I get asked many times about finger spools. Some people believe that they are an accident waiting to happen. Others, however, feel that they are critical tools, when used correctly, that can be used in a variety of diving environments. This post will discuss the uses for finger spools and how they can be safely stored to prevent entanglement hazards while in the water.

What is a Finger Spool
A finger spool is normally made out of some form of plastic. Delrin is the most common material to use for finger spools as it is very strong and is only slightly negatively buoyant. There are some finger spools that are constructed out of aluminum which are strong, but a little more negatively buoyant than Delrin. Some maybe made out of plain plastic. These are not very strong and can break easily. A finger spool is normally constructed as one piece. That is, a block of Delrin is put into a machine and a computer cuts the spool out of that one solid block. The result is a spool that is strong with no failure points. Below is a picture of a bare finger spool.

As you can see, a finger spool will have holes along each side of it. These holes are used to lock a double ender bolt snap onto the spool. This allows the line to be secured and a place to store the double ender. There is also a hole cut through the center of the spool. This allows divers to be able to grip the spool while it spins without having to fully pinch it. We should never stick our fingers into this hole while it is spinning. The spool can snag on our fingers and take a diver on a fast ascent. Most finger spools will come with a double ender bolt snap to secure the line to the spool. We’ll get more into detail about how to secure the line and double ender below.

Uses for a Finger Spool
Finger spools can have a variety of uses. Let’s look at a two of the most common uses of them.

1) Deploying a SMB
When scuba divers need to mark their position in the water column or need an ascent line, they may deploy a SMB (Surface Marker Buoy). See my previous post for more information about deploying a SMB. When deploying the SMB, a line must be attached to the SMB. This is where the finger spool comes in. It is small enough to stow in a dry suit pocket and can hold enough line such that divers can shoot a bag and use the line attached to the finger spool to ascend. This is the most common use for finger spools in an open water environment.

2) Searching
Due to the compactness of finger spools, they are great tools to use when performing underwater searches using the circular pattern. Divers can simply tie off the end of the line to an anchor/object and swim around in a circle to look for a missing object. In addition to doing circular search patterns, finger spools are used in overhead environments to do lost line and lost buddy searches. To learn to perform lost line/buddy searches in an overhead environment, I suggest you take a good cave or wreck diving class.

Setting Up the Line
The line most commonly used for finger spools is size #24 braided line or also known as cave line. This sized line is thin enough to get a good quantity of line on spools and reels and thick enough to hold up to wear and chaffing when used. Many wreck divers may use size #36 line (sometimes called wreck line) as it may hold up to chaffing on metal in shipwrecks. Due to it’s thickness, less line can be put on a spool than #24 cave line. The line is tied to the spool so that it will not come off the spool when all of the line has been run out. The line is then wound on the spool carefully so that it doesn’t knot up. After the length of line is on the spool a loop is created on the end of the line big enough to pass the entire spool through it.

A tip for those of you who may not know. You can create a small loop at the end end of the line (after the big loop was already created) that will create a lopsided big loop. The knot from the small loop will separate the line of the big loop when pulled tight. This small separation will be helpful when trying to pass the spool through it when wearing think gloves. It also gives a small loop to hook the double ender onto. This small loop is sometimes called a Jasper loop. Below is a picture of this the big loop and the small loop at the end of the line.

Storing the Line and Clip Correctly
When the line on a spool is not stored correctly, it can come slip over the spool. When this occurs, there will be more slack in the line. With this slack, more line can slip off the spool. This results in a possible entanglement hazard. When the finger spool is stored in a pocket, that line will just collect inside the pocket and not present an entanglement hazard unless removed, completely, from the pocket. There are people who store finger spools on d-rings on their harness/BCD. When stored like this and the line comes undone, a diver may never realize that the line has tangled around them or around something until it is too late.

As I mentioned previously, most finger spools will come with a double ender. This double ender is used to secure the end of the line to the spool, thus reducing the chance of the line coming off the spool. However, if the double ender is not clipped to the spool properly, not only can line come off the spool, but the double ender may also be in a position to come undone. Below are some pictures illustrating this.

Above you can see the correct way the double ender bolt snap should be secured. The gate of the snap should be facing the outside of the spool.

Above you can see the incorrect way to secure the double ender bolt snap. This method of securing the snap presents two problems. First take a look at the line. The line goes over the top of the spool. This will allow more line to come off the spool, especially when it gets wet. The second problem this presents is that as the snap moves around inside your pocket, the gate on the snap may hit or rub against the line. If it were to do this with enough force, the gate may open and thus allowing more line to come loose or perhaps the snap coming off the spool altogether.

Summary
Finger spools are very useful tools when used properly. Due to the presence of line, it takes a heightened level of situational awareness on the part of the diver to use the spool properly. The two common uses of finger spools are to deploy SMBs from depth and for performing searches (lost line or buddy). We also discussed the materials and construction of the spools and how the line is setup on the spool.

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Dive Safe,
Duane Johnson
Precision Diving

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