Forming the D-loop

An important aspect of Spey casting is the formation of the D-loop, which is used to restrict the amount of fly-line that extends backwards prior to making the delivery cast. The top of the D-loop is connected to the rod-tip and the bottom is held by water adhesion causing anchoring.

There are a number of factors to consider when creating the D-loop and these are:-

1. Anchor position
2. Anchor size (length)
3. Correct formation of the D-loop
4. Continuous tension

Anchor Position

With regard to anchor position we are told that the line-tip must be just over a rod length’s distance off the casting shoulder. It should also be aligned with the shoulders but during set up this is not always the case and so the line tip has to be pulled back during D-loop formation e.g. in the case of a double Spey cast. To get the fly-line to pull back there has to be sufficient force in the D-loop.

Anchor Length

The anchor size (length) depends upon the mass of the fly-line in the D-loop and so is variable. The bigger the D-loop, the greater the force generated and hence the larger the anchor length that is required.

In the diagram you will see that there is an equal force on the rod-tip and the anchor and both are equal to a half of D-loop force. Therefore to form a bigger D-loop with more mass you have to have more force required by line stick at the anchor point i.e. a longer anchor.

If the loop is allowed to drop, as in the case of a static roll, then there will be more force required in the vertical vector to overcome the greater gravitational force. The aim is to get as much fly-line as possible, straightened, behind the rod-tip. I have tried experimenting with the fly rod angled back and leading with the rod-butt to get more lift, which seems to work but wrist action was required to get the sufficient rotational velocity of the rod-tip.

Formation of the D-loop

Looking from above, the anchor and D-loop should be lined up 180 degrees opposite to the direction of the forward cast.
Efficient formation of a large D-loop is achieved by exploiting the leverage of the fly rod and sweeping as far out from the body as possible. Keeping the rod tip close into the body will reduce the size of the D-loop because the rod-tip will only mimic the movement of the casting hand, rather than magnifying it.
The diagram shows the difference in D-loop size using leverage (2) and casting hand mimicking (1)

Continuous tension

It is important to lead the fly-line round with the rod-tip when forming the D-loop, keeping the fly-line under continuous tension at all times. Some casters have a tendency to pause and let the D-loop drop, which is not conducive to a good cast. It is far better to change the tempo of the cast and to allow the rod-tip to dwell for a very short period (which may be perceived as a pause). This dwell also allows the anchor to be drawn back into position.

The fly-line must be controlled by the caster at all times and slack line should be avoided.