For years, I felt that the figure eights were too similar to be able to say something special about each one. As a result, I wasn't happy with the original figure eight pages. Scanning the web, I found out that I wasn't the only one that felt that way. The problem is, there are a lot of similar eights, and any two eights that are made of the same material, have about the same shape, and have about the same size are going to function similarly. How does one decide which eight to buy? My answer is to ignore the birdie going "Cheap! Cheap! Cheap!" and quit thinking that there is one right answer. I look for the following:
Most figure eights are forged from aluminum alloy and then soft anodized. Several have hard anodizing, or none at all, but the finish affects wear resistance more than performance, which depends more on size and shape. I decided to differentiate between forged aluminum alloy eights by measurement, and then I extended this to include all my deaf eights. I measured the following dimensions for each deaf eight in my collection:
The total thickness includes the effect of any bends. In other words, if you sandwich the eight between two parallel boards that are also parallel to the plane defined by the length and width dimensions, the thickness is how far apart the boards must be.
As the following chart shows, there is a correllation between height and weight that applies well for most of my eights, mainly beacuse most of the eights in my collection are aluminum and their shape is fairly standard. The two heavy outliers are the massive phosphor bronze Rocksport and the the highly unusual Spool Eight.
I grouped my "deaf" figure eights into several categories based on similarities in size, shape, material, and manufacturing method. The previous chart shows that if you view all the deaf eights at once, they do not fall into distinct size groups. Despite this, I was able to make reasonable groups when I looked at them in detail. For example, there are several similar yet different forged aluminum eights with a height between 129.5 and 132 mm., a width between 74 and 75 mm., and similar other dimensions as well. These plot as overlapping dots on the chart so the grouping is not obvious. These are my Standard, "Midi" Size, Forged Eights. The following pages provide tables showing the following key dimensions for each of the following categories:
I saw one complaint on the web about my site not explaining how to rappel with an eight. I don't intend to "teach rappelling" here. Nobody can learn to rappel safely with an eight (or safely learn any other form of climbing, SRT, or related activity) by sitting at a computer and surfing the web. To learn, you have to log off, get off your couch, go out into the real world, get some qualified instruction, and pay your dues.