OVERVIEW  
THE TRIANGULAR CARRIAGE   THE MIRAGE BURNER   THE FLEXNET ENVELOPE  

       FireFly Balloonstm are made at The Balloon Works in Statesville, North Carolina. More of a craftsman's workshop than a factory, The Balloon Works is where all aspects of a FireFly Balloon are designed and crafted. It's a place with the earthy, friendly smells of wood shavings, leather and wicker. Everything that bears the Balloon Works name is made there and the engineers still design the products in-house to ensure they're built to the exacting standards that have been progressively developing since 1972.

       Over 1200 separate inspections take place during the construction of each balloon. Every piece - valves, hoses, ropes, panels - whether fabricated in the workshop or not, undergoes a rigid incoming first-piece inspection. Every fuel tank is pressure-checked. Every roll of fabric is tested for tensile and tear strength, porosity and color variations, and flaws in weaving, before it's labeled airworthy. Each panel is inspected as it's sewn into its gore, and each completed gore is again inspected as it moves from one sewing station to another. Sewing machines are calibrated twice a day, every day, to ensure consistent conformity with their sewing specifications. When each balloon is finished, it's inspected again, fully assembled and inflated on the test field, under flight conditions. This almost fanatical attention to detail results in a quality-control program that is unrivaled in the ballooning industry.

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Concepts Behind The FireFly Balloon

An Overview

       The successful design of a modern Hot Air Balloon is an engineering problem that must combine three distinct components  - an envelope, an engine and a carriage - into an integrated, functional whole that is both safe and practical in its assembly. The Balloon Works, with its trademark FlexNet Envelope, Mirage Burner and Triangular Carriage has created the intelligent solution to this problem - The FireFly Balloontm.

The Triangular Carriage

       The Balloon Carriage is the most complex structure of the entire system and presents the most challenging design problems because of the variety of functions it must serve.

  • It must provide a structure strong enough to carry its Certified static and inertial loads safely.
  • It must provide secure accommodation for the pilot and passengers during the entire flight experience, particularly during landings.
  • It must provide secure, logical and convenient locations for instruments, fuel, plumbing and burner.
  • It should provide a safe and secure storage area for maps, strikers and tools.
  • It should be flexible, lightweight and well-balanced.
  • It should be easy and inexpensive to maintain and repair.
  • It should be aesthetically pleasing.

       The equilateral triangle is the most stable shape in nature and The Balloon Works has chosen it as the basis for many aspects of their product. Most apparent is the Triangular Carriage which is unique to The Balloon Works. For any given floor area, the triangle provides the most stable base and longest sides. The three 60 degree angles provide maximum floor space for pilot and passengers while storing the fuel cylinders, hoses and instruments safely out of the way in the recessed corners. The ingenuity evident in its construction is unsurpassed. The 9-ply birch hardwood floor is actually cradled in a net of six aircraft ropes certified to lift 18,000 pounds. Securely fastened to a central tie-plate by eye splices and protected from abrasion by super tough plastic tubing, the suspension ropes run through hardwood skids, up through the floor, up the carriage structure and out the burner supports to end in an ultra-strong loop used to fasten the toggles at the end of the envelope suspension ropes.
The wicker carriage is woven with a tight, vertical weave, well suited to resisting entanglement in branches or power lines. Horizontal weaves can easily snag. A finishing urethane coating inside and out ensures the wicker will resist drying out and becoming brittle or rotting from prolonged exposure to moisture. This maintains the wickers ability to flex, absorbing and distributing any bumps during landings.

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The Mirage Burner

The engineers at The Balloon Works, balloonists amongst them, developed a set of criteria by which they would design their burner system.

  • Burner Reliability - Both the primary liquid vaporization system and the pilot burner must be highly dependable to minimize malfunctions and flame-outs.
  • Burner Output - To increase flight safety margins, the absolute burner output must be extremely high.
  • Flame Characteristics - The flame must be efficient and clean burning, giving off a minimum of soot and radiant heat. The flame should be shaped to minimize scorches and burns to the envelope.
  • Mounting - The burner should be mounted so that the flame can be precisely directed, it cannot tip over or pose a danger to the people in the basket and it must be self-centering when the handle is released. The fuel lines should be isolated to prevent catching on branches or power lines. Passengers should be prevented from using them as support during landings.
  • Safety and Convenience - The burner should be comfortable to use and fully operational with one hand. It requires a fast on-off response time to reduce the likelihood of fabric damage during inflations and landings. It must not permit the flame to wash back onto the pilot or passengers.
  • Redundancy - In the unlikely event of a major failure in the primary burner, there must be an equally efficient back-up auxiliary system that is powerful enough to climb, arrest a descent and allow a controlled landing.
   

The result is the Mirage Burner. It has the highest heat output certified for balloon engines in the world - over 32 million BTU's at 240 psi tank pressure. Propane is forced through thirty-three feet of vaporizing coil, enters the flow guide to combine with air in a 60 to 1 ratio and is ignited upon exit by three pilot lights producing a long intense, nearly invisible blue flame. Pilot lights have their own pressure regulated fuel supply and the pilot flame burns deep inside pilot burner stacks making it next to impossible for air turbulence to extinguish them. Fire II was made more powerful and integrated as the auxiliary engine with its own separate plumbing, valves, withdrawal lines and burner outlets. Mounting on the uprights in a suspended tripod fashion places all the burner controls in the center of the carriage, equidistant from all sides or corners. Not surprisingly, the Mirage Burner and Fire II have become two of the reasons for the popularity of FireFly Balloons.

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The FlexNet Envelope

        Many modern Hot Air Balloons employ a system of horizontal and vertical load tapes into which the stresses of flight are transferred. Since these structures are rigid, the fabric panels of the envelope carry some of the load. This is known as a skin-stressed envelope. While not necessarily bad, it demands that heavier fabrics be utilized to maintain the integrity of the system for safe flight. Manufacturers of this envelope type tend to use nylon for its availability in heavier weights and its initial strength. They also favor using folded seems to join panels to each other and to the load tapes.
       The Balloon Works opted for a different school of thought. There is an obvious correlation between the volume of a balloon and its load lift capability. The system itself, of course, comprises part of that load and the difference between the system weight and its lift capability is what's left for the payload.
       The best way to understand a FireFly Balloon is to picture an orange with the segments running vertically. In balloons, these segments are called gores and the joints between them are called gore seams. In skin-stressed construction, a heavy web tape with adjacent panels sewn to it forms this seam. It's called a load tape because the carriage is suspended from it and the fabric stresses are hopefully transferred to it.

        The FireFly Balloon employs the use of a pocket running the vertical length of the gore seam. Inside the pocket, they've put a very strong and light rope, or load cord, which is free to move up and down inside the pocket. The rope is shorter than the seam and is attached at the top to the top girdle and at the bottom to the bottom girdle. The girdles are structural members in that they receive and transfer loads. Making the ropes shorter than the seams accomplishes two things. It provides the beautifully rounded gore shape and it ensures that the loads cannot be placed on the fabric panels. So, the only function of the fabric envelope is that it holds the air and provides a lifting surface.
       When it came to the task of sewing each fabric panel to its neighbour, The Balloon Works looked to a method of window construction that was used when glass was rare and expensive to replace. The mullions in a window today tend to be for aesthetics, but the original reason for this construction method was to isolate individual panes of glass. If breakage occurred, it would affect the panes individually and maintain the integrity of the whole, reducing the extent of the damage and hence the expense of repair.
       With Hot Air Balloons, restricting the extent of damage is a matter of safety so the Balloon Works developed the FlexNet Envelope Systemtm. In the system, each fabric panel is surrounded by a strong tape and adjacent panels are sewn into one side of the tape and not to each other. The tape acts as an isolating member, as a mullion in effect, and if a tear occurs, it may travel only as far as the tape before it either stops or is deflected back into the panel. With damage thus minimized, the pilot may be afforded more time to make a safer emergency landing.

The FireFly Envelope Valve

As a means of balloon deflation, the FireFly Envelope Valve, or parachute valve as it is often called, is by far the most ingenious approach to date. Its normal resting position is closed and it only operates by deliberate and continuous action. It is automatically re-sealable, irrespective of how many times it has been used, and no action is required to accomplish its closing other than letting it alone. It's capable of proportional valving, releasing huge amounts of air for deflation or small amounts for adjustments to vertical flight. Its position at the top of the envelope prevents its dislocation from snagging. How does it work? First, they put a hole in the top of the balloon with a stiffener around it to act as a seal. Next, they fill the hole with a fabric disc that's slightly larger than the hole. Attached to the perimeter of the disc is a set of lines that connect to each other at a focal point below, inside the envelope. This point is then attached to a rope which extends down to the carriage to act as the control for the valve. Another set of lines connected to the disc, are in turn connected to the envelope at the gore seams to limit the downward distance of the disc. To prevent the valve from popping out the top of the balloon, the load cords in the envelope (the ones sliding inside those pockets) extend past their attachment at the top girdle and connect to a central steel ring. The valve is held against this rope net with the push of the heated air inside the envelope. By using some simple laws of physics, the valve provides a venting capability and versatility superior to anything used before it in ballooning.

Click here To learn more about FireFly Balloons.




FireFly, Mirage and  FlexNet are registered tradenames of The Balloon Works.
The Balloon Works and FireFly Balloons Logos are registered trademarks
and are used here with the permission of The Balloon Works of Statesville, North Carolina USA.

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