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I thought I would ask here before I send off to line mfg's and get funky answers that side step the question.

Thanks Jay

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103 Posts

I thought I would ask here before I send off to line mfg's and get funky answers that side step the question.

Thanks Jay

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7,112 Posts

Based on the AFTMA Standards 30' of level 5 wt=4.67 grns per foot, 6 wt=5.33 grns per foot, 7 wt=6.17 grns per foot and so forth. All lines 1 wt-15 wt are listed on page 21 of Rio's 2004 catalogue so I think they are probably also on Rio's website. Barring that a Google search using AFTMA line weights should show you all of them.

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150 DT5 or for a 30 foot section...5 grains per foot

170 DT6------------------------------...5.6 grains per foot

195 DT6------------------------------...6.5 grains per foot

This is all dependent on my math being correct.

Vinnie

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AFTM DT #5... 5.8 grain/ft

AFTM DT #6... 6.8 grain/ft

AFTM DT #7... 7.9 grain/ft

These values are calculated, not measured from actual lines.

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Jay

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Absolutely so! However, I´ve lost the excel-sheet with which the forementioned grains/ft were calculated. Had only a print of the results available. Could have been something from 7 to 10 ft though (the front taper that is). Perhaps I have to do the calculation again :biggrin:peter-s-c said:You can't accurately calculate belly grains per foot without knowing the length of the front taper. Short front tapers produce lighter g/f than longer ones.

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Just did some math, which gave me a Formula:

m = M/(L-2/3*T),

where

m is the mass/length of the level part of the line, excluding the Taper, i.e. the mass of the level part divided by the length of the level part.

M is the Mass of the line (e.g. 140 grains for 30 ft of AFTM #5)

L is the Length of the line (e.g. 30 ft)

T is the length of the Taper (was about 10 ft in my calcs)

with e.g. 7 ft taperlength the results would have been:

5.53 grains/ft for #5

6.32 grains/ft for #6

7.30 grains/ft for #7

With your formula Peter (7 ft Taper), I get

5.06 grains/ft for #5

5.78 grains/ft for #6

6.69 grains/ft for #7

and for 10 ft taper:

5.25 grains/ft for #5

6.00 grains/ft for #6

6.94 grains/ft for #7

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This adds a whole new element to nerdy-ism and fly fishing! AWESOME! :Eyecrazy: :Eyecrazy: :Eyecrazy:

You guys got all complicated on the original question:

What I was looking for was if anyone had taken lets say a 5wt or 6wt or 7wt, we'll use a Double taper for instance. Cut the taper off so you have the level running belly of the line (no tapers just belly) and I was wondering what the grain weight per foot of those mentioned BELLY ONLY sections were.

The whole taper thing makes no difference at this stage of the little game I am playing. I just dont have the resources available to take a 5wt or 6wt DT line, cut the tapers off, cut a 12 inch section out of the middle and weigh that 12 inch section. Right on though, this turned into a kinda off the wall, but cool thread.

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I think that the problem is not in the way we formulate the formula, but the bottom line is, that we have differents formulas, which give different results. As we both are trying to answer the same question, one of us must be more right than the other... now we have to just decide, who that would be.

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167 Posts

Dont worry, as we are perhaps two of the most "line-crazy" nerds onlineLuv2flyfish said:Whooooaaaaa.....Holy Crap folks - Ya lost me a long darn time ago.

This adds a whole new element to nerdy-ism and fly fishing! AWESOME! :Eyecrazy: :Eyecrazy: :Eyecrazy:

You guys got all complicated on the original question:

....

I understand your original question (at least I think so), and was trying to give you an answer, without cutting any lines. Now we have a whole new problem ahead, as our calculations are giving difefrent results, being off as much as a 1 grain per foot. :chuckle:

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And people call me crazy!

:hihi:

:hihi:

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167 Posts

My cone is uncut, so it assumes a taper from zero to belly diameter... yours is cut, assuming a certain ratio between the line tip diameter and belly diameter. But I am not worried about this, as obviously different assumptions yield different answers... :razz:

Btw, I had somewhere an excel -sheet, that had the diameters as parameters, let me see...

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I can see real application in finding a formula for a given length of any line regardless of taper. And i have some thoughts.

I am assuming we are using the AFTM ratings for the first 30' here.

Break down the taper into its 3 independant geometric shapes.

So, level tip (cylinder), taper (frustum cone), and belly (cylinder).

We have a grain weight, yes ?.

Ok find volumes of each part, then find the percentage part by volume.

example:

lets say we get (real simple version).

level tip 10% total volume

taper 20% total volume

belly 70% total volume

It stands to reason that the core is a constant throughout the line so is factored in as a whole.

So a 300 grain 30 foot line includes coating and core as a whole.

level tip is 10% @ 30 grains.

taper is 20% @ 60 grains.

belly is 70% @ 210 grains.

we have already the length of belly from our volume calculations so dividing 210 grains by the actual amount in length of belly gives us grains per foot.

The actual grains per foot in the level tip would be arrived at in a similar fashion, whilst the taper would require frustum cone volume calculations per foot of length.

This is a simplified view, and i'm *NOT* an expert. But i do think it would work on any line, and any taper, so as to arrive at an accurate grain weight for a given piece of line before cutting.

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167 Posts

V = Pi*L*(r1*r1 + r1*r2 + r2*r2)/3,

where

Pi = 3.14

L = length of the part in question

r1= radius of front of the part = front diameter/2

r2 = radius of the end of the part = end diameter/2

If the part is level, then r1 = r2, if tapered, r1 < or > r2. Calculate the volumes of each part (level tip, taper, belly, or any part for that matter) as

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73 Posts

A conical frustum is a frustum created by slicing the top off a cone (with the cut made parallel to the base).(frustum cone?), is:

And the "Frustum" being...

The portion of a solid which lies between two parallel planes cutting the solid.

Yea, right :chuckle:In theory that is

Now all we need is a database of rods and optimum grain weights. use the formula and say 'X' amount of 'Y' line should work with 'Z' rod, and all that without getting wet. :hihi:

Its a thought.

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No, Its a Speyline standard, which has been adopted by both line and rod manufacturers. Maybe next year already we shall see those lines... about the rods I really dont knowmyfishcasting said:...

Now all we need is a database of rods and optimum grain weights. use the formula and say 'X' amount of 'Y' line should work with 'Z' rod, and all that without getting wet. :hihi:

Its a thought.

And ofcourse no standard can take into account personal preferences, but it would be easier, if I knew e.g. that a #9.5 Speyline would work well for me and my 11 rated Speyrod. Then choosing another length and make of line might be a little bit easier. We must have faith ... :biggrin:

G

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