Ask a Rigger | What’s Up with These Rubber Bands?
Ask A Rigger
Friday, February 16, 2024
Over decades, skydivers have enjoyed the consistent qualities of rubber bands available from Keener Rubber Company for retaining (stowing) the lines on their main-parachute-deployment bags. Then in late 2021, virtually unannounced, Keener closed the doors of its factory in Ohio. The remaining supply of Keener’s steam-cured rubber bands soon dried up, and the replacements that have been circulating are, suffice to say, different.
Rubber retainer bands may be the cheapest parts of a parachute deployment system, but you should never take them for granted. Failure of this key component can result in any number of opening problems ranging from pesky to fatal.
Alarms sounded last spring when some jumpers in the cooler climes discovered that their retainer bands had rotted over the winter. Many were of a type sourced from Alliance Rubber Company of Hot Springs, Arkansas. That company sold two grades of bands: one meeting U.S. military specifications (mil-spec) and one Alliance thought would serve the needs of sport jumpers more economically. Rather than steam cured like the Keener bands, all Alliance bands are salt cured.
Going down that rabbit hole a bit, any rubber band—the key ingredient of which originates from trees in Southeast Asian jungles—is subject to a variety of environmental factors, including heat, oxygen, light, moisture, sometimes strong electrical fields and who knows what else. Once a steam-cured band exits the curing process, it’s done and ready for service. Steam-cured rubber bands enjoy an indefinite—though not unlimited—shelf life.
However, salt-cured rubber bands like the ones Alliance produces keep on curing after the manufacturing process. Qualities such as strength, elasticity and durability evolve throughout their life no matter how they’re used or cared for. Compared to what skydivers were used to, they’re simply not as predictable or robust.
Alliance’s more economical “skydiver” bands had a lower natural rubber content than their mil-spec bands, and—sorry—everyone hated them. To their credit, once Alliance found this out, the company stopped marketing them to sport retailers and offered only the mil-spec variety— at least for the standard size of 2” x 3/8”. Last August, Alliance company representative Claire Leopard traveled to Providence, Rhode Island, for the bi-annual meeting of the Parachute Industry Association to address concerns and answer questions from the PIA Technical and Rigging Committees.
As a stop-gap measure, PIA issued an Informational Advisory from its Technical Committee in late November urging riggers to refresh all pilot-emergency-parachute rubber bands at each 180-day repack and cautioning skydivers to "inspect their main parachute retainer bands if not recently packed.” The Federal Aviation Administration already requires that any main parachute be packed no more than 180 days prior to use, but PIA didn’t clarify what is meant by “not recently packed.” One might wisely infer less than 180 days.
Based on the information Leopard shared with PIA, the Informational Advisory recommends storing unused rubber retainer bands in a cool, dark location inside airtight containers. Heat is apparently a real killer, so no keeping parachutes in hot vehicles or rooms (which skydivers are supposed to know already). Leopard even suggested refrigerating them. Talcum powder appears to extend rubber band life, but users should still track shelf dates and toss any bands older than two years in the dumpster (per Alliance). Skydivers’ already questionable habit of using stow bands until they break may prove a dangerous one with salt-cured bands in particular.
Keener’s departure from manufacturing left Alliance as the only U.S. manufacturer of rubber bands. So, for now, what we have readily available for the standard 2” x 1-1/4” retaining band is the Alliance mil-spec offering. Furthermore, Alliance provides the 1-1/4” x 3/8” bands used for many pilot emergency parachutes only in the lower-rubber-content formula, another reason PIA cautions riggers to replace them all at each repack. A few skydiving rigs use rubber bands for line stowage on the reserve in either or both sizes, so same deal. Check in with your rigger if you’re unsure.
T.K. Donle, chair of the PIA Technical Committee, invites skydivers experiencing noteworthy issues with the current supply of retainer bands to report them to PIA. And anyone needing more information on the status and developments regarding the rubber-band issue may also reach out to him at technicalchair@pia.com.
Kevin Gibson | D-6943 and FAA Designated Parachute Rigger Examiner
Rahlmo’s Rigging at Skydive Orange in Virginia