How much webbing?
Okay, before you say it, Yes I may have too much time on my hands, as economic times leave many of us only getting part time work.
Anyways, during some of my ever abundant free time, I thought "How can I take the guess work of grabbing the right length of webbing for my anchor?"
Well, thanks to the ancient mathematicians, much of the work has been done for us.
For this exercise we will do a wrap 3 pull 2 anchor using 1" flat webbing.
For starters, we need to set some standards for our webbing length, I will use the standards listed in my CMC Rope Rescue Manual
Green - 5 feet
Yellow - 12 feet
Blue - 15 feet
Orange - 20 feet
A memory aid for remembering the color code is, Get Your Boots On
Now lets get to it. For this exercise, we will use a W3P2.
We will need 1 math formula which is circumference. C= pi(Diameter of Anchor) or C=pi x D
For practical use we can say pi = 3
Diameter is simply the length of the anchor if measured through the middle of the anchor.
So knowing diameter, we can guesstimate circumference using Dx3
Since a wrap 3 pull 2 requires 3 times around the anchor we can use anchor circumference x 3, or anchorC x 3. Then we add 16 inches for anchor webbing to anchor to, and add another additional 20 inches to make the water knot. The last 2 steps can be simplified by just adding 3 feet.
Final formula for W3P2 is ((anchor Diameter x 3)x3) + 3 feet = proper webbing length.
for a post with a 1 foot diameter.
1' x 3= (3x3) + 3' = 12 feet. Based on this number the Yellow webbing is the proper length webbing to use. We have to multiply 3 for 3 wraps.
This may be something that the veterans just have a feel for, but for new folks, this may help. Also if there is interest, I may do this for other web anchors as well.
I should also add, while working the math, keep your units the same. ie. inches, feet, or meters. Don't do 3 feet multiplied by 46 inches.
Hope this helps some.
I should add, I apologize if this was too basic for the readers.