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Free Swinging Tube Fly Hook

How to make a simple heat-shrink Knot Guard allowing the tube fly hook to swing freely

First described by John Gray in Trout and Salmon Magazine, April 2022

click images to enlarge

Heat Shrink Knot Guards

Heat shrink tubing is available in a good range of sizes and colours, allowing knot guards to be made in a range of diameters to match the size of the tube and hook used. The Knot Guards pictured above are approximately 6mm long with an outside diameter of about 2mm, creating a very small, lightweight free swinging hook link. The clear knot guards are particularly unobtrusive.

Heat Shrink Knot Guard, Single Hook and Needle Tube Fly

Free Swinging Tube Fly ready to fish

A great advantage of tube flies is that the hook used at the rear end can be selected according to conditions and may be very easily changed or replaced, for example when damaged, thus extending the usable life of the tube fly. A common method of attaching the hook is to fit a short length of flexible tubing such as PVC or silicone rubber over the rear of the tube fly and then insert the hook into this flexible sleeve. This is a very effective way of keeping the hook in the desired position behind and in line with the tube, while the flexibility of the hook link tubing minimises leverage on the hook when a hooked fish is being played. A single, double or treble hook may be so employed depending on circumstance, preference and regulation.

Many fishermen, however, prefer to allow the tube fly hook to swing entirely freely behind the tube fly, believing that this freedom of hook movement makes for more efficient hooking of the fish and presents minimal leverage when the fish is in play. The tube itself often slides up the line out of the way when a fish is hooked.

However, if the hook is simply tied to the line behind the tube, there is a risk that the hook will not swim in line with the tube as intended but may instead slide round on the knot to stick out at an angle behind the tube. There is also a risk of increased abrasion, and associated weakening, of the nylon knot as the tube moves up and down the line when being cast. To prevent this, various protective sleeves, often referred to as swing tubes, have been devised, commonly using short lengths of various kinds of plastic tubing, e.g. PVC or silicone tubing, to protect the knot and help ensure that the hook swims, as far as possible, in a straight line behind the tube fly.

Illustrated below is a simple method of making such a knot guard/protector. The resulting knot guard, made here simply from clear, thin-walled, light weight  heat-shrink tubing, has the advantage of being very fine, unobtrusive and inconspicuous, which is particularly important when using very fine tubes such as needle tubes, for example in sea trout night fishing or salmon fishing in low clear water.

CLICK IMAGES TO ENLARGE

How to Make the Tube Fly Knot Guard

Clear heat-shrink tubing for making a fine knot guard (or swing tube)

I have used here what I believe is the finest heat-shrink tubing commonly available, shrinking from an internal diameter of 1.2mm to a minimum of 0.6mm. Heat shrink tubing is available online, in a variety of sizes and colours, from suppliers such as Hilltop Products . Suitable heat shrink tubing is also available from many other online retailers, on Amazon and on Ebay. I have found this size (1.2/0.6mm) of heat-shrink tubing suitable for fine single hooks up to about size 8. I use this size with needle tubes with a diameter of 1.5mm and 1.8mm and fine, small-eyed single hooks size 10 and 8. Heat shrink tubing of a larger diameter (1.6mm, 2.0mm and 2.4mm) may be matched to larger tubes and hooks (single, double or treble).

Note: Different brands of heat shrink with the same specification can vary quite a bit in size, wall thickness, flexibility etc. so it is worth trying a few different makes to find one ideally suited to your favourite hooks.

Guide to Heat Shrink Tubing and Hook Sizes

* The 1.6/0.8mm and 2.0/1.0mm heat shrink tubing are probably the most generally useful sizes for British salmon fishing. Note that heat shrink tubing in the larger diameters will also accommodate heavier leader material and larger knots.

Step 1 - Making the Heat-Shrink Knot Guard

Cut a short length of heat shrink tubing (I would suggest about 5 to 7 millimetres in length), being careful to cut the ends at right angles. Secure a fairly heavy sewing needle in a fly tying vice and slip the heat shrink tube on to the end of the needle, with the outer end lying over the taper of the needle. This makes it easier to slide the heat shrink tube off the needle when set.

Alternatively, the heat shrink tubing may be mounted on the end of a metal tube of suitable diameter with a millimetre or two of heat shrink extending beyond the end of the metal tube. An unlined stainless steel needle tube of 1.5mm diameter is ideal for the 1.6mm heat shrink tubing or the 1.8mm needle tube for the 2.0mm heat shrink tubing. In either case, apply the flame carefully as in this illustration, shrinking only the first millimetre or two of heat shrink tubing.

Step 2 - Making the Heat-Shrink Knot Guard

Hold a lighter flame near the point of the needle, gradually moving the flame closer to the end of the heat shrink tube, being careful not to allow the flame to touch the tube.

Step 3 - Making the Heat-Shrink Knot Guard

Slowly and carefully move the flame close to the end of the heat shrink tube until the closest millimetre of tubing shrinks on to the taper of the needle. Allow to cool before sliding the heat shrink knot guard off the needle. It is now ready for use.

Step 4 - Using the Heat-Shrink Knot Guard

Slip your tube fly onto the leader, then slip on a knot guard. Now tie on your chosen hook, be it a single, double or treble, and pull it into the knot guard, as shown below. Allow the tube to slide back down the leader, to rest on the end of the knot guard. I have used here a Needle Tube Fly dressed on a 15mm long needle tube, diameter 1.5mm, 12lb Maxima Chameleon nylon and a size 8 Gamakatsu F31 hook, with a knot guard made using clear heat-shrink tubing size 1.2/0.6mm.

As shown below, the tube fly will be held in place against the end of the knot guard by the force of the river current but can move freely and independently of the hook when a fish is hooked.

Note that the Gamakatsu F31 has a fairly long shank, which is useful if you want the hook point near the tail of the fly. If you want the hook point further forward in the fly dressing, a shorter shank hook may be used, as in the example at the top of the page. The length of tube and dressing can, of course, be varied as desired and used in conjunction with an appropriately proportioned hook, be it single, double or treble.

Shown below is a selection of Needle Tube flies, primarily for sea trout, which may be used in conjunction with the a very finest heat shrink knot guard, matched to single hooks, or the smallest fine wire double or treble hooks.

While the very finest heat shrink tubing (1.2mm internal diameter shrinking to 0.6mm) can be matched to the very finest wire hooks and slimmest tubes, the most useful sizes of heat-shrink tubing for knot guards on salmon tube flies are probably the 1.6/0.8mm tubing (i.e. tubing with an inside diameter of 1.6mm, shrinking to 0.8mm when heated - the starting (unheated) outside diameter is approximately 2mm) and the slightly larger diameter 2.0/1.0mm tubing.

The Knot Guard may be used with single, double or treble hooks

Examples are shown below - click to enlarge

Single Hook with Knotguard

Longer Shank Single Hook with Knotguard

Scottish Shrimps with Single Hooks and Knotguards

Shrimp fly with Double Hook and Yellow Knotguard

Sea Trout Needle Tube with treble hook and Knotguard

Coloured Knot Guards for Salmon and Sea Trout Tube Flies

Coloured heat shrink tubing in a range of sizes offers further options for use with our salmon and sea trout tube flies, allowing us to alter the appearance of the fly simply by changing the colour of the Knot Guard. Examples are shown below. The most useful sizes of clear and coloured heat shrink tubing for our purposes are 1.2 mm internal diameter (shrinking to 0.6 mm), 1.6 mm (shrinking to 0.8mm) and 2.4 mm (shrinking to 1.2mm).

Coloured Heat Shrink Tubing

Various Coloured Knot Guards made using 1.2mm and 1.6mm diameter heat shrink tubing

Knot Guard with Tube Fly Double Hook

Step 1 - Slide tube then knot guard on to leader and tie on a hook

Step 2 - Slide the knot guard down over the knot and hook eye

Step 3 - The knot guard will butt up against the tube while fishing and the tube can slide up the leader when a fish is hooked. Note that single and double hooks will tend to swim naturally with hook points uppermost.

Knot Guard Colour Options

Heat shrink tubing is available in a wide range of colours

Cascade Tube Flies with Free Swinging Double Hooks in various coloured Knot Guards

More Tube Flies with a variety of Free Swinging hooks and Knot Guards

Hook and Knot Guard Storage

I find it convenient to carry my hooks, with matched knot guards, together with my tube flies in my fly box. This box has a magnetic base, which is useful for the prevention of accidental spillage.

For those who like a free swinging hook behind their tube flies, the heat-shrink knot guard described here offers a simple, inexpensive solution. In the lowest diameters in particular, it adds virtually no weight or bulk to the rear end of the tube fly, allowing the fly to swim on a more even keel. The knot guard may be made in clear tubing or in a range of colours as illustrated above, to either blend with or contrast the colours of the tube fly. I have used Needle Tube Flies fitted with a knot guard and free swinging hook, such as those shown above, extensively during the past season. I have found the knot guard to be effective and durable, holding the hook securely in line with tube with no tendency for the hook to catch on the leader or fly dressing while casting or fishing, and I am confident that it will prove to be an efficient and effective method of attaching - or perhaps more accurately, detaching - the hooks on my tube flies, a variation on a swing tube theme already well tried and tested.

Spey sea trout taken in June 2021 on a Needle Tube Fly with free swinging single hook in a Knot Guard (the black and blue fly pictured above)

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