In the previous part 2 installment, TWO (2) hazards were discussed when trying to re-use the floating head line weight class for a sinking head. The Active-Line load appears to be a more telling story than the standardized effect of weight class. This part 3 installment is to explore what is behind Mystery door #3, an unpredictability we were left with from only having casted the unmodified final head in part 2. We will be chopping and assembling this unmodified head to get all 9 digits of the line matching zip code for that Zpey - or any other - rod. This is akin to getting both the right shoe length AND width size. At the end of this part 3, we will see behind door # 3 awaits some nice surprises, along with those that will make us ponder further depending on how far we want to go down the rabbit hole. Just as when we feel we are getting close to mastery, we are humbled when we simply end up as a better student.

Remember the saying that within a thick book is a thin book trying to come out? In this AFS Gen. 2 case, my discovery brought up that within a ONE (1) weight class for Scandi head are THREE (3) weight class trying to come out. And to boot, there is the added potential to obtain HALF (1/2) weight class in between whole numbers (not part of this installment's discussion). What you've got here is a highly tunable line loading system that can come in handy on days when one's casting timing has shifted from it's normal center. The only down side is your Scandi head will remind you of Frankenstein, with sections patched together with loop-to-loop connections. Hey, I too had the trepidation of playing chop-chop with oh-so-pristine-one-piece line, much like trying to tattoo your child's stomach. But for me - and perhaps you too - I soon discovered at the end something fulfilling and satisfying in customizing heads to my personal taste, creating many weight classes from one. And just as important, this discovery left me with more greenbacks in my wallet. Sorry kiddo about the tattoo.

Just like the fabled story of Jesus who had fed thousands with a handful of fish (bait fishermen, I cried), I eventually created my own combination chart centered around using ONE (1) head, capturing the many permutations for rods in my cache ranging from 11 to 15 feet, from rod classes #7 to #10. There is a lot to take in, but if we start with isolating the relationship between the THREE (3) heads for the Zpey rod, the rhyme and reasons that pervades in this chart will become self-evident.

Using Figure 1 below, let's start with the first Zpey head: the #10/11 AFS head as-is out-of-the-box (a restriction so as to make the line returnable as an option). As mentioned in part 2, I had used the #8/9 wt S4 head as my reference to what feels as a well-matched line/ rod combination. So, this # 8/9 weight reference pointed to using the S2S3 head as-is, although now shortened to 38' for cast-ability (footnote 3). This is known as Head A, with a total weight of 613 grains. The Active-Line loads for both the S4 reference and Head A calculate near identically to 347 and 336 grains respectively.

But as I became a better caster, I found Head A to be too heavy, not releasing the rod tip early enough for maximum line energy. I soon developed a greater affinity for the lighter #7/8 S4 head as a better reference to my improved casting style. After having performed a many-mental-line-cutting in my head, I emerge from under this near Ph.D. calculation marathon with Head B of 38', 554 grain. Both the lighter Head B and its respective S4 reference now have a near identical Active-Line load of 300 grain and 305 grain respectively, a shedding of about 40 grains for the same section in Head A.

Again, as if my casting evolution had a life of its own, I found that there was possibly a much finer tuned head that would make the same jump as if switching from an AM station to its FM equivalent. By now, my son had ran away from home after seeing me once again comatose with more foreboding mental calculations, fleeing before I woke up to find my hand unconsciously curled as if holding a tattoo pen all the while. Head C comes out - after I explained myself well enough to Social Services - a much lighter overall head by almost 50 grain than Head B. Even though the Active-Line load for both Heads B and C are almost identical - suggesting an equal load resistance - Head C now cast with a much quicker rod tip release than B, maximizing the line speed even more. And by this, this suggest to me that the weight of the Non-Active line (section C to E in Figure 1, part 2 installment) has an effect on the overall line/ rod matching. 

So, now that I have a well-suited Head C for the Zpey rod (effectively a #7 US class rod), I found that the heavier Head B loads (and releases) a #8 class rod well, whilst the even heavier Head D (a variant of Head A but with identical Active Line load) works equally well with a #9 class rod (footnote 1). I now have THREE (3) weight class heads from ONE (1) head.

While the Active-Line load alone simply loads the rod, it alone does not tell the story of how the Non-Active line portion eagerly allows the rod tip to recover that maximizes lines speed. This translates to either a clean and light rod tip recovery or a sluggish and heavy one; the former being the preference for Scandi casting, the latter coming closer to a Skagit cast. The neat thing about this is the separation between the two feels was made pronounced with a simple line tweak- the shedding of 50 grains in the Non-Active Line portion (footnote 2).

Using matching in BOTH 1) Active- Line load, and 2) Non-Active-Line release, Figure 2 below shows my array of chopped sections of the S2S3 head in conjunction with tips/ polyleaders to match the different rod lengths and weights classes in my cache (footnote 3). If you could follow the local example in Figure 1 for the Zpey and Echo rods easily, you will not only be able to understand this expanded table for the expanded group of rods, but perhaps you can see a combination I have missed (I can almost hear 'Wheeeeeeee' as you pass me by with your newly activated acumen).

And with this, I hope this series not only decodes AFS and the hidden realities masked by the weight class designation, but the explorer within you is now awakened so that when its foot hits the floor, the Satan of status quo thinking won't have a choice but to say 'Oh crap, he's up'. And this is how we overcome the common fault of trying to fit the dynamics of reality into the rules of language and numbers that simply causes a greater separation from - rather than an enjoining with - reality.

Footnote:
1) In order to do apples to apples comparison, Echo #8 and #9 weight Scandi rods were used as they are almost identical in length to the Zpey rod (measuring 12'4" and 12'6" respectively. Reference: 12'3" for Zpey rod).
2) The opposite is true for the heavier class weight #9, when compared to Head A, Head D has a more sluggish release, having 7 more grains for Active-Line load, but more importantly, 13 grains more in the Non-Active-Line load. This makes the D load more than A as the result of these two increases. The extra length is for a slightly longer #9 rod that requires a slightly longer anchor for more distance.
3) To be used with the recommended max Scandi head length in my previous blog (my on-stream experiments leads me to 3 times rod length for S2S3 max length).

In part 1, we introduced the maddening story of buying shoes in a fictitious deregulated shoe size industry. It doesn't take a large stretch of imagination to see that the setup for the shoe story is an appropriate analogy for AFS heads. Simply substitute your foot size with your Spey rod and your fitting shoe size with your matching Spey line (using the differing shoe colors for differing sink heads) and the connection is made.

My affinity for AFS heads largely comes from the ability to change the sink rate of the entire shooting head, giving me a much tunable sink rate to match differing depth presentation for various combination of fly and on-stream factors. So, my first step in properly loading the rod of choice, a Zpey 12'3" #8 EU class rod, was to find a proper loading AFS floating head. Although the rod lists a grain window of 338 to 416 grains, just like the process of finding the light colored shoe, I had to experiment with several heads; sometimes using heavier heads that came with truncated tips (perhaps in attempts to keep the weight within the rod's grain window) [footnote 1]. I eventually settled for a 400 grain AFS #7 floating head. This floating head discovery is akin to the light colored shoe process.

The next step was to find a sinking line. At that time, the only AFS sinking head was the Sink 4 (S4) head, tapered and weight balanced similarly to the floating version. Although Rio only offered this head in the #7/8 class category as the lightest head, weighing 460 grains, I found this line one of the most satisfying combination I enjoy casting over and over again (footnote 2). This is even after I had to cut back and substitute the last 8' of the head on the fly end with a #7, 10' Density Compensated type 6 tip (footnote 3). I enjoy the smooth accelerating turnover as well as the well match loading characteristics. My cast becomes one that has a non rushed forward cast and a fast recovery tip for prodigious distance while casting weighted flies. This S4 discovery is akin to the semi-dark shoe process.

But the biggest shocker was making the 'black shoe' purchase when fine tuning the Sink2/Sink 3 (S2S3 hereafter) head. Hey, if the #6/7 floater works, the blind obedience here is to get a #6/7 S2S3 head. But casting a #6/7 S2S3 head with the Zpey rod was a woefully underloaded and dissatisfying rod/ line combination. Yes, I was tiring myself quickly from not getting the proper rod bend. Fortunately, I contacted and arranged with Rio exchanging the under loading head (and several classes between #6/7 and #10/11 over several exchanges [footnote 4]) until I finally settled for the #10/11 head weighing 640 grains (footnote 5). This calculates to a 240 grain difference between the successful #6/7 floating and the final #10/11 S2S3 head, a woeful difference impossible to overlook. Even so, this final choice was an approximation at best because I could not modify the S2S3 head (or this would render it unreturnable) nor add any sinking leaders without grossly exceeding the maximum cast-able length (3 times rod length, water borne anchor, sinking head). Agh, more fine tuning with leaders/ cutting the butt end that could go either way in terms of proper loading. Mystery behind door # 3 awaits me with some unpredictability.
 
Because of this weight class jump from #6/7 (floating) to 7/8 (S4) to 10/11 (S2S3), I started to see that an allegiance to the floating weight class of #6/7 throughout the whole sink spectrum would not have led to a satisfying rod/ line result. Rather, the true line/rod performance now makes this weight class designation a misleading criteria. Huh, but why even have a weight class at all if this weight class is misleading?

While I got thinking what is the hidden reality untold by the standardizing effect of weight class, I remembered a diagram from Henrik Mortensen's 'Fly Casting Scandinavian Style' book. His diagram suggested that the portion of the line that loads the rod, the Active Line, is from the rod tip to the apex of the D loop. This corresponds to section from A to C in the Figure 1 below. 

So far, I have found that the best explanation I can come up with is that the apparent resistance from the THREE (3) differing weight class heads must be, or at least perhaps, close to each other. That means the load the rod experiences, whether with the 400 grain floater or the 640 grain S2S3 sinker, is approximately equivalent for my current casting style.

Henrik suggested that the section A to C is the dominant portion that loads the rod. He calls it the 'active line'. It is the portion of the line the rod tip feels as a load during the forward cast. With this and with a reliable grain scale, I performed a quick calculation between the THREE (3) scenarios, using some geometric assumptions (footnote 6), and found that the head- although they are remarkably different in overall weight- all calculate to roughly the same active line load. Perhaps this now 'active line load' is the unifying common reality behind them, a story that is simply not told by merely looking at weight class. This story is reinforced further when the active line sections all calculate out to be between 300 to 310 grains.

Remember the shoe story and the deregulated shoe size? Just as with the shoe, this discovery churned up some stumbling blocks that made the floater weight class unusable when selecting the S4 or even more worse for the S2S3 head. These stumbling blocks are 1) Leader Effect, 2) Weight Distribution Effect.

Referencing the above figure 1 again, the Leader Effect basically has more of the head in the active line zone (section A to C) than when casting without a leader. With Leader DE as the Anchor in play, the entire head AD is aerialized as a D loop, with C as the apex. But when anchor DE is absent when casting with sink heads, part of section CD has to become the new anchor. The Leader Effect becomes more obvious when we see that the recommended total length for a floating head/ leader system is 4.2 times the rod length (footnote 7), but only 2.3- 2.7 times the rod length for sinking heads/ tips. Since 4.2 is larger than 2.X, length AC is longer for the floater than the sinker, pushing more of the floating head into this active loading zone. Hey, there is a simple way to verify this. Simply cast your floating head with and without a leader, and your load- sans blowing your anchor with proper control and timing- will be woeful less for the latter. My #6/7 floater with a 3' leader is the closest thing to replicating a non-existent #6/7 S4 head (the 3' leader is to to keep apples to apples comparison with my #7/8 AFS S4) .

The next stumbling block is strictly a creature of line design. Both the floating and Sink 4 heads are part of the Generation 1 AFS family. They are somewhat triangular tapered made out of homogenous (constant density) material (see figure 2 below). Thus, their weight distribution is identical, with Gen. 1 being rear centric. Although not a problem for the floater, this rear centricity posed a down side for the now-discontinued S4 head: the butt end was sinking faster than the tip end,  an undesirable feature for actual fishing conditions. So, Rio introduced Generation 2 Sink AFS heads, a dual density head with a faster sinking tip than the butt end. But in order for the tip to sink faster, the Gen. 2 design had to re-balance the head with a design that is now level-line centric (see figure 3 below) [footnote 8]. This breaking rank with Gen. 1 rear centricity means what was casting good in Gen 1 may no longer be true when casting Gen. 2 heads, both using the same weight class. Hey, a quick way I proved for myself was to simply connect your Windcutter body with a 10 and 5 foot cheater, totaling 400 grains at 38', and cast it (footnote 9). I found this setup to be rather clunky in turnover, and even more dissatisfying in loading than the earlier mock AFS 6/7 S4 head, both products largely from the level-line centric weight balance.

Thus, when one tries to cross over from AFS Gen. 1 floating heads to AFS Gen. 2 Dual density heads, the hazards of Leader Effect and Weight Distribution Effect makes this cross over much like the fictitious shoe store experience when trying, but eventually failing, to use an earlier size for darker shoes. But these hazards from such crossing can be neutralized with a simple bridge that tells a hidden 'Active Line Load', a reality that is masked by the misleading facade of weight class. Knowledge is power, and in this case the power to go beyond the blind obedience of weight class that, while simple in its use, simply cast a false sense of safety.


Footnote:
1) The rod was sent to me with a AFS #7/8 floating head with the tip cut back. But as I progressively got better at casting, I found one weight class below gave me more consistent loops based on my casting style (for now). 
2) I initially settled for a #8/9 AFS Sink 4 head, weighing 520 grains. But the final #7/8 weight class became a better fit as I became a more proficient caster that loaded the rod properly with this lower weight choice.
3) This modification was needed to overcome the fact that the butt section was sinking faster than the tip section due to the non- density compensated properties of a tapered but homogenous density head.
4) This several exchanges allowed me to do some weight balance comparison, leading a line change recommendation to Rio (click here for pdf report [to be released soon]).
5) I opted for this #10/11 weight class (to be reused for a 14 foot #9/10 rod) although my latest casting evolution suggest I could drop down one or perhaps two weight class for the Zpey rod. But even still this drop down still means a 120 grains heavier than the #6/7 floater.
6) I approximated that the active line weight is the butt end (starting with A in figure 1) weight of 50% of total line system length (tips and leaders included). For a floating head, I approximated that 1/3 of the leader length needs to be subtracted before calculating the butt end weight of the 50% of this now shortened length.
7) The head length is 2.7 times, the leader is 1.5 times rod length.
8) Although this surrogate AFS diagram from Guideline Power taper shows a multi-step down design, the level-line weight distribution is still in effect as the density increases from the thicker butt section to the thinner tip section (the darker the color, the higher the density).
9) One possible recipe for making a Level-line centric 400 grain 38 foot head: Windcutter 6/7/8 Body (23', 230 gr.) + Skagit Cheaters 6/7/8 (5' [60 gr.] + 10' [116 gr.]). The 38 foot length mimics the length I currently use for my final S2S3 setup.

Let's indulge in a short discourse here. Imagine one day you went to a shoe store looking for a light colored pair of shoes. Knowing your size, you approach the sales person and inform her the size, the color, and brand you want. To your surprise, she politely informs you that the industry decided to deregulate the standards in shoe size, and that the only way to know the right fitting size is to actually try many sizes in the chosen color and brand. You find that news rather astounding, but you begrudgingly give in and instruct her to bring several sizes that came close in approximation. You try on a few sizes until you find size X that fit. The purchase is made and you move on with life.

Several months later, you decide you want a semi-dark color in the same size and brand. Again, you visit the same store and luckily you get service from the same sales person who remembered the earlier purchase and the fuss that went down. Ah, you thought, not only would this be easy with simply switching out the color and keeping the other variables the same, but I get the same person who baby sat me through the earlier fiasco of deregulation brouhaha. Shockingly, the salesperson kindly informed you that the mere act of changing the color would mean you would have to repeat the trial-and-error process because you cannot carry over the lessons learnt, and thus the final size. She went on to explain that the deregulation in size standards also proliferated within a brand across the color spectrum. Sh*t, you thought. Not another crazy-zany process just for a color change. Again, with a tense neck and a healthy restraint not to unleash onto the messenger, you repeat the entire process again.  Again at the end, you make the purchase and you move on with life.

Several months past by, and you find yourself in need of a black formal shoe. You go through the same approach, getting the same salesperson, hoping- no, actually pleading silently in your head- that the size for the earlier semi-dark shoe would give a close enough approximation to the size in black formal shoe. And that this close enough approximation would minimize and trial and error this time. However, by now the sales person is hanging her head low, a pretend dejection in full self defense against your wrath, as she explains that the semi-dark shoe size is a lot closer to the first light colored shoe than to the black one.

Can you see enough engorged veins in your neck and forehead simply reading this? And this is how we navigate the world of AFS Spey Heads, with equal confusion and confounded-ness, often leading to unbridled madness. Ever see Pro Golfers bend their putter across their bent knee after missing a 3 footer for the game winning prize? My purpose of this article is to provide a compass that would act as a shunt to bypass the inherent maze much like the deregulation shoe story above. Yup, after all, we don't want the urge to take our rods over a bent knee, huh? Or worst still, defect to the game of golf thinking meaningful respite from any frustration can be found there.

It is also important since this increased acceleration can also incur the wrath of blowing the anchor from a shortened anchor at the same time. I tend to think this min length should be called 'Max length under extreme casting conditions'. But we'll stay with this min. length terminology to avoid digressing and squabbling over a widely held public jargon.

For Skagit head systems, the new minimum (floating out there on the web as of January 2012) for the combined length of head and tip is 1.75 times the rod length, shorter than the 2.5 times that had been floating around for some time. However, this new minimum requires careful timing and control, driving up the demand for diligence afforded only to those who can hone in at this level on a consistent basis. But wading deep with little back room space will make this a useable cast while taking the pressure of precise timing and control (see Figure 1 above).

As for Scandinavian shooting heads, the new minimum is around 2.3 times rod length for full sinking heads. Although there doesn't seem to be a minimum for floating heads, the suggested working length is 2.5 to 2.7 times. 

But if you want venture outside of the above prescriptions and come up with your own (or at least understand the basis for minimum length) the following factors must be considered when going for minimum lengths.

Thematically, calculating the min. length- for whatever wading depth/ rod/ line sink/ fly combination- is driven by the ability to get your target distance without blowing the anchor, performing under a level of diligence that can be sustained for the period you fish. This means casting within the sweet spot of your casting rhythm that neither tires nor wears your out first (footnote 1).

Let's start with distance via proper rod loading. Hey, we all know shorter heads are distance killers. That is because the launch energy in the line system dissipates faster by a straightened out head (now pushing much like a wet spaghetti pushing a meat ball of air resistance) than when turning over itself. Although the line turnover speed are out of our hands (footnote 2), we have control in tuning our min head length so that it will achieve max launch energy via a properly loaded rod. This first tuning often requires us to bump up the class weight for line heads by one or two, or sometime three, class weights when cutting shorter heads than if cutting for max length heads for proper rod loading in both cases. This is especially true since a shorter head often precludes a V loop, leaving us with a passive D loop that needs more mass to be equivalent in resistance.

As for the second tuning for a proper anchor, if you are wading up to your armpits, casting a heavy fly and a fast sink line system, your casting technique can still greatly influence your min length even beyond the aforementioned setup conditions. For there are two casting maneuvers that will easily determine the chances of a blown anchor. The first is the angle of line stick. The second is Continuous Tension Load. 

The first technique, a horizontal line stick often used in Scandinavian casting as an air borne anchor (see Figure 2 below), is much more aggressive than an Inclined line stick (see Figure 3 below). A leader/ line sticking to and being pulled along the water surface is much more aggressive anchor than one that peels off the surface. Thus, a prerequisite anchor would only require a shorter horizontal line stick than an inclined (but now longer) one (footnote 3), further helping reduce the overall line length needed for deep wading. This more aggressive line stick is accomplished by having a flat and near horizontal back cast, a back cast technique made even more important as shortening the head now only affords a reduced length for anchor (footnote 4) which by now has to be aggressive so the anchor is not blown. Incidentally, some of this anchor loss is made up when you are wading deeper.

The second technique, Continuous Tension Load, is much more subtle and nuance. It is when the fly line is so energized (often after a Snake roll) that it feels like one inch of tip movement during the initial firing translates to one inch of the fly dragging along the anchor path (see Figure 4 and 5 below). There is absolutely no slack in the D loop as the D loop is in high tension and the rod tip is already in a pre-loaded state. This means the caster has to back off the power or else it would lead to an inevitable blown anchor. In fact, I often can see (and use it as a gauge for power) my fly dragging through my anchor line as I initiate the forward cast (hard to tell in Figure 5 below). This nuance technique can truly turn a 'meh' cast into a 'Wow' cast with a wind- cutting, hi- line speed; tight loops; line stretching out with authority; leading to solid turning over heavy flies.

But, again as with the first technique, the shorter the head, the more passive your D loop becomes, the less energy in your D loop, the greater the angle of the incline in your line stick, the more allusive this 'Wow cast' becomes without blowing the anchor. This is further compounded by the most common error in getting a horizontal line stick via an erred back cast technique: a level line drop, a low energy back cast that starts with a high stick initiating the back cast that is on a near vertical plane sector (see Figure 6 below).

So, it becomes almost like robbing Peter to pay Paul. Ultimately, the final min length is a subtle fine tuning whereby you avoid egregiously short changing either Anchor or Continuous Tension Load. But the benefits of a shortened line system, allowing a one-swoop movement that gets the fly from hang down to out where the fish might be, may be worth the price of this compromised place where Peter and Paul are at best civil with each other. Practicality co-existing with Luxury on what often feels like a knife edge.

In a later installment, I will be addressing Rio's AFS head tapers, Generation 1 and 2, and how it affects rod loading. This installment will shed insights where to add cheaters to an existing chopped head. This way, you can have both Min and Max head for a properly loaded system simply by adding and removing this cheater.

Footnotes:
1) For casting outside this optimal window drives up the demand for a heightened diligence in her ability to reproduce similar successful conditions, but this fussing robs the caster her being-there-in-the-moment experience.
2) This is largely a product of line taper, loop control (assumed constant here), fly air resistance (assumed constant here) and running line resistance.
3) Anchor Time On Water also has an impact on air borne anchor, especially for fast sinking leaders or tips. For floating leaders that need more stick, introducing more time on water can also introduce slack in the D loop, reducing the Continuous Tension Loading. However, timing is essential for water borne anchor cast, such as the Skagit, where your sink tip and fly must be allowed to sink long enough to get sufficient anchor. The Continuous Tension Load is unaffected by water borne anchor since the loading occurrs after the anchor has performed its prerequisite sinking.
4) See three point geometry for D loop in Part 2.

In part 1 of this series, the weight of a spey line that properly loads a rod was shown to be a weight dictated by power and tempo. The analogy used for this proper weight was a favorite book between the book ends. Moving on from this, we'll now be looking at the max and min length of the line akin to the two book ends holding up the weight proscribed above.

However, let's tackle one book end at a time, with the maximum spey line length for this Part 2 piece. The max length starts with- but does not necessarily fully comprise of- a length the caster can carry in his D loop just before the D loop catches water and sticks behind him. But before we fully get into this discussion, and because this out-of-water max length is highly dependent on how deep or shallow the caster is wading, let's assume the caster is standing in 30" of water so as to not confound this max length any further.

Calculating this max out of water length is simple. It is simply the line length that forms the D loop just before it touches the water. Referring to the radical back cast picture below, this length is defined by 3 points comprising of 1) rod tip height from water (footnote 1) after the D loop fully forms, 2) the apex of the D or V (footnote 2) loop, and 3) the point which the line first contacts the water (known as Point P). Notice how close the portion of the D loop between points 2 and 3 comes to touching the water; this is as close as you want it to get (footnote 3).

If you are casting a floating head, Point P (3)  is where your fly line ends. Simply add a long enough leader to that end and cast away. Mathematically, your max out of water length is measuring the line marked between point (1) and point P (3). In the picture, the leader is anything downstream from point 3 since we only want only the leader as the only anchor for floating heads. Incidentally, the leader length does not count as part of the floating spey line length. The rule of thumb length for leaders are 1 to 1-1/2 times the length of the rod. The rule of thumb for floating spey heads floating around in the cyber world varies from 4 to 5 rod lengths, the higher number corresponding closer to long distance tournament casters.

Generally, the floating max length can somewhat be your new sinking tip spey head length using the same air borne anchor technique, providing three (3) conditions are met. These three conditions are 1) there is enough thickness and mass on the spey line portion upstream of the sink tip to turn over both the sink tip and fly, 2) the sunk portion of the line has to be either close enough or there is  enough driving mass so you can dredge up the sunk portion with only 1 or 2 roll cast before you start your next cast, 3) the combine system tires and wears you out equally as discussed in Part 1.

Now, in switching over from the air borne anchor to using sinking tips with water borne anchor cast, you might say to yourself 'Hey, I got my sinking max length for air borne anchor, let me reuse this and call it the day'. Whoa, not so easy, John Spey Wayne. There are too many changes that cannot reuse the calculation above. The biggest change is you now have a sunk portion that is a lot more aggressive anchor than one that is simply laying briefly on water. And because of this more aggressive anchor, the D loop section between the apex (2) and point P (3) needs to have a higher angle of attack to have a better chance to pull out this more aggressive anchor. This higher angle of attack can only happen when the apex (2) is closer to the caster, thus reducing the max length. And for this reason, the Skagit system that uses water borne anchor has a max rule of thumb of 3-1/2 rod lengths, less than the 4 to 5 times for air borne anchor.

As you can see, if we simply followed a knee jerk reaction of adding a sink tip to our unmodified floating head, we end up with a line system no more useful than having a spaghetti push on a meatball stuck in a viscous sauce.

The sink tip length now counts as part of the spey line. However, just as we did not count the floating head leader, the 4' or so leader connecting the fly to the sink tip is also left out from the calculation. In your experimentation with getting the right sink tip length for water borne anchor, you know you have it right when 1) you are not roll casting endlessly like you are flogging a dead horse before you relocate your anchor, and 2) when you have allowed enough time for both the sink tip and fly to sink, this sunk portion provides just enough resistance to achieve a 'Half out and Go' water borne anchor technique (footnote 4) on a consistent basis. Don't forget the power and tempo in Part 1. Successfully satisfying these three (3) conditions now gives you your new max sinking tip spey head length for water borne anchor.

There are several caveats here. As a caster evolves in his proficiency, the max calculated length can also increase with his increased ability to throw more energized V loops. Not only the D is now a V shape, but the apex of the V loop (2) will be further away from the caster. This increased storage of energy also means an increased head length that is the foundation for the final max spey line length. Another caveat is the more you cant the rod on a side angle, the less max length calculates to be. When you cant the rod, your rod tip distance to the water also drops, decreasing your head length. This is particularly useful when needing to cast under a branch, but you are now required to pull in some line to shorten the max length. And the final caveat for now is the further back Point P is in relation to the caster, the longer this max length becomes. In fact, I often see Point P behind the caster for distance casting, giving more overall line for the loop to unroll, producing prodigious distances. Just think, if the line never touches down on the water, there is no max line length.

Combining rules of thumb with an understanding behind it (3 point explanation) allows the caster the ability to dial in all 5 digits of his equipment matching zipcode. Sometimes having the 5th zip code digit can turn a day of casting chore to one that is effortless and luxurious, especially when the wading depth is not constant (line has to pulled in for deeper wading). Max length is no longer a hard and fast book end that is  dialed in and held fixed by sink and anchor type, but rather one that is further fine tuned dynamically to wading depths, cant angle, and how point P lands on water as among many other on stream factors.

In part 3, we will be talking about how to calculate the minimum length, the other book end.


Footnotes:
(1) This assumes this is the start of the rod tip loading at this point
(2) an aggressive belly version of D loop, as seen in the picture.
(3) I have seen in some professional distance casting videos the D loop segment between apex (2) and point P (3) briefly touches the water. Because these pros have the deft timing of using this form of water load that deeply loads the rod, they keep the line from sticking any further that would otherwise have collapsed the cast.
(4) This water borne technique is executed when a properly sunk sink tip is halfway out of the water just as the rod tip fires forward. The fly should have just already left the water when the rod first straightens out (maximum line velocity).

Picking a proper loading spey line for your spey rod is not much more clearer than when I started spey in 2005. Part of the problem is today's commercial offerings provide one size fits all lengths without giving a clear guide how to fine tune them. This only leaves the typical angler wanting to get his proverbial spey line wet just as discombobulated as when I started. My aim in writing this article is to give that person perhaps some understanding what makes a line properly load one rod but not another; you know, giving the tools how to catch than actually catching the fish for the reader.

Getting the length and weight of a spey line 'right' is much like going to your personal library of books saddled between two book ends, a row of books from which you have a favorite one you enjoy going back to repeatedly. This analogy is a good visual start that demystifies the mystery behind picking a proper loading spey line for a particular type of rod. Just remember 'Two book ends, one favorite book' and you have your navigational compass that would lead you out of a maze.

One caveat here. The weight and the length of a spey line are interdependent on each other. Locking down on a perfect weight first, only to alter it's length later, may require a minor change in weight class. But at least you have 4 digits to the zip code to get the 5th easily.

Let's start with the weight because this is critical in properly loading your rod of choice. Given a fix rod, the suitable choice of line weight- given the same taper and density design- is now left to be determined by the casting tempo and power you are most comfortable performing for long lengths of time. Too much power to properly load will tire you out first, too fast tempo will wear you out next. So, the trick is to repeatedly cast from a window that will neither tire nor wear you out first, but rather feeling tired and worned out at the same time (the equal drawn down of both means you have gone as far as your casting stamina has allowed you). So, the perfect weight is like finding a favorite book you enjoy going back to repeatedly.  It neither reads like quantum physics (requires too much to power through) nor is it too watered down and predictable (requires too little effort making you read fast). The books ends with close to equal drawn down of both power and reading appetite.

What is too fast of casting tempo causing early wear out? This is the tempo that disproportionately wears you out first before it tires you. Simply underline your single handed 5 weight rod with progressively increasing weight class drop. By the time your reach 2 or more class drop for proper loading, you will find you are casting like a marooned ship wreck survivor in frantic need to be noticed. Soon, the survivor has to stop not because his arms are heavy from applying power, but from the wear and tear of waving back and forth too fast.

Once you found your weight, the next is to achieve the proper length (to be continued in part 2).