This thread is opened for answsering Vince question about choosing a real seat to control the second harmonic of fly rods.
Positioning the reel seat and the way to lock the reel (up or down) is a question as old as the fly rod. Putting aside the fact that the very end of the butt might catch something during fishing (a cloth, the line), the mechanical issue is linked to the second harmonic of the rod.
One important thing to know is that depending on the way we hold the rod (a firm or a loose grip), the value of the second harmonic varies very little but a node of vibration can appear in the butt in case the grip is loose. It does not if the grip is strong.
The reel has a role in this problematic since it is a dead weight that will attract the position of the vibration node along the shaft. Then the question is to try estimating the location of the node to put it just below our hand, for two reasons: avoid our hand to be moved around the node, and control the vibration around the node.
I found only one reference to the reel problem trying to solve this issue, it was published in 1979 by a US “spiral” cane rod maker, Letcher Lambuth (The Angler’s workshop). The author speaks about the “zone of comfort” where the handle must be placed, and here is his rule of the thumb: the middle of the handle must be at equal distance from the reel and the center of gravity of the rod + reel (with its line). When I read that I quickly made the parallel with the vibration node of the second harmonic.
Some 15 to 20 years ago (I can’t remember exactly when, I should dig in my very old files), I asked a scientific laboratory to compute the place of the node for a given (cane) rod and a reel, the parameter being the ratio of the mass of the reel to the mass of the rod. You may know the good old rule: the reel should be 1 to 1.5 times heavier than the rod. Today, the rods are so light that even our lightest reels made of space age material can’t follow that rule (especially if you add the line).
Here are the results
Letcher Lambuth was quite close from the “exact” solution, bear in mind that the node is likely just one or two inches just below the point he recommended. Take a reel 1.25 times the rod weight, the node is about 8% from the reel position that is two say 8.5 inches from the reel for a 9 feet rod, or 6.5 inches for a 7 feet rod. These are order of magnitudes, the reel here is supposed to be at the very end of the rod.
With very light rods, the recommendation would be to use a lock up reel seat, but it does not forbid to use skeleton real seats for small rods. Just move a little bit you hand, or said differently, use a handle shape that allows moving your hand up or down if necessary.
Merlin
Fly rods are like women, they wont´play if they're maltreated.
Charles Ritz, A Flyfisher's Life
Thank you Merlin, that will take a while to digest.
With very light rods, the recommendation would be to use a lock up reel seat, but it does not forbid to use skeleton real seats for small rods. Just move a little bit you hand, or said differently, use a handle shape that allows moving your hand up or down if necessary.
I tried this in my last build but for different reasons, Firstly, I think that the reverse half wells forces a cocked wrist:
This feels a lot more comfortable to me but places my hand close to the reel. A secondary effect is that I can relax my grip more because the reel mass tends to have less effect during the cast.
The next build is a small Steffen fibreglass, my reason for asking the question was to shave weight, I was looking at a cap and ring seat, something like this:
Hi Merlin, hi Vince,
funny, just yesterday I was playing with the position of my reel trying to put down some differencies.
I focused on mainly three points:
1. How the reel position gives possibiltiy to use a longer leaver.
The lower I put my reel the longer the leaver I can use will be.
2. How to use the fighting butt as a "conter point" on my underarm (to keep wrist firm).
The lower I hold the rod the more force has to come only of my wrist. If I hold the rod little higher I can lay the figthing butt against my underarm. That makes the firm wrist more easy to controll.
3. The effect to the stop positions on the fc & bc.
For example the Krieger arm helps for easy rotation on the forward cast. But it may not help for a high forward stop though.
Holding the rod in balance and the effect of reel position relative to stop position.
While casting the Krieger arm is cool to play with but one should no longer change the plane of reel during the stroke but keep in plane directed to the cast. Which in my casting is a clear disadvantage.
Didn't think of the second harmonic here. Thanks.
Greets
Bernd
p.s.: This whole test made me think of a reel directly below the rod. Ari t Hart had a very intersting reel seat which allowed kind some different positionings of the reel.
No slight intended on Lee by using that picture bt it is the best example of the poor ergonomics of many grip designs. The thin gripped reverse half wells always leave a gap between rod and forearm and cause the forearm tendons to tighten.
What were your conclusions? It appears that a downlock would be better for a light rod and the reverse if you really want to lay on the power with a bigger rod?
I don't like the Krieger arm as long as I want to be able to change plane of my reel relative to the direction of the cast.
Mostly my reel is twisted outwards to some degree. That does not work well while using such a reel arm extension.
Besides that it feels very little more easy to stop the rod high in the back cast and little lower in the forward cast. So it matches the downwarded trajectory on short to medium distances while using a style in which you keep the reel in plane as good as possible. I understand this to work well for the short stroker using the squared stance like this for example: http://www.youtube.com/watch?feature=player_embedded&v=Qy3qLM3EOEI
Comparing the reel to be close to the rod but lower or higher postioned it depends.
The lower positioned reel offers the possibility to hold the rod little lower = longer leaver. Good for distance (upto a certain length when it will get too long for the caster).
The standard reel position felt best to me when laying the figthing butt against the underarm - which I like to in certain situations to help my wrist for being mostly firm.
So it's a mix of pros and cons and one has to sort out which fits best with one's personal style.
I tried to cast without a reel but put a weight directly to the end of the rod instead. That is quiet an interesting feeling. Have to test it more but it feels pretty cool (as long as I strive for identical rod movements on the bc & fc).
Is the node for the first mode assumed to be at the center of the hand holding the rod, or would it at the same point as the node that is located near the butt for the second mode?
Since the fundamental mode is so much larger than the second mode wouldn't its position be the dominate effect thing you would feel?
I tried to cast without a reel but put a weight directly to the end of the rod instead.
From a MOI standpoint wouldn't it be better to not apply any additional mass to the rod?
I know that Rene Gillibert uses a home-made, light-weight reel mounted in the center of the rod near his hand in the anglers distance game to reduce the MOI of the reel as much as possible. That makes it possible for him to get more angular acceleration in his cast. I think he is looking to maximize his line speed more so than worrying about the feel that comes from different node positions.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
Hi Gordy,
good question.
Try it and let us know what you think/feel.
I personally think the reel also works as a counter weight.
And I prefer casting with a reel instead of without a reel.
Not sure who came up with the old concept of the reel being 1 - 1,5 times the weight of the rod as Merlin put in and what are the reasons. But I think there have been some good reasons?
I find that the reel damps some of the feel of tip bounce and it is very odd not to have it. Perhaps that is habit.
Looking across the various builders sites, the majority plump for down locking on light rods and uplocking for heavier/longer rods for the reason Bernd put and due to static balancing. I could not find any discussion on 2F.
I may have confused you with my terminology. The comparison (Lambuth estimate versus calculation) is made for the "first free-free" harmonic, which is close to the "second clamp-free harmonic". I use to refer to "second harmonics" because these modes just differ by the node in the butt (there is another one in the tip).
Bernd
As you can se on the graphic, the rule of the thumb "1 to 1.5 times the weight of the rod for the weigth of the reel" is derived by experience from Lambuth. It roughly corresponds to the place of the butt node in case the grip is loose. This is the result from calculation. Today we may have some difficulty to follow that rule since although our reels are lighter than before, our rods are much lighter and that may raise a problem.
Vince
I never found a discussion on NF2, you know that most rodbuilders just ignore that, and it may also be valid when speaking about NF1
Merlin
Fly rods are like women, they wont´play if they're maltreated.
Charles Ritz, A Flyfisher's Life
is made for the "first free-free" harmonic, which is close to the "second clamp-free harmonic".
Merlin,
Does the first free-free mode shown below for a uniform beam have two nodes? After looking at the video referenced in this [url=C:\Users\Administrator\Documents\Downloads\Documents\Beam_vibration.pdf]paper.[/url] it appears the first node is about 20% down the length of the beam as shown below.
If you add a mass that is equal to 1.5 times the mass of the rod will it move that first node from the 20% point (for a uniform beam) to a point that is about 3.5% up from the center of the reel seat of a tapered rod? That value would put that node about 10 cm from the center of the reel which would still be below the center of the grip on one of my rods.
Sorry for the dumb question as I don't understand what these free-free modes are all about. Is there a zero order mode where the hard clamp would be near the middle of a tapered rod such that the ends would move up and down together when you shake the middle back and forth? That would seem to be the superposition of two clamped-free cantilevers or a free-clamped-free mode.
Do you assume the first node for the second mode of the clamped-free rod at the clamp (x=0) as shown in Huan's thesis?
In that case do you assume the clamp function is provided by the grip of the hand or would it be at some other point that would be impacted by the "softness" of the hand the mass of the reel?
My experience with vibrating a hand held rod made me aware that the grip of the hand is much different than a hard clamp, so all of this gets to be a bit fuzzy for me.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
I have to put my hand up and admit I did not understand your response. Looking at Gordys graphics, I do not know if we need to get our hands as far back as possible to avoid feeling the nodes or if we are moving our hands forward to provide additional damping.
The graphics you are showing are correct, the "first" free-free mode (in blue in the first graphic) corresponds quite closely to the second one of the "clamped-free" one (the green line in the second graphic): they both have one node in the tip and practically, their frequency is comparable. When calculating the clamp-free" second harmonic, my assumption is that the beam is supposed to be embedded 8 inches from the butt (the middle of the handle approximately). This is not very different from the value you would get by assuming the rod is exactly embedded at the butt. If there was a "zero mode" for the "free-free" case, it would correspond exactly to the first harmonic of the "clamp-free" system. There is no mode with a node in the middle of the beam in "free-free" conditions.
You are right saying the "clamp" condition is not perfect, this is why I consider the "clamp" condition in the middle of the handle.
Vince:
I take your point that a potential damping effect could come from the reel. That needs to be invetsigated, because its seems to me that the "resonator" that would be made of part (half) of the handle and the reel has a quite high frequency. But I shall give a look. I have heard different opinion about the reel, some casters preferring to use no reel at all (I remember one who had the reel attached on a board hanging from his neck!). Maybe this damping effect compensates the node one, and after all, that would mean that Lambuth's experience would be a good compromise (without getting a headache for looking after equations to explain that).
Merlin
Fly rods are like women, they wont´play if they're maltreated.
Charles Ritz, A Flyfisher's Life
The graphics you are showing are correct, the "first" free-free mode (in blue in the first graphic) corresponds quite closely to the second one of the "clamped-free" one (the green line in the second graphic):
Merlin,
So that means you are comparing the node locations that are roughly 80% up the length of the rod not the first node for the free-free mode (that is located about 20% up from the butt) when you say those nodes are close to each other at some point on the rod.
In your plot I assume the 3.5% point for the first free-free node using a reel having a mass=1.5*(mass of the rod) was measured from the center of the reel. That would put that node about 3.78" (9.6 cm) up from the reel location. That short of a distance would seem to argue for using an up-locking reel so that node would be closer to the center of the grip.
Also since the mass of many reels is more than twice the mass of modern graphite rods the use of the Krieger arm might be desirable to get that node closer to the center of the rod hand. That arm would also put the reel closer to the wrist rotation center and thus reduce the MOI of the reel about that point, although it would be going in the wrong direction when the rotation is coming from the elbow or shoulder.
That assumes you are trying to move the first node for the free-free mode to a point near the middle of the grip so that mode does not tend to move the hand as the rod vibrates with a bendform that comes from the first free-free mode. As such it does not have anything to do with the x=0 node location for the clamped-free second mode.
This is a bit of speculation, but I am wondering if the reason the rod butt rotates forward and produces the rebound hump as the rod goes through counterflex is because the rod has a strong free-free mode as it returns from counterflex.
I have always wondered why the rod butt goes forward as the tip is coming back towards the caster after counterflex. That U-shaped free-free mode would fit with that relative dynamic motion of the tip and the butt.
Gordy
"Flyfishing: 200 years of tradition unencumbered by progress." Ralph Cutter
gordonjudd wrote:I have always wondered why the rod butt goes forward as the tip is coming back towards the caster after counterflex.
I would want to see a CA graph sycronised with a slow mo to back that up in detail .
I think this second move of the butt section starts with cf. But it may pass mcf due to the process of stopping again needs "time". That's what I see in many slomos.
It also seems to be logical to me that mcf means force against our rod hand pulling up on it, making it move.
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