I am now in consideration of improvements for designing a rod by manipulating its deflection.

If you have good idea about this, please advise me.

I have one rod (a known classic taper or a sample taper) which now shows its deflection as a calculated result.

I can have a degree of deflection which is the angle made between butt end and tip top (like a bow and its string).

One method of designing a deflection is this angle, I am thinking. This is related to how deeply the rod would deflect in a certain assumptions.

I can manipulate the angle when I design a rod, which is to be related to "fast", "medium" or "slow".  Then if the deflection design is fixed, I can get a corresponding set of dimension, that is taper.

But!!!  One angle of deflection can be made in various ways. By linear (straight) taper, by bumping several points with straight sections in between, flexing at butt with less flexing at mid or tip, flexing mid with less flexing butt and mid,  entire rod would evenly flexed, etc..

What method could you consider practical next in trying to implement such variations into the target deflection as an input specification?

Example:

Specifying a section in from-to form, then specify like straight, a little flex, mid flex, much flex. Specifying a percent to increase/decrease flex degrees over an entire part of sections evenly. Specifying a specific point to flex more or less. Have a set of patterns of deflection, parabolic, progressive, crescent and apply it totally. Specify 1" flex degree number one by one.

Of-course we can do these along with looking at the corresponding stress curve by calculation.   This is a repeated work.

It is very much appreciated if your have any idea. Which helps me very much.  (Max Satoh)

In this discussion I think we all have decided that NO two casters are alike and therefore no two guys will cast the same rod to the same effect.  So, we are left with trying to STANDARDIZE more variables so we can begin a "ball park" design.  The Garrison method has made assumptions so that a stress analysis could be accomplished but only after a set of dimensions was decided, or conversely, a set of dimensions could be derived after a stress curve was determined.  But designing a stress curve for a particular application is not an easy, intuitive project without A LOT of experience with many different rods.

I think the challenge is to define the Quarter Circle (or less) deflection shapes for fast, medium, and slow tapers. This could be done by a panel of respected casters evaluating what are considered to be good examples of each class.  Then, measure the tangent angle at some increment along the QC deflection curves of each of the rods tested.  The change in slope along the curve would define the shape and hopefully be similar in each class.  If a change-of-slope graph consistently defined a fast, medium or slow taper then it could be used to back-calculate stress and cross section.

So then you could TRY to determine if a prospective customer needs or wants a fast, medium, or slow rod to suit his style.  Maybe then you come close to satisfying him with a rod design.

But you are still hoping  to have consistent  quality bamboo, heat-treating, fabrication techniques, glues, varnishes, etc, etc. from maker to maker!  (Al Baldauski)

I've been sitting this one out (except for reading and attempting to digest most of it) but now I have to toss in a new thought.

As I understand it, Robin's "quarter circle" doesn't truly describe a quarter-circular arc, it is a curve defined by the fact the the butt is pointing skyward and the tip is horizontal (for example). Then the two tangents would intersect at right angles. If my interpretation is correct, then the faster the rod, the farther away from the butt the tangents would intersect. I don't think you'd need anything more than to measure that distance UP the (imaginarily - still vertical) line of the rod's butt. You can get those tans to be at 90 degrees and have the the top 6" bend over, or the top 3 FEET contributing. The more rod that goes into the bend, the farther down the action starts, the lower the tip with respect to the level of the butt and the slower the rod, no?

This may be useless to indicate whether the rod is linear of parabolic or a club (TYPES of action) but it SHOULD tell whether it's faster or slower.

You'd have to reckon the distance with respect to the rod's length (4' up a 6 footer is faster than 4' up a 9 footer), but that could be accomplished by using a %age of rod-length, couldn't it?

Bill Fink, that would take the Common Cents idea beyond measuring the angle at a certain position to continuing the bend till the tip points at the floor, then seeing from the tangent intersection where the rod BEGAN to bend, relatively.  (Art Port)

A very valid approach I think but it may be difficult to define the point you measure down the rod to the point where bending starts as this will involve  a degree of subjectivity.

An alternative that may also achieve what I think you are after would be to do the quarter circle load test (in the UK the load that is needed to cause this 90 degree  rotation is called the rods test curve) and measure the actual deflection of the tip at 90 away from a line passing through the butt.  This dimension will be more for a through action rod and less for a tip actioned rod.

You could then characterize a rod  by the ratio between its right angle deflection and its length.  So a rod with a ratio of one would have described a genuine quarter circle and be a real through action whereas a rod with a ratio less than one would be a faster action, smaller the ratio the faster the rod.

Again this is not all the story as a rod that bends throughout its length may give the same answer as one that bent primarily at the butt but the method would certainly identify the more tip actioned tapers quite well.

Any takers?  (Gary Marshall)

Yes, I do think it's an after-the-fact thing, Jerry. I never considered it to be anything else. You HAVE a rod, and you want to describe in an objective manner to either copy it or make it faster  or  slower.  I  think  that  must've  been  the way the seat-of-their-pants guys did it too, no? Make one, like it or dislike it, make another.

But Gary, I don't think you need to measure where the rod BEGINS to bend, since the point I'm talking about would be very precise - where the two perpendicular (OK, orthogonal for you math/science guys) tangents meet. The distance from that point to the butt plate of the rod could be measured to the 32nd of the inch or even more accurately.

If I'm not clear, consider fixing the rod so it's vertical and drawing a straight, vertical line from the butt upwards. Then apply force till the tip POINTS horizontally. Now draw a level line from that tip top's position back to intersect the vertical. Now the tangents of the two ends will be crossing at right angles somewhere directly above the butt. The height of that point above the butt should tell how far down into the rod the curve begins, but just relatively to that measure of other rods. I can see where one type of rod might begin to bend and then continue bending (faster and faster) to the tiptop, and another might begin to bend,  sort of straighten out, then resume bending. That last example is probably what a para would if, if I understand paras.

Lemme know if I make sense AND if you agree or disagree!  (Art Port)

With you now, what you describe would give a useful parameter for rod description and can readily be measured as you say.  Being able to express the result as a percentage of rod length appeals.

It was actually clear on your original post, or would have been if I had read it properly!  (Gary Marshall)

This QC thing is very interesting, I would think if you had a database of several thousand rods whose deflections were measured you would know something. The other variable is the weight it takes to get the deflection. The CC system seems to make more sense. But they are not trying to make some larger assumption about the rod (speed) but line size.

The other fallacy I think in this QC issue is it just shows 1 static point in a rods deflection and trout rods bend more than 90 degrees.

I think Robin’s findings may involve the type of rods he is measuring.  (Jerry Foster)

On the contrary, the CC system DOES try to assess the speed, by measuring the angle at which the tiptop is inclined to the ground when it deflects that distance (I forget what it is now, but think it was 1/3 the rod's length) CC prescribes from level.

I found, when doing the grunt work for Bill Fink in the Catskills that the CC part actually had little reference to the line weights of the rods tested - I think Tom Smithwick threw up his hands and said "That's it, I'm gone" when the CC said that a Garrison 212 was a 3 wt at an earlier test at Bills home! But the angle (I think it's called the "action angle") seemed to predict pretty well what the builder considered the rod to be!

I'd have to see that they bend beyond 90 in photos to be sure, but I guess you're right that when the butt is slanted forward at the end of the forward cast, just before the stop, the tiptop is pointed rearward beyond the 90 deg point (but not necessarily below horizontal).

I suspect though, that while some may not want to bend all of 90 and others may grudgingly go beyond, it's as reasonable a place as any other to COMPARE lots of rods, one to another.  (Art Port)

I have been slow to comment on this QC thing.  But I think people are paying it too much attention, while all the while it is just a construct in the mind of Robin Haywood. In practice, it could be 90 degrees or 20 degrees, or 37 degrees for that matter - you just need a constant parameter.

I am inclined to think that rod design is a bit like that.  One must not get obsessive about small details, not, at least, at every stage.

I have enjoyed this discussion, am still enjoying it, and hope it goes on as a core thread.  But I am not certain even now that I quite understand the implications of Garrison's stress curves.  As an analysis tool, OK, I can see that;  but I have my serious reservations about their pertinence in rod design.  There seems to me to be a fair bit of "begging the question" when we try to use them for that.

The reason that Ferraris are different from Maseratis and Mercedes Benz is that perfectly sound design principles , applied rigorously by competent designers, can still produce very different end products.  (Peter McKean)