplicity is desired, then 1 is the best.  The primary issue with rip panels is that it should pull out easily when landing in a strong wind.