A week with Berlin!

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A week with Berlin!

Post Number:#11  Postby Berlin » Mon Dec 19, 2016 6:50 pm

Mel Krieger provided a unique service to fly casting with his soft Fenwick rod and his whump. He's probably the only caster I know of that cast in the primary frequency so eloquently. When he goes for distance he called it his Madison cast and in doing so that was when he changed to the secondary frequency. Its the perfect example of rod frequency and loop shape change.
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Post Number:#12  Postby Merlin » Tue Dec 20, 2016 2:52 pm

Hi Berlin

I am most interested in reading your explanations about the trebuchet. To me a rod works with its first "clamped-free" frequency during loading and more or less with its first "free-free" frequency during unloading, that depends on the possibility for the caster to drive the deceleration of the butt. In the case of a DH rod, the energy stored by the rod is large and the free-free mode must dominate. You then have two nodes, one in the tip and one in the butt. To me the trebuchet aims at positionning the node in the butt, maybe just in between the hands, or at the reel level, or even lower, I cannot tell yet, but in a sense it places the rod frequency within a certain range.

These frequencies can correspond to large amplitudes, which is not the case for the second clamped-free mode (and the third). Incidentally, the free-free mode can be about 75% of the second clamped-free one, which has also a node in the tip (but none in the butt).

The reel and rod balance is also a subject interesting competition casting (precision). I expect interesting discussion on this point.

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Post Number:#13  Postby gordonjudd » Tue Dec 20, 2016 4:39 pm

the free-free mode can be about 75% of the second clamped-free one, which has also a node in the tip (but none in the butt).

Merlin,
I assume your 75% value is comparing the loaded frequency of the first free-free mode compared to the loaded frequency of the second clamped-free mode not the relative effect they will have on the tip speed as the rod unloads.

As Tom showed on the old board the affect of the second mode on tip speed is quite small and could well be out of phase with the speed produced by the first mode at RSP1.

I guess it depends on how you count nodes, but isn't there a node at the clamped end of second mode?

From Wikipedia:
A node is a point along a standing wave where the wave has minimum amplitude. For instance, in a vibrating guitar string, the ends of the string are nodes.


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Post Number:#14  Postby gordonjudd » Tue Dec 20, 2016 5:13 pm

We load the rod in the primary frequency and then unload it in the secondary frequency.

Carl,
I don't know how you could determine which mode is in play as the rod unloads but I don't think the relative amplitude of the second mode is very large compared to the amplitude of the first clamped-free mode, or as Merlin has suggested the first free-free mode. The residual second mode shape that you see at RSP1 is quite small.

As I understand it Merlin's model only deals with first clamped-free mode and it seems to give a close estimate to measured tip speeds. That fact would seem to argue that the rod is unloading with a dominate first clamped-free mode, but Merlin may have some more recent results that favor the first free-free mode.

Your Trebuchet system is very interesting and may be a way of getting the node of the first free-free mode to move near the hand as Merlin has been investigating in this reply to Chris Korich on the relative mass of the reel in regards to the "feel" of casting (whatever that might mean to different casters).

"The best way to cast a rod is to take the reel off and out it in your pocket"

When it comes to producing the highest amount of angular acceleration for a given amount of torque applied in distance casting I think that would be true because the MOI of the reel could be quite significant when the rotation center of the caster is near the elbow at MAV.

With that in mind, Renee Gillibert is famous for the cardboard reel he made to comply with the ACA rules that requires a reel that can hold all of the line is attached to the rod in the single handed distance game. I would expect that rule is there for a reason.
Image

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Post Number:#15  Postby Berlin » Wed Dec 21, 2016 12:47 am

How does one quantify a feeling? :-) You adjust the dampening of the rod until it "feels right" with the Trebuchet system. The harmonics of the rod feel best. the tip doesn't bounce and the rod feels crisp.

I would imagine Renee's rod would feel really bad when casting it. However, maybe because he's using a very thin running line the resulting wave imbalance in the rod and the lack of dampening on the tip would not have that much effect on the overall cast.

It looks like I have a lot of reading to do tonight to catch up on Merlin's work. I can't comment on it as I haven't read it yet.

My missus thinks we're watching xmas movies tonight. I can't wait to tell her that I cant because I have to read about the free-free unloading conditions for the butt node of a fly rod. I may not survive! :-)

In the mean time. I finally got my server sorted out and I'm currently uploading about 2000+ casting flies to it and once up I can start posting vids.
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Post Number:#16  Postby Merlin » Wed Dec 21, 2016 9:35 am

Hi Gordy

Yes, the comparison is in terms of frequency values, not tip speed. The Wiki definition of a node is a bit wrong to me, there must be a rotation around a node, and this does not apply to a clamp. Incidentally, if you consider a loose grip, then you may consider a virtual node behind the handle (this is what I read for tennis rackets). But let's keep things as simple as possible, the issue is the butt node for me. One can experiment it with a wiggle test.

I am preparing something for a specific thread abour rod & reel balance.

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Post Number:#17  Postby t.z. » Wed Dec 21, 2016 10:03 am

yeahhhhhh ... so cool to see you back on the board :-)

I always loved your humour and enthusiasm.
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Post Number:#18  Postby Berlin » Wed Dec 21, 2016 4:17 pm

Thanks TZ :-)

The weathers breaking here in Terrace and that means Steelheading. I may be missing for Thursday and Friday :-)
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Post Number:#19  Postby easterncaster » Thu Dec 22, 2016 3:19 am

small detail:

Looks like Renee is casting Angler's Fly distance (not Single-hand Fly distance) in the photo Gordy posted.

As you were...
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