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I’ve come up with a question I can't answer for myself. And I hope some of you can bring a little light in the dark.

Is there a rule of thumb for the tip diameter regarding to the line weight ?

Lets say:

0.059 inch at the 0 Station for a 2 wt.
0.064 inch at the 0 Station for a 3 wt.
0.066 inch at the 0 Station for a 4 wt.
0.070 inch at the 0 Station for a 5 wt.
0.076 inch at the 0 Station for a 6 wt.
0.081 inch at the 0 Station for a 7 wt.
0.087 inch at the 0 Station for a 8 wt.
0.094 inch at the 0 Station for a 9 wt.
0.096 inch at the 0 Station for a 10 wt. ...... and so on?

If I compare my taper archive this numbers comes out when i take the average for certain line weights.

But when I look at the maximum and minimum values there are also great differences from one rod to the other.

Any suggestions or theories??  (Markus Rohrbach)

    I think that if you are building straight tapered rods, you will find that you can have such rules of thumb. There was a wonderful post back in the archives in which AJ Thramer discussed how classic rodmakers would determine a rod's line weight by ferrule and tip size. Also in the Wise Fisherman's Almanac there are suggestions for tip size and rate of change for every 6". So, yes they work for straight tapered rods. BUT, most parabolic actioned rods will be thicker in the tip and throw off the theory. Not all taper schools will be so easily fit into these sort of "rules of thumb." Interesting to hear what others have to say.  (Bob Maulucci)

    There is no correlation between these two parameters, but for various reasons, none of them very good ones, you might find some correlation between line weight and the diameter about 10'' back from the tip!  (Robin Haywood)

      Darryl Hayashida had a theory that the last 10 inches of the rod were critical in determining whether the rod will cast a tight loop or not.  If you search the archives for "Tight Loop Tip" in December 1998 you will see the posts.  Some people disagreed, of course.  (Frank Stetzer, Hexrod, Taper Archive, Rodmakers Archive)

        I think that the first 5 t0 6 feet holding the rod is critical to forming a tight loop.  (Ted Knott)

          No doubt about that, but everything else being equal you can change a tip configuration to cast a tighter or wider loop.  (Darryl Hayashida)

        I still make my dry fly rods with that tip configuration, seems to me to add to the accuracy of a cast, but if I am interpreting the question right, the diameter at the zero station is of very little consequence. That particular part of the rod is going to be inside the tube of the tip top guide anyway. The only other consideration I would pay attention to is that for heavier lines that means the rod will be used to go after bigger fish, so the tip should be thicker to handle the stress of fighting a heavier fish.  (Darryl Hayashida)

          Thanks so far for your information.

          One reason for the question is, is there another starting point to recalculate the taper than add or subtract 0.005" at each station to change for one line size.  Or in other words, if you design a new taper (lets say a 4 wt.), where do you start?  I wrote about the rise or slope of a rod taper that can characterize a rod (fast, slow one or somewhere between).  But at this point I have to decide where I want to start draw the line and this point is the 0 Station of the taper.  (Markus Rohrbach)

            It's a design concept and can be adapted to any rod design. The easiest way to understand it is through stress curves. Look at the stress curve of the Cattanach 7' 4 weight at the RODMAKERS site.  Go to Tapers, Wayne Cattanach, catt7042. See the way the stress curve makes a sharp peak at the 10 in. station. If you follow that concept, only you make the sharp peak top out at the 5 in. station that tip will throw a tighter loop. On the other end of the spectrum look at the stress curve of the Orvis Battenkill. You will see that the tip stress curve is flattened out with no sharp peak. This is a lot slower rod, but just looking at the first 10 or 15 inches of the tip, if you had put this tip design on the catt7042 and casting the same, you will throw a lot wider loop.

            This isn't saying that the Battenkill will never throw a tight loop. A person practicing enough with the Battenkill with the intention of casting a tight loop will be able to compensate and cast a tight loop. What I am saying is with everything else being equal - including casting stroke - a tip design like the catt7042 will cast a tighter loop than a tip design like the Orvis Battenkill.  (Darryl Hayashida)

              I think the two stress curves opened my eyes.

              If the tip is heavy over the first 5 -10 inches the bend of the rod is only moderate at this position and the rod will throw a more open loop than with a lighter tip that will bend more. Is this correct?  (Markus Rohrbach)

                The Common Cents line-weight-measuring scheme (rejected by cane rodmakers for some reason - don't we want the truth?) makes it very clear that the last few tip station dimensions dictate rod performance more than intuition would suspect.  (Bill Fink)

                  That’s clear, but how would you describe the characteristic and performance of two  rods without casting?  (Markus Rohrbach)

    I too had looked at this and came up with values very close to yours as follows;

    4 wt    0.0685
    5 wt    0.072

    The rest of the line sizes had too few rods to get a valid number. However if you take the 5 wt diameter at 1 inch, which is where I start so that I can plot and calculate values for this point, and use a constant value increase per station of 0.0135" and plug this into Hexrod, you come up with a very usable one piece Straight Line Taper using a 5 wt line weight of 420 grains and a length of line of 50 feet. This stress curve I use as a standard for comparing all other 5 wt Rods. Further I use this stress curve to establish the tip values for the other line sizes, as follows;

    Stress at each station held constant.

    3 wt    64.5
    4 wt    68.5
    5 wt    72 ( reference )
    6 wt    75
    7 wt    79
    8 wt    82
    9 wt    86.5

    If you use the 5 wt taper in Hexrod and then change the line size you will come up with these values and the SLT for a one piece rod for each line size. I use a one piece rod so that the ferrule does not add to the stress curve and distort it. If you tell me the rods you are comparing I will send you the graph for you to look at, all you need is MS Excel to view it.  (Bob Norwood)


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