Bamboo Tips - Tips Area
Rod Design - Converting Materials


< Home < Tips Area < Rod Design < Converting Materials

Rule

I was wondering if it is possible to measure the tapers of a graphite fly rod and make them work for a bamboo fly rod? I realize I am surely oversimplifying this but I was just wondering if this can work. Granted, as I have mentioned in other emails I am an artist not an engineer, nor a mathematic so forgive me if this is really an ignorant question.  (Phil Crangi)

    In theory, you can put a graphite rod on a deflection board with a known weight and graph the curve it produces.  Then you can calculate the cross section of bamboo necessary to give the same deflection and there you have it! NOT QUITE.  The problem is that the resulting bamboo rod is MUCH heavier than the graphite and it will feel different both statically and during casting.  So you can't get an exact match.  (Al Baldauski)

    Because I didn't know the first thing about tapers when I made my first rod, I did just what you suggest. I measured the tip of the last graphite rod I built and the butt, divided the difference by the length and used that as my taper. Found out later it was a Powell 8.7B taper. It cast a 5 wt line quite nicely. It also made me wonder about whether there are any truly original tapers being designed today.  (Jim Healy)

      How did you find out that your taper matched the Powell taper? Was that an accidental discovery?  (Ron Grantham)

        Yes, I saw a published taper somewhere that looked familiar so I matched it up to the one I had completed and the match was exact. The name on the published taper was Powell 8.7B. At that point I didn't even know who EC Powell was. I have since become a real fan of the Powell formula as a starting point for taper development. BTW I have seldom found a published Powell taper that matches a Powell ABC formula.  Could be due to planing error, measuring error or maybe Powell used his formula only as a starting point rather than an end result. Does anyone know? (Jim Healy)

          I believe that the differences between Powell's tapers and the measured dimensions of his rods were due to quality control.  Powell did not plane strips or mill them, he used a saw he designed himself.  They've got one of his saws in the museum at the RL Winston shop in Twin Bridges (at least they did in 2003).  The strips were sawn in 3 passes and glued up.  This did not generally  produce tolerances as tight as can be achieved with a mill or by hand planing.  The advantages were that it was fast, and it was very compact.  One benefit of his taper system for a production rod shop, especially the B tapers, was that you could set up the saw and crank out a lot of strips, and then produce rods of different lengths and line weights by simply cutting the strips in the appropriate spots.

          I have a Powell B-9, 3-pc and there are places were the flat-to-flat dimensions differ by more than 0.010".  If you plot the taper out, it is clear that the intent was for a linear taper of 0.0015" per inch  on the strips. (Robert Kope)

          The E C Powell 8.7 Taper that you are asking about is the B part of the ABC system. It's a straight taper with a station increase of .0145" per 5 inch station or 2X8.7 = 17.4 or .0174" per 6 inch station. Powell specified his tapers as 1/2 the 6 inch  station value  or for this case 8.7 thousands.

          I think you must also specify the TIP value to accurately determine the real taper. If you use a tip of .072 you will have a good 5 wt, using .076 will give you a good 6 wt. The slope limits the line weight range. If you wanted a 4 wt I think you should change the slope to about .01383 per 5 inch station or specified by Powell as a B 8.3. It gets a little confusing switching between the 6" Powell and the 5" stations we use today, a tip of .068 to .070 will work for the 4 wt.

          Hope this is understandable, I sometimes get confused switching back and forth.  (Bob Norwood)

            Since Powell tapers are under discussion, do you have a feeling for what the limits on amount that can be added or subtracted per station for the A and C tapers and still give a rod of reasonable action?  (Mike McGuire)

              The Powell ABC method, to my knowledge, has not been used very much, not even by Powell himself. I have found one or two B type (straight tapers), but not much of anything else, nothing attributed directly to E C Powell.

              Mr. Hartzell wrote a short paper where he discussed the ABC type 9 +-1/5 tapers in a paper Titled "The Taper System of E C Powell". He also selects .062 as his tip value which for a 5 wt line, will give a soft tip and a strong butt for the "B" and a soft tip and very strong butt for the "C" and a soft tip and very soft butt for the "C". Actually the C might make a better 4 wt Parabolic. Ed's paper can be found in the Best of The Planing Form Vol 2 and additional info in the Golden Witch "Rod Design - Powell Tapers."

              Neither of these papers stress the need for accurately selecting the Tip Value, only certain ones will work for each line size.

              I have built a 8'6" A type given as A8.1 +1/8 with a .072 tip, (these are values for the 6 inch station taper Powell uses). The rod is OK as a 5 wt. I would describe it as having a soft tip and slowly increasing into the butt,  but it's not a real strong rod, just somewhat average.

              I have made a Taper Calculation worksheet for these tapers, which I can send you if you are interested, but my suggesting values for a rod taper is not as straight forward as a regular taper is.  (Bob Norwood)

                Thanks for your reply. I had read the Hartzell article in BOTPF2 and based on it, built A8.7+1/5 and C8.7-1/5 rods with 0.075" tips, 8' long, 3 pieces. To handle the ferrule problem, I took the tapers into RodDNA as a one piece rods, and had it do the conversion. The process adjusts the taper for the ferrules by forcing it to match the 1 piece stress curves.  The A to my taste is a real cannon, and does well throwing 200 gr shooting heads. The C I haven't used much, finding it somewhat mystifying. I did some analysis of the A and C tapers and was able to prove to myself that they are actually sections of a parabolic curve (parabolic in the geometrical sense). Looking at them with RodDNA it's interesting to note that all the ABC tapers have very smooth stress curves, none of kinks one sees in other tapers. At this point in my rodmaking, I pretty much have the rods with which I want to fish. So I am interested in exploring the limits on the Powell design approach. I am willing to "go too far" to see what those limits are, but info from anyone who has been to some of these places would be of interest. I couldn't find anything on the Golden Witch web site on Powell tapers, so if you have it and could send it to me and also your worksheet, it would be of great interest.  (Mike McGuire)

Rule

Site Design by: Talsma Web Creations

Tips Home - What's New - Tips - Articles - Tutorials - Contraptions - Contributors - Search Site - Contact Us - Taper Archives
Christmas Missives - Chat Room - Photo Galleries - Line Conversions - The Journey - Extreme Rodmaking - Rodmaker's Pictures - Donate - Store