The percent decrease in force the friction hitch needs to apply during two different descents from a tree compared with a frictionless situationz.
| Rope | a = 2 m/s2 | a = 30 m/s2 | ||||
|---|---|---|---|---|---|---|
| μk | μk | |||||
| STEEL | PAL | AL | STEEL | PAL | AL | |
| AP | 60% | 57% | nm | 88% | 87% | nm |
| AP used | 71% | 69% | 69% | 91% | 90% | 90% |
| BLAZE | 59% | 55% | nm | 88% | 87% | nm |
| BS | 62% | 58% | nm | 88% | 87% | nm |
| FLY | 65% | 62% | 65% | 89% | 88% | 90% |
| SB | 61% | 58% | nm | 88% | 87% | nm |
| SB3 | 60% | 58% | nm | 88% | 87% | nm |
| SBHV | 58% | 56% | 55% | 87% | 87% | 87% |
| SBHV used | 65% | 62% | 63% | 89% | 88% | 89% |
| SP | 60% | 57% | 60% | 88% | 87% | 88% |
| TB | 58% | 56% | 61% | 87% | 87% | 88% |
| TM | 61% | 58% | nm | 88% | 87% | nm |
| XTCP | 60% | 57% | nm | 88% | 87% | nm |
| XTCS | 60% | 57% | 60% | 88% | 87% | 88% |
↵zDuring a controlled descent, acceleration (a) during stopping ≈2 m/s2 and friction at the cambium saver rings reduces the stopping force. During an emergency descent or hard swing, acceleration during stopping ≈30 m/s2. “nm” indicates no measurements were taken. See Table 1 for rope and ring abbreviations. μk is the kinetic friction coefficient.