I'm starting to work on the guide spacing for my back bouncing rod and want to make the tip section as sensitive as I can to detect bites - I know that's a challenge on this heavy of a black. I've located two straight axis positions - tip bows up and tip bows down.

If we go back to 8 years ago or so when spine orientation seemed to dominate the topics, I've found that this blank has two "spines" or whatever those magical things are that cause a blank to roll to a certain relaxed state position. However, one is more dominent than the other. When the blank rolls to the most dominent relaxed position, the tip sags down. When the blank rolls to the lesser relaxed position, the tip bows upward.

Is there one position that would allow for better bite detection? Thanks.

I don't THINK that any of that will have any effect on sensitivity at all. Even those that worry about the spine do it for aupposedly cutting down on torque. Straightest axis is done ro produce the straightest rod. Belly down on spinning rods, belly up on casting rods so that the weight of guides will help "straighten" blank. Sensitivity is more affected by weight, blank material, characteristics and configuration. Just my opinion!!!

Mike (Southgate, MI)
If I don't want to, I don't have to and nobody can make me (except my wife) cuz I'm RETIRED!!

Tim,
Mike is correct that sensitivity is a function of weight, mass actually, but it is also a function several other variables including one that you can affect which is stiffness. It will not make a great deal of difference but if you want to get the absolute maximun sensitivity allign the guides on the stiffest plane. This stiffest plane should be close to 90 degrees from the normal spine or soft plane.

Thanks Mike and Emory, actualy the stiffest and softest planes are 180 degrees apart. So if I put the guides on the stiffest plane (spiral wrap), the weight of the guides should pull the tip down to straight.

Secondary question - if the blank had only one stiff plane and the rod was flexed downward, I would think that the stiff plane is on the 12 o'clock side. However, with two planes 180 degrees apart and the blank flexed to a relaxed position, I would think those planes would be sitting at 9 o'clock and 3 o'clock - would I be correct in that thinking? Thanks.

IMO, you would need a very sensitive mechanical device to tell the difference ... not your hand. Build it on the straightest axis and don't worry about the rest.

Tim,
The two stiffest planes are actually 180 degrees apart and the two softest planes are 180 degrees apart and the stiffest and softest planes are 90 degrees from each other. However, they will rarely feel as if this is the case when you look for a blanks spine because they are offset. By offset I mean that where the two stiffest planes cross the two softest planes is not in the center of the blank but offset to one side or the other. Depending upon where they cross each other relative to the center of the blank can make it appear that the stiff and soft planes can be almost anywhere.
In your case, where you are after the maximun sensitivity I would put the guides on the stiffest plane regardless of where it occured relative to anything else.

As a general note, in response to Mike Barkley's post, only a very large helium balloon tied to the tip will "straighten" a rod built with the belly up. Both spinning and casting rods should be built with the belly down to allow the weight of the guides and tip to straighten the blank. This also may put the stiffest axis of the blank in the fish fighting position.

Emory has given you good advice. Generally the straightest axis (oriented in the concave position) positions the rod so that the fish, or the bite, will be pulling against the stiffest axis. Thus you have the most stiffness for the weight in that particular orientation.

The only problem is that your line may not be directly in line underneath that axis. If it's behind or fore of that plane, any pull will be against an axis that isn't quite as stiff.

Realistically, of course, it's not going to make very much difference.

.............

I would eat my hat, and yours, if you can tell any difference in sensitivity between one way or the other.

Peter,
Would you like some ketcup or mustard? Some blanks have very slight spines and I might tend to agree with you in the case of some blanks. However, some blanks have very pronounced spines and I will eat my hat if I cannot detect the difference with these blanks.
I have done a lot of testing of sensitivity with strain gages and an oscilloscope and also with my own hands. It is surprising how sensitive your fingers are.