This is not a page for actually learning to Double Haul. If you want to learn, have a look at the video in this page https://www.sexyloops.com/flycast/the-double-haul/ It’s not difficult to learn the Double Haul and if your loops are reasonably consistent, and in particular good enough to shoot line into the backcast, then it’s should take five to ten minutes to learn. Mastering and tweaking it however will take longer but the hard work will have been done.
So as Bernd mentioned in his excellent FP, some instructors still believe and teach that the primary function of the Double Haul is to add load to the rod, which in turn then releases more spring energy at the Stop. This is what most people believed 20 years ago. However the rod does not actually function merely as a big spring when casting. Indeed it was Ian Walker who I first heard describe the primary function of rod bend as being to turn rotation at the rod butt into a straight path at the rod tip. This statement was written over 20 years ago on one of the early Sexyloops discussion Boards. And while the rod does in part undeniably behave as a Spring it is only a small, minor part of its function.
When the first digital “cybershot” camera appeared in around 1999 it cost 600 pounds and I bought one. One of the abilities it has was to shoot videos at 15 frames per second. I actually made a bunch of movies on Sexyloops using it - remember Underpant Coffee? https://youtu.be/UF8NnbbF9-M
Another of the movies I made was double hauling and the interesting thing was instead of the rod being fully bent when the haul completed it was straight. Indeed sometimes the haul not only continued right up the “Rod Straight Position” but also into rod counterflex. In other words, while the haul might be adding rod load (physics tells us it must), the rod was in fact unloading during the haul. So if anything, adding load with the haul was in fact retarding rod unloading - which is exactly the opposite of what I and everyone else expected!
I posted the video on Sexyloops. Frank LoPresti on the Board (remember Frank?) wrote “Joan Wulff hauls to butt stop, Simon Gawesworth hauls to butt stop, Lefty Kreh hauls to butt stop whereas Paul hauls to Rod Straight Position” - in other words I was doing something wrong! Anyway I knew Simon very well and pinged him an email. Interestingly, while videoing himself he had also noticed exactly the same thing, which kind of took the wind out of Frank’s sails for a bit! :D
I messaged Bruce Richards about it. He also thought I was doing something different to everyone else and messaged Noel Perkins. Noel confirmed that despite hauling as the rod was unloading - and therefore slowing its release of energy - the combination of tip speed and line speed was greater than without the haul and that’s when it became the accepted view.
Of course we now know that virtually everyone hauls to RSP. Finishing the haul significantly before this - to max rod bend (or Minimum Chord Length) for example - as we used to believe - will actually most likely cause a tailing loop.
And when you think about it, this must be the case: we are pulling the line with both the rod tip using the rod hand, as well as pulling the line through the rod tip using the line hand. In other words hauling has a direct impact on line speed.
Grunde Løvoll at one of the Scottish Meets suggested that since hauling actually retards the rod tip while it is unloading, that it may in fact help in straightening the tip path and showed me some videos of Mathias Lilleheim casting that potentially demonstrated this possibility (have a look at this article from Jason and Grunde https://www.sexyloops.com/articles/rodcast.shtml which is mostly about the Spring and the Stop - Mathias is casting). Despite this line of thought from a long time back, I’m not sure that we have proof either way, but it is one possible further benefit of hauling.
However, there can be absolutely no question, that the primary purpose of hauling is to accelerate the line directly, using m the line hand. It is not to add load to the rod which in turn results in greater acceleration. We have known otherwise for over twenty years.
I have a cunning plan to try to ask all these sorts of questions on the Board and have easily digestible answers. I think this would be of great assistance to the Instructor world so they can easily find this information. Of course it is sometimes difficult to have physicists and engineers agree, but if they disagree I will simply post several answers. You know, sometimes there is not only one answer and besides, having to work through a couple of answers helps show where we really are in our current understanding. For example the rod is now currently seen by some as being a Spring, Lever and a Whip, so it has three characteristics.
This is the Board and it’s a great place to ask questions. https://www.sexyloops.co.uk/theboard/
Right, I’m sitting on my boat, it’s two days from being a full moon. So I might have a look later for some Gourami. Because as we all know, they are blacker than black.