With nothing more than a low power heat gun, a concentrator nozzle, and some heat shrink, it’s possible to make loops that look factory made and are just as tough. The typical loop takes me roughly five minutes to make and then it’s good to go fishing.
Make sure to use a concentrator nozzle on the business end of your heat gun. Trying to weld without a nozzle can be difficult and frustrating.
Lines and Heat Shrink Information
The heat shrink I use is polyolefin 2:1 in 1/8” O.D. and 3/16” O.D. tubing. This tubing has a very flexible, rubbery feel to it and is suitable for rolling the softened coatings smooth when it’s occasionally necessary to roll. Stiff heat shrink doesn’t roll very well and shouldn’t be used. Coloured heat shrink should never be used as we cannot see when the line has properly melted. Opaque heat shrink will result in over or under done welds.
Fly lines made out of polyvinyl chloride (PVC) melt at higher temperature than those made out of polyurethane (PU). All manufacturers use PVC except for Airflo, which uses PU.
It’s important when welding on running line loops, that the material for the loop is the same as the main body of the fly line. As a general rule don’t mix PU with PVC. It is possible sometimes to weld a PVC running line to a PU main line as the smaller PVC running line will heat faster than the thicker PU main line. Test on some scrap first. The best way is to make sure that your fly line and loop material is made out of the same stuff.
Preparing the tip and heat shrink
Cut the end of the fly line at an angle so that the tag end flows evenly into the main body of the line, not leaving edge that could be snagged later on.
Cut a piece of heat shrink that is large enough to hold the line doubled over, yet not too large to be sloppy.
The heat shrink should be long enough so that both ends can be held by the fingers, clear of the hot nozzle.
Position the line in the heat shrink
Feed the fly line through the heat shrink, double it over, an push it back through. Then pull on the line to draw the loop into the heat shrink. Do not allow the loop to protrude from the tubing as not only are you likely to burn your fingers from a lack of room to hold it, the heat shrink edge is likely to leave ridges in your loop.
Heat the assembly lightly to shrink the tubing down to a snug fit over the line. Squeeze with your fingers to position the line parallel with itself. Don’t go directly to heating the line without this snugging process first, for without it, the line is likely to shift as it’s being heated.
Welding by section
Weld only one nozzle width at a time, starting with the tag end. Do not move to the next section until the plastic has melted and flowed together. Except for necking loops (explained in “Necking the Loop”) it is usually not necessary to roll the melted line.
Here’s the finished loop. In this case, the plastic (PU) material was translucent so the core can be seen. When the weld is held between the fingers, the welded section feels like a smooth oval in cross section. With a poor weld, it will be possible to feel the separate sections of line. A good weld will feel like it is one piece of plastic.
Preparing the butt and loop
Thicker fly line needs a loop made out of a piece of running line as the line is too thick to be folded back on itself to form a loop. Typically we use this technique for attaching loops to the butt end of shooting heads, Skagit heads, and when cutting a fly line for sinktips.
When making butt end loops, for the back end of a shooting head for example, we need three components: the main line, the loop material cut from spare 30 lb. core running line, and the heat shrink. Cut the end of the main line at an angle to facilitate necking (see “Necking the Loop”) and the insertion of the line into the tubing. PU melts at a lower temperature than PVC, so the looping material should be the same material as the main line, e.g. PVC to PVC and PU to PU. It is not a good idea to mix materials, though PVC loops to PU main line sometimes works as the narrow PVC loop material will heat faster than the larger PU main line, on account of its smaller size.
The heat shrink should be considerably longer than the loop itself to allow holding spots for our fingers.
Positioning the loop and line
First insert the loop material into the tubing, making sure it is entirely in the tubing and the ends even. Also make sure that the line is parallel to itself. It’s normal that the tag ends won’t behave, but we’ll fix that at the next two steps.
Now insert the main line into the tubing leaving about ¾” of loop at the end of the main line. If it’s reluctant to go in as the line can be a bit sticky, wet the main line and it will go in smoothly.
Now use your fingers to squeeze the looping material so that it lies on either side of the main line and all sections are parllel to each other.
It is important to snug the heat shrink down by some gentle heating, using your fingers to hold the line sections in place. Start in the middle and work out, heating both sides of the tubing. If the heat shrink is not snugged down, the line sections will shift during heating and melting. This snug down step ensures that everthing stays in place.
If the line shifts during this process, squeeze it back into place with your fingers.
Welding by section
Weld only one nozzle width at a time, starting with the tags end of the loop. Do not move to the next section until the plastic has melted and flowed together. Except for necking loops (explained in “Necking the Loop”) it is usually not necessary to roll the melted line. Make sure that you weld past the end of the main line to ensure that the loop is necked.
Roll the end of the main line while it is still hot, to neck the loop. Watch out for burned fingers!!!!!
Necking the Loop
The first welded back-end loops that I had made for shooting heads didn’t close the loop beyond the end of the main line. I later became concerned that these edges could be levered open while casting. This lead me to tapering the butt end of the shooting head down and making my loops longer. With the longer loops, I was able to weld part of the loop together producing a ‘neck’ made out of two strands of the loop flowing into the tapered back end of the head, as shown in the picture. Since then I’ve not had to worry about any back end loop levering apart.
However there has been one big surprise plus from creating these necked loops -- they slide right through the tiptop with ease even when the rod is being held at an angle sharper than 90⁰. Unlike braided loops that can catch on the tiptop, these necks bend as they enter the tiptop, flowing the back end of the head into the guides. There’s just a little bump as the loop-to-loop connection slides through and then the rest just glides through the guide. No more catching and jamming, no more having to hold the rod close to parallel to the line to get the braided loop to feed through. No more risk of snapping off a tiptop.
Here’s our finished butt end loop. I like to colour code my loops so that I instantly know the line rating by the colour.
This loop is not perfectly symmetrical, yet I chose to use this one as an illustration to show that loops don’t have to be perfect in appearance to be functional. However, this less than perfect example has two essential aspects that have been done right: the tag ends have flowed into the main line leaving nothing to catch or snag, and the butt end of the main line flows well into the loop. If you want to see a pretty loop, look at the “Necking the Loop” example.
Technique tips & tricks
Just some things I’ve run across that makes welding easier.
- A good line welding heat gun should have a nozzle concentrator with an opening in the range of ½” to ¾” wide.
- The gun should produce heat around 200 - 300 C.
- Weld only a nozzle-width at a time. Always start by welding the tag end(s) of the loop.
- Always use clear heat shrink tubing, never coloured, as we need to see what is happening to the plastic.
- Use soft heat shrink like polyolefin 2:1, not the hard stuff. The hard, stiff heat shrink is difficult to manage and results in lumpy welds.
- Butt end loops are made using a piece of running line that’s roughly 5” to 6” long and welded to the butt end of the shooting head. Use at least 30 lb. core running line to insure a strong loop. Use only fly line type running line.
- It’s handy to colour code our back end loops by line weight. For example, I use yellow running line loops for 7/8 heads, orange for 8/9, green for 9/10 and blue for 10/11. This is a quick and easy way to make sure we don’t get our shooting head line weights mixed up.
- Always bevel the tip of the line (or the ends of the piece of running line) so that when welded, it flows smoothly into the main line. If the ends are welded with a straight cut, they’ll leave a nub that will catch on the guides and could eventually lift.
- When applying heat, watch for the plastic to begin to soften and in some cases slightly change colour. In some cases it may be necessary to roll the heated section to ensure a smooth weld. Remove the line from the heat and roll it back and forth under your fingers on a smooth, hard surface (preferably not your wife’s prized antique coffee table).
- The welded section should appear to be one piece. If we can still see a separation, repeat the heating and roll if necessary. Once it looks like one piece, move on to the adjacent section, heat and inspect. Keep on going until the loop side(s) are completely welded up to the main line.
- If the line has a permanent colour change after cooling, then it has been heated too much. Cut it off and start over.
- Be generous with the heat shrink so as to provide adequate grip for your fingers. Too little heat shrink and we’ll probably burn our fingers and may leave gouges in the line where the heat shrink ended.
- When making back end loops using running line, be careful not to heat too far past the tag ends of the running line and on to the main belly. Heating well past the tag ends can cause a weak spot in the belly. I try not to heat more than a 1/16” beyond the tag ends.
- Always pull the loop completely inside the heat shrink. This has three benefits: ample room to hold the line and not burn your fingers, makes a smooth transition from weld to open loop, and prevents a ridge in the sides of the open loop caused by the edge of the heat shrink.
- Once the line is well position inside the heat shrink, gently heat the tubing to snug it down so that the line is held in place. Only shrink down the section that will be welded.
- The butt end of the belly should be tapered down to make the transition to the loop smoother. Simply slip on a couple of inches of heat shrink on to the end of the belly, heat and roll the end down. Once cooled, snip or pull off the little of “tail” of plastic that will be left behind.
- When making back end loops, always leave about ¾” of open loop beyond the tapered end of the belly, then when heating it, make sure to weld past the end of the belly so that some of the open loop is welded shut. This prevents the loop-belly junction from being levered open during normal casting motions.
- After the loop has cooled, give the loop a pull test. If too much heat has been applied and the core has also been melted, it will break easily.
- If the loop test passes with flying colours, go fishing.