Tonto 1 #1 January 20, 2004 What makes some manufacturers use one or the other - or the same manufacturer use different webbing for articulated Vs. Non articulated harnesses? tIt's the year of the Pig. Quote Share this post Link to post Share on other sites
councilman24 37 #2 January 20, 2004 Type 7 is 0.060-0.100 inches thick with a breaking strength of 5,500 lbs. min. Type 8 is 0.040 to 0.070 inches thick with a breaking strength of 3,600 lbs. min. Type 7 is a double plain weave and Type 8 is a 2/2 hering bone weave. (These are the old mil specs. I didn't look to see if there are new, revised PIA specs and if they are different.) source Poynter's "The Parachute Manual". As to why any manufacturer uses one over another in any particular application you'd have to ask them. If you have a particular case in mind I'm sure the members of this forum would be glad to offer their opinions.I'm old for my age. Terry Urban D-8631 FAA DPRE Quote Share this post Link to post Share on other sites
Tonto 1 #3 January 20, 2004 It seems most manufacturers use double type 8 on articulated harnesses, and type 7 and 8 stitched together for the lift webs, and only type 8 on the leg straps for unarticulated harnesses. Is an articulated harness weaker as a result of sections being stitched together at the rings vs. continuous webbing? tIt's the year of the Pig. Quote Share this post Link to post Share on other sites
riggerrob 643 #4 January 20, 2004 Type 8 webbing is plenty strong enough for most skydiving harness applications, especially if it is doubled. The main reason that Type 8 is used for main lift webs is to reduce the bulk at the shoulder joint (just below 3-ring). Reducing bulk eases construction. Type 8's shortcoming is that it is not very abbrasion resistant. That is why MLWs start to fray first at 3-rings and why most tandem rigs have extra buffers sewn on the outside of shoulder joints, to protect them when they get dragged across the floor. That is why tandem risers and the front layer of many harnesses is made of more durable Type 7 webbing. Yes, a single, straight main lift webb is stronger than a ringed harness. However, most harnesses are so over-built that this is not an issue. One advantage of ringed harnesses is that straps can swing/slide along the ring to take loads exactly in line with their axis. The disadvantage of this is premature wear from the sliding action. You can also get pre-mature wear if straps are not allowed to slide (i.e. 2002 service bulletin from Relative Workshop). The flip side of this dilemma is straight harness that do not allow straps to swing ... For example, on a Vector I hip joint, the top stitch where the upper leg strap meets the MLW is always the first to break. Decades ago we learned special stitch patterns (see Tandem Vector service circa 1994) that reinforce this stress point. So again, most harnesses are so over-built that strength is not an issue. Quote Share this post Link to post Share on other sites
KevinMcGuire 0 #5 January 20, 2004 Something to keep in mind is that the hardware is actually the weakest part of the whole system. Your standard thread through leg adapters are only rated to 2,500lbs, so using T-7 or T-8 becomes more of a choice based on slip factors or suppelness. Often people see the double wrap of material around their articluated hardware and assume that their harness is twice as strong. Not true. for the reason stated above One manufacture claims they have the strongest harness on the market because they use T-13 rated at 12,000lbs. How can this be when the hardware on the rig fails at 2,500lbs? A system is only as strong as it's weakest part but fear not. If you manage to generate 2,500lbs of force during opening, you would most likely be torn apart (or wish you had been) Quote Share this post Link to post Share on other sites
skydiverek 63 #6 January 20, 2004 Thank you Riggerob and KevinMcGuire, great answers! I also found a report of harness failure on Jumpshack website. It says there that "Recent events and the data received from them, i.e.: the fatal harness failure in Europe and the Type 17/Mini-Ring problem, should make us look into the structural integrity of our harnesses (...) The harness was not certified under the TSO system and it was not manufactured by a U.S. firm. The design is one in common use, however. The risers were type 8. The webbing according, to Hans Ostermunchner the investigator, was mil spec. type 7 and the thread was mil spec. 5 cord. Both were in spec. as determined by the investigation. Other sources report that the other side failed at 1800 lbs. - a differential from design of about 700 lbs., maybe 25%. This is not a surprise and could be explained by differences in the dynamometer mandrel diameter or testing methods. Whether the number is 1800 or 2800 is academic. We are in the range of potential failure, and shock load predictions and measurements - and field failures demonstrate this fact." and "Fact: an unreefed ram air parachute at terminal can destroy a parachute harness. It has happened. A harness has failed. A man is dead." Whole article here: http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=FAILSAFE&SortBy=TITLE_A Anyone knows more details (country, container type, etc.) on these harness failures? Quote Share this post Link to post Share on other sites
mjosparky 4 #7 January 20, 2004 Years ago, before the advent of riser covers, manufactures used Type 7 for the front reserve riser and Type 8 for the rear. The theory being that when packed the front rise was exposed to UV and the rear riser was not. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
