How the Drag increases on an emptying spoolThis is a subject that most anglers should be aware of and understand, in order to avoid disasters.
When a big fish is taking line off a reel, the tendency for most anglers is to tighten up the Drag to try stop the fish or to try and turn it. All good and well. A serious problem arises however, when the line being taken continues. The tendency again is to tighten the drag once more - this is a recipe for disaster!
Torque is the turning force required to rotate an object around a fixed axis.
Torque (T) [Drag] depends on the Force applied to the object being turned (F) [force on the spool] and the length of the lever arm connecting the axis to the point of force application (r) [amount of line left on the spool].
In this article, we are simplying things for the sake of understanding them. There are many other variables that would need to be taken into account in order to measure this effect accurately... eg: line drag in the water, lubrication of the reel, line diameter, heat buildup in the Drag washers, air temperature, rod characteristics etc etc etc.
Simple physics tells us, (all other factors being equal), that the Force needed to rotate a spool (Moment inertia) is inversely proportional to the amount of line left on the spool.
Halving the line on the spool will double the Drag Force applied to it! Removing 2/3 of the line on a spool, will TRIPLE the Drag force applied to the spool. One can now see, that tightening the Drag while playing a big fish is courting disaster, and rather than burn-offs being the main reason for lost fish, the increase of the Drag on the spool is the most likely cause.
Anglers need to resist the temptation of tightening up the Drag on a fish heading for the horizon - rather they need to hope and trust that the drag of the line in the water and fatigue to the fish on an already tightened drag, is enough to slow a fish and turn it. Braid backing is usually between 4-600m in length, there is more than enough line right there to slow down most fish without tightening the drag further. If it's not enough, well then, you win some and lose some! But tightening the drag at this point will almost certainly result in the Drag force going beyond the breaking strain of line already being stretched to the maximum.
This principle applies mainly to the Rock and Surf angler that uses a Star Drag Multiplier reel. The Lever Drag reels used in off-shore situations usually have their Drag settings pre-set to 'Strike' settings, (normally25-30% of the breaking strain of the line). Lever Drag reels are capable of precise drag settings and this should never be a problem, as long as the angler doesn't interfere with the Drag settings during the fight! Pushing the Drag up during the fight will have the same effect...
HALF the line on the spool means DOUBLE the Drag force applied. 2/3 of the line off the spool will TRIPLE the Drag.
With Fixed spool spinning reels, the principle also applies, but there are complicated angular moments of inertia that need to be taken into account as well.
Next time you're on to a Big fish on a Multiplier reel... don't tighten your Drag once it's passed half way! Rather, loosen it, otherwise your line will snap!
Maybe this will help someone land the next big one!
