Ok, I'm sure you guys have had some discussions about this one but, I 'd like to ask a question or two concernenig the spline (spine). First as I understand it the spline is wear the blank (fly) wants to naturally bend but is the spline the outside of the arc or the inside? I usally check two ways Finder and Table top on each blank.
Also in guide placement: should you place guides on the "natural" inside curve or out?
I 've read opinions on both It seems logical to me to put them on the inside to negate any twist of the blank when fighting fish especially big fish.

To appease my curiosity I prefomed the CCM on a Rainshadow Rx7 8'-4wt 2pc blank
with the tip on the inside of the " natural" curve the DBI= 4.16/ 62
with the tip on the outside of the " natural"curve the DBI= 4.16/ 63

The only differance I noted was a very minor change in AA 1degree or less which may be due to the fact I was on my second beer. :-)
I did however note that when the blank was "loaded" (w/ penneys) the rod seemed to want to twist when the natural curve was up.

what do you guys do? and why?
thanks
Joe

Check out the FAQ's page. Should answer all your questions.
If the blank has a bend in it, let the tip bend upward, mark as top, guides would go to the bottom or 180

The spine is not a thing - it is an effect. Where you mark it really makes no difference, as long as you know where it relates to the position you refer to.

Most builders stress the blank, allow it to roll to its preferred location, and then mark the outside of that curve as the "effective spine." As you noted, the power and action are only marginally different from the spine to off-spine positions. It does not have the sort of effect that many believe it does.

Twisting will not be a problem once you add guides and load the rod via the line. This is what we do when actually fishing and the spine has little to no effect in this area. In fact, spine is one of the least important things to worry over when building a rod.

Do a search here on this board for "spine" and read some of the past conversations.

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RBO SEARCH = SPINE [Mssg Body + Subject] LAST YEAR

For rods without dramatic spines or curves, any orientation will do.
Millions of factory rods have been built this way.

For some rod blanks with more intense spines or curves, IMO, you'll probably feel more comfortable deciding which is dominant and choosing an orientation which reduces (the effect of the spine) or (the extent of the curvature) on your rod's overall design and intended use.

That's my own take-home lesson on this, and the rest is strewn thru-out the RBO archives with everyone else's comments. ...

I like the soft side of the rod - the axis with least resistance - toward the fighting fish for ALL rods, myself. But I am not a fly-fisher, where back-casting may influence your opinion. ... -Cliff Hall+++

T&T likes to put their guides on the hard spine or the outside of the curve. However, if you put the guides on the soft side it ok. I'm building a T&T Horizon II and going to put my guides on the hard spine. Bill

Joe, Cliff makes some good points. Generalizing about the spine is a little hard to do until 1) You determine how hard the spine(s) are in a blank and also depending on what you're trying to accomplish. Actually, I wouldn't expect the difference between reversing the inner and outer curve to be very large since you’re just switching the material from tension to compression along the same orientation.

If the rod has a very soft side, you'll typically find a much harder/stiffer axis somewhere 90 degrees to the relaxed curve. You can easily test for this effect by bending and pressing the blank into carpet, and slowly start to rotate it. If you feel some resistance followed by a tendency for the rod to jump past that point, you've found the stiffest axis.

mark

The stiffest and softest axis are usually not 180 degrees apart, nor exactly 90. Generally they fall about 110 to 170 degrees opposite each other.

...

The position of the spine orientation is really not worth arguing about since it takes all of about 30 seconds to measure it. A far as the position goes, rod spines are a lot like snowflakes, and no two are exactly alike.

Some blanks don't even have a noticeable spine, and others vary in intensity and orientation depending on the cause.... the wandering spine for one example. A hard spine from eccentricity could be fairly straight, and maybe it's safe to say that the stiffest axis will typically be somewhere off the relaxed 0-180 axis.

mark