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Spey casting dynamics

Started by Malcolm, August 14, 2012, 02:04:46 PM

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Wildfisher

Quote from: Inchlaggan on August 15, 2012, 06:44:18 PM
So DF or WF?

Never seen a WF rubber balloon or even  DT come to think of it. But the type of balloon model makers  twist and shape into donkeys and stuff might be good. You can make them any shape you like. Even long belly multi-compound  front and back tapered if you are really good at it.   If you  don't catch  anything with them  you can even make them look like a fish and pretend you are as good as Stan.  Everyone is at it.  Add a few mirrors and a bit of smoke and  they could be the next big thing in fly fishing.   :D

Traditionalist

#21
Quote from: Alan on August 15, 2012, 10:47:53 PM
come on Mike this is daft, would you cast a shooting head by aerialising it beyond the head?

Yes, that is what I invariably do.It is the only efficient way to haul a head for distance. The head must be completely outside the rod tip.  I have at least one meter overhang as a  matter of course when casting heads for distance, and have used more on occasion, but this is very difficult to do and the timing becomes very critical indeed.  I also double haul as a matter of course when fishing most heads.

I don't think that is what you really wanted to know.  But as I wrote there is no point in further discussion unless one can agree on some basic matters.

You need more force to cast 70 feet than you do to cast 35 feet. Force is what translates to line momentum.  The momentum ( of a head) is what governs how far it travels when you let go.  The greater the distance you wish to cast, the greater the momentum required, and the more force is necessary. I can aerialise a head and let it go and it will just drop to the ground.  I can aerialise a head and then double haul it a very long way, I can also increase my stroke length and power application and cast it even further.

Without doing any of these things it will merely fall to the ground when I let it go, it might pull a few feet of backing with it, but what that effectively means is that you used more force than required to aerialise it.

http://en.wikipedia.org/wiki/Momentum

http://en.wikipedia.org/wiki/Kinetic_energy

There is absolutely no point in discussing various aspects of casting unless the relevant parameters are known and accepted. It is merely confusing and frustrating, and apparently it even annoys some people, who apparently consider it crap, but obviously read it anyway, or they don't bother reading it and just call it crap because they don't understand it, and don't want to.

TL
MC

Wildfisher

Quote from: Mike Connor on August 15, 2012, 11:03:47 PM
There is absolutely no point in discussing various aspects of casting unless the relevant parameters are known and accepted. It is merely confusing and frustrating, and apparently it even annoys some people, who apparently consider it crap, but obviously read it anyway, or they don't bother reading it and just call it crap because they don't understand it, and don't want to.

Could not agree more. I'm enjoying reading this stuff. Just to state it's "crap"  adds nothing constructive, is provocative  and is not the way we do things here. I missed that post but it has now been  removed.

Malcolm

Mike is absolutely right Alan. With A WF line and a 5 line it is quite straight forward to cast to any given distance from 30 to 100 feet+ if you have the strength and ability to do so - both are important. What governs the distance? It is the energy that you put into the line. If I intend to shoot 10 feet of line that is what I do - by adjusting the force. If I want to shoot 60 feet of line - shooting head, WF or DT  I still need to adjust the force. By your argument the head would fly forever.
Quote from: Alan on August 15, 2012, 06:21:26 PM
i was just saying if you arialise the head of a WF line you can shoot it to 70', no extra effort required than casting to 35' or whatever because you have only cast 35' and let go, the extra effort is letting it go rather than casting 35'...by not letting it go.


Any line no matter how thin creates resistance (drag) in many forms: skin drag, form rag, wave drag to name a few. There is drag against the rod rings and against air - counteracting that drag isn't free. What does differ is the amount of extra effort - a DT creates much more drag than a WF or Shooting head.

Moreover there is a law of decreasing returns. The increase in force required in order to cast (with the same outfit) is exponential as the faster the line travels the greater the drag. This is a general rule not just for fly lines but for many things - for example in order to double the speed of an olympic rowing boat the effort required is approximately cubed.

There's nocht sae sober as a man blin drunk.
I maun hae goat an unco bellyfu'
To jaw like this

Traditionalist

#24
With regard to the original topic : the purpose of a short heavy head when Spey casting is to lift heavy flies ( and usually a sink tip), easily. This can only be done if the rod is loaded properly and the line is heavy enough and has sufficient momentum to actually carry the flies concerned.  The short heavy head loads the rod immediately, as all the weight is in the D-loop ( assuming you do it correctly).   Such a loading could otherwise only be achieved by extending a long less heavy line in an overhead cast.

Heads are used for a lot of things, and how you use them depends on what you are trying to achieve.  I habitually carry a size #8 28 foot head for use on my #5 weight rod. When I want to cast heavy streamers I just loop the head on and I can cast a size 6 long shank heavily weighted woolly bugger with no problem at all.

This is impossible with a "standard" #5 weight line, the line is simply not heavy enough to carry the fly, and you can not load the rod enough to generate sufficient momentum to carry such a fly.

I use a 34 foot #12 head on my 9' 6"  #7  for seatrout and other fish in the salt for much the same reasons.

Using a half DT one or two line weights below the designated rod weight will give you very delicate presentation, but will only work with small flies.

There are also various other scenarios.  I have a large collection of heads, which are basically just purpose built and matched pieces of line, of various lengths and weights, for doing lots of different things.  Half a standard 90 ft DT is just a a 45 foot head.

As the majority of (trout) rods are designed to withstand being loaded with at least a  full line of the designated weight, you can go up at least two line sizes with half a line, and even more if you use a shorter head.

There are some limits however, trying to use a head less than twenty feet or so for "normal" casting will cause problems.

TL
MC

Traditionalist

#25
Quote from: Alan on August 16, 2012, 12:00:35 AM
its pretty hard to let a line drop to the ground without it unrolling, to collapse a loop(as you do with some aerial mends) is harder than letting it roll out, you have to go into less than no power,
an instructors trick to show beginners they don't need to use too much power(thats all of them and experienced fishers too) is ask them to cast 40' with zero power stopping the rod at vertical after a back cast, there is a slight lead but no forward stroke as such, try to make the cast collapse, the trick is it doesn't, anyone can try this,
then ask them to cast further with the same minimal power but with a harder stop, then further with the same power, a harder stop and a lengthened stroke and so on, when they can lift no more line with zero power you tell em to let go, when they build on this they have a a very efficient base to work from.

Malcolm, you read it right, by my argument the head flies forever..up to the point that the line is designed unroll, thats head length + and whatever you can shoot, so yes, it flies forever within this distance with the same energy put in, with leader etc, most WF lines reach 70' with little effort, this obviously needs some energy to power the cast, and beyond this critical distance you need to use more energy because your rotating a heavier lever, and for every foot beyond this you will use more effort exponentially hence diminishing returns.

its just occurred to me that you guys are applying more force when you want to shoot further?


You can not cast at all with "zero power" that is just a casting colloquialism designed to encourage beginners not to use too much force. The act of lifting even a rod length of line requires force, just not very much.

You can collapse a cast immediately at any time up to the actual release of the line simply by relaxing the tension.

After you release a line, then you have very little control, with a head basically none once it is outside the rod tip, because you can not mend the fly line by mending the backing, it simply will not transfer the required energy to the fly line.   

With a full line, ( or a head which is still inside the rod tip ), you have more control, you can mend and do a few other things.

Tension is what keeps a line in the air, (and also causes it to unroll).  If you relax the tension it will fall to the ground immediately, it will not unroll, no loops will form etc   It will just drop to the ground.

Once you release the line on the forward stroke then it begins to fall, but the momentum you have imparted to it keeps it traveling forward.  The more momentum the further it travels.

If you want to shoot further then you MUST apply more force. There is no other way to do it.

TL
MC

Traditionalist

#26
There are loads of weird and wonderful descriptions of casting, how it works, and how to do it.  But the method I have always taught all my beginners, (WITHOUT TELLING THEM ANYTHING ELSE AT ALL), is just to keep the line taut and try to make it even tauter just before you stop the rod at the release point.  None of them have ever had any problems with it.

The worst people to teach are those who have already tried to teach themselves or been taught incorrectly by others. It is well nigh impossible to eradicate bad habits and retrain muscle memory.

This works with anything by the way, even a piece of string in your hand, and also teaches intuitive timing.

It is also largely neglected.  In order to cast you just need to keep the line taut under either constant or constantly increasing tension.  Practically ALL faults which occur are caused by not doing this.

This also obviates a lot of difficult concepts like "line speed" and a lot of other stuff. What does a haul do?  It increases line tension.  How? By pulling the line against its own inertia. You have to move the line faster and faster in order to at least maintain or increase the tension. Any decrease in tension before release will cause tailing loops and things like that. Complete loss of tension simply collapses the cast. IT DOES NOT MATTER WHEN IT OCCURS!  Loss of tension at any point in the cast will cause it to collapse.

That is basically it. If you manage to do that you will cast perfectly.

TL
MC

Traditionalist

#27
Quote from: Alan on August 16, 2012, 12:27:23 AM
Mike you don't read my replies :lol: if i film myself casting 35 and 70' with the same 3'' long forward stroke will you believe me?

No, because it is not possible. Stroke length does not equate to applied force.  ( Although of course there are limits to the force you can apply with a short stroke). I read all your posts very very carefully indeed. I do not on any account wish to write something that is incorrect.

TL
MC

Traditionalist

Quote from: Alan on August 16, 2012, 01:09:12 AM
I'm with you on the tension thing, but it appears you don't believe a word i write :lol:

I'm surprised you think a 3'' stroke is impossible, if you let me haul this would not be difficult.

i can't think of another way of proving that I'm imparting the same force at both distances, don't get me wrong, the distance the line travels with the same power is determined by the head length, i need to pick up at least 35' of head to reach 70', beyond this distance the line would start to collapse, i normally measure from foot to fly so if i can include an 11' leader/9'rod it should be pretty easy.

I did not say that a 3" stroke was impossible. I said that it is impossible to cast 70 feet with the same force as 35 feet.  It is what I have stated all along. If you add a haul you are adding more force.

You can not be imparting the same force at both distances. It is impossible.

Stroke length, or any other factors are completely irrelevant. The force required to propel a line 70 feet is greater than the force required to propel it 35 feet.

There is no way to gainsay that simple physical fact.  It does not matter what you do or how you do it. What you are saying is a physical impossibility.

TL
MC

Traditionalist

#29
Quote from: Alan on August 16, 2012, 01:47:49 AM
its taken a while but we have reached the nub of it :lol: i would say that a WF head needs the same force/power to cast any distance around what the head length/weight allows, irrespective of stroke length, i see this as the whole point of a weight forward, beyond what the head allows, sure you need to do a pile of things to add even minimal distance.

You would be wrong.  ANY increase in casting distance with ANY line, or indeed any object at all, requires an increase in force.

That is an immutable  law of physics;

Air friction, or air drag, is  fluid friction. ( Air is classed as a fluid). Such friction forces are velocity dependent. The frictional drag is approximately proportional to the square of the velocity:



where ρ is the air density, A the cross-sectional area, and C is a numerical drag coefficient.

The faster you try to move something the greater the drag. As the distance you can achieve is governed by the velocity, (  momentum = mass x velocity   or   p = mv ), the further you try to cast something the harder it becomes, and the more force is required. Since the velocity you can obtain is limited by the amount of force you can apply you soon come up against diminishing returns for the force applied.

The power needed to push an object through a fluid increases as the cube of the velocity.

Unless you accept that, there really is no point at all in any further discussion.

The scenario you suggest is simply not possible.

TL
MC

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