Fishtailing and porpoising: what arrow flight says

Part of the complete guide: How to improve your score in archery

There is a moment on the range when someone behind you says it: "your arrow is wagging". And they are right, you really can see it: a tail flapping sideways, or a shaft that seems to swim to the target rather than fly there. The typical reaction is to shrug and check the score. That is a wasted opportunity, because arrow flight is a diagnostic channel of its own: reading the target tells you where you are going wrong, the flight helps you understand why.

First, though, an honest disclaimer, so this guide does not become a paranoia factory. Every arrow oscillates. High-speed photography showed it a century ago: the shaft leaves the bow flexing and vibrates for the first few meters. That is the archer's paradox, and it is physiological. That fine, fast oscillation, the one that dies out quickly, is barely visible to the naked eye, and it is not a problem. What you can see with the naked eye is something else: a wide, slow undulation that stays with the arrow for much of its flight. That is a symptom, and it goes by two names.

Fishtailing: the tail wagging sideways

The first flaw lives on the horizontal plane. Seen from behind, the flight shows the arrow's tail snaking left and right, like a fish's tail, hence the name. The point more or less holds its line, the tail does not: the shaft flies "sideways-crooked" and straightens out with difficulty, when it straightens out at all.

The causes all live on the horizontal plane of the system, and they come in three families. The first is spine that does not match your bow: a shaft too stiff or too soft does not wrap cleanly around the riser and leaves the bow already untidy, with a wider sideways oscillation that is harder to damp. The second is clearance: the arrow or its fletching touching the rest, the plunger or the window on the way out, a contact that dirties the flight at its root. The third is the release: fingers leaving the string in a rough or asymmetric way add an extra sideways push to the tail, and no amount of tuning can fully erase it.

One clue to tell the three apart: consistency. A spine or clearance flaw is systematic, it shows up identically arrow after arrow. A rough release is variable: some arrows fly clean, others do not, often getting worse as fatigue sets in. If the fishtailing comes and goes, the first suspect is you, not the equipment.

Porpoising: the tail waving up and down

The second flaw lives on the vertical plane. Seen from the side, the flight shows the arrow waving up and down, the tail rising and falling like the back of a surfacing dolphin, hence the name. It is less common than fishtailing but more unambiguous, because its dominant cause is a single one: a nocking point set at the wrong height.

The mechanism is straightforward. If the point where the nock sits on the string is too high or too low, the string's push does not travel in line with the arrow's axis: the tail gets kicked upward or downward at launch, and the shaft crosses its flight waving on the vertical plane. More rarely a nock gripping the string too tightly, or a poor vertical seat on the rest, can contribute, but the main road stays the same: when you see the dolphin, look at the nocking point.

Vertical first, then horizontal

Here comes the rule that saves more time than any other, the same one the manufacturers' technical manuals write into their protocols: you fix the vertical plane first, then the horizontal one. Nocking point first, then spine and clearance. It is not manual-writer pedantry: it is diagnostic logic.

The reason is that a vertical flaw contaminates the reading of everything else. An arrow kicked out of line on the vertical plane flies untidy, touches what it should not, and produces sideways symptoms that look like spine and are not. If you correct the spine with the nocking point at the wrong height, you are tuning the shaft to a defect, and as soon as you fix the nocking point you will have to redo it all. The right order costs ten minutes up front and saves hours later. It is the same principle as the whole tuning process: the steps have an order, and reversing them produces surface-level optimisations.

The confirmation: the bare shaft, read on two axes

The eye, however trained, remains an imprecise instrument: it sees the big flaw, does not measure the fine one, and with adrenaline it also sees things that are not there. The real confirmation happens on the target, with the bare shaft test: fletched arrows and unfletched shafts, same distance, and you look at where one group lands relative to the other. With no fletching to straighten and mask, the flaw comes out naked. The twist, compared with how the test usually gets told, is that the bare shaft is read on two separate axes, exactly like the flight.

Mind the order here too: first you bring the bare shaft to the same height as the fletched arrows by working on the nocking point, and only then do you read its sideways offset to judge the spine. Reading both axes together, with the vertical still out of place, is the fastest way to correct the wrong thing. And the usual rule applies: one change at a time, then shoot again. Changing nocking point and point weight in the same afternoon means never knowing which of the two did the work.

When it is not the equipment

It needs saying with the same honesty I use for the target: not everything that flies crooked is the bow's fault. Flight reads the whole system, and you are part of the system. A release that changes from arrow to arrow produces flights that change from arrow to arrow, and no tuner can chase them: if the flaw is inconsistent, the road does not go through the screwdriver but through the shot, and if anything through a properly filmed video to actually see it.

The separation criterion is the same as in all shooting diagnostics: systematic versus variable. Equipment errs the same way every time; the shot errs differently every time. Fishtailing that is identical across twenty arrows deserves the workbench; fishtailing that shows up on three arrows out of ten, perhaps late in the session as fatigue climbs, deserves a mirror. And when doubt remains, the bare shaft is the referee: it carries your release with it, true, but over a full series it averages, and the average does not lie.

The questions I get asked most

Why does my arrow wag in flight?
If it snakes sideways it is fishtailing: the causes live on the horizontal plane, a spine that does not match, contact on the way out, or a rough release. If it waves up and down it is porpoising, and the first suspect is the nocking point. The plane of the oscillation is already half the answer.

What is porpoising and how do you fix it?
It is the vertical undulation of the arrow, the tail rising and falling like a dolphin. It almost always comes from a nocking point set too high or too low: the string's push does not travel in line with the shaft. You fix it by moving the nocking point in small steps, checking with the comparison between fletched arrows and a bare shaft.

Does fishtailing always mean the spine is wrong?
No. Spine is one of three suspects, along with clearance and the release. A useful clue is consistency: an equipment flaw repeats identically on every arrow, a rough release comes and goes. The confirmation comes from the bare shaft test, not from the eye.

Do I need a high-speed camera to understand arrow flight?
No. High speed is the laboratory's tool, but the two macroscopic flaws are visible to the naked eye and, above all, they are confirmed on the target with the bare shaft test, which reads in the result what the flight only hints at. The camera helps, the target decides.