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Re: Fly Line Database

Posted: Sat Jun 08, 2019 1:31 am
by Paul Arden
I got a few comments from Bruce...
I'm back from the wilderness and will have some time to contribute to the database/line design project now. I've read about half that thread and have a few short comments.
First, calibration of both balances and micrometers will be very important. Everyone must commit to accurate measurements. That said, without cutting lines accurate weights aren't really possible so maybe balance calibration isn't necessary.
SA, and I'm sure Rio, already have most of the info. you want and I suspect both would be willing to provide. It's a LOT of data though, would take some time. And, who is going to maintain this database? The data will change annually. Initial data collection is just part of the job if the database is to remain relevant.

A couple quick line design comments. Head design - how a line carries and delivers a fly is probably the key design parameter. The mass profile of the head largely determines that. Too "delay" turnover you put more mass in the front part of the head. Think of the loop top leg only. As it gets shorter it accelerates, or tries too. As top leg mass reduces the energy is focused in a smaller mass, that's the cause. But since wind resistance is exponential any increase in velocity is met with increased resistance, the reason that it is SO important that the top leg be very straight. If the line is designed like the MED, with more mass toward the front, the mass of the top leg doesn't reduce as quickly as it shortens which delays the acceleration, slowing the top leg, allowing it to carry farther before turning over. The MED is designed with a rather long front taper for smooth turnovers, but with an oversize tip to insure it does turnover at distance.
The Wulff TT lines are just the opposite, but designed for a very different purpose. A big subject but very simple physics really...

I can help with the database if you want.

Bruce

Re: Fly Line Database

Posted: Sat Jun 08, 2019 3:00 pm
by Merlin
Bruce is right when he speaks about the difficulty to keep a database alive, it is really a tough job.

One thing would be to avoid ending in something like that for SH lines:
Spey Lines.JPG
Spey Lines.JPG (65.53 KiB) Viewed 786 times
You have a different standard for a number of typical lines :(

I wonder if the target (database) is what we really need, for sure it will be helpfull, but maybe there is another issue hidden behind that, and I am not able to clearly identify it for the moment.

Merlin

Re: Fly Line Database

Posted: Sun Jun 09, 2019 4:12 pm
by gordonjudd
the mass of the top leg doesn't reduce as quickly as it shortens which delays the acceleration, slowing the top leg, allowing it to carry farther before turning over.
Bruce,
Thanks for your input.

When you were coming up with the complicated profile in MED line did you have the means to measure the fly velocity history and/or the layout time for the different designs?

Or did you play around with the negative taper in the belly section (thicker at front) and then determine which taper gave you the longest casting distance?

If you did not have to try to meet the AFTMA mass standard for the first 30 feet would you have used larger mass values to get more distance?

Also did you intentionally push the mass density value higher so that its specific gravity was just below 1 (.962) and still call it a floating line?

Gordy

Re: Fly Line Database

Posted: Mon Jun 10, 2019 7:29 pm
by crunch
I think the diameter table does not produce accurate data because line density is not constant. Accurately measuring lengths which then are put to a scale will produce good and accurate data. Marking one meter from table end is fast and accurate way to measure line length. Someone wrote that he can accurately weight calibration weights. They can be almost what ever cheap steel like nuts, washers, bolts etc which then is sent to us. Scales which have good reading accuracy and repeatibility accuracy are very cheap but their accuracy is not very good but with calibration weight it is simple math to get accurate weights. When we cast a fly line it is the weight of it which we cast!

Esa

Re: Fly Line Database

Posted: Mon Jun 10, 2019 10:22 pm
by gordonjudd
I think the diameter table does not produce accurate data because line density is not constant.
Esa,
What causes the nominal volume mass density of the line to vary along its length? I would think the PVC and/or Polyurethane coating material would have a uniform density. The same for the core material.

Is it the ratio of the line diameter to the core diameter variation that results in the volume mass density variation you have noted? Have you measured how large that variation might be?

I could not find any information on the density of different core materials but have noted that the volume mass density of floating lines vary from 810 to 960 kg/m.

Here is all that I could find on the density of different core materials at https://www.cabelas.com/product/Fly-Lin ... 532659.uts
Fly-line cores are generally made of either braided multifilament, braided monofilament or monofilament.
• Braided-multifilament line is best in cool to moderate temperatures. It’s too supple for tropical heat. Its hollow center makes it more buoyant.
• Braided-monofilament line is stiff so it stands up to tropical heat, but it is too stiff for cold temperatures. Its lack of air in the middle hinders its flotation.
• Monofilament line is moderately stiff and good for all climates. It is small in diameter and makes excellent fast-sinking line. Monofilament is the only core that can be used to make clear lines.
Gordy

Re: Fly Line Database

Posted: Wed Jun 12, 2019 12:42 pm
by crunch
But when the core and coating densities are not constant the diameter does not very well produce comparable data. Perhaps you can calculate profiled line volume but you still need to weight same length as well. I have first measured length of solid scrab line weight in a cup and then cut it and it has came almost the same. I believe water absorbation has more effect so lines need to be dried few days first?

Trout line part which is not weighted can be kept ten centimeters out of cup and length mark five centimeters out because they are so soft that disturbing reading either pressing cup down or lifting line up does not happen much but when you know that you can change scale reading it is easy to learn avoid testing this effect.

Esa