I'm looking to start building a 30" four-string soon, and I was worried about tension since I wasn't wanting to change strings from what works on my P bass. I was going to use a TOM-style bridge and run the strings a few inches past the saddles before going through the body, trying to help with the tension. I got to thinking, and I don't know if this is a stupid idea or not, but couldn't I run some long strings further through the body? Like, have less than a 90-degree angle at the bridge, and the ferrules somewhere around the sweet spot on the back. It randomly occurred to me how awesome and punchy a 30" strung BEAD might be. Would it work? A 30" B-string that was usable?
I can't say how well a 30" scale B string would work. But I can say that your ideas about attempting to increase tension by using long strings will not work. If anything, doing what you've suggested may actually reduce perceived tension.
Tough to go against physics on this one. Your best bet would be to make the neck as stiff as possible.
Any of the things you mentioned will have exactly zero effect on your string tension. The tension depends on the distance between the nut and bridge saddles and the mass of the strings. You can extend the strings a mile beyond the bridge, and the strings will have the same tension when you tune to the desired pitches. So yes, it is a stupid idea (although one believed by some noted bass players), but we'll give you a pass on this one.
+1. Tension is governed by linear mass, tension, and vibrating length. If you choose to use the same strings (keeping linear mass constant), then tension is a direct function of vibrating length, and no amount of adding string will increase tension. A really stiff neck, and no "play" beyond the nut and saddle, will help in a tight feel. Headless basses, smaller headstocks, an increased headstock tilt-back angle as well as a steeper break angle at the bridge will help the strings "feel" tighter. Of course, using thicker strings would really help.
I'll throw in my 2 cents. Years ago the player I learned from had one off short scale 5 string made by Mike Tobias. The B string sound great, wasn't floppy and didn't fart out. We believe this was due to it being built with a reverse peg headstock which added the string length required to make the B work properly. Might be something to keep in mind when planning your build.
fwiw - a Bass VI has a .095 for E. More akin to guitar tensions but it works just fine. A .130 would be right as a consistent B string in such a set.
Adding string length between nut and tuner (or bridge saddle and anchor) has no effect on string tension. Haven't we flogged this dead horse into a greasy spot on the ground yet?
I hate flogging dead horses. What about the pitch of the headstock. If it's at a steeper angle there's more down force at the nut. Would that play into the overall tension of the string? On a couple of my Jazzes I added string trees to the A string to help eliminate rattle at the nut. I never put much thought into how it would affect string tension as a whole. Any thoughts?
Refer to my above post: "A really stiff neck, and no "play" beyond the nut and saddle, will help in a tight feel. Headless basses, smaller headstocks, an increased headstock tilt-back angle as well as a steeper break angle at the bridge will help the strings "feel" tighter." It will feel tighter, but it doesn't change the tension. Actually you reduce the play of the string at the nut, so it feels tighter.
For a 30 inch bass with good tension, just make sure you use large inches. Say, 30mm each. That'll fix it!
The only things that affect string tension are string mass per unit length, pitch, and distance from nut to bridge saddle. Break angle and string length outside the speaking section of a string could only make a difference to "stiffness" if the strings were moving through the nut and/or over the bridge saddles as you play. I have my doubts that that happens on my basses, anyway.