I thought I’d spend a little time discussing spool tension and magnetic braking. The relationship between the two has stumped many new bait cast reel owners over the years, and making adjustments on-the-water can even cause a veteran caster to wonder at times. In addition, when you consider spool tension components can wear and need servicing just like others in the reel, someday you might find “the mag winch” just isn’t responding the way it once did at preventing backlash.

Let me start-off by saying that it really doesn’t matter what type of brake a casting reel has; spool tension and braking need to work together in order to prevent backlash, while also providing optimum casting or pitching performance.  If spool tension is not balanced properly with magnetic, centrifugal, friction or even electronic braking; it can result in a noticeable reduction in distance and accuracy, backlash, and may even preclude achieving repeatable casts.

Backlash

The mathematics and physics involved in making a cast is extremely complicated.  It starts with the initial transfer of energy from the angler’s arm to load the rod; continues from the loaded rod to launching the lure; and ends with the flight of a lure that ultimately enters the water.  The dynamic processes involved include those of a cantilevered bar,  tension catapult, and ballistic trajectory of a projectile, respectively.

If one were to model a typical cast, some of the variables would include the modulus (stiffness), length and moment of inertia of the rod; mass and aerodynamics of the lure; force applied by the angler on the rod; exact point when the spool is released; and wind.  The neat thing is that, in the real world of a magnetic braked reel, all of these variables lend insight into what actually can lead to a backlash. Oh yah, did I mention that it would be great if the reel itself should not be a factor in any of the processes? Ideally it would provide only the exact amount of braking torque on the spool to prevent backlash! Needless to say, it’s good that baitcast reels have adjustable spool tension and braking controls, because there are a lot of variables involved!

So, what is a backlash anyway? A backlash is a tangled mess of line that has wrapped itself around the circumference of the spool during a cast.  Some anglers refer to it as an ‘overrun’ or ‘overflow’, and others simply refer to it as ‘a bird’s nest’ (what it looks like the first time you see it?).   Backlashes can range from a minor two wrap tangle, to a major heron’s nest that can never be untangled, and reel manufacturers have spent a lot of effort in developing backlash systems to preclude them from occurring.

What causes backlash? A backlash occurs when the speed of the spool becomes greater than the rate at which line is being pulled from it by the lure. During a cast the spool instantaneously begins to rotate from a dead stop when it and the lure get released, it initially accelerates and then decelerates as momentum is lost from the lure during flight, and eventually stops rotating as the lure enters the water — and a backlash can occur in any one of these phases. Some factors that can ultimately influence spool or lure speed, and lead to backlash include:

• Poor casting technique: Snapping, jerking  or whipping the rod tip does not provide for a smooth and controlled spool start up.  Releasing the spool late can cause the lure to crash into the water with significant velocity a short distance from the angler. Having the lure inadvertently hit an object before reaching its target can result in an instantaneous loss of lure momentum, while the spool continues to rotate at the same speed.  [The previous picture is the result of one rod contacting another at the beginning of a cast.  Yes, there is a spool in there!]
• A rod that is too stiff for the weight of the lure: The rod does not load properly, so the angler knowingly/unknowingly tries to compensate for this by applying more force on the rod.  Overrun occurs because spool start up is not as smooth or controlled as it otherwise  should have been.  (Uncontrolled spool start-up of this type will challenge just about any braking system on a reel; unless spool tension is set extremely high.)
• Poor line characteristics: Line that is too heavy or stiff, or does not easily bend as it moves from the spool to the line guide.  This can cause the line to loosen or “fluff” on the spool as it rotates, and not flow smoothly through the guide.  (Smaller diameter spools and lower profile reels tend to be most affected by line characteristics, especially with lighter weight lures.)
• Skill of the angler: Not using a “trained thumb” to stop the spool as the lure enters the water.  Not allowing the rod to adequately load before releasing the lure will result in some spool rotation, but it usually won’t propel the lure sufficiently to prevent immediate backlash. If spool tension is too loose for a heavy lure, or if the lure is too light and excessive effort is put into the cast, it may result in a backlash. Having the magnetic brake set too low, so insufficient counter torque is applied on the spool during the cast. Having spool tension set so light, that magnetic braking is not able to produce enough counter torque, even at the maximum brake setting.
• Lure aerodynamic properties and effects of wind on the lure: Lures that have significant drag or lures cast into a headwind will decelerate quickly, and the spool may not depending on the brake setting and how responsive braking is.  Lures that are extremely light retain little momentum; and an overrun can occur if the spool does not loose momentum at the same rate.
• Problems with the magnetic braking or spool tension components.

Ballistic Trajectory of a Typical Lure
(With and Without Air Drag Factored In)

The trajectory of the lure is affected by air drag, gravity, and wind; especially in the later part of a cast when the lure decelerates. Putting a small amount of tension on the spool will usually keep it from spinning at too high a speed as the lure starts to slow, so that magnetic braking can prevent backlash.

The most likely time a backlash occurs is when an angler tries to “eek” out a little extra distance from his cast.  [I'm sure we've all had this happen to us at least once or twice while out on the water?] Without knowing it, you can apply enough force on the rod (and lure), to exceed the braking capabilities setup on the reel. So, a backlash occurs unless you readjust the reel ahead of time or feather the spool with a thumb.

Setting Spool Tension

Putting a small amount of tension on the spool will go a long way at preventing backlash. However, it’s easy to go overboard; cranking it down to the point that spool speed and casting distance are significantly reduced and little braking actually occurs.  On the other hand, you can have tension set so loose that braking never really has a chance to slow the spool (or because the acceleration of the spool far exceeds the capabilities of the braking system) — and backlash was inevitable.  So, it is best to strive for just the right balance between sufficient spool tension and braking to achieve optimum casting performance.

There are a few different ways to initially set spool tension on a magnetically braked reel, and I’ll eventually describe what I do.   However, far be it from me to try to persuade someone who has had good success setting spool tension one way, to change anything or switch to another. In addition, some manufacturers may even provide recommendations in the instructions that come with their reels, based on the configuration they use for spool tension, braking, etc.

I initially set the spool tension on my mag casters whenever I switch lure weight. While holding the rod and reel parallel to the ground at about waist height, I release the spool and let the lure slowly fall to the ground.  If the spool is still turning when the lure contacts the ground then the tension is too loose, so I add a little tension and repeat again.  If the lure doesn’t move or it stops before reaching the ground, then the spool tension is too tight, so I loosen the tension a bit and try again.  When I get tension adjusted to the point that the spool stops turning as the lure hits the ground, then I’ll make a few casts/pitches and dial in the magnetic braking, or maybe fine tune spool tension and braking a bit further.

Let’s face it; some magnetic braking systems are not as resilient as others, so maximum counter-torque and responsiveness can vary from one brand or model to the next.  Because of that, spool tension will usually need to be adjusted to keep magnetic braking within a usable range.  Spool tension and magnetic braking may also need to be rebalanced if you use a trained thumb to feather the spool during the cast.  (The more you use a reel and “educate your thumb”, the fewer adjustments you’ll need to make, and the better the reel will perform.) Lastly, characteristics of the rod, your casting style, effort you put into your casts, the lure, and other factors previously described can all influence final reel settings.  What you are ideally striving for is:

• Sufficient spool tension to mitigate over-run for normal conditions,
• Least amount of spool tension required to keep magnetic braking within an adjustable range, and
• Modify spool tension and brake settings to accommodate your ‘trained thumb’ and casting style.

Maintaining Spool Tension Components

Spool tension schemes usually employ friction acting on both ends of the spool shaft, which can be varied with a threaded cap.  Most involve the use of shims, washers, or disks to compress against the spool shaft; and Daiwas even employ a pinion that applies force on the spool tip. I won’t go into any detail or the mechanics of any of these designs, because they are fairly straightforward. So, just look at the reel schematic and you’ll likely be able to recognize the method(s) employed.

The important thing to remember is that spool tension components will require maintenance, just like other parts in the reel.  For example, shims and washers can scratch or dimple; disks can crack or wear; and the spool shaft tips that they contact can become scored, blemished or affected by corrosion.  So, all will likely require some amount of periodic cleaning, lubrication and replacement to ensure consist performance.  Excess noise, vibration, loss of tension adjustment range, and erratic operation may result when the components need service.

The threads for a tension cap and the slot that the top of the pinion rides in, can be another source of problems for a Daiwa bait caster.  Burrs can cause the pinion to hang up or the spool tension adjustment knob to not turn as far as it should, resulting in erratic or inadequate spool tension adjustment.  [I marked a small blue 'X' in the previous picture of a TD-Z +R handle plate, where a small burr left from manufacturing was interfering with pinion travel.  The top part of the pinion would periodically hang-up when I thought I was changing spool tension. I ended up knocking the burr off with a sharp knife.  (You might have to right click on the picture and click on 'view' to see the area that I dressed-up in full size; you can page back to the blog after viewing it.)]

Baitcast reel modders and tuners have long known that blemishes and corrosion on shims and spool tips can result in erratic or non-linear performance of the tension knob.  So they polish shims and other tension components as part of their super-tuning ritual.

In one of the next blogs I’ll get into disassembling a Daiwa palm plate.  Some of the spool tension components located beneath the spool bearing, require special care and maintenance!

-DModder

Tags: bait casters, Daiwa, magnetic braking

This entry was posted on Wednesday, May 13th, 2009 at 3:58 pm and is filed under Maintenance, Reels. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.