A question of Overhang

A question of Overhang

Paul Arden | Monday, 21 September 2020

A good question was asked on the Board last week about what is the purpose of overhang and what does it achieve? And it’s a good question because the answer involves some understanding of line profiles and shooting line.

First of all, overhang is the length of running line between the rod tip and the rear taper of the head of the flyline. For example if you have a WF fly line with a 40’ head and have 50’ of flyline beyond the rod tip, then you have 10’ of overhang.


One other thing I will mention in this Front Page is Carry. Carry is the amount of flyline held during the cast, measured from line hand to the front end of the flyline, excluding the leader. So if for example, you are a top level competition caster and you were to “carry” the entire fly line to the backing knot, then you would be carrying 90’ of flyline and your overhang would be 90’ minus 40’(head), minus 9’ (rod length), minus distance from line hand to the rod butt (let’s call that 1ft - I realise that that will vary depending on where you are with the haul - more on this later) so the maximum overhang in this case would be 40 feet. That’s a pretty extreme example but in the competition casting world not at all an uncommon skill.


So this question is not just about overhang, because I think that one has to understand that there is a rule of thumb in that one can only shoot on the forward cast approximately half of the length of line being extended on the previous backcast. Now this is kind of a strange rule and actually I don’t think it applies too well. However the theory is that if you have 30’ of flyline beyond the rod tip on the backcast, then you can shoot an addition 15 feet on the forward cast.


The problem with this is that it doesn’t take in account the diameter (or sometimes slickness!) of the shot line, which varies considerably. Perhaps you are casting a DT and it wants to shoot very little. Perhaps the running line is very thin, imagine for example an integrated shooting head, in which case you would hope to shoot significantly more than 50% of your carry.


However the point is this, and it is always true, that one of the casting components that governs/limits how far you can cast on the delivery is the amount of line you are aerialising outside the rod tip of the backcast, no matter what that percentage may be!


Now let’s say that we need a long cast and we have a WF line with a 40’ head. If we are to take the 50% shooting line rule of thumb,  then by aerielising 40’ of line outside the tip this will allow you to shoot to 60’ of line outside the tip. Even if everything was perfectly straight (which is never the case!) with a 9’ rod the end of the flyline is only 69’ away from your feet. In order to cast further, then it follows that you must carry more line on the backcast.


So let’s take our nimble competition caster, who has the ability to carry the entire line and has 40’ of overhang. He has the potential to cast the full 80’ (line outside the rod tip) PLUS 40’ (half of aerielised backcast beyond the tip) plus 9’ rod length. So if everything landed perfectly straight the end of the fly line would be 129’ away from his/her feet.


While I, like others, can certainly carry virtually every 90’ flyline to the backing knot, it’s very difficult to put the fly/fluff (not merely the line end!) on a 9’ leader much more than about 120’ away with such a line. So there is something wrong with the “shoot half of what you carry” formula. But also you have to take into account that there is always slack - if you don’t believe me then make your longest cast, go to the other end and see how much further you can extend the line until it pulls straight!


Furthermore, carrying the line to the the backing knot is not always the best way to cast such lines, even in competition. Indeed with these short WF heads, carrying to around 80’ seems to give better results. I don’t think that this is because of loop instability either - although it is undoubtedly less stable as you extend the overhang. Rather I think it has more to do with how loops propagate poorly when the loop that is unrolling after the initial loop formation is running line. [whether that is angular momentum or momentum change is a Hot Topic on the Board!]


So the point is that overhang is always necessary when dealing with a short headed WF flyline for distance.


Now let us compare two identical carries, one with a line that has overhang with a line profile such that the initial loop being formed by the rod tip is running line and the other where the loop being formed is the head. Let’s be specific for more clarity. One head is 60’ and the other is 70’ and our backcast has 70’ of flyline outside the rod tip.


In the case of the 60’ line you have an overhang of 10’. In the case of the 70’ line the head extends to the rod tip and there is no overhang. The dynamic differences between these two lines are very apparent when the loop forms. In the case of the line with overhang, the initial loop is formed with running line, and the resulting loop morphs tighter and is noticeably more “dynamic”.


Let’s now extend the carry by ten more feet in the above examples and for the first line you now have 20’ of overhang and with the second 10’ overhang and compare these two.  The first line, while certainly castable, is now the more challenging. When the loop forms there is significant running line that has to unroll before the head reaches the front of the loop. This creates instability and requires some deft skill to manage.  The second line however is now morphing tight and is highly castable in the way that the first line was in the previous example - consequently for all-out distance you should choose the length of head that you can comfortably carry such that the initial loop formation is running line and the end of head is reasonably close to the very front top of the loop.


You can shorten or lengthen those numbers as you see fit, the same applies for head lengths of 30 and 40 feet. Most casters seem to struggle to aerielise much more than 50’ of flyline in the air, which is probably why most WF lines are around 40’ long in the head giving them 10’ of overhang. Although you could also argue that *the reason* they struggle to aerielise much more than 50’ is because the head is 40’!



One final consideration to take into account when you think about this is the haul, which I touched on earlier. My hands actually finish slightly over 5 1/2 feet apart at the end of the haul. So when you look at the competition distance casting numbers, the real.figures - for me anyway - are 5 1/2 (haul), 9’ (rod), perhaps 6’ in the loop. That’s 20 1/2’. The 5WT Mastery Expert Distance head is 68’. So that would require an 88 1/2’ minimum carry length to be dynamic. And that’s actually about the right number.


I’m off to Rompin to catch some Sails.


Cheers, Paul

PS here is the discussion in question: