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Suggested method for measuring lines

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Viking Lars
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Suggested method for measuring lines

#1

Post by Viking Lars » Fri Sep 20, 2019 8:07 am

Hi All!

In order to get the fly line database off the ground, we need to settle on a standardised way of measuring the lines, and I have had a bit of a think. Let me know what you think (especially you physics-geeks).

Length:
I suspect any length measuring device is precise enough? I have a few different tape measures and when checking them against each other on 2, 5 and 10 meters, they are very similar (maybe half a millimeter to a millimeter off). I realise that temperature is important, but if we agree on measuring indoors every time, at least we can eliminate variation.

Measuring head- and taper lengths is difficult as some are very long, and for instance on a MED, telling the end of the back taper from the beginning of the running line is impossible without precision instruments. Here I suggest that a standard caliper is sufficient, as long as one is aware than compression of the plastic is a issue and only use light pressure. Measure down a taper until you get say 5 uniform readings, and there's a good chance you're on the runningline. Measure back and find where the taper begins. Search for a level tip in the same way.

We can hardly expect people to cut up flylines for this project, so a way of weighing heads is:
Measure out the head length given by the manufacturer. Checking it using the above method would be optimal. As you can put a light downward pressure on the scales through the stiffness of the line, I simply hung in a clothing pin with the mark of the head length on the scale. This also prevents relieving weight by lifting a portion of the line off the scale.

Weight:
I think it's unnecessary for us to use the same scales across the participants, but some form of calibration or check is imperative. I suggest we check out scales (that read at least one decimal) with mint-new coins. I know that for Danish coins and Euros can find official standard weights. A 1-euro coins for instance weighs 7,5 grams. Coins are generally minted to a *very* high standard as weight is one way of exposing counterfeits. Weigh say 5 coins of a known, standard weight and use that to check scales. I've done so with a scale that's unfortunately not mine, but it worked well. 2 one euro coins came in at exactly 15,0 grams. I controlled the reading by zeroing the scale with a small plastic container in which I put 15 cm3 of (fresh)water - luke warm. I use a medical syringe as this was the most accurate weight of getting a precise volume of water. The water also came in at 15,0 grams. For weighing flylines, I think this is precise enough and enough of a calibration.

What do you think? Graeme, James et el., please kill me if I'm way off here - I'm not a physicist, mathematician - just an archaeologist :-).

Lars

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Paul Arden
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Re: Suggested method for measuring lines

#2

Post by Paul Arden » Fri Sep 20, 2019 9:03 am

I think accurate measurements of the beginning and end of the taper is going to be really very challenging. I hadn’t considered this until you mentioned it some time ago. With regards the front it’s very important for the subsequent AFFTA measurement. What are everyone’s thoughts here?

Great tip with the clothes pegs. Should the lines be stretched first? Since this will make a difference too. Cold and warm measurements I hadn’t considered. We need to do some testing. Maybe we can measure the air temp and put in the notes to get started.

Not being able to measure every field in the database shouldn’t mean that the user doesn’t submit fields that he can measure. For example without callipers the AFFTA number can still be measured. I shall order some callipers immediately since mine are in Hungary!

While there may be some variation in scale calibration I don’t think that the way we measure the lines - suspended above the scales - is accurate enough for this to be a problem.

Maybe in order for us to work out our variations in measuring we can send several lines around that everyone can measure independently and blind. Then from the results of that we will know how accurate we are. Ie I can take say 5 lines from here, measure them up, post them to Graeme. Graeme measures them up and sends me the results and posts to Lars. After ten or so measurements we will have margins of error.

Cheers, Paul
It's an exploration; bring a flyrod.

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Graeme H
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Re: Suggested method for measuring lines

#3

Post by Graeme H » Fri Sep 20, 2019 9:22 am

Viking Lars wrote:
Fri Sep 20, 2019 8:07 am
What do you think? Graeme, James et el., please kill me if I'm way off here - I'm not a physicist, mathematician - just an archaeologist :-).

Lars
Sounds fair to me.

Cheers,
Graeme
FFi CCI

crunch
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Re: Suggested method for measuring lines

#4

Post by crunch » Fri Sep 20, 2019 4:43 pm

Weighing is better than taking diameters because we cast weight in the first place and diameters usually change and line can be oval. Yes diameter has some effect to wind resistance but it effects weight because line densities are not constant.

When length is measured first and then line is coiled and put to a cardboard cup on a scale. Then the line section which is not weighted is kept in hand horizontal so that length mark/length marks come 5cm out of cup and hand holds line 10cm out of cup rim the line section weight comes very accurate. When line is stiff there is possibility to either increase or decrease scale reading but when this is understood it can be made insignificant following reading while lifting and lowering.

If someone who has very accurate scale can buy and weight about 20g washers and send them to us we can cheak our scales and calculate the difference using this factor.

Esa

crunch
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Re: Suggested method for measuring lines

#5

Post by crunch » Fri Sep 20, 2019 4:51 pm

I have marked 1000mm and 1500mm lengths from the table corner and holding line between left hand index finger and thumb I put index finger to the table edge and thumb nail is aligned to length mark while pulling line thru right hand fingers the length is very fast to measure.

Esa

Viking Lars
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Re: Suggested method for measuring lines

#6

Post by Viking Lars » Fri Sep 20, 2019 8:41 pm

Esa - my point in using callipers is not to take diameter measurements as such, but to determine where tapers end and begin. Both to get correct head-weight readings, but also to check that taper-lengths are as stated by manufacturer.

Lars

carlz
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Re: Suggested method for measuring lines

#7

Post by carlz » Sat Sep 21, 2019 5:05 pm

Viking Lars wrote:
Fri Sep 20, 2019 8:07 am
As you can put a light downward pressure on the scales through the stiffness of the line, I simply hung in a clothing pin with the mark of the head length on the scale. This also prevents relieving weight by lifting a portion of the line off the scale.
I weigh all my fly lines (first 30 ft, but this thread has got me thinking about measuring the full head) and in practice, the biggest variation is from measurement and figuring out how to not let the tail of the line effect the measurement. It usually gives me a + or - 2 grains on a 6wt line.

The other question is whether to weigh the first 30 ft, or the first 30ft from where the taper starts. With a welded loop, that isn't a problem, but for an old style line, the first foot might be a low diameter level line (where you tie your nail not on). The difference of one foot of tip vs one foot of the thickest part of the head is big.

I also have no idea on how to define where the head ends, especially with distance lines. That's the main reason I don't measure the full head. I would suggest from a practicality stand point, measuring at 10, 20, 30, 40, 50 ft should give you enough points to get a good characterization of the line. And it's easy to do in a repeatable fashion.

crunch
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Re: Suggested method for measuring lines

#8

Post by crunch » Sun Sep 22, 2019 1:31 pm

carlz wrote:
Sat Sep 21, 2019 5:05 pm
Viking Lars wrote:
Fri Sep 20, 2019 8:07 am
As you can put a light downward pressure on the scales through the stiffness of the line, I simply hung in a clothing pin with the mark of the head length on the scale. This also prevents relieving weight by lifting a portion of the line off the scale.
I weigh all my fly lines (first 30 ft, but this thread has got me thinking about measuring the full head) and in practice, the biggest variation is from measurement and figuring out how to not let the tail of the line effect the measurement. It usually gives me a + or - 2 grains on a 6wt line.
2 grains repeatibility is very good. The key to weight line sections accurate without cutting is to keep the length mark just in the middle between clothing pin or hand outside of cup/scale. With softer trout lines 5cm is fine when 10cm of line does not "sag" too much. For thicker salmon lines I keep lenght mark about 7,5cm out holding "the tail" 15cm out.

Esa

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Paul Arden
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Re: Suggested method for measuring lines

#9

Post by Paul Arden » Thu Sep 26, 2019 12:55 pm

crunch wrote:
Fri Sep 20, 2019 4:51 pm
I have marked 1000mm and 1500mm lengths from the table corner and holding line between left hand index finger and thumb I put index finger to the table edge and thumb nail is aligned to length mark while pulling line thru right hand fingers the length is very fast to measure.

Esa
What an excellent idea!! That saves a lot of walking :laugh:

On Sunday Flavio and I will be in Gerik. I’ll take five lines out the storeroom and we will measure them separately. I’ll then post these to the next measurer.

I’ll also get the datatables cleaned up and we can make a start next week.

Cheers, Paul
It's an exploration; bring a flyrod.

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Paul Arden
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Re: Suggested method for measuring lines

#10

Post by Paul Arden » Mon Sep 30, 2019 6:23 pm

So far the results are interesting... I’m sure Flavio will have something to say soon!

Cheers, Paul
It's an exploration; bring a flyrod.

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