Shock and abrasion leaders
by Chris Tan S.G.
A fellow angler once observed me preparing my leader for trolling. He commented that all the knots and different lines looked very complicated! He did not think that it was worth all the effort. Well, to this date I have never had any of the mysterious break-offs that plague anglers who do not use these "complicated" knots. When these mysterious break-offs occur, the normal excuses like "old line, line not strong enough, some fish must have bitten the mainline" are given the blame.
Often the cause of the line breakage is caused by shock or impact. This is a sudden violent increase in stress. This is well portrayed during the sudden strike on a lure.
Understanding the concept
First we have to understand what happens when the game fish strikes the trolled lure with great force! The first thing that receives the impact of the initial strike is the terminal hardware, the lure, wire leader and swivel. As all these items have practically no stretch, the sudden force of the strike is passed on directly to the main line. Without a shock leader, the main line will be the first weak point to get stressed.
The other occasion when the sudden shocking force is applied to the tackle is when the fish jumps. When the fish is airborne it is able to apply a lot more force to the tackle than when it is in the water. During the jump, the combination of its body weight and its higher momentary speed out of the water can generate a much higher force than when it is in the water. Remember that force equals mass times acceleration. Also setting the hook during strikes, sudden runs or violent head shakes all are possible times when shocks or impacts are made on the fishing tackle.
Supposedly the mainline of mono is supposed to stretch some, dissipating the force, and then the force goes further up the mainline all the way to the rod, flexing it and more force is absorbed. Finally the drag comes into play, smoothly slipping, preventing the mainline from snapping! Bear in mind that all this happens within split seconds sequentially so it does seem to happen simultaneously to our slow human eyes.
However the strike of the big game fish is so fast and powerful that there is practically no time for the force to be dissipated by the mono mainline, rod flex and reel drag. What really happens is that the peak of the strike exceeds the strength of the mainline and the mainline parts near the terminal tackle, as there is no time for the mainline to commence to stretch, nor the rod to flex and reel drag to give. Think about it, every time the mainline breaks, it is normally near the source of the application of force.
For example, this happens when bottom fishing and the terminal tackle gets snagged. If the mainline is pulled by hand to break off the snagged rig and the line is not abraded by rock or coral, the main line will always break at the upper half of the main line, nearer the application of the force, the pull of the hand.
Absorbing the shocks
By using a shock leader to absorb the shock, as the name indicates, it prevents this sort of line breakage. The shock leader should have a large surplus of unstressed strength in reserve or it must have built in-forgiveness or shock resistance (elasticity). Heavy mono line is probably the best material for this purpose as other leader materials like wire, dacron and superbraids have very little elasticity/stretch. A shock leader which is made of heavy mono is tied on immediately after the wire leader. I normally use a 100lb shock leader with 25-30lb mainline. What a shock leader does is to stretch a bit upon impact, absorbing some of the force (shock) of the strike, giving time for the mainline stretch, rod flex and reel drag to come into play. The shock leader being so strong it is unlikely to break.
Another function of a leader
The shock leader should be at least 6-7 feet long, as another use of the shock leader is to ensure that large fish with flukes on the tail do not cut through the mainline. Thus the shock leader also can function as an abrasion resistant leader. The use of a mono shock leader allows the utilisation of shorter wire leaders which should just be long enough to prevent razor sharp teeth from biting off the artificial lures. I find using short wire leaders of about a foot long when using artificial lures sufficient. Short wire leaders are also less visible, giving better chances for strikes!
The mono shock leader also doubles as an abrasion resistant leader when it is used in areas with rocks, timber, coral reefs, wrecks and so on. It all depends on how one views the heavy mono leader. It can be primarily a shock leader with the abrasion resistance as a secondary function. Or it could be an abrasion resistant leader first and a shock leader second. When fish like siakap, mangrove jack or tarpon that lack razor sharp teeth are targeted, the use of a heavy mono leader is sufficient to prevent cut-offs from the abrasive or mildly toothy mouths of these fish.
Putting it all together
I use leader knots that allow the leader to be wound on to the reel through the rod guides. This is done by using suitable knots to connect the lines together. Wind on leaders allow the fish to be controlled with the rod at close quarters, and landed single handedly if need be.
The shock leader is tied to a ball bearing swivel/mcmahon or coastlock snap with a nail knot with a loop. I have found the nail knot to be a strong and neat knot that is suitable for heavy mono. The short wire leader that is attached to the lure is connected to the ball bearing swivel and the heavy duty snap, the snap allows easy lure changes. I prefer not to use a snap at the lure itself when I can, as the snap reduces the action of the lure and sometimes the snap can be levered open against the lure as the fish twists and turns during the fight. All the lures used for trolling offshore have a short length of wire rigged to them. All that is required is to attach the snap from the shock leader to the loop at the end of the wire leader attached to the lure.
Two good knots to tie doubles
Connecting the mainline to the shock leader requires a double to be made on the mainline first. Knots are generally not 100 percent in strength. In other words, tying a knot weakens the monofilament line. A good knot allows the monofilament line to maintain 90% of its strength; better still, 100%! Preferably we want to try to keep the full 100% available all the way through, preventing any weak points. Thus a double knot is used to do this.
There are two knots used to make doubles that allow the monofilament line to maintain 100% strength. The "plait" and the bimini twist. The plait is a good knot and because of the way it is tied, the knot itself has some shock absorbing qualities, but it does take some time to tie. The bimini twist is a fast knot to tie a double; in addition it is a compact and neat knot.
When the double is knotted to the shock leader, even if the knot reduces the strength of the doubled mainline a little, the overall strength of the doubled mainline and shock leader is still well above the breaking strength of the mainline. In fact the double also works as a secondary shock leader.
The "improved shock leader knot"
There are a few knots used to join thin monofilament to thick monofilament lines. These knots must have maximum knot strength, and be compact, to allow the knot to slide through the rod guides smoothly. The albright knot is a well known knot used for this purpose, but I personally prefer to use a knot called the "improved shock leader knot".
Note (latest update): recently I have also tested out the "improved leader knot" a variation of the albright knot and have also found it to be very reliable. I use it for the light lines as it doesn't slip as easily as the "improved shock leader knot", thus not requiring "superglue" to lock the overhand knot for added insurance.
One point about the knots, is that they have to be tied properly. Heavy mono line should be locked tight with pliers as our fingers are not strong enough to do the job. Blaming the knot for slipping or breaking is fruitless as the fault lies not in these knots I have recommended but with the person who ties the knot. If the knot does not look right, cut it off and tie it again. It may make the difference between landing or losing a great catch!
The new superbraid lines also known as GSP lines that are made of materials like spectra or dyneema have been giving anglers problems due to the slippery nature of the line. Some knots commonly used for mono are often not able to be used for these superbraids. However, the superbraids can be connected to a mono shock leader with the "bimini twist" and the "improved shock leader knot" without giving away. Just note that when using superbraids, the number of turns required for these knots may need to be doubled or even tripled to ensure the knot does not slip.
There you have it - the technique to improve the connections all the way from the reel to the lure with no weak points. This ensures that the game fish will stay connected!
Suggested reading: Geoff Wilson's Complete book of fishing knots & rigs. ISBN no 0 646 001175. Published by Southern Angler Publications. This book is also available from Braid Products. All the knots mentioned in this article can be found in Geoff Wilson's book.