Perhaps this has been discussed before.
What generalizations can we make about the quantity and spacing of guides on a fly rod based on:
1. length
2. action

I've noticed many antique bamboo fly rods have fewer guides than modern glass/carbon.
Maybe this is because a slow action rod bends evenly along its' length to a greater degree than a fast action rod and therefore the radius of the bend is more constant.

Being a science guy/guitarist I want to come up with a number slightly less than one that when multiplied by the longest guide space (grip end) equals the next guide space. Use this number over and over again multiplying by the previous guide space until you get to the tip of the rod. - this is like fret spacing on a guitar. Coming up with that number is dependent on the desired number of guides, the length of the rod and where you want the first guide closest to the grip which is a variable dependent on how much room you need to strip line easily - sorta complex. This assumes that your rod will bend with a shrinking radius due to constant blank taper. I believe fast action rods have less of a constant taper than slow therefore this upsets the logarithmic method I suggest.

I've read that temporarily mounting guides to the rod with small rubber bands and threading it up with a line, anchor the end of the line, and with the rod at a 90 degree angle, pull back flexing the rod. Measure the gaps between the line and the blank at the apogee for every guide space. They should all be roughly the same. This is quite iterative requiring much time. I would think somebody has published guide spacing/quantity based on rod length and action as a starting point.
Thoughts?

First guide at 32 inches from the butt. Why measure from the butt instead of the grip, I don't know, but talk about putting it anywhere else and you'll get lots of help.

Many blank makers publish guide spacing charts which should work fine, especially as a starting point to be tweaked by the stress test you mention. It's really not that critical, and doesn't need a fancy formula, in my opinion. If you don't find a chart, just progressively space them closer towards the tip, total number about 9 + tiptop for a 9 foot rod, maybe one more. Then tweak it based on the stress test.

You will most likely get a lot of good responses on this one-we have a good number of expert fly builders.

This is a good article from the Library: [www.rodbuilding.org]

Jim,
Each fly blank unfamiliar to me goes through the static flex test to determine both the number of guides and their location.
It goes without saying that blanks flex differently.
So, I don't pay too much attention to distances - except I do place the stripper at 32-33" and the guide below the tip-top at 4.25".
I then place 12 neoprene "O" rings of various sizes onto the blank and threada single line (fly line backing) through the "O" rings and slide them back and forth to get as smooth a curve as possible.
I generally don't need more than 10 guides - so, the excess "O" rings just get "sistered" to the one closest.
I then mark with a greese pencil at each "O" ring.
Using the "O" rings dispenses with attaching and unattaching guides - also the "O" rings don't scratch the finish.
Herb

Good advice Michael and Herb.
I do have the stripper at 32" on version 1. I Also had 9 guides total so I think I'm comfortably within your recommendations.
I like the idea of the O-rings for both experimenting with spacing and the follow up of winding them on permanently. I used to use small pieces of tape which was a PITA.

Jim,
You have received quality information from respected veterans such as Michael and Herb; I’m taking note as well. There is no better substitute for 2-line static load testing for guide placement, no matter what type of rod. I static load test 150lb tuna blanks with 30lb + of weight inducing a deep bend in the blank as well as for UL trout builds. Please do not read that as if I put 30lb of weight on an UL. Guide-spacing charts and formulas can only afford a starting point!!! The ultimate position of the guides of any blank, light or heavy, short or long, fast or slow, will be very obviously shown by the 2-line static load test. Granted, this has more to do with the runners than the reduction guides, but including the reduction guides in the overall static load test is certainly beneficial as well.

Mark Talmo
FISHING IS NOT AN ESCAPE FROM LIFE BUT RATHER A DEEPER IMMERSION INTO IT!!! BUILDING YOUR OWN SIMPLY ENHANCES THE EXPERIENCE.

So i went to a guide spacing chart on the flexcoat website
[flexcoat.com]
This is the first thing that came up when I googled "fly rod guide spacing chart". I thought this would be a good start.
I'm quite sure the 4th entry down for an 8+1/2 foot rod is erroneous.
The spacing between the guides does not decrease contiguously. The 7th snake guide location is way off and is easily detected with the eye.
Here's the progression of the dimensions from tip to guide starting at the stripper in inches listed in the chart.

70.5 stripper
60.25
51.75
41.5
33.125

Lets convert this to distance between guides by subtracting adjacent numbers form each other
70.5 - 60.25 = 10.25
60.25 - 51.75 = 8.5
51.75 - 41.5 = 10.25
41.5 - 33.125 = 8.375
What!
Look at that second entry, ie 8.5 verses the rest.
What's funny is I must have used this same chart when I originally built the rod a few years ago as my original blank guide spacing reflects this error.
I was thinking that maybe that's compensation for the fact that the ferrule adds stiffness in that area.....nah...the other rod length entries are contiguous.
Let this serve as a polite warning if you are going to use that chart and you are building and 8+1/2 foot rod.

Herb,
Where did you get such small o-rings?

Jim,
Save yourself all the time, effort and aggravation of measuring and recording / relaying your measurements. Simply placing the guides where they “look good” in a nice progressive spacing will often get you 95% of the way there that the 2-line static load testing will make obvious.

Mark Talmo
FISHING IS NOT AN ESCAPE FROM LIFE BUT RATHER A DEEPER IMMERSION INTO IT!!! BUILDING YOUR OWN SIMPLY ENHANCES THE EXPERIENCE.

Jim Pitman Wrote:
-------------------------------------------------------
> Herb,
> Where did you get such small o-rings?


Jim,
From my local hardware store.
But The Home Depot has them - [www.homedepot.com]
Also @#$%&.
Herb

Great idea Herb, thanks.

Jim, regarding the unevenness in some published charts I encountered the same thing with interesting results today. Like you were first complaining about I set about electrical taping the guides onto my new fly blank. Tedious. I've been writing progressive/logirithmic spacing sets all week and my gut told me I was going to be off. They have worked REALLY well in the past when I was building fast action surf spinning rods but as I got flexing the fly blank I could tell there were flat spots and soft spots. It's a batson RX7/ old rev blank but the St Croix chart looked better to me. I laid out, taped up guides, and taped a reel and seat onto the butt and took it outside. I was very close. Super close. It was so close to being dead on despite being extremely goofy spacing. I'm also a guitarist, I've built a couple too, and I've built 5 surf rods with a formulaic layout so this might drive me off a cliff. But it was so close. spacing was basically 5, 5.5, 7, 7.75, 8, 8.5, 9.25, 10, 11. The 7 and 7.75 could shrink a hair, and the first 2 could maybe stretch a little bit, but we're talking individual millimeters difference in arc. Literally not more than 3mm in the only really different spot. Now can I live with the oddball progression? I don't know. It sure felt nice casting about the yard in the ripping wind.

2 things surprised me the most: how heavy electrical tape is compared to thread and epoxy, and the flat spot in the tip. I wonder if that's mechanical in nature or if they do it so we can snap a couple inches off the rod and still sort of have the same rod afterward?

Anyway, thought I'd share since we're right at the same point.

It was thought of maybe 20 years or more ago,. Look up "Equal Angle" method or much longer ago, "Story Pole".

Elastic thread, available at sewing supply stores, can be wrapped rather tightly around the guide feet/rod blank and secured with a square knot. It will hold the guide in place while still allowing minor adjustments in guide placement. You can even test-cast with guides secured with elastic thread and still make minor adjustments in guide placement. When you are satisfied with guide location just touch the elastic thread with a razor and the thread will jump off the blank, leaving no sticky residue.