RE: a canopy cell that blew out - someone speculated that perhaps the fabric color might have had anything to do with it.
Excerpt from Poynter's "The Parachute Manual":
* * *
9.3.1.8.15. Sun Damage
The ultraviolet rays of the sun will damage nylon and will ruin a parachute in short time. The angle of the sun's rays, the position of the material in relation to the sun, the time of the year and the time of day, screening factors of glass, etc. all determine the extent of the damage. Glass absorbs some of the ultraviolet rays, but it does not screen them out entirely. Fluorescent lights work on nylon only half as fast when in close proximity, which is bad enough. Incandescent lights are relatively safe.
Type I Fabric, Percent Breaking Strength in Ibs. lost
-----------------------------------------------------------
Outdoors, summer sun: Outdoors, summer sun, behind glass:
--------------------- -----------------------------------
one week 52% one week 40%
two weeks 71% two weeks 61%
three weeks 94% three weeks 85%
As demonstrated in the above chart, the sun's rays deteriorate the nylon quite rapidly and glass slows the process but little. The parachute's exposure to the sun must be kept to a minimum. Tests indicate that once nylon is exposed to the sun, the damage is done; it will not regain its strength if then stored out of the sun. Some new nylon yarns have been developed which resist damage by ultraviolet rays and they do not deteriorate quite as rapidly. The thinner the material, the quicker the damage; thick materials screen the sun from the inner fibers.
Some late 1957 and early 1958 Pioneer manufactured Navy 26' conical canopies have been known to come apart like tissue paper; there were 200 to 300 in the batch. Prior to 1958, a titanium dioxide delustrant was used to treat nylon fibers to make them dull. It was soon discovered that when exposed to light, this chemical treatment accelerated fiber deterioration. MIL-C-7020 was rewritten to specify only bright, untreated nylon for canopies. See the 1962 report released by the National Research Council of Canada (No. C-98-935).
It is interesting to note that many sport parachutists pack outside in the sun and that if we assume that their canopies are exposed 15 minutes each time, then after 280 jumps, the assembly has been in the sun an equivalent of seven 10-hour days which is probably enough to lower the strength 50% and this does not count the two minutes per jump when the entire parachute is exposed.
Dyed fabric, such as international orange, deteriorates faster than the natural (white).
The damage is identified by a yellowish color when viewed in daylight and a white fouroescence when viewed by ultraviolet light. Dyed components are usually excessively faded.
* * *
The above was printed prior to the invention of zero-P nylon fabric, so I don't know if that changes anything...
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Excerpt from Poynter's "The Parachute Manual":
* * *
9.3.1.8.15. Sun DamageThe ultraviolet rays of the sun will damage nylon and will ruin a parachute in short time. The angle of the sun's rays, the position of the material in relation to the sun, the time of the year and the time of day, screening factors of glass, etc. all determine the extent of the damage. Glass absorbs some of the ultraviolet rays, but it does not screen them out entirely. Fluorescent lights work on nylon only half as fast when in close proximity, which is bad enough. Incandescent lights are relatively safe.
As demonstrated in the above chart, the sun's rays deteriorate the nylon quite rapidly and glass slows the process but little. The parachute's exposure to the sun must be kept to a minimum. Tests indicate that once nylon is exposed to the sun, the damage is done; it will not regain its strength if then stored out of the sun. Some new nylon yarns have been developed which resist damage by ultraviolet rays and they do not deteriorate quite as rapidly. The thinner the material, the quicker the damage; thick materials screen the sun from the inner fibers.
Some late 1957 and early 1958 Pioneer manufactured Navy 26' conical canopies have been known to come apart like tissue paper; there were 200 to 300 in the batch. Prior to 1958, a titanium dioxide delustrant was used to treat nylon fibers to make them dull. It was soon discovered that when exposed to light, this chemical treatment accelerated fiber deterioration. MIL-C-7020 was rewritten to specify only bright, untreated nylon for canopies. See the 1962 report released by the National Research Council of Canada (No. C-98-935).
It is interesting to note that many sport parachutists pack outside in the sun and that if we assume that their canopies are exposed 15 minutes each time, then after 280 jumps, the assembly has been in the sun an equivalent of seven 10-hour days which is probably enough to lower the strength 50% and this does not count the two minutes per jump when the entire parachute is exposed.
Dyed fabric, such as international orange, deteriorates faster than the natural (white).
The damage is identified by a yellowish color when viewed in daylight and a white fouroescence when viewed by ultraviolet light. Dyed components are usually excessively faded.
* * *
The above was printed prior to the invention of zero-P nylon fabric, so I don't know if that changes anything...Share this post
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