This page aims to debunk some rope sport myths that continue to be propagated even though recent research has shown them to be wrong, or at least in need of qualification.
Please read the disclaimer.
Myth 1: Carabiners should be retired if dropped from above waist height
There is no evidence to show that this is the case. A number of informal studies have shown no difference in breaking strength to destruction between dropped and undropped carabiners, particularly over short distances ie 10m-20m. However, there are no formal studies that can show what distance a carabiner might be dropped safely. Carabiner manufacturers generally advise to inspect gear carefully, and discard if it shows signs of damage. In the end, you are the one relying on the gear and you need to make the decision to discard or continue using. If you feel uncomfortable about using gear that has been dropped, then you should probably retire it.
For me? It depends on the piece of gear and what it is used for. Probably anything that has taken a 10m fall or greater, or shows signs of damage would get retired.
See :
- Black Diamond Equipment: Customer Service FAQ
- SportExtreme.com: How to Choose Carabiners
- the fat canyoners club - Do you need to retire dropped carabiners?
Myth 2: Nylon ropes rot if left in the sun
It is true that nylon is affected by UV radiation. However, the nylon that climbing and abseiling ropes are made from is UV-stabilised, so the impact of UV radiation is minimal. It's probably not best to leave them out in direct sun for weeks on end, but short periods aren't going to affect the strength significantly.
See: Journal of the UIAA - Equipment and its Application(PDF)
Myth 3: Nylon ropes rot if left wet
This is not the case. Nylon simply doesn't rot. However, it is advisable to dry your ropes out, as nylon does lose a signficant amount of its strength when wet. This is something to keep in mind while canyoning - your ropes will not be as strong as they are rated.
See: Journal of the UIAA - We Won't Climb It, Will We? (PDF, 2Mb)
Myth 4: The double fishermans knot is the best to tie two ropes together
The double fishermans knot is a strong knot. However, research has shown that strength is not the only criteria to use when choosing a knot to join two abseiling ropes. It can be very difficult to pull the rope down after abseiling with a double fishermans knot, as the knot has the propensity to catch on edges. Where there is a risk of this, it may be better to use a double overhand knot. This knot is weaker, but is much less likely to catch, and is still sufficiently strong for most applications. However, it must be tied with sufficiently long tails.
See
There are some other pages with similar aims: