Mornin' folks,
Recently there have been some discussions on this board regarding the validity of the mult-modulus design, mainly regarding the CTS blanks that I am now carrying. Emory made a post last week stating that it would be nice to hear from some of the manufacturers regarding some of the more specific technical information that goes into these lay-ups. Well, I proposed many of Emory's questions to Stephen Pratt at CTS, and am at his approval providing the information below. However I'd like to add something first: If for some reason you disagree with the Stephen, and the CTS philiosphy, I will expect that all responses will be polite, considerate and not in anyway condescending and derogatory towards Stephen or CTS. After all, Stephen has gone out of his way to answer these questions for all of us...something I haven't seen anyone of the other manufacturers step up to the plate and do on a public forum. I think this says a lot about the guys at CTS....keep that in mind when your making future blank purchases.

Emory: Several manufacturers have introduced blanks that incorporate graphite material with different modulus of elasticity in different sections of the blank. The couple that I have talked to are using a higher modulus toward the butt of the blank and lower modulus toward the tip. I have thought about this a little and would be very interested in the thoughts of others. My thoughts go like this. Most rod breakage tends to be in the tip section so a lower modulus material toward the tip will make the blank tougher and therefore reduce breakage.

Stephen: That is Correct.


Emory: However, a rods sensitivity is more a function of the distribution of the weight than the actual total weight and the effect of added weight increases dramatically as it is added toward the tip.

Stephen: Probably not entirely true. A larger diameter glass rod of the same stiffness and weight distribution as that of a carbon blank will not be as sensitive as the carbon blank.


Emory: So this approach will result in a blank that is more durable than a blank made entirely of high modulus material, is slightly less durable than a blank made entirely of lower modulus material, is only slightly more sensitive than a blank made entirely of the lower modulus material and not nearly as sensitive as a blank made entirely of the higher modulus material. Therefore if these blanks are priced like the lower modulus blanks then they make sense but if they are priced like the higher modulus blanks they do not make much sense.


Stephen: There is a little more at play than simply weight and modulus. We have factors which influence the action and feel of the blank such as wall thickness, weight distribution and diameter. Specific lock up points will create different loading patterns in the blank.



Emory: This approach may make a bit more sense if only a little of the lower modulus material is used just in the tip section in very fast action blanks and less sense in blanks with slower actions.


Stephen: That is Correct.


Emory: I think that the comparisons of other blanks to the CTS is a valid comparison. Multi-modulus construction is actually becoming quite common and in fact a number of the blanks from several manufacturers are using it. It is not a big secret. And in fact some of the Rainshadow blanks also are multi-modulus. It would also be nice to know how much of each material is used and exactly where it starts and stops in the blank.

Stephen: You are correct, Multi-Modulus has been around for a long time. But, in the past some manufacturers have placed a single strand of boron filament in their blank in order to claim that the rod is a boron composite. Many manufactures will place a token amount of high modulus material into a blank in order to claim it is a high modulus blank. The plain fact is, High modulus carbon is around 3 to 4 times the price of standard modulus carbon. To put enough to really make a difference in an asian imported rod is well out of a lot of the price sensitive Asian sourced blanks scope. The basic construction method currently for a multi modulus blank is to lay the first flag, which travels the length of the rod, on first. Then a second shorter flag on top and then in some cases a third and forth flag. Generally each progressively getting shorter. In most cases the final shortest flag will be the higher modulus material.
The CTS MRT (modulus replacement technology) is COMPLETELY different. We do not have any flags running the length of the rod. The lay up we employ, allows us to solely have a single modulus at the tip area, a different modulus through the mid area and then a total different modulus at the butt area. There is no mixed modulus at the butt area as in standard lay up procedures explained, and our rods can claim to be entirely 100% high modulus in the bottom half of the blank. In most cases our Elite tournament range is made up of 60% high modulus material. That’s not intermediate modulus -44msi (which is what a lot of manufactures claim their rods to be) but 100% 57msi material. You only have to compare our blank diameter, power and feel to any other blank on the market to realize these blanks are the "good oil".
As far as the helical construction is concerned, when the fiber is at an angle relative to lenthwise on the blank, as is the case with helical construction, the effective modulus drops very quickly. Our helical construction places the fibers very close to the 90 degree hoop angle. (picture on website is as dramatization for illustrative purposes only) It is soley to create hoop strength and hoop stiffness’. Not torsional rigidity, Not longitudinal stiffness.

Emory: At 45 degrees the modulus is effectively cut in half.

Stephen: Actually, it’s a lot more than that.


Emory: However, the strain energy or toughness does not increase by alligning the fiber at an angle as it would increase if a lower modulus fiber were used because the modulus is a property of the material itself.

Stephen: Emory’s not totally clear here, what he’s saying is that by placing a higher modulus fiber on an angle you will not increase its strain rate to the same strain rate of a low mod fiber tensioned in the 0 degree direction. This is correct. This is a mute point and not really applicable to this post. When the fiber is at an angle the hoop strength or the strength at 90 degrees, the strength against torque and crush or sheer does increase but that is what the scrim in a blank is for. Scrim plays no part in torsion. It’s sole purpose is for hoop strength.The fiber in the scrim, usually glass which has about 4 times the strain energy or toughness of graphite, strain for glass is around 4 to 5%, High strength std modulus carbon around 2.1% so it’s more like 2 times.
To make things even more complicated, placing a kink in a fiber such as weaving it into a scrim material, will reduce it’s strength by around 40%. Try ripping a linen shirt (flax fiber). Not too hard, but try ripping a piece of flax where the fibers are all straight with no kinks caused by weaving.


Emory: You could accomplish the same thing that helical construction accomplishes by increasing the amount of fiber in the scrim a little with the added advantage over helical construction that the strain energy or toughness would increase.


Stephen: Problem here is 50% of the scrim fiber is traveling along the rod, doing nothing for the hoop strength and adding nothing to the longitudinal strength. The kinking of the scrim fiber arguably reduces the strain rate close to that of an un-kinked uni directional carbon fiber. 5% x 0.6 =3%. High Strength std mod carbon is 2.1% Then factor in density (glass = 2540, carbon = 1800) and we get a relative specific strain rate (strain over weight) of 1.18 :1.16. But remember, half of the scrim fiber is running in the wrong direction so that pushes the glass scrim weight to double that of carbon to achieve the same hoop strength. We also need to take into account the 40% resin content (over a tight knit uni directional carbon’s 33%) that the scrim needs due to it’s weave porosity (that’s 20% more resin) and we’re getting beyond 2 x the weight.


Emory: But the problem with increasing the fiber content in the scrim or the amount of scrim is that the blanks efficiency or the stiffness divided by the weight drops.


Stephen: Correct. In most scrim based materials, the glass scrim runs at between 16-24% of the overall weight. You could indeed create the same amount of hoop strength of our carbon helical core with scrim. However on the very rough calculations above we would have to double the weight of glass over carbon to achieve this. But here’s the crunch. We’re only talking strength here. Not stiffness. Carbon is double the stiffness of glass, 3 x if we take weight into consideration. A stiffer cross-sectional area in the form of hoop will give a livelier feeling blank that does not begin to ovalise /give way under increasing pressure.


Emory: Again I do not think that this is a big secret or is proprietary to any manufacturer. In fact, if it were not for the above problem I think that probably most blank manufacturers would be using the helical design.

Stephen: Creating our helical rods is a lot of work, engineering and quality control. It’s a huge amount easier to roll up a scrim blank than a helical blank. We also do cheaper scrim based blanks. However their strength, weight and feel does not compare.



Emory: Unless I am very wrong the CTS blank is going to be heavier and have a lower resonant frequency then a blank with comparable CCS measurements from either Rainshadow or Lamiglass.

Stephen: Based on the above points I can not agree. But the proof is in the pudding so to speak and with out exception our customers claim our blanks are the most responsive, nimble blanks they have had. Our anglers eat some of the best tasting "pudding" around.


Emory: The CTS blanks may be beautiful blanks.......

Stephen: That is Correct (haha)

Emory: but frankly I think that the helical construction is a marketing ploy


Stephen: CTS is not a marketing gimmicks company. "Frankly" using the helical construction is a pain in the butt to produce, quality control and design. I would not for a minute continue to produce blanks using it if scrim was better. We would make a cheaper scrim based blank, keep the price the same and put that money into marketing.


Emory: Because it seems to me that the advantages that it offers could be achieved several other ways with less disadvantages

Stephen: Hopefully someone will let me know this when he finds out. We spend a huge amount of time researching this.


Emory: There are a number of blank manufacturers using several different modulus graphite in their blank construction. Neither CTS nor anyone else can spiral the fibers up a blank, as opposed to running them straight up the blank, without it resulting in higher weight for a given stiffness unless they have rewritten the laws of physics that I am familiar with.

Stephen: As above, the helical's sole purpose is for hoop strength and hoop stuffiness not longitudinal strength or stiffness. Not many people will argue that glass is superior to carbon. Unless you’re talking impact resistance, cost or wanting something to bend a long way.


So there you have it folks.....the last word on Multi-Modulus and helical layup? I doubt it! I am sure many of you engineer types will have differing views....please express them respectfully.

I say, at least we have a manf. who is willing to share the deatils! Thanks to Emory for providing some questions that enlightened me to some things I had not thought about.


Andy Dear
Lamar

Andy - does CTS have any "heavier" 20-80# Multi-mod, helical, or whatever blanks I can build? Personally I could care less about all that, give mea blank, let me fish it, I'll tell you if it's worth the money I paid for it.

I, for one, would like to thank Andy & Steven for the great post (which I copied and saved). I actually understood enough of it to know that I want to try one of their blanks!!

Just the fact that Steven provided such detailed answers/info to us, makes me want to try them. It's refreshing to see a manufacturer respond to questions with solid info instead of hype



Mike (Southgate, MI)
If I don't want to, I don't have to and nobody can make me (except my wife) cuz I'm RETIRED!!

Excellent discussion! I look forward to seeing the continuation and even have more interest in seeing the CC numbers for the CTS blanks begin to show up on the CCS site. I hope those of you that have the opportunity to take CC readings will begin to post them there.

Stan Grace
Helena, MT
"Our best is none too good"

Andy,
Bless Stephens heart and thank him for his responses. The discussion could really be a very, very interesting one but I think that it is probably not practical to try to do it through a third party.
Stepen makes several good points about the blank construction as opposed to the blank material
but there are several areas where I do not think that Stepen understood what I said or where we do not agree. For example, and central to several of the points is, I did not say strain rate, I said, or at least I thought that I said, strain energy. Strain energy is the area under the modulus of elasticity curve and is what determines how much energy a material can absord or how tough it is. Strain energy drops in direct proportion to the increase in modulus. Strain energy or toughness in a material can only be increased by increasing the tensile strength or LOWERING the modulus (larger area under the curve) of the material itself. When we talk about modulus it is actually tensile modulus that we are normally referring to. When a material is wrapped on a mandrel this tensile modulus is at the angle that the material is wrapped on the mandrel. If it is wrapped at an angle and does not go straight up the blank the hoop strength, strength around the blank or 90 degrees from straight up the blank, will increase in proportion to this angle as Stephan points out but it will at the same time drop directly in proportional to the angle in the other axis or straight up the blank.
Anyway Andy please thank him for his candid response and tell him that I would love to discuss this with him directly someday.

Andy,
I went over your responses from Stepen again and I do not really think there is really much disagreement between us. He makes the point a couple of times that the issues are not as simple as I stated earlier and I completely agree. My focus and what I said may have been more on the material while his focus was naturally more on the construction or the application of the material. For example, his comments about diameter and wall thickness with which I completely agree. Had I been talking to him directly I think there would have been even less disagreement. But there is one area where I think that he may have also over-simplified and that is his statement about scrim and its strength and allignment. There are a number of different types of scrim and it can and is applied several different ways each with different trade offs.
Again, thank him.

Stephen and CTS will be in Charlotte for the National Rod Builders Show in February. He'll have his blanks on display and this will be a great opportunity for interested builders to pick one up and give it a shake, or to discuss the technology with factory personel.



............

Emory,
In stephen's treatise h does say "MOST" scrin mabed materials....not ALL scrim based materials.


Andy

So I'm a bit confused by this statement

Emory: At 45 degrees the modulus is effectively cut in half.

Stephen: Actually, it’s a lot more than that.


Stephen or Emory, does this mean that the 'angle' is more than 45 degrees, or that the modulus decreases by more than 50% when at a 45 degree angle. In one case it's an answer to a design choice (helical wrap is near 90 degrees comment), in the other it opens a whole other set of questions regarding modulus.

If it is the case where modulus decreases more than 50% at 45 degrees, does anyone have the mathmatical description of this? I'm trying to figure it out, but the naive way of doing this would be do something like:

m = module of material

x = angle of material

Naive forumla would be m * cos(x) (assuming that modulus is highest when fibers are placed in parallel)

Of course this falls apart when x >= 90 degrees as it goes negative.

in order to compensate you could do the root mean squared or something but then you end up with issues at the values at 45 degrees

squareroot(x * square(cos(x))

If anyone has further info on this I would *really* love to hear about it!

-- Cheers
-- James

The structure's modulus would drop by more than half if the fiber is put in 45 degrees rather than completely linear.

............

James,
I think that you are trying to make it more complicated than it is. If the fibers are running straight up the blank than all of the modulus is realized on the axis running up the rod and none of the modulus is contributing to hoop strength or on an axis that is 90 degree out. If the fibers are all wrapping around the blank at 90 degrees to the length of the blank then all of the modulus is contributing to hoop strength and none to the length or stiffness of the blank. Half way in between is 45 degrees so half is contributing to hoop strength and half to the blank stiffness.
It is not quite this simple because what actually contributes to hoop strength is mostly the fiber under compression not under tension and the modulus under compression is lower than under tension but that it an additional complication that is not necessary to consider when looking at the effective modulus of the blank on the long axis and I do not think that is what Stephen was referring to.

Emory Harry Wrote:
-------------------------------------------------------
> James,
> I think that you are trying to make it more
> complicated than it is.

I tend to do that (make things more complex than need be), but I figured this technical discussion was a good way to find out how things *really* worked rather than just assuming a rule of thumb was how rods were engineered ;) If this is something that is too complex or time consuming to discuss online, then I totally understand this :) But if there are specific docs that can be referenced to find out more about this subject that would be awesome :)

> If the fibers are running
> straight up the blank than all of the modulus is
> realized on the axis running up the rod and none
> of the modulus is contributing to hoop strength or
> on an axis that is 90 degree out. If the fibers
> are all wrapping around the blank at 90 degrees to
> the length of the blank then all of the modulus is
> contributing to hoop strength and none to the
> length or stiffness of the blank. Half way in
> between is 45 degrees so half is contributing to
> hoop strength and half to the blank stiffness.

Yeah, that's the pretty basic description, and that would have worked, but it was mentioned by the CTS guy (forgot his name) that it wasn't really 1/2 the strength, and I was wondering why :)

> It is not quite this simple because what actually
> contributes to hoop strength is mostly the fiber
> under compression not under tension and the
> modulus under compression is lower than under
> tension but that it an additional complication
> that is not necessary to consider when looking at
> the effective modulus of the blank on the long
> axis and I do not think that is what Stephen was
> referring to.

It was the not quite so simple part that I was asking about :) After thinking about it a while I came to the conclusion that the fact that the fibre is bent and under pressure must account for the loss of strength. I figured at some point there was a table of emperical data that described the characteristics of the graphite under various strains (in this case, the diameter of the bend of the mandrel and also the affects of tension on the graphite).

Thanks for the reply Harry and I hope that I'm not bogging things down by asking such technical questions :)

-- Cheers
-- James

James,
You are not bogging things down. These discussions are often very interesting and informative, to me at least. Someone at one of the rod manufacturing plants might have some empirical data that they have taken but I kind of doubt it because making the measurement would not be easy. I too have thought about it some more and I may be over looking something, it would not be the first time, but I can not see any reason why the effective modulus would drop off any faster.
I do not think that you are on the right track with it dropping with increased strain. Hooke's Law states that there is a very linear relationship between stress and strain. In fact, that relationship is by definition what modulus of elasticity or Young's modulus is. The only thing that occurred to me is that if the dimensions changed, the blank becomes oval when deflected, it could change the stiffness of the blank. The material itself and the modulus would not change but the stiffness, the spring constant, of the blank could drop which would have the same effect as the modulus dropping. Also because modulus of elasticity is measured in Msi the i could change slightly if the blank became slightly oval.



Edited 1 time(s). Last edit at 11/30/2005 07:52PM by Emory Harry.

Emory Harry Wrote:
-------------------------------------------------------
> James,
> You are not bogging things down. These
> discussions are often very interesting and
> informative, to me at least. Someone at one of
> the rod manufacturing plants might have some
> empirical data that they have taken but I kind of
> doubt it because making the measurement would not
> be easy. I too have thought about it some more
> and I may be over looking something, it would not
> be the first time, but I can not see any reason
> why the effective modulus would drop off any
> faster.
> I do not think that you are on the right track
> with it dropping with increased strain. Hooke's
> Law states that there is a very linear
> relationship between stress and strain. In fact,
> that relationship is by definition what modulus
> of elasticity or Young's modulus is. The only
> thing that occurred to me is that if the
> dimensions changed, the blank becomes oval when
> deflected, it could change the stiffness of the
> blank. The material itself and the modulus would
> not change but the stiffness, the spring constant,
> of the blank could drop which would have the same
> effect as the modulus dropping. Also because
> modulus of elasticity is measured in Msi the i
> could change slightly if the blank became slightly
> oval.
>
>
>
> Edited 1 times. Last edit at 11/30/05 07:52PM by
> Emory Harry.

Some other thoughts that popped into my head concerning this were about the specific properties of the resin used. But even neglecting those affects, I'm very much curious as to why the CTS folks state that the modulus drops off faster as the angle increases. Perhaps they are refering to some sort of 'effective modulus'?

At any rate, what kinda surprises me is that there isn't some form of mathematical description of the properties of the graphite fibres from the manufacturer. I'm coming from a computer science background where things as bizzare as transisters are characterized. I would expect that the stress/strain of graphite would be significantly easier (for a single strand) to simulate than parasitic capacitance dude to 2 wires being a certain distance apart!?

Are there any material science guys out there that could shed some light on this? I plan on reading up a bit on Hookes Law and Youngs Modulus, but that seems like only the begining of this whole "what does modulus do for a rod" discussion! :)

James,
I am a retired Electrical Engineer and you are talking my language when you talk about modeling a transistor and the capacitive and inductive reactance between two wires.
The material from which rods are constructed that contains the graphite, the scrim (usually glass) and also the resin is described in detail by the manufacturers of the material called prepreg. short for preimpregnated. However, there is nothing to my knowledge, used by these manufacturers or blank manufacturers that is nearly as sophisticated as the electrical models being used.
If you are a computer science guy that has worked on electrical models you have probably worked on an analog model called SPICE. It is used by literally tens of thousands of electrical engineers and has been continually updated and optimized for 30 years by a number of large companies, colleges and research groups. The kind of resources that have gone into improving SPICE are several orders of magnitude larger than the resources available to blank manufacturers. You probably studied stress and strain in you Property of Materials or Physics class and they have been extensively modeled for structural engineers, civil engineers, mechanical engineers and aeronautical engineers for many different materials including graphite but I do not think that any of this modeling is used by and maybe is not appropriate for blank manufacturers. If you are that interested I would start by looking into what aeronautical engineers are using because a lot of graphite is used in aircraft and aerospace applications.

James,
There is a two part article in two past issues of RodMaker magazine, Volume #6 Issue #6 and Volume #7 Issue #1, that you might want to get and refer to before you put too much effort into your research. The article explains the Characteristics, Properties and Terms for the materials used in graphite and glass blanks. It explains stress, strain, modulus of elasticity, stiffness, efficiency, resonant frequency, damping etc. It would at least be a start for you.

Interesting discussion!

James,

The relationship between the fiber orientation and the modulus of the composite is fairly complicated which makes it a little tricky to calculate. There is a really neat application out there ....nickname ERICKA, that can model this problem given the physical properties of the resin, fiber along with the fiber orientation in 3 dimensions, but that's not available on the street.

I've got some numbers on materials I've measured, but in general, the modulus vs. fiber orientation is not at all linear. The modulus falls off very quickly once the fiber angle exceeds about 10 degrees, drops quickly up to about 45 degrees, and then levels out again to 90 degrees (transverse direction) . The shape of the curve depends on a lot of variables such as fiber density, aspect ratio, etc., but one root cause for the non-linearity is that you're putting the fibers into shear as the fiber angle increases toward 45 degrees. It also depends on a property called poisson’s ratio , but the shear modulus of many materials is about 1/3 of that in bending, tension, or compression. In any case, I probably told you more than you wanted to know but bottom line is; it wouldn't be unusual for the modulus of the composite fiber at 45 degrees to be 1/3 of that in the longitudinal ( 0 deg) orientation.

markG

I suspect that there are a lot of observers to this thread, like myself, who are unable to constructively contribute. Most will be able to comprehend the thoughts when presented like the above responses. Emory and James provided information on their background. I really would appreciate those who work in the blank design field to do also. This information really will be valuable to builders who are really interested in upgrading the quality of custom rods. The information is essential to the marketing aspect and increasing the sale price of the end product. I am really interested in gaining enough information about blanks to minimize the impact of "marketing gimmiks" on my blank purchase decisions.

Gon Fishn

Ahhh, I see the error of my ways. I apologize, I was dead wrong about how the modulus is affected by the angle. I can now see that Stepen, Tom and Mark are correct and I was wrong and oversimlified the problem.
Thank you Mark and I apologize to Stephen and Tom. The effect of Poissons ratio did not even occur to me. I did think about the change to shear though so it should have occured to me. I still suspect that this effect is still small for all but small diameter blanks. I do think that we were assuming that resin content and fiber density were constant regardless of angle though so that only the fiber angle was the issue.
Mark your comments, or maybe I should say corrections, brings up another interesting question and the whole issue gets even more interesting. Poissons ratio should also have an affect, but maybe smaller, on the longitudonal fibers as well changing the modulus as the rod is deflected.



Edited 2 time(s). Last edit at 12/01/2005 10:28AM by Emory Harry.

Mark Gibson Wrote:
-------------------------------------------------------
> Interesting discussion!
>
> James,
>
> The relationship between the fiber orientation and
> the modulus of the composite is fairly complicated
> which makes it a little tricky to calculate.
> There is a really neat application out there
> ....nickname ERICKA, that can model this problem
> given the physical properties of the resin, fiber
> along with the fiber orientation in 3 dimensions,
> but that's not available on the street.
>
> I've got some numbers on materials I've measured,
> but in general, the modulus vs. fiber orientation
> is not at all linear.

So I'm making an assumption here, so correct me if I'm wrong. From what I know xx modulus fibre ( regardless of the manufacter ) itshould be pretty consistant in terms of physical properties. If this is the case, do you have a spreadsheet that describes those characteristics for common graphite fibres (or more germaine to this discussion, prepreg)?

> The modulus falls off very
> quickly once the fiber angle exceeds about 10
> degrees, drops quickly up to about 45 degrees, and
> then levels out again to 90 degrees (transverse
> direction) . The shape of the curve depends on a
> lot of variables such as fiber density, aspect
> ratio, etc., but one root cause for the
> non-linearity is that you're putting the fibers
> into shear as the fiber angle increases toward 45
> degrees. It also depends on a property called
> poisson’s ratio , but the shear modulus of many
> materials is about 1/3 of that in bending,
> tension, or compression. In any case, I probably
> told you more than you wanted to know but bottom
> line is; it wouldn't be unusual for the modulus of
> the composite fiber at 45 degrees to be 1/3 of
> that in the longitudinal ( 0 deg) orientation.

Heck no on telling me too much! This is *exactly* what I was looking for. In fact this adds quite a bit of interesting food for though on how CTS does their work. It also explains why going to such an extreme angle for their helical design doesn't add any (or negligable strength) to anything but hoop strenght. Interesting, interesting... :) Also it sounds like there is a *lot* of complexity related to the kinds of strain that the blank is undergoing. Rather than just having the modulus property of the blank (modulus of elasticity) being the dominant factor for helical design scrim, it sounds like there are other property measurements (for strain) that affect how the graphite reacts. There's a lot of terms here that I don't fully understand, but I'll be reading up on them. Granted I won't be an expert by doing so, but at the least I'll feel a @#$%& of a lot more informed! :)