Math is definitely not my strong point but I did a little to try to answer some questions I’ve been getting about the Japanese line rating system for fluorocarbon level lines and what it translates to in diameter. Please note: lb. test is irrelevant. Diameter matters more for turnover than test. And, test per diameter varies from company to company so I narrowed it down to the most relevant and popular diameters for tenkara. Also keep in mind that these are approximations that seem to have consensus. But some companies’ ratings might slightly vary outside these diameters. Anything outside this range is specialty and I don’t think applies to most of us so I didn’t include it. I hope this helps.
Hello – Here is another good source for choosing line and tippet diameter sizes: http://www.letsflyfish.com/fishing_flies_fly_lines.htm
Good chart. Although I would disagree with some of their choices. For example, to me, 4X on a #16 hook is way too heavy. I would use 5X or 6X. Same with 5X on a #18. I would use 6X or smaller. But, to each their own.
I had a little bit different with Japanese size lines 3 & 3.5.
Japan — mm. — inches – Tippet* – Lb. Test**
——————————————————
# 6 = .405mm = .0159″ 25 lb
# 5 = .370mm = .0146″ 20 lb
# 4 = .330mm = .013″ 16 lb
# 3.5 = .310mm = .0122″ 14 lb
# 3 = .285mm = .011″ 0X 12 lb
# 2.5 = .260mm = .010″ 1X 10 lb
# 2 = .235mm = .009″ 2X 8 lb
Hi Lynn, well, like I said, these are approximations that will vary by manufacturer. The intent was just to give people a rough idea of the diameters to looks for if they’re searching for fluorocarbon that isn’t specifically marketed as “tenkara” line.
…gotta agree with you there….4X is pretty stiff and will present as such with small flies….thin and flexible will better assist one with fooling the wary trout…
Hey Bob, yes, that article seems to focus on turnover more than presentation. I would argue that once you get down below a size #14 or #16 fly, turnover is irrelevant but tippet size starts to matter exponentially.
Interesting Jason, I was just writing about lines over at tenkara corner today. I haven’t really fished a line below what might be considered a #3, I recommended too that anglers concentrate on diameter rather than #ratings and lb test. I’ve been testing various lines since I started tenkara fishing and it’s very interesting to experiment.
For Western fly fishing, I usually divide the size of the fly by 3 to determine which tippet to use, i.e., Size 12 = 4X, Size 16 = 5X, Size 18 = 6X, etc. For Tenkara I just use 5X and call it good.
My understanding is that the Japanese only have an industry standard for nylon line. Specifically for 1号 = .165mm in diameter. Actually they measure line by weight. The unit of measure is the denier(grams/9000m) or the decitex(dtex) (grams/10000m) For nylon 1号, dtex = 244. The .165 mm diameter is calculated from this weight per length and specific gravity of their line. Everything else is derived from the standard for 号1. If 10,000m of 1号 line weights more than 244g then the line is > .165 mm in diameter. The formula is
Diameter = {square root of [dtex/(10,000 x 1.14 x Pi)]} x 2. Where 1.14 is the specific gravity of nylon line.
Fluorocarbon, PE line etc., only more or less follow, the standard for nylon line. SG-Fluorocarbon 1.78, dtex= 380. High density FC SG = 1.85 & dtex = 394. I’m sure different line makers have variations on these numbers. The 号 system is almost as vague as the flex index ratio numbers used for rods. But 1号 is the anchor point.
Thumb rules for nylon line; double the 号 number and the dtex doubles, and the diameter increases by x 1.41. example 2号 = .233mm and dtex = 488. 4号 = .328mm rounded to .330 and dtex = 276.
Because of the way the Japanese calculate an average test strength based on cross sectional area of the line given in kg you can’t really convert kg to Lbs test by x 2.2 and compare it directly to lbs test as specified for American lb test line because they use different measuring standards. The American lb test is supposed to be maximum lbs vs Japanese average kg.
The standard for 1号 line goes back in history to how silk line was measured and when the nylon standard was made it applied only to nylon line because FC, PE , vectran, dyneema etc had not yet been invented. And I guess they don’t want the expense of writing new standards that includes the new type line materials, being happy to just reference the nylon line standard.
Opps, sorry a typo. Nylon 4号 dtex = 976. Not 276. And 976 will calculate a line diameter of .330.
I have used Cabela’s No-Vis Fluorocarbon Premium Fishing Line
for leader construction quite successfully for years, and also
for level and tapered FC Tenkara lines more recently. One of the
appealing things about this line is its cost, $12.99 for a 200
Yard spool of the 4, 6 and 8 Lb test ratings, which is
comparable to the the cost of 25 yards of FC tippet material
from many of the fly fishing brand makers.
I prefer the TenkaraBum HiVis Orange Sunline in the #3 line size
(10 Lb. test) to the Cabelas line as it is more supple and
easier to straighten than the Cabelas line is in that weight.
But here are the diameters given for the 4, 6, 8 and 10 Lb. test lines so you can compare them to Jason’s T-line Chart.
4 Lb. test DIA. .006″ – #.5 T-line ? equivalent – ?
6 Lb. test DIA. .008″ – # 1 T-line equivalent – ?
8 Lb. test DIA. .009″ – # 2 T-line equivalent – .009 per JK
10 Lb. test DIA. .011″ – # 3 T-line equivalent – .012 per JK
Which I believe compares pretty favorably with the T-line diameter measurements for thickness. The Cabela’s Premium Fishing line also has enough body to cast well on T-rods. The visibility sucks but where you are going to sub size #3 lines, I would think you would want all the stealth you can get.
Hi Karl,
As always, great information and I think you make a good point about light clear lines and stealth. I wonder if in those situations it would make sense to use a high vis Tenkara line with a length of lighter clear fluorocarbon at the end.
Jason,
I have tried that and it works well. What it amounts to is a cross between a level FC and a tapered FC lines. You get all the visibility and most of the casting muscle you get with a level FC line, but with the more delicate presentations and the stealth of a No-Vis Hand-Tied Tapered FC line close to the fish. Give it a try and see what you think.
Since sub #3 lines are difficult to get at present, the Cabela’s Fluorocarbon No-Vis 100% Fluorocarbon Premium Fishing Line offers an alternative source at a reasonable price for what you get.
Just to be sure there is no confusion as Cabela’s has so many different types of lines that they stock, Here is a link to the line mentioned above: http://www.cabelas.com/product/Cabelas-No-Vis8482-Fluorocarbon-Line-200-Yards/702377.uts?Ntk=AllProducts&searchPath=%2Fcatalog%2Fsearch.cmd%3Fform_state%3DsearchForm%26N%3D0%26fsch%3Dtrue%26Ntk%3DAllProducts%26Ntt%3DCabela%2527s%2BNo-Vis%2BFluorocarbon%2BLine%2B200%26x%3D11%26y%3D8%26WTz_l%3DHeader%253BSearch-All%2BProducts&Ntt=Cabela%27s+No-Vis+Fluorocarbon+Line+200&WTz_l=Header%3BSearch-All+Products
Thanks Karl!