Help, I would like to know how to locate the spine on a three piece blank. I have no problem locating the spine on a one piece and two piece blank using the flex method. Is the proper procedure to assemble all three sections and flex the blank trial and error method untill there is a consistent bend?

Second question, The blank I have has an open hole in the end of the male section of the blank. I would like to plug the hole what type of material can I use to do so. On the manufactured rods I own the male end of the blank is plugged. Can anyone advise what the manufactures use and where I can obtain that material?

Check out the FAQ page to the left , for the multi-peice rod.
As for the plug, I use Rod Bond to fill the male end, hope this was some help.

You always want to find the effective for each section. If you assemble the sections and then try, it will be impossible to locate an effective spine - you'll only get an average of the distances you are off on each section.

The butt sections can be hard to spine as they are rather short and stiff. If you can't find it by normal methods, try to locate the blank's natural curve (nearly all have a gentle overall bend or warp) and mark the effective spine as being on the outside of that natural curve. That won't be it (rather what you have located is the section's straight axis), but it'll be close and it will be the upper 1/2 of the rod where the spine effect is most obvious and has the greatest effect. Thus the butt section isn't nearly as important in this regard, but by putting it's straightest axis into play you at least keep things starting off on the right foot.

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Get two small blocks of wood or use some books stacked up and put them about far enough apart as the section is long. Place one end of the butt section on one block or stack and the other end on the other block or stack. Just the last 1/2 inch of so of each end should be supported. It will automatically roll to the curved position that Tom mentions. The bottom side you can mark for alignment with the spined upper sections. As Tom said, this won't be the spine but it will be the straightest axis and will allow the upper sections to do their job and work with the spine on them without the butt section interfering. Good luck!

Thank You Wes, Tom, Mike, I have found the spine. R. C.