The Triple or Check Haul

[Paul Arden]

Hi guys,

I thought it would be an interesting topic to revisit. How does the Haul function as the loop is unrolling. If the loop looks like it will fail we add a little “haul”. I often use it Into the wind, indeed when fishing I use it just about every cast

Am I right that the reason it works is predominantly an increase in Tension in the rod leg? I also realise that it shortens the fly leg, and indeed would also accelerate it slightly but these both are marginal effects?

Hope you physics chaps are all well

Thanks, Paul

Incidentally if someone can write a really clear description then I’ll pin it to the top of the thread.

[gordonjudd]

Am I right that the reason it works is predominantly an increase in Tension in the rod leg?

Paul,
I think it is more important in how that pull back force impacts the rho_l*v_tangential.^2 tension at the top of the loop. That is the source of the line tension that helps to overcome the drag force on the loop and fly leg.

The tangential velocity of the line going around the loop is equal to 1/2(V1-v2) where v1 is the velocity of the fly leg and v2 is velocity of the rod leg. When v2 is increased (it has a negative value) the tangential velocity is increased and ultimately the resulting tension increase at the top of the loop will add a positive acceleration force to the fly leg and increase its velocity over time.

You are doing some work by applying that haul force over some distance and that added energy has to go somewhere. I doubt that there is an exact one-for-one increase in the KE of the fly leg relative to the work done by the haul, but there should be an increase.

Of course the pull back distance also shortens the length of the cast, so any velocity increase comes at the expense of making a shorter cast.

Gordy

[Graeme H]

I use the rod tip to do the same thing but with a little more finesse and earlier in the cast. A little bit of additional controlled tension in the rod leg helps the loop progress nicely.

I have a "physics explanation" for how it's working but it's not one accepted by the majority of the people on this board and I don't feel like opening that can of worms again.

Cheers,
Graeme

[Paul Arden]

I didn’t realise there was disagreement on this. I see three conditions, shooting line, not shooting line and the check haul.

If there are two opposing clear understandable conflicting reasons then I’ll post them both and readers can make up their minds

Cheers, Paul

[Mangrove Cuckoo]

I see three conditions, shooting line, not shooting line and the check haul.

Cheers, Paul

Maybe 4?

What about a anti-check haul?

Non-shooting short cast as in trout fishing where the tip is deliberately fed forward to reduce tension and puddle the leader?

I seem to remember practicing that sort of cast from Mac B's "enlightenment casts".

[Paul Arden]

You’re right! But it’s not 4, it has to be number 5.

The interesting thing about that though is that the loop can still unroll. So it needs to have insufficient line speed to begin with. (I think).

Cheers, Paul

[Merlin]

It took me some time to build a small model for the inclusion of a check/haul during the rollover of the line. Hopefully we get what we know we can expect: an increase in speed but a reduction in distance, there is no free lunch you know. To make my life easier the line is a level one, of moderate diameter to get some loss in speed during the flight. Because the line has no taper the velocity of the fly leg raises sharply before the end of the rollover, but what we are interested in is the evolution of that speed as we check the line. I used a 1.1 m length check within 0.15 s of time, so it is pretty quick (figures are rounded).

The first graphic illustrates the effect of the check on speeds, including the “travelling speed” of the loop and its “rotation speed” (the tangential speed around the loop). During the check the loop reduces its forward speed and increases its tangential speed. There is a slight increase in fly leg speed due to the check in this situation (early check).

early check.JPG (23.05 KiB) Viewed 3594 times

Now let’s see what happens if we use different timings for the check, an early one and a late one:

check comparison.JPG (23.46 KiB) Viewed 3594 times

Calculation is stopped as the fly leg length comes to zero. We just lose the check length in distance but speed is rising at higher level by comparison to the base case (no check). Consequently, as we know from practice, we get some benefit at the very end of the cast, if the reduction in distance is not an issue. There is nothing strange here since we add some energy to the line with the check/haul motion. The only extra information is that the time at which the check is made does not appear to be important.

The mechanics behind is just the application of N laws for a simplified case. The usefulness is to visualize what type of phenomenon is at work with a check/haul: a late increase in fly leg speed.

Merlin

[gordonjudd]

The usefulness is to visualize what type of phenomenon is at work with a check/haul: a late increase in fly leg speed.

Merlin,
This is a great tool to see the effect of changing the rod leg velocity as the loop is rolling out.

I was surprised that as a function of distance there does not appear to be much of difference in the fly leg velocity increase for an early check vs the change for a late check.

First I was thinking the early check would produce a longer time period for the effect of the acceleration increase that results from an increase in the tangential velocity produced by the pull back of the haul. Thus the early check would produce a higher fly velocity.

On the other hand (speaking as an economist) the work energy produced by the late haul would be larger for the late check since you are increasing the negative velocity of a larger rod leg mass with the late check haul. If there is some kind of energy balance going on that would say the late check should produce a larger fly velocity.

Calculation is stopped as the fly leg length comes to zero.

What size loop are you using for this simulation? I would not expect that large of a velocity increase in the fly velocity for a loop that has 3 meters or so of line going around the loop.

Could you decrease the Ct value in your simulation so the fly velocity tends to increase slightly over time and then plot the fly velocity history of the early check and late check cases as a function of time rather than distance? Based on the assumptions above I don't know which case would produce the largest fly velocity so it would be good to see the difference with your model.

Nice work. Thanks for taking the time to put a little physics into modelling the effect of the check haul.

Gordy

[Paul Arden]

To be sure I think that the only time I don’t check the shoot is when distance casting in competition. When fishing I always check the shoot to straighten the leader. The check-haul on the other hand I apply to force over a leader that looks like it will fail to turn over. That haul is probably about a foot long.

(Just to be sure that we are all on the same page here )

Actually that is not strictly true. On a non-shot cast there is no shoot to check!

I’m very surprised about the timing mechanism being unimportant Merlin. That certainly gives me something to play with into the wind.

Thanks,
Paul

[Merlin]

Gordy

The loop is small (a little bit over one foot). I changed the input (Ct) to fit your request and here are the data:

check low Ct.JPG (24.99 KiB) Viewed 3563 times

When looking carefully at speed differences there is some advantage for an early check, but is it the same in real life?
I guess that most people check when they realize they need it, towards the end of the rollover.

Paul

I had some runs with a small check (one foot), and as can be expected the differences in speed go down. Problem: with have no record to compare with.

Merlin