ABOUT REELS AND SPOOLS
Our Advice: All divers should carry a Delrin fingerspool with 30m | 100ft line. Cave divers should carry a Delrin primary reel with minimum 100m | 330ft line and several Delrin jump spools with various line lengths. Use 24-gague braided nylon line. Line markers should be personalised for look and touch.
Primary reels carry upwards of 100m | 330ft of line and are used in cave and difficult wreck penetration.
The primary reel consists of the following components:
- Frame – Holds the axel, lock down screw, and line guide. Provides a handle for holding and a hole for clipping off the reel.
- Spool – The round drum on which the line is stored. It spins freely on the axel. The height of the sides will determine how much line the reel can carry. Manufacturers will fill the spool to the height of the sides to meet consumer expectations. However, for use you will want only 4/5th carrying capacity to avoid dropping the line or overfilling the center when reeling in.
- Line guide – A slit to feed the line through before the spool. It ensures the line is controlled and orients the reel.
- Winding knob – Used to wind the line back onto the reel (reeling in). It’s found on the outside of the spool. It should turn freely on its own stainless steel axel for comfort. It should project approximately 2cm | 0.78in above the spool so that it is long enough to hold comfortably but maintaining a low profile to avoid snags and interference with other equipment. Some reels use a handle instead of a knob.
- Lock down screw – Applies tension to lock the spool (keep if from turning).
The primary reel is carried with a medium double eye snap which is removed and clipped to your harness while the reel is in use. The reel should be clipped through the hole so that the gate is on the outside. If the gate is on the inside then small movements of the gate will cause the reel to slip off and be lost.
Shielded vs unshielded reels (Open vs closed reels)
Closed (shielded) reels have a cover around the spool so that the line can only enter and exit from a single opening (in place of the line guide), and the line while on the spool is completely isolated from the axel. In theory if the line is within a closed drum it cannot become tangled. However, if the line does become tangled it is more difficult to fix. Closed reels are more commonly used with large gauge line.
Open (unshielded) reels rely on the line guide and user control to avoid line tangles but offer more line access to fix problems.
Finger spools / Jump spools
Finger spools hold up to 50m | 165ft of line, and are used with a stainless steel double eye snap. Most divers will require a 30m | 100ft finger spool for shallow water (20m | 66ft) SMB deployment.
In cave diving, a finger spool is also known as a jump spool, and is used to bridge two unconnected main lines (e.g. to follow a side passage) and as an emergency reel for cut line, entanglement, and lost line drills. Cave divers will carry a selection of different sized finger spools with different line lengths.
Jump spools should be personalised for identification (e.g. by applying tape or writing within the inside ring to identify the dive team that left the jump). Different line colours are available as a further aid to identification.
The regular centre hole diameter is 2.5cm | 1in, but larger 3.2cm | 1.25in holes are available for cold water (thick gloves).
Spool and reel materials
For spools and reels it is necessary to consider which material achieves the right combination of price point, weight for travel, buoyancy underwater, and durability:
Delrin – Moderate price, light weight, slightly negative buoyancy, very durable.
Plastic – Cheap, light weight, positive or slightly negative buoyancy, not durable.
Aluminum – Expensive, light weight, slightly negative buoyancy, very durable.
Stainless steel – Expensive, heavy weight, negative buoyancy, very durable.
Braided nylon line is best
Nylon is negatively buoyant so will sink if it comes loose underwater. It is better to have a line laying along the floor where you can see it instead of floating at the ceiling. Nylon is also very resistant to the elements and can be left in place for years without noticeable deterioration.
Dyneema line is stronger than nylon for any given line thickness (so you can get more length on the same reel or spool), is negatively buoyant, and resistant to the elements. However, Dyneema is, for the moment, unjustifiably expensive for scuba diving applications. Other line types are not suitable for various reasons (e.g. polypropylene floats and cotton line rots very quickly).
The two main types of nylon line are twisted and braided. Twisted nylon line has a high tensile strength and braided nylon line is more abrasion resistant. The purpose of laying line is not to hold any great weight or tension, it is to provide a reliable marking through cave or wreck environments. Therefore braided line is more appropriate.
Line thickness is measured in gauge. For scuba diving we use 24-gauge for most applications, and otherwise:
- 18- gauge to achieve extra distance on the same spools where abrasion is less of a concern,
- 26-gauge for wreck penetration or other circumstances where abrasion and sharp edges are a concern,
- 36-gauge and above for permanent fixed lines in high traffic areas.
The start of the line should be a loop tied with an overhand knot. The loop should be large enough for the entire reel or spool to pass through. Putting a smaller loop in the very end of the main loop makes it easier to handle the line, especially when wearing gloves.
Arrows (triangle) – A directional marker for the line generally. The arrow points the way out of the cave. Used when laying new line, and on fixed main lines.
REMs (square) – A directional marker for a specific dive team. The square points the way out of the cave. Used by individual dive teams to avoid confusion between the permanent markers and temporary markers on fixed lines.
Cookies (circle) – A non-directional marker for individual divers. The collection of cookies at the start of the main line will tell which divers are still in the cave.
The different line marker types are designed to be very different, both by look and by touch. The blank markers should then be personalised by look and by touch to identify individual divers, but personalisations should be consistent for all markers used by that diver. E.g. a diver might write their name and add a patch of red reflective tape (look), and drill a hole in the bottom left corner (touch) of every marker.