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gordonjudd
Posts: 1795
Joined: Sat Jan 19, 2013 11:36 pm
Location: Southern California

Does it make a difference?

From my simple understanding of the transverse wave energy transfer through the junction of two different mediums the transfer coefficient at the interface depends on the mechanical impedance of the two types of lines. As given in this summary on transverse waves

http://imageshack.com/a/img923/989/GY7Irk.jpg
An example of the wave transmission down a rope with two different linear mass densities is shown here: on YouTube

He does not say how he joined the two rope sections, but I wonder if it would have made a much of a difference in his experiment since the length of that junction would have been so short compared to the length of the transverse wave he was using?

The same consideration applies to our fly line to leader junction. Since that junction overlap distance is so short compared to the length of the wave traveling down the line will it have much of an effect on the energy transfer? The relative linear mass density of the line and leader will be important to the energy transfer as given by the transfer coefficient above, but will the type of connection by itself have much of an effect on the relative smoothness loop layout?

Maybe some high speed videos of the propagation of the loop as it goes through the line/ leader junction would show how different types of junctions affect that transfer. Obviously the design of the taper in the leader will have an effect on the layout of the fly, but the taper used in the leader is another complicated matter that I was surprised did not come up in the recent discussion with line expert Bruce Richards. For this topic the impact of the leader design will not relevant since the same leader was used in all the tests.

I thought it might be interesting to compare the transfer from a line to a leader where the only variable was the type of connection used to join the two. Three popular types of connections were used in this series of experiments. My personal favorite is Dave Whiltlock’s Zap-a-Gap connection where the end of the leader is “welded” to the inside of the fly line.

There are a number of sites on the web that show how to make this really slick (no pun intended) connection. Mr. Whitlock says he has never had one of these junctions fail, but I have had the leader pull out from the line when applying a lot of tension in the leader to straighten it. So buyer beware of using this elegant connection for big fish.

The second connection used was standard 5 turn nail knot where I did not bother to run the end of the leader through the end of the line to make a smoother junction that is less likely to get hung up on the top guide.

The third was the much maligned loop to loop connection where the loops were made by whipping a short folded back section either the line or the leader to make the loops.

I thought I could do the tests by taking videos of the loop against a dark background to see how smoothly the wave went through the three different types of junctions. However that was easier said than done as I found the leader had no problem in going through the relatively wide DN loops that I produced in casting. There was really nothing to see using the Whitlock connection going through this loop as shown below. The black mark on the end of the line marks the junction in this video and you can see it goes through the loop with amazing smoothness.

Consequently after trying different approaches I found the most demanding loop could be produced by hauling a length of line on a piece of tar paper on the ground. This produced a very small loop (approximately 11 cm diameter) and had the added bonus that the path of the junction stayed within the close up frame of view of the camera. For dimensioning purposes the markers on the tape are 20 cm apart.

So in no particular order here is the transition I observed with the three junction types.
Connection #1

Connection #2

Connection #3

I would be interested so see if most people can see a difference that the junctions made on the transfer. Which video do you think is associated with each junction type? Can you pick out the one that was produced with the loop to loop connection?

The video for these comparisons are on vimeo at url=https://vimeo.com/154426156 if you are interested in being able to pause the playback. I blackened the end of the fly line with a marker to delineate the junction point in these videos.

Gordy

P.S. added on Feb. 15, 2016

Since Paul was the only one brave enough to hazard a guess on which connection was which I assume the consensus opinion is that the connection type had little or no effect on how the loop rolled out.

For the record:
Connection #1 was the loop to loop
Connection #2 was the Whitlock splice
Connection #3 was the 5 turn nail knot

Paul Arden
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Is 2 the loop to loop, Gordy? Very interesting post!

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

Flycasting Definitions

gordonjudd
Posts: 1795
Joined: Sat Jan 19, 2013 11:36 pm
Location: Southern California

Is 2 the loop to loop?
Paul,
No.

This surprised me also as I thought there would be more of a difference.

If I get inspired I may connect the two with a short length of thread to simulate what happens when you get a hinge behind an old nail knot.
Gordy

John Finn
Posts: 247
Joined: Wed Jan 01, 2014 8:35 pm

Hi Gordy, There seems to be more bounce in 2. How would gravity effect this ? Interesting the wave seemed to go back through the flyline . What was the butt diameter compared to the line tip ? They seem very similar. Would a long leader make the difference between connections even less . ..................John

Paul Arden
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Joined: Thu Jan 03, 2013 11:20 am
Location: Belum Rainforest
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Interesting, Gordy! I was going by the length of the returning wave. I'm also surprised to see so little variation. I certainly think I can see it clearly in the field. Maybe your loops are far better than those braid sleeves that are glued on the end!

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

Flycasting Definitions

Viking Lars
Posts: 694
Joined: Thu Jan 10, 2013 10:45 am

Interesting, Gordy - are the materials used flyline to mono, or something else? Flyline to flyline? The "leader" looks quite dense.

Lars

gordonjudd
Posts: 1795
Joined: Sat Jan 19, 2013 11:36 pm
Location: Southern California

What was the butt diameter compared to the line tip
and
are the materials used flyline to mono, or something else
Paul and Lars,
The line and leader used in these different cases remained the same, so that the only variable was the type of connection.

The line was a Snowbee ED8 floating line that had a tip diameter .001016m an assumed volume mass density of 860 kg/m.^3. That gives a linear mass density of the line tip of of 0.00069723kg/m.

The leader was a Scientific American 16 lb Bonefish leader that had a tip diameter of .0006604m an assumed volume mass density of 1140 kg/m.^3. That gives a linear mass density for the leader butt of 0.00039049kg/m.
How would gravity effect this ?
John,
For a vertical loop traveling in the x direction gravity would be pulling in the -y direction and thus its force would be orthogonal to the direction of travel and thus not have much of an effect on the loop propagation other than causing it to fall. Drag forces of course would complicate that simple picture.

Gordy

Posts: 436
Joined: Tue Aug 06, 2013 10:11 pm
Location: Melbourne

Hi Gordy
Intriguingly unexpected compared with what traditional wisdom would have us expect. Equations, densities and quant aside what I found surprising is that the transition leads in all cases to a slight kick from the flyline with a return wave as others observed. With reference to Bruce Richards, density profile seems to be the main game.

Cheers
Mark
"The line of beauty is the result of perfect economy." R. W. Emerson.
https://thecuriousflycaster.com

Viking Lars
Posts: 694
Joined: Thu Jan 10, 2013 10:45 am

Thanks, Gordy! This does concur well with my real-life experiences that loop-to-loop connections are just fine :-).

Lars

gordonjudd
Posts: 1795
Joined: Sat Jan 19, 2013 11:36 pm
Location: Southern California