Rod evaluations and comparisons - a peek

[Peter Patricelli]

About 6 months ago I promised to do rod action and flexion evaluations during ACTUAL casting conditions. Here is an interesting peek at some results.

 

In photo #1 3 rods are overlaid/compared in as identical conditions as I can make them during actual casting. All 3 are 9', 8 wt, 4 piece, cast with an identical #8 line with a fully loaded (my maximum) single handed stroke, no haul (the shutter trigger was in my left hand...and I wanted to keep conditions as simple and identical as possible.

 

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Eventually I will complete this on 6 8 wts.

 

The good news is that, so far, the casting flexions reflect nearly identical characteristics to a static deflection data set up in which I can (and have already) measure and control the weight. The reason this is important is demonstrated by picture #2.

 

http://www.stripersonline.com/image/id/1692753/width/1000/height/500]

 

Overlaid on the rod flexion is a 1" pegboard wall I installed in my garage for rod measurements. By precise measurement of the flexion IN CASTING I can work backward to the weight equivalent to create the same flexion....which is a measurement of the force of my casting stroke. Calculating that force lets me compare and double check the photos for validity AND tell me what weight deflection on a static rod will re-create the flexion curve (and shortening) that will occur during actual casting.

 

Note that rod deflection in some rods approximates and even exceeds 50% of rod length.

 

More to come.

 

Peter Patricelli

[Spigola]

Peter, those are great. Thank you.

[crunch]

Very interesting Peter! That much bend and without haul I would say that the line is way too heavy for your casting stroke.

 

If that pegboard has one feet between pegs it looks like there is scale difference between photos.

[JonC]

Peter,

 

This could be very interesting, I'm wondering what you could do with some of the new video features and the ability to cut out stills?

 

Upon seeing these photos I can't help but wonder what a side by side look at some other people's casting styles at maximum load would show?

 

The other really important factor is time, how fast does the rod come up to straight after the stop, that acceleration of the line is what translates to the actual power available in the rod. This is where the video might tell a lot because you could see the whole casting stroke in time.

 

Good start anyway, we may all learn something about casting dynamics even if the rod stuff is inconclusive.

 

JC

[Andrew S.]

Neat idea.

 

With a tripod and iMovie software, you could probably very easily select stills or even superimpose multiple video clips on top of each other that would illustrate the differences in rods.

 

 

[crunch]

Actually haul should start around that point of casting stroke and perhaps even later.

 

TiCR seems to have significantly stiffer butt section than S4s and GII. How much difference there are in static weights?

[Peter Patricelli]

Crunch,

Let me see if I can connect the dots. First, 6 months ago you were the one who refused to accept that real-life casting loads in SW rods were way over the 30% "common cents" evaluation system. Three months ago you stated in another thread that "no one ever had more than 30' of 'shoot'. When I countered that I routinely shot 50-60 feet you basically called me a liar and implied that was physically impossible. (Ask Steve S, he spent a week casting next to me). This week when I stated (and can easily prove) that with my fiberglass rod I can cast within 95% of the same distance I can get with an equivalent graphite rod...you disagreed since YOU have a fall off from 80' to 60' with fiberglass. Now you say" I would say that the line is way too heavy for your casting stroke."

 

An 8 wt head is "way too heavy for your casting stroke" on 3 8 wt rods????? That is completely ridiculous and again shows that you have no basic understanding of a serious, efficient, fully loaded casting stroke. Maybe it is your LACK of understanding that results in only 30' of shoot for you. Has it occured to you that my loading of the rod IS the reason I can cast routinely over 100' and routinely shoot 50-60 feet....and now you want to find FAULT with that?? In my opinion you should spend way less time arguing with people who are seriously better casters than you are and more time listening and learning....and maybe your casting will improve.

 

I have, for the last 6 months largely ignored your posts and refused to get into a casting discussion with you because those discussions go nowhere. You are dug in clinging to a wimpy, incorrect concept of casting that only gives you an excuse for mediocre results. I may very well ignore your posts in the future unless I see some willingness to LEARN from a presented, successful reality.

 

Jon and Andrew, funny, I had thought of using video for another purpose but never thought of extracting stills. Perhaps if I had a different video camera since my GoPro fisheye lens causes way too much distortion. I want to get as precise measurements as possible. Video WOULD allow 30/sec analysis....see below.

 

Jon, the "rod stuff" is far from inconclusive. Actually it is a treasure-trove. I have a lot more info already and much more testing to do. I presented those pics at this time specifically to show what a fully and correctly loaded SW rod really looks like....and why we must re-think old, inappropriate stuff from light, short-casting trout fishing, AND to make the point about the difference in rod shortening given differences in "taper". A real, in depth discussion of that issue I am going to leave for the future when I have completed my testing.

 

What I really hoped to get has so far eluded me, rapid-fire strobe pics that allow point by point segmental analysis of the accelerations occuring through the stroke. My Nikon D2X will only fire at 8 fps. I have 4 strobes that will fire at 20/sec BUT I cannot synch all the flashes between the 4 of them once initiated. I tried. I have to operate either off of one single strobe OR find an affordable strobe synching timer. Strobe slaves don't work either...I tried.

 

What these photos, together with my static testing, really do is give me a ball park working figure for my arm strength, "F" in the equation F=Mass x Acceleration. And that F, for purposes of distance casting, is largely a constant, limited maximum. The treasure trove is how, applying that F to rods statically can predict the flexion curve of the rod in actual casting.....but even more.....how shortened the rod is at that point AND HOW MUCH STIFFNESS OR FLEXION THERE IS AT THAT POINT WHEN THE HAUL IS ADDED!!

 

Peter Patricelli

 

[JonC]

Peter,

Standing by.

Crunch,

At the point pictured in the cast the haul should be complete, it's right at the stopping point.

Jon

[Steve Schullery]

Peter,

 

Neat photos, but, like JonC, I'm standing by to see where you're going with this. I'm afraid I sense a physics quagmire in our future.

 

One concern I have about equating static and dynamic bending forces is that the bare rod, with no line attached, when waggled in the air will bend a fair bit due to air resistance. So, for a given amount of rod bend, more line weight will be required statically than dynamically. I believe that the air resistance, and resultant bending, is a sensitive function of rod diameter, which may further complicate comparison of your fiberglass and graphite rods.

 

Another thing that wonders me is whether the relevant lever length is going to be the shortest vertical distance between the line the fly line is traveling in and the handle, or the instantaneous chord length from the handle to the rod tip that is actually propelling the line. It's my inability to confidently answer little puzzles like that that had me become a physical chemist rather than a real physicist.

 

Regarding your casting and shooting expertise, I will totally vouch for you. In fact, I remember feeling surrounding by Oregonians all of whom made my efforts look rather pathetic! I was reduced to doing what I could to compensate with a good fly.

 

Steve

[Jim DE]

Some interesting work there Peter.... Using scientific methods to quantify real life on the water results. Now, there's a novel idea for fly fishing board discussions ;) . I have to watch this play out!

[Mike Oliver]

Bloody hell Peter. My head hurts already from way too much retcina wine drunk alongside my wife on vacation in Greece. And now you hoist this on me/us.

 

Not sure what your end game plan is here truth is as I am too thick to figure when sober to I fear. Me I am still struggling as to what really is a straight line rod path with a lever that is progressively bending as more load is applied through a decent cast and therefore its height is constantly getting less so how does it go in a straight line.?

 

Another wine please Waiter.

 

Mike

[HL]

Peter,

 

One concern I have about equating static and dynamic bending forces is that the bare rod, with no line attached, when waggled in the air will bend a fair bit due to air resistance.

 

Won't inertia figure in here - maybe even more than air resistance??

Herb

[JonC]

Steve,

First, the length of the lever has to be from the handle to the nearest point in the line path, the tip is totally out of action, it might as well be part of the line.

Second, Herb is right, inertia is what bends the rod, if you swing the rod around in a circle at a constant speed you will see how much air resistance will bend the rod. Try not to get dizzy whilst experimenting.;-)

JC

[Steve Schullery]

Peter,

 

One concern I have about equating static and dynamic bending forces is that the bare rod, with no line attached, when waggled in the air will bend a fair bit due to air resistance.

 

Won't inertia figure in here - maybe even more than air resistance??

Herb

 

As we tentatively wade about in the shallows of the quagmire ...

 

Inertia of the rod certainly matters, but I'm thinking that--depending on exactly what point Peter winds up trying to make--it will be swept into the pile of rod characteristics, like the elastic modulus of the material, that wind up being combined into a statement such as "this is an 8 wt rod". My hunch is that for my old steel casting rod and perhaps for bamboo rods, inertia may be more important than air resistance, but for graphite it's probably less important. Don't know about fiberglass.

 

Here (from Wikipedia) is the equation that defines Bending Stiffness:

 

 

This shows how inertia would figure in IF the rod ("beam") were of uniform cross section rather than tapered and IF the rod were of uniform composition (modulus) rather than, for example, having variable fiber/binder proportions over its length or, worse, a boron butt section or somesuch. For the non-calculus persons, that funny fraction with all of the "d's" is a way to assign a number to sharpness of curvature. Another assumption is that the curvature is uniform. As the cross-section and possibly the composition and definitely the curvature vary along the length of a fly rod, so would the stiffness vary--One hardly needs an equation to tell you that but it does highlight how devilish it might be to assign an "overall stiffness" to a rod.

 

Finally, notice that the time variable does not enter into the equation, although the stiffness parameter can certainly be featured in other equations dealing with dynamics. That's where air resistance would come in. Too bad Peter couldn't get in on the last shuttle ride and do this study in a vacuum.

 

Steve

 

 

 

[Steve Schullery]

Steve,

... the tip is totally out of action, it might as well be part of the line. ... JC

 

Jon,

 

Maybe so; it certainly sounds good if you say it fast. But, I'm not so sure. If "the tip is totally out of action", why does which direction it's heading at the moment-of-stop and how much it's bouncing around matter so much for the quality of the cast? Does casting a very stiff short rod really feel like casting a long limber rod?

 

Steve