Why balloons are expensive

and a simple way to make them less so

9/15/2000

Every major balloon manufacturer publishes a maintenance manual (instructions for continued airworthiness) that indicates that only fabric purchased from their factory is approved for use in their envelopes. If asked they will tell you that their fabric is the only one that they have tested and is therefore the only one included in their design approvals. This is true enough and of course this requirement extends to the webbing, thread and other materials used in the envelope as well as the actual tolerances and construction techniques used in building the flight system. There is also the issue of items purchased from the manufacturer going through an approved quality assurance process before they are supplied for use in repairs.

An experienced repair person can tell you however, that there is considerable difference of opinion between manufacturers as to the proper way to do things and the proper materials to use. All of these different design features and materials have been demonstrated and deemed to be airworthy by the FAA. Some of these FAA approvals are based on testing done in the United States and some are based on approvals from other countries.

A few examples by way of illustration are flat seams (TBW) vs french fell seams (everybody else), thread material (nylon for Cameron, with a warning that anything else renders the balloon unairworthy) vs polyester (Aerostar and others), stitch spacing (anywhere from 1/4" to 1/2"), edge distance minimum for stitching (1/8" for Aerostar) vs almost none at times (Cameron).

I'm not leading up to suggesting that balloon design be standardized, although that would certainly make my job easier and my inventory of materials and equipment smaller. What I do suggest is that when rebuilding, the owner should explore all the options as to material selection and not be forced into using only manufacturer supplied materials.

Owners should know that there are FAA approved procedures for the use of fabrics that typically cost less than half what the major manufacturers charge. This translates to a saving of about 25% on the cost of a major fabric replacement.

Are these fabrics safe? Of course they are, although people wanting to sell the expensive stuff will say no. Remember that they will be tested at each annual and they must meet requirements that the original manufacturer has established. Will they last as long? My experience tells me no, therefore I wouldn't recommend them in balloons that see a lot of use, at least not in the top portions. More on that later.

Who will benefit then? I have many customers who put on 20 to 40 hours per year. The difference for them between 300 hour fabric and 500 hour fabric is ten years vs seventeen years. Another point to consider is that over seventeen years the 500 hour fabric isn't going to last 500 hours anyway. Aging is going to significantly shorten it's life.

Who says that a balloon must be completely made of the same material? The manufacturer would obviously prefer to do so as he is interested in reducing his inventory as much as possible. In fact, most manufacturers do offer more than one fabric, although the options they offer are an expensive fabric and a more expensive fabric. When I built my experimental balloon, I chose to use parachute fabric for light weight, realizing that it's life won't be as long. Within that parameter then, I chose three different fabrics.

Approximately the top 1/2 is Soarcoat, expensive but silicone coated, producing good tear strength and zero porosity. From there down to about 20 feet above the mouth, I used F111 a "standard" parachute fabric with porosity measuring about 40 CFM on the Aerostar tester. The remaining fabric is some really cheap stuff with no coating at all. I found it so difficult to work with that I wouldn't bother with it again, but it does serve it's purpose. Total cost for all materials for the 65,000 CF envelope ran just about $5000 in 1995. Envelope weight is 115 pounds vs about 180 for a comparable Aerostar. Inadvertent dynamic testing of the envelope during an attempted tether over this past Labor Day weekend confirmed that even this light weight and cheap fabric is strong enough for balloon use.

The fabric in the bottom 1/3 of an envelope doesn't do much except contain the air during inflation. Aerostar for example considers it a "non-key" area with no porosity limits and only minimal strength requirements. It hardly sees any heat at all, so the deterioration on it comes from handling it. Why not use the $5 per yard stuff here? The savings for replacement of this portion of a 140 envelope would be $2600 or 40% less than using standard Aerostar fabric.

In summary, what I have described here are some alternatives that are FAA approved when the proper paperwork is completed and filed; they can produce a product which is good enough without the added expense of making it "too good".

Pete Asp

2000