Jump to content


Photo

Stress Curves?


6 replies to this topic

#1 River Rat

River Rat
  • Members
  • 146 posts
  • Gender:Male
  • Location:St.Charles, MO
  • Interests:Fly fishing, bamboo rod making, canoeing, educating kids about the natural world.

Posted 06 January 2014 - 02:34 PM

I'm wondering if stress curves are available for the various graphite and fiberglass blanks like those for bamboo rod tapers. I've made a cursory search of the internet and found nothing so I thought I'd ask the question here.

Thanks,

Cliff Parmer

If it's worth your time to do, it's worth doing to the best of your ability.


#2 Washougal

Washougal
  • Members
  • 1,179 posts

Posted 11 January 2014 - 12:55 PM

Know nothing about the stress curves you're talking about, other than I have seen them. Would a stress curve graph be of any real use since your not building the blanks? I can see how messing with your taper to pick up or take away a bit of what you see on the graph may be beneficial.

#3 Tim Anderson

Tim Anderson
  • Members
  • 147 posts
  • Gender:Male

Posted 11 January 2014 - 05:02 PM

Garrison's stress curves assume that bamboo is homogeneous and that the blank is not hollow. Today's graphite and glass blanks are mostly empty space inside a thin-walled tube whose walls. The stress curves for bamboo rods also require assumptions about the blank material's modulus of elasticity. That can be approximated for bamboo, but is pretty hard to do for fiberglass and graphite blanks what with the proprietary nature of the product.

Tim

#4 Carlin

Carlin

  • Members
  • 4,766 posts
  • Gender:Male

Posted 12 January 2014 - 07:15 PM

The stress curves you see for bamboo are simply static deflection calculations - static stress values along various points of a rod, assuming certain rod and material parameters, under a given load determined by the weight of the fly line. They can easily be modified for a hollow rod, assuming you know the wall thicknesses. I don't see any reason one couldn't make the same sorts of calculations for graphite. You would need the rod diameter, exact wall thickness (measurements off of the original mandrels and the cloth patterns or OD measurements) for a bunch of points along the rod as well as some technical info on the properties of the graphite. From there it is a simple matter of calculating then summing all the moments of inertia along the blank.

However, the static deflection calculations don't, by their definition, give a real idea of how a rod acts under various loads through a casting cycle. For that you need something that calculates dynamic rod deflection. Max Satoh has a computer program he has written that does this, and, like the Garrison model, it can make its calculations regardless of what the rod is made of as long as you have the needed technical specs for the material and the rod. DynaRod gives a much clearer picture of what happens to a rod all through its casting cycle.

I have seen some photos of a computer program that, I assume, Winston uses that seems to show what looks like a deflection curve of some sort so I expect stress and/or deflection programs for graphite rods exist. Or rather, I would be surprised if something doesn't exist given its advantages for designing rods. Here is a screenshot from an older Winston video that shows a computer simulation of some sorts of a rod and below that a design sheet for the cloth and mandrel(?) for a 5 piece LT.




Chris

FNRSBanner1.jpg


#5 angry john

angry john
  • Members
  • 18 posts

Posted 12 January 2014 - 10:23 PM

Tackle tour posts what your looking for on the rods they test. Might be useful if you want to use a blank from a rod they have tested.

#6 Carlin

Carlin

  • Members
  • 4,766 posts
  • Gender:Male

Posted 13 January 2014 - 11:49 AM

QUOTE
Tackle tour posts what your looking for on the rods they test. Might be useful if you want to use a blank from a rod they have tested.

Close. What they post is a static deflection chart that shows how much a rod flexes (rather than how a rod flexes) using various amounts of weight. In a way the flex characteristics of the rod can be figured but it isn't terribly intuitive. Then again, neither is Garrison. wink.gif

Bravo to them for doing the measurement as any objective way to compare blanks is a good thing.

Chris

FNRSBanner1.jpg


#7 River Rat

River Rat
  • Members
  • 146 posts
  • Gender:Male
  • Location:St.Charles, MO
  • Interests:Fly fishing, bamboo rod making, canoeing, educating kids about the natural world.

Posted 14 January 2014 - 11:37 PM

The stress curves for bamboo give you some idea of how the rod behaves, i.e. soft tip, stiff mid-section and so forth. I think that they would be somewhat more helpful than the action description of "fast", "medium fast" etc. that I've typically seen for graphite and fiberglass rods. The reason I've asked this question is that I'm searching for a way to understand more fully how a particular blank will behave.

Cliff

Cliff Parmer

If it's worth your time to do, it's worth doing to the best of your ability.




Reply to this topic



  


0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users