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Rod bend in roll cast

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Massew
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Rod bend in roll cast

#1

Post by Massew » Tue Feb 04, 2014 11:23 am

Hi,

since Paul encourages lurkers to post questions I thought I'd give it another go. I'm no lurker but I do lurk. :)

About rod bend/load in roll casting. I know that the rod doesn't bend because of the anchor or D-loop. Well, I think I understand anyway but most regulars here only state that rod load doesn't exist in this context but no one really explains why.

So my thoughts are: the anchor prevents the leader from slipping, the D-loop forms and the forward stroke follows. The leader (and fly) don't move until the forward cast is nearly done. The rod bends but not because of the weight of the fly line but because when the rod is moved it will bend due to acceleration. So the rod bends and that provides enough arc to make the rotation of the rod tip efficicent. Am I anywhere close in this?

I've watched some of Aitor's films on this subject but I just want to make sure I understand this.

If there are any threads about this in the older boards, as I'm sure there are, please point me in their general direction. I've only managed to open the threads one by one and it takes quite a while to find the interesting ones.

Kind regards,

Mathias
IFFF CCI
"The motives of fishermen are dreadfully obscure" - David Eddings

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Marc Fauvet
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Rod bend in roll cast

#2

Post by Marc Fauvet » Tue Feb 04, 2014 12:53 pm

Massew wrote: The rod bends but not because of the weight of the fly line but because when the rod is moved it will bend due to acceleration.
hej Mathias,
mostly, yes. of course the aerial part of the line in the D-loop will make the rod bend a bit more. (for equal force applied to the rod)
a good way to work this out on your own and to understand the importance of the acceleration is to replace the fly line with some thin mono or backing. sure, it's easier with the weight of a fly line but you'll still make the cast.
cheers,
marc

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Paul Arden
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Rod bend in roll cast

#3

Post by Paul Arden » Tue Feb 04, 2014 2:04 pm

Yes that's pretty much all correct I think. I see the purpose of the anchor to stop the bottom of the loop slipping backwards during the casting stroke. The rod definitely bends against the weight of the line in the top part of the D loop as well as because of air resistance.

Cheers, Paul
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Massew
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Rod bend in roll cast

#4

Post by Massew » Tue Feb 04, 2014 2:58 pm

Thanks Marc and Paul. You are right that the aerial part of the D-loop bends the rod a little, should've thought of that.

Is there any difference between a static roll and a dynamic roll in this sense?

Kind regards,

Mathias
IFFF CCI
"The motives of fishermen are dreadfully obscure" - David Eddings

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gordonjudd
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Rod bend in roll cast

#5

Post by gordonjudd » Tue Feb 04, 2014 3:35 pm

The rod definitely bends against the weight of the line in the top part of the D loop as well as because of air resistance.
Paul,
I think the force required to accelerate all (not just the top portion of the loop) of the moving mass in the D loop would be much larger than the force required to overcome its air resistance.

Since the moving mass in a D loop is smaller than the mass being carried in a conventional cast the relative amount of bend due to inertial bending (and to a smaller degree the air resistance effects on the rod) is probably a much higher percentage of the overall bend in in the rod as compared to the 30-40% that Dr. Spolek has estimated for a conventional cast.
Gordy

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Walter
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Rod bend in roll cast

#6

Post by Walter » Tue Feb 04, 2014 4:42 pm

Spey lines, especially skagit and scandi lines, have significantly greater linear density than a single hand line that is listed as the same AFTMA weight. This is because the upper half of a D loop is roughly 1.5 times longer than the rod (less than 20 on average? remember I'm talking scandi and skagit) - any longer than that and we wouldn't be able to place the anchor. In overhead casting we have 30 feet or more of line in the air. If we want to use our long rods for overhead casting without getting the feel that we are trying to cast a pig it is best to drop to a lighter line - one designed for overhead casting with the given rod wt rating.

A long winded way of saying that the upper half of the D loop is the part of the line that is used to load the rod in roll casting.
"There can be only one." - The Highlander. :pirate:

PS. I have a flying tank. Your argument is irrelevant.

PSS. How to generate a climbing loop through control of the casting stroke is left as a (considerable) exercise to the reader.

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Marc Fauvet
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Rod bend in roll cast

#7

Post by Marc Fauvet » Tue Feb 04, 2014 4:53 pm

hi Mathias,
a friend explained to me that my reply
the aerial part of the line in the D-loop will make the rod bend a bit more. (for equal force applied to the rod)
was incorrect so please ignore it. :)

i also hadn't noticed that this topic was in the tech-anal section. i don't like it here...
double-bad for me ! :D
cheers,
marc

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Lasse Karlsson
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Rod bend in roll cast

#8

Post by Lasse Karlsson » Tue Feb 04, 2014 5:38 pm

Walter wrote:Spey lines, especially skagit and scandi lines, have significantly greater linear density than a single hand line that is listed as the same AFTMA weight. This is because the upper half of a D loop is roughly 1.5 times longer than the rod (less than 20 on average? remember I'm talking scandi and skagit) - any longer than that and we wouldn't be able to place the anchor. In overhead casting we have 30 feet or more of line in the air. If we want to use our long rods for overhead casting without getting the feel that we are trying to cast a pig it is best to drop to a lighter line - one designed for overhead casting with the given rod wt rating.
.
Say again?

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Lasse
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Walter
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Rod bend in roll cast

#9

Post by Walter » Tue Feb 04, 2014 6:12 pm

Lasse Karlsson wrote: Say again?

Cheers
Lasse
How about this? It is difficult to find one single line for your switch rod that gives you optimum results for both spey casting (especially scandi and skagit styles) and overhead casting.
"There can be only one." - The Highlander. :pirate:

PS. I have a flying tank. Your argument is irrelevant.

PSS. How to generate a climbing loop through control of the casting stroke is left as a (considerable) exercise to the reader.

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Walter
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Rod bend in roll cast

#10

Post by Walter » Tue Feb 04, 2014 6:16 pm

Marc Fauvet wrote:i also hadn't noticed that this topic was in the tech-anal section. i don't like it here...
double-bad for me ! :D
Ditto. :evil:
"There can be only one." - The Highlander. :pirate:

PS. I have a flying tank. Your argument is irrelevant.

PSS. How to generate a climbing loop through control of the casting stroke is left as a (considerable) exercise to the reader.

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