fatdad wrote:Also, I don't really buy into the wisdom of you're purpose. What's the urgency that would warrant three people rapping on the same line at the same time?
Yeah, a 600-pound rappel. I hope you are using a bomber anchor and thick rope. I'm not saying it would break an undamaged rope, but of course the forces involved are more than the 600-pound static weight, and that much mass on a rope is narrowing the safety margin a lot, just for the sake of saving a minute.
I've done a lot of single-strand solo rappels and also a few tandem rappels (one person on each strand), and I personally feel comfortable drawing the line there. Barring extreme circumstances, I wouldn't want three simultaneously on a rope or anchor, just for the sake of saving time.
Being unfamiliar with those, I need to ask: What is one's descent speed on one of those, in comparison to using a conventional rappel device? In other words, considering the original poster's inquiry for the purpose of speed, would the descent speed of two people on a strand using a descender be enough more than half the speed of one person using a standard device to justify doing the multiple rap?