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> Design
and Construction > Containers
> Modern Design Concepts
The containers of today do more than simply
enclose the canopy and deployment device. Sport containers in
particular need to be designed so that they contribute to the
deployment needs of the specific parachute. Piggyback designs
have separate requirements for the main and reserve containers
The reserve container is generally small, tight,
and mostly wedge-shaped. Virtually all popular sport systems
are designed around the use of a ram-air canopy. The deployment
method of choice is a Type 5 deployment bag. In the early days
of the ram-air reserve, there were certain container design
requirements specified by the manufacturer. These were
1. A hesitator loop configuration secures the
bridle and holds the bag in until the reserve pilot chute is
deployed and under drag. [Figure 2-9]
Figure 2-9. Square reserve hesitator
loop configuration.
2. Nonrestrictive corners to allow the bag
to be lifted off by the bridle in the event of a horseshoe-type
malfunction. [Figure 2-10]
Figure 2-10. Nonrestrictive container
corners.
These requirements were adhered to for many
years. Today, containers achieve the required holding and deployment
needs through design tailoring. The bottom corners of the reserve
container are designed so that the bag is held in place while
the pilot chute and bridle deploy and then releases the bag
to the airstream. At the same time, the bag can still deploy
quickly in the event of a horseshoe-type malfunction
These requirements were adhered to for many
years. Today, containers achieve the required holding and deployment
needs through design tailoring. The bottom corners of the reserve
container are designed so that the bag is held in place while
the pilot chute and bridle deploy and then releases the bag
to the airstream. At the same time, the bag can still deploy
quickly in the event of a horseshoe-type malfunction.
The main container is less restrictive than
the reserve in holding the main canopy in place during deployment.
This is important so that there is no tendency for the bag to
twist or be unstable on deployment. With many of the main canopies
used today, if the bag is unstable, it results in the main canopy
opening unevenly and causing spins and possible malfunctions.
Along with the main bag, the main risers must be able to deploy
evenly for the same reasons. In the early days of skydiving,
the primary body position was a stable, face-to-earth position.
This resulted in the main container being behind the parachutist
out of the airflow. One of the primary problems faced during
those days was the high incidence of pilot chute hesitations.
This was the result of the container designs
and the relatively poor performance of the available pilot chutes.
The advent of the hand deploy pilot chutes reduced the incidence
of hesitations.
In the face-to-earth position, the primary
purpose of the container is to hold the canopy and pilot chute
closed and then allow it to open during deployment. Today, body
positions experienced during free fall range from headdown to
feet-to-earth and everything in between. Where speeds formerly
experienced ranged from 110 mph to maybe 140 mph, today speeds
in a head-down position can exceed 200 mph. This has changed
the container dynamics to ensure a more secure system and increased
protection from the wind blast. These changes have resulted
in more secure and streamlined configurations to accommodate
these new requirements. Figure 2-11 shows a modern container
design shaped to meet the high-speed airflows of today.
An additional area that needs to be addressed
when designing piggyback systems is the main riser covers. In
the early days of sport piggyback designs, the main risers were
held in position by webbing keepers. As the sport progressed,
the use of fully enclosed main riser covers became the norm.
In their attempt to protect the main risers during high-speed
free fall, some designs tend to restrict the deployment of the
reserve container in the event of a “total” main
pack malfunction. When this happens and the main container remains
closed, the main riser covers do not open. Because of this,
there is additional restriction over the upper corners of the
reserve container. This contributes to higher reserve bag release
forces when deployed. In severe cases, this can result in a
reserve pilot chute in tow with potential serious consequences.
The balance between sufficient main riser protection and the
need for full reserve deployment freedom can be an important
design feature.
Figure 2-11.VoodooTM container profile
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