How do you determine whether a blank broke due to:
Over stress?
Manufacture?
Tight wraps?
etc.?

There was a length article in Rodmaker last year on that very subject. I do not remember which one offhand, but you can use the link on this page to go to their site and check the contents of the back issues. I think maybe it was the Jan/Feb 2000 issue but an not sure. It was a really good article and very educational.

There is almost too much for anyone to go into in a simple message board post here. But I will say that you need to take a good look at the overall condition of the rod to help you determine why it failed.

Most rods fail due to some sort of impact or overstressing of tip sections. Impacts sometimes damage the rod but the actual failure will occur later, when the rod is stressed. Thus the fisherman believes a defect was present because the rod "broke on a fish".

Look at the area around the break. Do you see scratches, dings, chips, ect.? This could be evidence of an impact that occured before the rod broke. Did the rod break at the edge of a guide foot?

I'd like to say just return it to the manufacturer and go with what they say. But most of the time the manufacturers are so interested in customer goodwill that they replace many abused blanks for free, adding to the misconception that the blank was defective.

Most defective blanks will fail very early in their lifetime, not a year or two down the road.

The Jan/Feb 2000 RodMaker does have a good article on all this. It might help you. Included are remarks from a warranty/repair person working for one of the leading blank makers.

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As a general rule when a rod breaks and there a lot of fibers around the break. The break was caused by some type of impact.
This is strang but gun racks in the back of pick up trucks causes a lot of failurs in graphite rods.