Denis –
I have to admit a good bit of what you’ve laid out is a little over my head. Please forgive me if I’m asking questions that are off, but I’d suspect I’m not the only one feeling this way the past few days! I’m not so worried about ratings, etc right now as just grasping some of the concepts being put out there.

If possible, if there is a way to put some of this in simpler terms, I would really appreciate it (I’m not a math/physics person… so rather confused). I think it’s good to look at contrasting viewpoints because of the perspective it yields and I really want to understand this all – not just follow a set of directions.

“The cumulative effect of accelleration ( not in the static test ) and the deflection effect of the line tension on the guides ..............when the formulae were applied explained what was happening
or at least it did to me...............and especially when it came to spinning & casting lures rather than flies................as the accelleration in the cast is higher.”
Are you saying the blank accelerates more with spin/cast than a fly rod? Previously I was corrected by saying both fly and spin/cast throw are designed to throw weight… well seems to me you’re saying there is a difference. Is it in the way the blank loads? Is it the difference in a lightweight line with weight at the end vs. weight spread along the length of the blank? Seems to me the blanks should load and respond differently because of the way the weight is laid out.

Regarding guidetrain:
“Where you put the guidetrain.............forward' or 'rearward' and why, makes a significant difference. “
When you say rearward or forward, are you referring to spacing from the tip vs spacing from the butt? If so, what advantages does this have over real world applications - Casting vs fish fighting? Are the guides initially spaced with progressive loading, fully loading, etc?
How do are you adjusting/laying out guidetrain to find the best blend for a finished rod and maximizing blank potential? Are you using the formula presented to assess the best guide locations?
“cross section of the blank in the most structurally at risk locations enable qualitative & quantitative decisions on guidetrain location and progression to be made rather than 'black art' guessing”
How are you determining the most structurally at risk locations?

Again, I’m a little lost with the formulas and have a feeling some of what I am asking lies within those. Lots of questions in my mind. Thanks for your patience and time.

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Alex Dziengielewski Wrote:
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> Denis –
> I have to admit a good bit of what you’ve laid
> out is a little over my head. Please forgive me
> if I’m asking questions that are off, but I’d
> suspect I’m not the only one feeling this way
> the past few days! I’m not so worried about
> ratings, etc right now as just grasping some of
> the concepts being put out there.
>
> If possible, if there is a way to put some of this
> in simpler terms, I would really appreciate it
> (I’m not a math/physics person… so rather
> confused). I think it’s good to look at
> contrasting viewpoints because of the perspective
> it yields and I really want to understand this all
> – not just follow a set of directions.
>
> “The cumulative effect of accelleration ( not in
> the static test ) and the deflection effect of the
> line tension on the guides ..............when the
> formulae were applied explained what was happening
>
> or at least it did to me...............and
> especially when it came to spinning & casting
> lures rather than flies................as the
> accelleration in the cast is higher.”
> Are you saying the blank accelerates more with
> spin/cast than a fly rod? Previously I was
> corrected by saying both fly and spin/cast throw
> are designed to throw weight… well seems to me
> you’re saying there is a difference. Is it in
> the way the blank loads? Is it the difference in a
> lightweight line with weight at the end vs. weight
> spread along the length of the blank? Seems to me
> the blanks should load and respond differently
> because of the way the weight is laid out.

Alex the accelleration I am referring to there is the accelleration of the lure during the loading phase of the cast.
- typically a faster taper rod
- lure is compact as the loading weight
- vs flyline , which might be the same weight but has a lot more resistance & typically generates a slower rod rotation in the cast as a result.
- the key element being that the actual force on the rod tip and the resultant line tension is not just Wt its Wt times accelleration.
...........with a static test lacking that accelleration factor in the load

>
> Regarding guidetrain:
> “Where you put the
> guidetrain.............forward' or 'rearward' and
> why, makes a significant difference. “
> When you say rearward or forward, are you
> referring to spacing from the tip vs spacing from
> the butt? If so, what advantages does this have
> over real world applications - Casting vs fish
> fighting? Are the guides initially spaced with
> progressive loading, fully loading, etc?
> How do are you adjusting/laying out guidetrain to
> find the best blend for a finished rod and
> maximizing blank potential? Are you using the
> formula presented to assess the best guide
> locations?
my previous posts about rod dynamics identifies that the rod is a compromise of a bunch of individual parameters affecting the dynamic
and the rod typically has two different modes of use............casting & pulling.
The decision on the guidetrain design is driven by worstcase situation ( highest deflection ) of the two use scenarios. for most casting scenarios the pulling deflections are usually the more severe, and particularly so for the rear section of the blank.
some casting styles can be strongly tip deflection oriented and are replicated in highsticking type rod attitudes.
I often find that the rear section of the blank is under-deflected ( under stressed relative to its capability) and this is altered by moving the stripper forward............not rearward.
Guide spacing progression is optimised relative to the change in blank strength ( hoop cross-section ) down the rod.............so the rate of spacing increase from one guide to the next reflects the rate of change of the blank cross section ( OD and wall thickness ). and is optimised quite differently on a thin wall slow taper blank compared to a blank with a fast taper in OD and wall thickness.
When you look at the torque (bending moment) formulae you reralise that CCS type numbers are not the only thing you want to know about the blank to engineer its optimum build.
what you don't get from the manufaturer you have to find out for yourself.
> “cross section of the blank in the most
> structurally at risk locations enable qualitative
> & quantitative decisions on guidetrain location
> and progression to be made rather than 'black art'
> guessing”
> How are you determining the most structurally at
> risk locations?
In general terms the highest torque ( bending moment) is at the midpoint of a guide pair)
it is exactly there for a parallel tube, but forward of there for a tapered tube................midpoint is a good guess without blank cross-section details.
without those details the stress is estimated from torque at that point of the rod length divided by the ( OD / 2 )of the blank at the same point.
Simplistic estimation of maximum stress without the blank details, but gets you in the ballpark for comparative purposes.
>
> Again, I’m a little lost with the formulas and
> have a feeling some of what I am asking lies
> within those. Lots of questions in my mind. Thanks
> for your patience and time.

No worries Alex
Patience I have.............time can be an issue.

Thanks Denis - that really helped me understand some parts. Time to digest!

"the rate of spacing increase from one guide to the next reflects the rate of change of the blank cross section ( OD and wall thickness ). and is optimised quite differently on a thin wall slow taper blank compared to a blank with a fast taper in OD and wall thickness."

Wouldn't the only way to determine this involve chopping up a particular blank and measuring at various points, especially considering the blank could vary in thickness throughout it's length?

"the stress is estimated from torque at that point of the rod length divided by the ( OD / 2 )of the blank at the same point."

Just using where the rod reel seat may be - use 10" from butt on an 84" rod. Would you use 74" or 10"? OD at that measurement is .4". So I get two different numbers - 50 (10") or 185 (74") - how is that defined? I understand that details the stress, but what quantity is that (ft/lbs, psi, distance of flex, etc)?

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I seem to want to ask if maybe someone isn't having a bit of fun at the expense of the board users here?

Denis,
I've a few spreadsheets I would like to pass on to you.
One on mathematic analysis of rod blanks and one on dynamic guide placement.
These have evolved over the last several years and maybe you can see some avenues I've missed.
Do you have a software app for opening ?
Would you be inclined to look them over and see if it turns on any lights ?
Only in the pursuit of advancing my hobby.
What is the best way to handle this ?

Rob
No its basic physics............you might not have considered it in rodbuilding in this aspect, but its there
critique of the relevance of the physics welcome
inferring its a joke is demeaning genuine interest in rod building on both your behalf and mine.

I have not seen any negative critique of the physical principles of other issues I have posted about rod dynamics sharing with my fellow rodbuilders
knowledge evolves over time............whether you choose to use it .............is up to you
some of it is simple
some of it is complex
some of it we have to toss around and refine............because it befuddles you in one big bite.

Alex
In the context of using just where the reel seat is at 10" from the butt on an 84" rod
this assumes you are gripping the rod at the reelseat and not infront of the reelseat.

i)
the effective lever length of the tip load is not 84-10 = 74" ( for an 84" long rod )
you have to measure the direct distance from the tip of the deflected rod to the front of the reelseat
( the front of the reel seat will be the hinge point of the torque/bending moment. )
the effective lever length of the deflected rod at the front of the reelseat will be significantly less than length of the undeflected rod to the same point
Have a look at the diagrams again and it should start to make sense.
The first diagram is the one of relevance in this situation.

ii)
the bending moment of the deflected rod at that point is acting at a notional pivot in the centre of the blank .
the lever length that bending moment is acting at is the distance from centre of the hoop of blank
iii)
the units in the calculation you are doing is simply ;-
force ( lbs) X one distance( ins ) =ins.lbs divided by another distance = lbs force of compression on the underside of the blank at that point.
iv)
My last post to you identifies that this calculation using only knowledge of rod OD is an estimation of the stress for comparative purposes in different locations down a blank.
Yes, the text of my posts identifies that the compression force is spread over the cross section of the blank at the point you are assessing the total torque/bending moment
Yes you are correct in confirming the difficulty in determining wall thickness at that point.
My posts identified that ideally the information from the manufacturer that a builder would like to have about the blank is not just CCS data to select the blank but also the taper profile of the wall of the blank so you can optimise the build of the blank.
v)
The calculations you are making without knowledge of the modulus of that blank or the wall thickness of the blank is simply a total compression force equivalent at the OD of the blank
it is not the actual stress on the blank.
a) unless the rod is a really heavy wall jigging type rod and more of the trout./bass type a couple of significant factors in the stress comparison equation become fairly irrellevant.
b) the blank will be single modulus in most cases so you don't need to know about the modulus of the material its made from to do a detailed stress calculation
c) the wall will be thin and less significant as an error in the estimation compared to a detailed stress calculation.
d) the torque / bending moment at the hoop of blank you are assessing its impact on is actually spread over the entire hoop of that blank.
the maths to do this is rather complicated and you don't have the information available to you so you are generating a comparative estimate that uses the major parameters of relevance.
e) the errors in estimating the relative force at play from the bending moment in this estimation process understates the relative stress force for larger diameter hoop compared to smaller diameter hoop ............so the conclusions you draw from your analysis are safe as the smaller rod sections are the ones most at risk.

To be sure of the manipulations you are doing, post an image of your deflected rod and post the link..........together with the length from the front of the reelseat to the butt and the vertical load .
We can then work thru the calculations together as an exercise. I have a program from a collaborator on this work that will enable me to interrogate the info as we go.
I am happy to do this as a "one off " exercise with you.