alan tani @ alantani.com fishing reel repair rebuild tutorial break my 1st blank performing an static test before building it
Reel Repair by Alan Tani
October 28, 2020, 12:56:42 PM *
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Author Topic: break my 1st blank performing an static test before building it  (Read 1085 times)
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jurelometer
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« Reply #15 on: October 16, 2020, 02:46:21 PM »

If I bend the rod well past 90 degrees (let's say a full 180 degrees), the bottom half of the rod will now be experiencing very little load, with the load concentrated near the tip with  a huge difference between the inner and outer radius of the curves on the blank on each side of the bend.  Bang pow crash.

That is called high-sticking.

I have a lot of respect for Gary Loomis.  You can read about his life and times online.  In his demonstration (referenced above) he is holding the rod at the tip while someone holding the butt tries to break it at a 90 degree angle, but cannot.

Early hardwood rods had only one ring and that was the tip-top.  Running guides were added over time to keep the line from rubbing on the rod, not to transfer the load to the butt. It is taper that transfers the load to the butt.

Load up a rod, reel and line with a bend.  Measure and sum the downward force of the line on each guide.  That downward force of the line on the guide is really small.  You can flick the line up and down with your fingernail.  The tip-top is the only guide that is handling a lot of downward pressure.

If guides could distribute load and make a beam stronger, then a boom truck or dragline or crane would have guides.  They don't.

When building heavier and heavier rods, you would start replacing the ring tip-top with a roller tip.  Only when moving up the ladder would it be worthwhile to put on roller striper and roller running guides.

Prove it to yourself.  Take two cheap dowels with uniform diameter (no taper).  Put a line with guides on one dowel.  Tie a line to the tip on the other dowel.  Now break them by pulling on the line at a 90 degree angle.  The guides do not make the dowel any stronger.

-steve



As I noted in my my long, boring, infrequently read to completion post Smiley, high sticking is the case where  extreme rod angle concentrates load toward the tip (where the rod is weakest).  Which sort of proves that we have some control over which section of the rod gets loaded, and that it does makes a difference.    In the really boring part, I noted that it was the progressive elasticity of a rod blank that makes this important, and if the rod was more like a dowel, it would matter much less.

The angle of the load determines which part of the rod is being flexed. As long as there are enough guides in the right spot to push on the blank.

Now as to why they only put a tip on some vintage hardwood rods, perhaps  it was good enough to get the job done, and they were not asking the rod to do much more than a combination lever and shock absorber.   But if you look at vintage split cane fly rods, you will see the same sort of progressive guide placement as modern rods.

Here is one article on the goals and a method for guide location on split-cane rods.  While they are using a 1/3 rule, it ends up being very close to my 90 degree method.

https://splitcaneinfo.com/?page_id=1227

This is essentially  a method for static guide placement optimized for full useful bend.

So while I think the dowel analogy is not the best example, I think that Steve might also be getting at the interesting and difficult question from Cor  (although a bit hypothetical in the end IMHO) about whether having just a top guide or a bunch of guides would change the load distribution if the rod bend was exactly the same.  I keep wanting to say yes based on intuition, but intuition has a way of biting you in the a** when it comes to physics.  And I can't think of a reason to back up my intuition.   My analytical side tells me If the bend is the identical, shouldn't the load distribution be identical?  Here is where Cor (and Steve?) may have a point that I would tend to agree with.

Under this line of reasoning, what guide placement and rod angle do is give us the ability to change the shape of the bend, but the shape of the bend is what determines the load distribution. We can choose a bend shape that is optimized for casting light lures, or a bend shape that concentrates load toward the stronger butt section of the rod, etc..    Some of this choice is baked in by guide placement, but some of it is variable based on the fish fighting or casting angle.

-J
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happyhooker
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« Reply #16 on: October 16, 2020, 05:13:08 PM »

Great series of posts; I'm not a scientist, so some of the technical discussion shot by me, but I'll take a chance and add my two cents worth anyway (and, maybe that's all it will be worth.)

I liked point 2 of jurelometer's first reply/post.  I took it as meaning you get a truer test of the strength of a blank by testing it with the guides in place vs. just applying a weight to a tiptop.  In that same vein, I like TFH's method of applying "serious weight" later in the build process after the guides are in place (even if only in temporary positions).

After all, the vast majority of blanks must be manufactured to end up as rods with a tiptop and multiple guides; they aren't meant to be made into rods with only a tiptop and fished that way (with a respectful tip of my cap to the old timers who used rods with only a tiptop).  If that is the case, then why bother testing a blank in an artificial circumstance (weight tied to a tiptop) that does not come close to duplicating what you expect the blank to do when the finished rod is fished?  I know it would be a bummer to build a rod only to find out, after all that work, that the blank had a defect.  Temporarily attaching guides is perhaps an acceptable compromise, along with a close inspection of the blank first.

Two thoughts that I add in closing:

1)  What is the "magic" of a 90 degree bend in testing?  Or, is it only some sort of "tradition?

2)  I have always been under the impression that the stress on a blank is at the locations BETWEEN the guides, not AT the guides.  Am I wrong thinking this?  Does it enter into the discussion in any way if it is true?

Oops, one more thing: I look with a bit of a questioning eye on the terms under which this blank was vended.  No warranty?  But, you won't be disappointed?  Can't tell you the manufacturer's name? 

Frank
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JasonGotaPenn
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« Reply #17 on: October 16, 2020, 05:35:03 PM »

Not telling you the manufacturer on a deeply discounted item is not unheard of. I'm kind of a cheapskate when it comes to work clothes, I do a lot of my shopping on the clearance rack and at outlet type stores that sell off overstock items. You see stuff with the brand tag removed all the time. Because the fancy clothing company doesnt wanna admit they'll allow their stuff to be sold for so low. Some of my favorite work slacks are made by a brand I'll never get to know.
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jurelometer
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« Reply #18 on: October 16, 2020, 06:19:12 PM »



1)  What is the "magic" of a 90 degree bend in testing?  Or, is it only some sort of "tradition?


lots of reasons from physics, no magic.

a.  When you bend a blank past 90 degrees (tip perpendicular to the butt), you are bending the rod into itself- this will concentrate the load toward the tip where the rod is the more likely to break.

b.when casting, you want the direction of force on the spring load on the blank to be aligned with the direction you are intending to cast.  This means a that the tip should be in a straight line toward the lure (or in the case of a fly rod, the tip section  and the fly line collinear). A 90 degree bend maximizes the energy loading into the rod while still keeping the direction intact.  If you go past 90 degrees, the rod will try to fling the lure more upward rather than outward.  you will also not be able to load the butt of the rod as much.  The resistance is strongest toward the butt, so this is where the greatest amount of energy is stored.

c.  when fighting a big fish, you will need to pump and wind to bring the fish in. A 90 degree bend is about as high as you can go before the benefit from the the line gained from lifting is outweighed by the mechanical advantage the fish gets from leverage on you.

d. As the blank bends, the distance rod becomes longer on the outside curve of the blank (side with the guides on a conventional rod) and shorter on the inside.   The fibers don't stretch much, the resin is handling this. so the fibers on the outside of the rod curve  are being pulled apart and the inside are being crammed together, forcing the sides to swell outward.  Ounce you get past 90 degrees the rod is bending on itself and concentrating the deformation at a single point. Bang pow crash.

It is still useful for a rod to have the ability to bend well past 90 degrees without blowing up to provide some margin of error.  But you are usually giving up some stiffness/backbone.   No free lunch.

Or to put it more succinctly, there are use cases for bending the rod up to 90 degrees, but not really after 90,  and bending the rod into itself generates a lot of stress.  Nothing good happens after 90 degrees.

Quote
2)  I have always been under the impression that the stress on a blank is at the locations BETWEEN the guides, not AT the guides.  Am I wrong thinking this?  Does it enter into the discussion in any way if it is true?

Agreed.  This is what I have been pointing out on several threads on this subject. More specifically at the apex of the inside curve caused by the guides being drawn toward each other by the load.  My apologies if I screwed up the explanation somewhere.

-J.
« Last Edit: October 17, 2020, 03:25:24 PM by jurelometer » Logged
Brewcrafter
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« Reply #19 on: October 16, 2020, 07:01:51 PM »

Great point Steve!.  I respect your experience and insight on this; it's what makes the forum great and I thank you.  Now not to confound things (or even my own misshapen theories regarding rod guides) how will this all play out with one of the "through rod" setups discussed in another related thread?  And unlike my previous post that is one where I will not say "ignore friction" since I think it might be significant.  As a matter f fact, under load a "through rod" design is actually going to add friction (drag) ...wow..it is fun trying to wrap my head around this...-john
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MarkT
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« Reply #20 on: October 16, 2020, 07:27:43 PM »

A 12-30 rated blank is not a 30# rod! It’s a 20#rod at best. For some no-name blank 20# is probably pushing it... just sayin’, ya know what I mean?
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« Reply #21 on: October 16, 2020, 07:47:07 PM »

I know nothing about rod building,,,,, Embarrassed but I have had 1fly rod and 3 spin rods,,,, same line rating as yours break in about the same place.
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jurelometer
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« Reply #22 on: October 16, 2020, 07:56:35 PM »

A 12-30 rated blank is not a 30# rod! It’s a 20#rod at best. For some no-name blank 20# is probably pushing it... just sayin’, ya know what I mean?

Good point.

If the blank maker does an honest dead lift at 20% of 20 lbs (48 oz), that is plenty to expect from a light pure carbon fiber swimbait rod.   

As a side point, you can dead lift 30 lbs with a trout rod if you do not bend it much.   

Alex:  I still think that if you stick a scale on the built rod when you do a 90 degree bend, you will have some useful information to share with your customers about safe drag settings.

-J
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MarkT
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« Reply #23 on: October 16, 2020, 08:41:02 PM »

All the Fenwick, Sabre, Seeker, Calstar, and other 270, 12-30# rated rods I’ve seen are 20# rods that can go up or down (mostly down) a line class or so. I wouldn’t use 10# of drag on my classic Seeker 270 pulling at 90+ degrees and certainly not on some unnamed blank of unknown pedigree. Rods are rated at the middle of their rating, not at the high end. Keep that in mind going forward. A 270 (12-30) is a 20# rod, an 870 (15-40) is a 25# rod, a 670 (20-50) is a 30# rod, a 665h (30-80) is a 40# rod, a 6465h (30-80) is a 50# rod... and so on.
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« Reply #24 on: October 16, 2020, 11:50:36 PM »

A good rod cannot be broken by a human being if the butt is held not more than 90 degrees to the pull of the line.  That is part of the design process.... make the butt substantial enough that it cannot be broken and then give it a smooth even taper from there, ending in a tip that has some spunk and will not be overloaded by the swing weight of the bait or lure or fly line.  Rod design is an art but it's not witchcraft.

I think that Alex's stress test that pulls the tip without guides is valid and that a rod that fails his test would still fail if guides had already been installed.  I also think that if Alex had bought a high quality blank (like those listed by Mark as well as others) he would not have broken it.  I also think that the GetBit rod did not fail because of a design flaw, but because there was a flaw in materials or workmanship.  

Rod design is an art, but so is the construction process.  One slip in cutting, tacking to the mandrel, rolling, or sanding will mess up that smooth taper so the load is not transferred smoothly making the rod vulnerable to failure.  An incongruity in the woven fiber (broken fibers, lint) will also mess it up.  Little globs of lint will make a bulge and that bulge will have to be sanded off in finishing.  In sanding that bulge, you are as likely to sand away intact fibers as you are to sand away useless lint.

I have talked myself into believing that the guides have nothing to do with how the rod bends and how the load is transferred.  I base this mainly on the lack of significant downward pressure where the line presses on the guide and the guide presses on the blank.  Yeah, that is controversial so I may have to find a way to prove or disprove it.  The only caveat here is that the wrapping thread, epoxy and lack of flex in guides will stiffen the area around each guide.  This stiffening may throw off the bend and load transfer a little.  That is also why a rod might break between guides rather than under the guide.
-s
« Last Edit: October 16, 2020, 11:56:12 PM by oc1 » Logged
Cor
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« Reply #25 on: October 17, 2020, 07:26:25 AM »

I once took a 11 ft rod, made locally by Purglas, a strong rod, by the tip and lifted it that way to see how it would bend.   It did not bend, it snapped right next to my hand, cleanly off.     Perhaps it's obvious that that would happen, but at the time it was not to me.    I then went home and tried to break some tip pieces in my "scrap box" and found that I could break them like a twig in my hand.

This obviously has nothing to do with guides, but just a characteristic of graphite.    You hold it with two hands and snap it with little effort because you force it to bend more than 90 degrees at that spot.

One day a friend asked me to shorten a rod for him.    It must have been about 11'6" as it would not fit in my van.    I had already worked out that I would need to shorten it on both sides, so to fit it in my vehicle i proceeded to snap 4 inches from the tip in front of the guy.   I will never forget the look on his face.    It became a successful rod!

Something about guides.     When I make a rod I nearly always stick guides on to it with duct tape.     I then adjust the guides by fixing the rear section horizontally and then hanging a weight on it.    
This will determine  how many guides are required and the spacing to keep the line away from the blank under load.    When I started making my own rods, a rod had 7 guides, simple. Grin  I must say that most blanks we used were from the same manufacturer and very similar.   Only much later did this change.

I also go and cast with it like that and play around with the guides again if needed, slightly adjusting them.    Sometimes I have cast a rod with only a reel and a tip guide, it can be done but does not resemble the same characteristics as a rod with a full set of guides, you can feel the weight or then lack thereof.   It also tends to feel like a soft slack bad blank! (Steve describes it as squishy, a good word choice)  So in that case the extra guides seem to give the whole thing more body or stiffness.   I don't think that is because of the effect of the bindings and actual stiffening effect of the guides on the rod or perhaps it is.

The attached photo I think I have uploaded before.   It was a way to see what a blank does under maximum pendulum casting load.
It is rated 2 to 5 oz = 155 gram.    I think the rod is tilted slightly to my right perhaps distorting the curve but to me it is clearly over loaded.
This rod has never casted nicely and I now limit my casting weight with it to 125 gram which feels better.   Perhaps it should have broken as it looks like the curve is more than 90 degrees from the but.





* vlcsnap-2018-02-08-15h17m45s518.jpg (205.98 KB, 800x601 - viewed 3 times.)
« Last Edit: October 17, 2020, 12:42:28 PM by Cor » Logged

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« Reply #26 on: October 17, 2020, 10:44:42 AM »

I have cast a rod with only a reel and a tip guide, it can be done but does not resemble the same characteristics as a rod with a full set of guides.   If tends to feel like a soft slack bad blank!   So in that case the extra guides seem to give the whole thing more body or stiffness.   I don't think that is because of the effect of the bindings and actual stiffening effect of the guides on the rod?

I never tried that but can imagine it.  As the rod bends on the cast the straight line distance from the tip to the reel would become shorter and the distance from the tip to the lure becomes longer.  It would feel squishy like you are letting some line off the spool in the middle of loading the rod on the cast.
-steve
« Last Edit: October 17, 2020, 10:45:25 AM by oc1 » Logged
Dominick
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« Reply #27 on: October 17, 2020, 12:01:05 PM »

I hate to join in in this discussion as I am new to rod building.  I just use the Mudhole guide for the weight of the rod.  On the other hand I learned to not high stick.  I only lift the rod to a 45 degree angle and in most cases the tip is not quite at 90 degrees.  So to sum up (with all due respect for his rod building acumen) I believe Alex overloaded that blank and it failed.  My feeling is that if he had built it with the guides in place it would not have failed.  My opinion only.  Dominick
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« Reply #28 on: October 17, 2020, 07:30:00 PM »

I don't put any serious weight on until I have the guides wrapped.
thanks for your input, as I said, I still learning from the pros, let me ask you this, how much it would be "serious weight" for a 30# blank?
actually "serious weight for a 30# blank" was the million dollar question.
I only use enough weight to put a slight bend in the rod with the rod held at a 45° angle...and I'm going to have a hard time explaining what I mean by a slight bend  Grin
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« Reply #29 on: October 17, 2020, 07:40:00 PM »


I have talked myself into believing that the guides have nothing to do with how the rod bends and how the load is transferred.

Who am I to argue with faith?
Quote
 I base this mainly on the lack of significant downward pressure where the line presses on the guide and the guide presses on the blank.  Yeah, that is controversial so I may have to find a way to prove or disprove it.  The only caveat here is that the wrapping thread, epoxy and lack of flex in guides will stiffen the area around each guide.  This stiffening may throw off the bend and load transfer a little.  That is also why a rod might break between guides rather than under the guide.
-s


OK,  I am ready to argue now Smiley

I think this is where things are going sideways for Steve.  You are basing your theory on an incomplete data set.  There is significant pressure on the bottom guides if you angle the rod appropriately, and the rod is built correctly.  As mentioned in my long, boring, infrequently-read-to-completion post (in the second most boring part Smiley  ),  when using the proper big fish fighting technique with a fly rod, the tip is not bent at all,  so the tip cannot be under load.   So what is bending the rod if not the load on the other guides?    Here is an example that I found on the web:

http://oregonflyfishingblog.com/wp-content/uploads/2011/07/Caddis-Fly-Shop-Jay-Nicholas-Fly-Rod-position-2.jpg

I think the assumption that only the tip has load is incorrect.   It depends on the total load and the angle of the load.

When we get tangles fighting a fish and another angler's line is wrapped around the tip of the fly rod fighting the fish, the rod can be heavily loaded, but the tip wiggles around easily when untangling the other line. The tip is not experiencing enough load to bend the rod as much as it is bent.

Lots of easy ways to test your theory if you are not still convinced.

I once took a 11 ft rod, made locally by Purglas, a strong rod, by the tip and lifted it that way to see how it would bend.   It did not bend, it snapped right next to my hand, cleanly off.     Perhaps it's obvious that that would happen, but at the time it was not to me.    I then went home and tried to break some tip pieces in my "scrap box" and found that I could break them like a twig in my hand.

This obviously has nothing to do with guides, but just a characteristic of graphite.    You hold it with two hands and snap it with little effort because you force it to bend more than 90 degrees at that spot.

One day a friend asked me to shorten a rod for him.    It must have been about 11'6" as it would not fit in my van.    I had already worked out that I would need to shorten it on both sides, so to fit it in my vehicle i proceeded to snap 4 inches from the tip in front of the guy.   I will never forget the look on his face.    It became a successful rod


Which reminds me.  You can also break a rod much more easily buy reaching up the past the grip.  The higher up the reach, the more load is concentrated toward the tip where the rod is weaker.  Cor's example is an extreme one (four inches from the tip), but very illustrative.  When load testing a rod or blank, it is important not to reach past where the front grip will go.  People blow up fly rods all the time reaching up the blank to get leverage on a big fish.  Don't know if this contributed to the blank failure for Alex, but thought it might be worth mentioning.

-J
« Last Edit: October 17, 2020, 07:41:16 PM by jurelometer » Logged
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