Understanding Wide Arbor Fly Reels

The ability to understand a question from all sides meant one was totally unfit for action. Fanatical enthusiasm was the mark of the real man. – Thucydides on the Athenian mood during the Peloponnesian wars (circa 455 – 400 B.C.)

“Large arbor” fly reels were first introduced (I believe) by Swedish manufacturer Loop in the mid-1990’s. Since their introduction, that brilliant innovation has become standard throughout much of the fly fishing world – especially in salt water. The large arbor concept is superior to traditional spool designs for several reasons and it has influenced fly reel design ever since its inception 30 years ago.

However, the very description of this innovative design – “large arbor” – immediately gives rise to a common misconception. Yes, these reels often do possess diametrically larger arbors than traditional reels of comparable caliber. However, if you took a traditional fly reel and simply increased its arbor diameter while leaving all else the same, would that singular modification yield a better design with superior performance, or would it only diminish the reel’s capability by reducing its backing capacity? It might reduce weight a tiny bit because less backing is now stored on the reel, but it would accomplish nothing more. If, however, you widened that reel’s spool instead, you could then simultaneously enlarge the arbor diameter without loss of backing capacity and achieve a greatly improved design that’s functionally superior in many ways. You could even leave the arbor diameter alone and still improve the reel’s performance by simply widening the spool.

Before diving into the mechanics of wide arbors, it’s important to examine two broadly different realms of fly fishing – fresh water and salt water. I believe the wide arbor concept has broad significance in saltwater angling, with limited significance to the fresh water community. If you’re pursuing high-powered game, such as Atlantic salmon or steelhead in big water typically associated with Norway, Russia, British Columbia, the Maritimes, and similar waters, the wide arbor’s enhanced performance becomes meaningful. The majority of freshwater fish, however, rarely engage your backing – trout, bass and many other mainstream species are hooked, played and landed right off the fly line, making backing capacities and drag systems somewhat irrelevant. Saltwater fishing is a much different story . . .

Back to spool design capacity – most traditional (non-wide) reel designs specify backing capacities that include an essentially unusable volume of backing – that which is buried deep within the spool, close to the arbor. After loading the reel, that backing near the arbor rarely ever again sees the light of day. In my few experiences getting “spooled”, I haven’t had time to maneuver closer, or even gain strategic angle on the fish quickly enough to secure control of the situation. For anglers lucky enough to experience getting “spooled”, the experience probably goes something like this: your reel screams ever more wildly, spool and handle spinning ever faster until the tippet snaps due to a combination of factors that amplified your drag – without ever touching the setting knob. It’s an unstable angling experience that spirals into unmanageability very quickly. The wide arbor design introduces stability into these events, allowing anglers some level of control . . . and time . . . to at least have a shot at managing the catch in such extreme circumstances.

In this post, I explain how wide arbor designs enable more than just an increased backing retrieve rate. In the following bullets, I’ll examine four unique benefits provided by this concept, starting with the obvious and advancing to the obscure.

  • Enhanced backing recovery (improved retrieve rate)

This is a very well-known benefit of wide arbor reels and is often cited first when discussing these reels. With the backing now entirely stored near the perimeter of the spool, it’s clear that backing retrieval after long runs becomes much faster and effective, as every turn of the spool regains a much longer length of backing than with a traditional small arbor. No more seemingly-endless winding episodes where backing is regained at a snail’s pace after such long runs. When anglers experience the wide arbor’s luxuriously enhanced retrieve rate for the first time they often wonder why the design took so long to become mainstream.

  • Preservation of drag setting

This enhancement gets too little attention, in my opinion, yet it’s perhaps most important. It’s understandably less obvious to certain sectors of the angling community, particularly fresh water folks (excluding aforementioned salmon and steelhead anglers) because the majority of their fishing usually involves playing fish “on the line” and backing is rarely even seen. When fish are played from the reel, winding in fly line is not an issue, as it’s stored entirely within the diametrically large outer periphery of the spool. If quick fly line recovery is needed, one can rapidly hand-strip in to recover it quickly. When backing encounters do unfold, they’re usually short – about 20 yards or less.

In salt water, however, long runs are often part of the everyday game where traditional narrow-spool designs present a second, less apparent, concern – preservation of drag setting. With 200 or more yards of backing no longer concisely stored within the reel’s large outer perimeter, long, fast runs can quickly reduce on-spool backing diameter – the level of remaining backing. For the very same reason the recovery rate of inbound backing is improved, the reduction of on-spool reserve backing diameter with outbound backing is mitigated during such long runs. Traditional spool designs experience rapid on-spool reserve backing diameter shrinkage, which results in unintended drag setting increase . . . the smaller the effective backing diameter becomes, the greater the effective drag setting becomes – without ever touching the drag knob! It’s insidious. This is a directly proportional relationship: when your reserve backing level is reduced to half its original diameter, your drag setting increases two-fold; when your backing shrinks to a third of its original level, your drag setting increases three-fold, etc. The wide arbor design effectively reduces this phenomenon, keeping the drag setting relatively constant . . . and smooth. Seasoned anglers are well aware of this phenomenon and smartly reduce their drag setting during long runs. Less experienced anglers, on the other hand, are routinely caught off guard and often lose prized fish as a result of this surprise. The rookie response, in fact, is to tighten up, rather than correctly backing off the drag – it’s counter intuitive.

  • Tempered spool & handle spin rate (rpm) . . . and a cooler drag

The same physics that stabilize the reel’s drag setting in “hot” situations provide further benefits – namely reduced spool and handle spin rates and a drag system that remains cooler during long, high-speed runs. Is a spool’s spin rate (angular velocity) really that big of a deal? Not really, but a spinning handle can be hazardous and intimidating (my knuckles swear to it : ). What’s not readily obvious, however, is that wide reel drag systems (either disc or sealed) are subjected to substantially lower frictional heating than with traditional designs. Heat generation can change the effective drag setting by altering the drag system friction, which may increase due to thermal expansion of drag mechanism parts and/or lubricant breakdown. These phenomena introduce uncertainty in the reel’s operating characteristics when playing high-octane game fish under extreme conditions, and may cause permanent drag system damage.

  • Reel stability during extreme angling events

This performance characteristic is a combination of the “drag preservation” and “tempered spin rate” phenomena highlighted above. This may seem redundant, but it’s not – it’s a unique performance characteristic that becomes relevant during long, high-energy runs commonly encountered with big bonefish, tarpon, tuna, and billfish, for example.

Drag preservation and handle spin rates are easily grasped when examining things in a moment in time – a “snapshot” of your reel’s performance after 100 yards of backing has evaporated, for example. But instead, by examining the rate at which your drag setting and spool spin speed are changing in time – rather than momentary performance in time – is revealing. It’s akin to comparing velocity to acceleration (velocity’s rate of change in time). Grasping “dynamic stability” requires a bit of imagination to really comprehend it. Imagine a big bonefish racing off at 30 mph, hell-bent on getting to deep water. You stare at your blurry spool in disbelief as your fish speeds away to another country. You’re fishing a traditional reel with 175 yards of backing. Time stands still . . . the fish is not cooling off . . . your backing level is shrinking at an ever-alarming rate as your fly line vanishes into the horizon . . . suddenly, your line goes slack. You wind in your backing for what seems an eternity as you contemplate what just happened. Leader cut on a sea fan or coral head . . . the tiny fly pulled loose . . . the hook straightened . . . all run through your mind. Eventually, the truth is revealed – your fly is gone, your leader is clean as new, but your tippet has snapped cleanly.

The traditional fly reel described in this example was subjected to a greater and greater spool spin rate, an ever-increasing drag, and intense frictional heating . . . all of which were increasing ever-more quickly as the bonefish endlessly ran at a constant speed. The more backing the bonefish took, the lower the backing level became, the greater the drag became and the faster the spool spun, which amplified all of these adverse effects at faster and faster rates – the very definition of dynamic instability. The wide arbor concept conquers dynamic reel instability brilliantly by quelling these adverse phenomena and stabilizing reel performance.

A Mathematical Look at Wide Arbors

This image depicts the key parameters relevant to arbor design – spool diameter, arbor diameter and spool width – and illuminates the interrelationship of these dimensions in spool design. The Hardy MTX-S 7/8/9 on the left specifies a 20-pound Dacron capacity of 115 yards with an 8-weight floating line. The Tibor Gulfstream on the right boasts a monstrous 30-pound Dacron capacity of 300 yards with a 12-weight floating line. The Hardy is a large arbor, not a wide arbor, with a spool roughly half the width of the Gulfstream. This drives the spool diameter to become nearly that of the Gulfstream, but its capacity is roughly just 1/3 that of the Tibor. And the Gulfstream specs are based on a 12-weight, not an 8-weight line. I love my MTX-S, by the way – it’s very lightweight and a beautiful reel with an excellent sealed drag

Your line and backing are stored on your reel within a volume that mechanical engineers would describe as annular – a cylindrical volume bounded by an outer diameter (the spool’s rim diameter), an inner diameter (the arbor diameter), with some annular depth (the spool’s width). Essentially a donut-like shape with a volume (V) that’s calculated as follows:

V = spool width x 0.7854 x (rim diam squared – arbor diam squared)

Now, assuming your backing – whatever that material and strength may be – possesses uniform thickness over its length, then its length and associated volume are directly proportional such that a given length may also be characterized by an associated volume – regardless the shape of that volume. In other words, by doubling the volume of backing its associated length is also doubled, tripling the volume triples the length, etc. Then, two different annular shapes with equal volumes – one narrow with specific outer and inner diameters, and a second one that’s wider with the same outer diameter, but with a larger inner diameter will hold identical lengths of backing and may be characterized has having equivalent “capacities”.

Examining three different spool designs based on the above discussion reveals the geometric leverage of the wide arbor concept:

1 –    a 1-inch-wide spool with a 4-inch rim diameter and a small 1-inch arbor diameter yields a spool volume of 11.80 cubic inches

2 –    a 2-inch-wide spool also with a 4-inch rim diameter, but a larger 2-inch arbor diameter now yields a volume of 18.80 cubic inches (a 59% increase in capacity)

3 –    a 2-inch-wide spool also with a 4-inch rim diameter but with a spool volume equivalent to case 1 above (11.80 cubic inches) now allows a much larger arbor diameter of 2.91 inches (a 191% increase).

These examples demonstrate that by simply widening the spool allows much larger arbor diameters to become practical features that enable all the fantastic reel performance characteristics described in this post.