Conn 36j leadpipe

[DaveC]

So I won't be starting this project for a while (I have to finish my current Olds O99 project first) but I recently acquired a Conn 36j as a restoration horn. I'll be completely disassembling and rebuilding it, and hopefully rebuilding the valves myself. I'll also have to fabricate some new guard strips. But the main thing I want to ask here is regarding the leadpipe. The leadpipe on this horn has a big splice/patch in the middle of it, and I'm thinking of making a new one. I think it will be (hopefully) fairly simple to measure the current leadpipe and make a close matching mandrel, but this got me thinking. Are tuba leadpipes usually constantly opening tapers from the end of the mouthpiece, or do they vary along their length? I know that trombone leadpipes have a narrowing after the mouthpiece before the opening taper begins, and I believe this is also true on at least some other brass instruments. I might even try making a few different taper profiles (slow taper then fast, fast then slow, venturi before taper, etc) just to experiment. Any ideas on this? These projects are all evening/weekend off-the-clock sort of things, mostly for fun and self education, so I'm not in a hurry. I've been fascinated with instrument design and acoustics since before I started doing repair as a job, and I figure this might be a way to experiment and learn(even if I'm learning from my failures). Thanks for any info or ideas!