Guide number question

[George C]

Putting aside issues with friction and weight, do more guides on a fly rod provide a theoretical casting advantage by forcing the line to conform to the blank rather than 'cut corners' as the blank is unloading? If so, why and is it quantifiable in some way?

I have seen this claimed by several fly rod builders, one who supposedly builds for the US team, and another who claims he built a test rod for Scott with 15 guides (!) that outcast "everything else" but gave no details.
I also recall Diawa marketed an "Inline" surf rod at one point where the line ran down the center of the blank.....and supposedly this was a driving factor in Fuji developing their initial "lowrider" LC guide layouts that were popular for some years with the distance surf spinning crowd.

Thanks for any enlightenment you can provide.

George

[Graeme H]

I've got a couple of very cheap rods with very few guides. They are awful to cast. Hauling is terrible and even without a haul, they are sort of "sticky".

I think that's due to the bend the line must make at any given guide to accommodate the bend in the blank, kind of "wrapping" the wire guide with fly line.

The sweet spot seems to be about as many guides as the rod measures in feet. 9' rod takes nine guides, 8' takes eight, and so on. It's not a hard and fast rule but it works for me. (Using that as a guideline, I'd rather put too many on than not enough.)

Happy to hear the views of others on this one.

Cheers,
Graeme

[VGB]

I roughly follow the static checks for guide spacing that Dale Clemens uses before wrapping the guides and like Graeme use one per foot of rod length as a rule of thumb, although some sources recommend 1 per foot + 1. If I have to make adjustments, I shuffle up from the butt end, rather than put an extra guide in

[George C]

Hi VGB,
My question is not about static loading (or spreading load equally between guides) but rather is there a physics/mathematical reason that makes rod B above (ignoring guide weight effects on rod inertia, unloading speed, and on friction) cast further than rod A when throwing a fly line?

For example, and obviously taken to the extreme, does a fly rod built with just a tip and one other guide 1/2 way down "throw slack" into the system as it unloads relative to a rod where the line is forced to follow the blank with many more guides, or does it not matter?

Thanks
G

[Merlin]

Hi George

It does matter dynamically speaking. The part of the rod shaft lying in between two guides is subject to compression due to the tension in the line. If you just take a tip top and a stripping guide, you greatly influence rod deflection because of that compression and it does not cast properly.

On one hand you are tempted to hold the line as parallel to the rod shaft as possible (many guides) and on the other hand you need to minimize the weight of guides on the tip (influence on equivalent masses) to avoid making the rod too slow.

I know that Jim Bartschi (Scott) studied the issue some time ago, and the question was about one extra guide or not mainly, looking for the best location for the stripping guide. There are several means to define guides location, all based on static deflection. I have one summarizing several possibilities on an Excel file, if this is of interest for you, just let me know, it handles multipiece rods.

Merlin

[gordonjudd]

mainly, looking for the best location for the stripping guide.

Merlin,
Can you share what criteria was used to determine the best location for the first stripper guide?
Gordy

[Paul Arden]

I’d be interested to see that file too, Merlin. Or post as a download if possible? Mostly guide placements are such that the spacing and line angles “look right” during static tests. No doubt more distance between guides can result in more line vibration. I haven’t done any tests on this however. I’ve tested between different guide types but not increased numbers. Even testing between different guides takes a lot of experiments and is open to interpretation.

I’ve read that two oversized stripping guides, positioned a short distance apart, are beneficial for shooting but I haven’t tested this.

Cheers, Paul

[Merlin]

Gordy

It is the result of a compromise and there is no ideal formula. It depends on rod length, if you have long or short arms, etc.

Merlin

[Merlin]

Paul

OK, I shall send you a copy. Then I suggest to try using it to see if it is user friendly enough.

One can find an article published by IBRA (Bamboo Journal, issue 20, december 2019) where I explain the origin of the concept I used for the calculation file.

To make a long story short I calculated (cane) rods deflection for several rods knowing their guide spacing chart: tilted 45 degrees from horizontal, with static load representing 20 times the reference mass of the corresponding line. Then I looked after guide spacing giving the same rotation angle for each individual section at guides locations. That showed that most of the time the calculation was in good agreement with actual guides spacing.

The file allows using two methods, one I found in litterature, with a progressive multiplication factor for distance in between guides (supposed to be used for spinning rods), and the most popular one with an additive factor, already in use by amateur fly rod makers, slightly improved to be able to find a chart for 2 sections, 3 sections, and four section rods, and based on my study.

Merlin

[gordonjudd]

It is the result of a compromise and there is no ideal formula

Merlin,
What factors are involved in that compromise?

If the guide is too close does it result in a too big of an angle between the line on the ground (or a stripping basket) and thus inhibit the shooting of line on a delivery cast? If it is too far does it allow too much line to loop in front of the guide and thus also inhibit the shoot?

Did Jim Bartschi at Scott take high speed videos of how the line passed through the first stripper guide with different stripper guide placements to arrive at an optimum (however that might be defined) placement.

I would think that placement would also depend on whether the caster let the line go through a circle formed with his is finger and thumb on his line hand when shooting line. I see good casters doing that when fishing but never see that done in distance casting competitions.

And Tom Kirkman's advice at Rodbuilders is:

Put the stripping guide 32 inches beyond the butt. End of story. 32 inches. Period.

Gordy