Faster Inflations (Don't Spread Out the Balloon)

[hotairballoonist]

We have all seen this but has anyone thought it thru?

 

Do you spread out your balloon before the inflation?  WHY? 

 

Lets talk about the inflation.  In simple terms "Inflation" is the process of putting air into the balloon.  So lets think about this. 

 

I have a water pitcher with a gallon of milk in it and I have a standard plastic gallon milk jug.  Who can pour out the milk the fastest?  Yes the Pitcher because the mouth of the pitcher is much larger than the gallon milk jug. 

 

So what does this have to do with the balloon you ask?  The smaller the mouth the longer it takes to put the air in.  The larger the mouth the more you can put in. 

 

When you first start to inflate your balloon the balloon is empty.  As you put air into the balloon a bubble begins to develop at the top of the balloon.  The rest of the balloon is laying flat.  As the bubble at the top of the balloon grows it extends down the balloon toward the mouth of the balloon.  When the bubble reaches the mouth of the balloon it begins to enlarge the opening.  The bigger the opening in the mouth of the balloon the more air you can put in and the further back the inflator fan can sit.  SO.....

 

If you spread your balloon out on the ground it will take longer for the bubble to reach the throat of the balloon because it will have to fill the entire area you have spread out on the ground before the bubble will start to head to the mouth of the balloon.  Spreading out the balloon will actually make the inflation time longer.  If you wish to help the balloon inflate the part of the balloon that could benefit from you pulling it out is the bottom third of the balloon near the mouth.  The formula for Force is area X pressure.  The fan has a static pressure.  The middle of your balloon has a large area so the force (area X pressure) is greatest in the middle of your balloon and least at the throat.  If you want to help your balloon inflate faster help the part that has the least force, just up from the mouth of the balloon.

 

JT

[Apex Balloons]

Excellent explanation!

 

Another benefit of the no-spread method of inflating is that your crew will have a much easier time holding the mouth open, since the air filling the balloon tends to hold open the mouth automatically after a certain amount of air has entered the envelope. A very exaggerated example of this is the "blow it out of the bag" technique (or a more refined alternative: strategically removing envelope straps from a fully-snaked-out envelope) which concentrates the volume of air at the bottom portion, which keeps the mouth size at or near maximum diameter through the entire inflation process. I do not practice either of those methods, but simply start the fan(s) when the balloon is snaked out but not spread out in any way. One or two crew members are only necessary to hold the mouth up for a minute or two until enough air is in the non-spread balloon such that the mouth holds itself open. A skirt makes it necessary for the crew to hold the mouth for much longer, and in many cases, all the way through hot inflation. One notices that most all commercial advertising and ride balloons have scoops. This is not a coincidence.

 

Pilots who go through the needless effort of spreading their envelopes out prior to inflation also force their mouth crew to perform a much harder task if there is a moderate or stronger amount of wind, due to the tendency for that bubble of air to retreat to the top of the balloon before allowing the lower portion to fill out last. The lower half of the balloon (including the mouth) is tightly-stressed along the vertical load tapes, low, and flat (oblong) with much more force required of the crew to hold the mouth up and open because of the stress on the load tapes. Flapping of the fabric in the roof of the mouth is another negative side effect of spreading the envelope prior to inflation. This can damage the fabric over time. In one case, I have even witnessed a lower panel tear away and up from the Nomex during inflation of a balloon that was close to the end of its service life and inflated in that manner.

 

Any envelope spreading efforts are best practiced after the balloon has enough air in it (at least 40-50% full, otherwise the mouth risks closing up) that one can walk underneath one side, fluff a significant amount of air underneath that side near the equator (to use as an air cushion to protect the fabric from anything on the ground), and walk the bottom of the envelope fabric back out to the side entered from. Repeat the process on the other side once and you can get almost all the loose fabric spread out with minimal ground contact, avoiding abrasions and possible tears. A modified technique to this that I learned from another large ride balloon pilot is simply to lift the bottom of your mouth, skirt, scoop, etc. in order to deliberately let air from your fan(s) blow underneath the envelope as it's about 30-60% full. The air will form a giant cushion underneath, and the envelope will actually spread itself out even quicker than with manual intervention, without even having to leave the basket! This affords a quicker inflation with less risk of tearing the fabric on unforeseen gremlins.

 

One final note: There is almost never a person on the mouth of my balloons by the time the burners come on. Use your fans, wait until the balloon is completely cold-packed if it's windy, and sneak some heat into the balloon until your cables are taut before you go full-blast (if that's your style).

 

Happy flying!