Fly Line Stretch

Fly Line Stretch

Bernd Ziesche | Wednesday, 6 October 2021

You may want to check your fly line and leader for the level of stretch and match your whole system to each species of fish you are planning to catch!

A while ago I started to ask several fly fishig shop owners, if their customers would ever ask for the level of stretch that each fly line would provide for their fishing. The anwers all were a clear NO.

Since all the customers are not asking for the level of stretch of their fly lines, it seems to be a logical consequence, that no fly line manufacturer yet offers any numbers for the level of fly line stretch.

Then I asked a serious number of fly fishing experts and in addition I also asked on my facebook site about how much stretch a fly line should provide or not.

The answers made it clear to me, that 95% of fly fishrmen have little if any clue about the impact stretch in their whole fly line and leader system has to their fishing and hardly ever thought about it yet.

Myself I have been studying the effects of stretch in general to my fly fishing results for many years now.
I differentiate between 5 steps:

1. Presentation (fly casting)
2. Fly movement
3. Feeling the take
4. Setting the hook
5. Fighting the fish

Stretch in general (not fly line stretch) has significant impact to all these 5 stages in catching fish.

I can add a specific, constant amount of stretch to my system (fly to line hand) by using shock absorbers (like power gum, Drennan) or stretchable leaders (like many nylon leaders) or I can use a fly line providing inconsistant stretch.

The one difference with the stretchable fly line is, that the amount of stretch changes with the length of fly line outside the line hand. This may become a disadvantage in some situations. "May", because it all depends on how much force  we put to the line and how.

Fly casting wise it depends on what fly I am casting. Casting a truly heavy fly I like to have some stretch, because it helps a lot when I fail to perfectly hit timing and instead start the next cast a millisecond before or after the leader was perfectly straight. Feels much smoother with some stretch in the system. Casting a smaller or at least less heavy fly and (almost) zero stretch is fine for me. In the end we often love, what we are used to cast the most.

The more stretch we add, the harder it gets to add aggressive jumps to our fly. Whenever we need these I prefer low stretch for sure! No need to tell, that without a take we have no need to talk about the rest! This is for example very critical on asp when using shock absorbers. I can't make them very long, when I want agressive movement. Too much stretch and I often fail to get a bite! The fly line system may not provide much (if any) additional stretch here, because the force we add by stripping may be too little based on the fly usually not providing much resistance (thanks Lars Bentsen for making me think here).

Do we want to feel the take? In most situations, yes of course. With some fish though it is not so important, because they will not spit the fly and instead keep it and run off. But the more stretch our fly line has, the more takes will be dampened away - at least those happening on distance! By the way the craziest fly line I checked was coming from China offered by a young German brand. It had easily significantly more than 3m stretch on 30m length (12-13%) without me going anywhere near to break the line. I have no idea how one would feel a Sea trout take on that distance here!? Amazing though that the core stretched the same amount as did the coating!

For setting the hook a (almost) zero stretch fly line is best. But of course, if we need stretch in order not to break the thin leader we may have to use, than we have to use thin hooks making it easier to get it into the fish! This is hardly ever black or white. There are a lot of key factors to adjust to each other. No doubt that for setting a huge hook into the bony mouth of a Tarpon the last thing you want is a stretchable fly line. But then again when you want to fish an IGFA conform leader coming with low breaking strength, I would not recommend to have zero stretch in your line system (fly line and leader). Just to give one example. Offering a size 24 dry fly I assure you, that setting the hook is easy even when using an XXL shock absorber in addition to a stretchable fly line.

For fighting big fish in my experience it's very helpful to have stretch in the system. It helps to quickly get the fish tired, and it makes it hard for the fish to get rid of the hook. Espcially when big fish get close, stretch can be very helpful not to end up in a broken leader or a straight hook.

There are more aspects coming along with fly line stretch like for example live span of the fly line. The more stretch the line has, the easier the coating breaks in my experience.

The less stretch a fly line has, the easier it has memory again causing damping between line hand and fly. This is a very important point to understand! Thanks to Bruce Richards for putting my nose into this aspect.

I was listening to Tim Rajeff talking about fly line stretch here:

Tim Rajeff video

Tim claims 20% stretch to be normal for a trout fly line. That made me wonder how people would measure stretch on their fly lines?

Of course, if you stretch your fly line until it breaks, you get such high stretch numbers. But this is not what usually happens in fishing! We put much less force to our line system in fishing... Also you would put very different levels of force to the fly lines for such a test, because breaking strength varies with line weight and from line type to line type mainly depending on the core material.

For testing I prefer to stretch my lines in the same way I expect them to be max stretched during some of my fishing situations (catching rocks is not included). Here are some numbers:

SA Mastery XPS floating 5wt. ca. 8-10%

RIO InTouch sink6  6wt. ca. 4-6%

Wulff TT floating 8wt. ca. 7-9%

Guideline Triple D shooting head s1/3/5 ca. 2-4%

Flat Beam mono shooting line 50lbs. ca. 9-11%


As you can see, I very much doubt, that we want (and usually will have) a 20% stretch to take place in our fishing. It's far less according to my experience!

After all I very much believe, that not having a number for the amount of stretch in our fly line and leader system is one of the biggest missings in fly fishing tackle today! I sure know exactly what my fly lines, leaders and absorbers are about, because I check and match my whole tackle system for whatever species of fish I am after!

Right now I am about to chase pike. Here I have zero use for stretch!

I hope I could make you think and ask for stretch next time you choose a fly line.

Great stretchable week to all of you!

All my best

P.s.: Some current pictures...