Fly line weights and stress curves
Posted 14 June 2006 - 01:05 PM
For DT lines this is close to an accurate estimation of the actual line weight. The estimates do fall a bit on the low side as the first 30' of fly line includes a taper, which means the weight of the non-tapered running line after the initial front taper is calculated to be lighter than it actually is. The difference is much greater when looking at WF lines, as the running line is usually considerably smaller in diameter than the belly, so the farther out the line you go, the less accurate the estimated line weight.
Below is a chart that shows the calculated weights of 6 different fly lines that takes into account the taper and dimensions of the different lines, not the average. Line weights are in grains, with the AFTMA weight measured at 30' (after removing the non-tapered tip).
Cortland 444 lines were used as Cortland is cool enough to post taper data on their website: http://www.cortlandl.../444_specs.html
Notice that 80' of WF6 line weighs the same as 80' of DT4 line, and at 48' a DT4 and WF5 weigh the same!
Of course all of us who have used various lines know the effect of longer casts with WF line, yet for me it is very revealing to see the scope of the difference. Using data like this it'll be interesting to experiment with different lines and rods such as 'overlining' a 6wt with a WF7 or even WF8, and casting the rod at varying ranges.
As far as how this information affects rod design, below are 3 stress curve charts that use the averaged DT line weight, the calculated DT line weight and the calculated WF line weight. The Z-axis on the stress charts is the line cast in feet from 3' to 60' in 3' increments. The reason for using this type of 3D chart is to more easily show the effects of the line weights and where those effects start to reveal themselves.
As a reference point, the running line (body) of a 444 DT 4 line is .043". The diameter of the body (of the WF head) of a 444 WF 4 line is also .043", but the running line after the front taper ends at 32' is .035".
This chart is calculated using the standard averaged DT line weights. Basically taking the weight of the first 30' of line, averaging that out to find the weight per foot, then using that number to calculate the stresses at the various line cast lengths.
This chart uses the actual calculated DT line weights taking into account the front taper (and back taper if applicable). The only real difference is the stresses are slightly higher overall as the actual weight of the various lengths of line cast are slightly more than the averaged weights above.
This chart is created using the calculated weight of WF line, including the front taper, body, back taper and running line. You can see that once the end of the front taper is reached at around 30', the stress curve grows at a slower rate which illustrates the effects of the lighter running line on the stresses.
Posted 14 June 2006 - 02:51 PM
Posted 15 June 2006 - 07:19 AM
Lee Orr - Maker
Posted 27 June 2006 - 05:33 AM
Posted 27 June 2006 - 12:44 PM
To get a good look at some differences, check out this chart from Rio:
The Selective Trout DT looks like a cross between a WF and standard DT line, and the WF version of the Selective trout is as well due to the 2 sizes of running line. Nice ideas for tapers IMO.
The Selective trout is somewhat opposite of the Wulff TT taper.
The Bonefish taper and some of the spey lines are similar to a Wulff TT in shape.
The Long Cast is basically a DT line (~70') with the addition of some extra running line.
Posted 07 July 2006 - 08:48 AM
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