Damp rags are more likely to make it worse. Wait until compmetely dry and use a sanding sponge, rather.
What pieces are these? What interior shapes are you working with and how large are they. As @MrDibble suggests sanding the interior and then maybe a coat of something more putty-like that can be smoothed might be a better approach. Maybe light weight auto body filler.
The papier-mache pieces are the curved sections of tube. Each one is approximately half of a torus (except slightly tapered). The smallest one is about an inch in diameter, while the largest is about five inches in diameter.
So you’re making half tubes and putting the together clam-shell style. I haven’t used paper mache much, hardly at all since making a big animal shaped pinata in the Cub Scouts mainly using crepe paper streamers. I have seen in the past and recently on line paper mache powders which may be easily smoothed but don’t really know.
Sanding the interior sounds like the best approach based on my minimal experience. Obviously you want to start as smooth as possible but you probably need to sand to finish. Not sure if it makes a difference but you can bind your paper with white glue which may make it more shapeable as it dries.
Also wondering if you considered rotary valves instead of pistons. I don’t know how actual rotary valves are configured on brass instruments, but perhaps with printed parts not that difficult to achieve.
No, whole tubes. Cut the torus the other way. Like a macaroni noodle (I really should have taken some pictures last time I worked on it). Which, for the smaller ones, makes the interior difficult to access.
And I did consider rotary valves, but decided that piston valves would be simpler. I can’t remember the precise basis for that decision, because that was one of the first decisions I made on the project, six-ish years ago. I was probably influenced by the fact that most (though not all) existing tubas use piston valves. It might also be because rotary valves need more moving parts (you need some sort of linkage connecting the lever you actually press with your finger to the valve, as opposed to just sticking a flat button on top of a piston valve).
How did you (or planning to) make these macaroni elbows? How is the interior shape formed?
I’d suggest some kind of mold but can you remove a mold from these shapes? Maybe make a polystyrene foam mold. Shape it, leave a hollow core so it can be broken apart to take it out. Not sure what to use as a release from paper mache.
OK, I finished the curved tubes on the bottom segment today (aside from allowing time for it to dry), and got some pictures:
The first image was before I did the last layer of newspaper (and hence dry), and the second one is after (and hence still wet). I decided to use comics pages for the outermost layer, for decoration, but the dry pictures probably show the idea better.
I see, you’re doing the tubes in situ, I hadn’t realised that.
Yeah, it’d be too hard to match the shapes exactly, if I did them separately and then installed them.
I did have a new idea, though: What if I made the tubes out of cloth, stuffed them with fiberfill in situ, and then coated the cloth with… something (some sort of resin?) to stiffen it, and then removed the stuffing? All of those steps seem like they’d be much easier than what I’m doing now, and so now I just have to figure out what to use on the cloth. It would mean I’d need to create a pattern for the cloth tubes, but I’m trying to optimize for assembly work, not for design work.
See what you can accomplish with a pool noodle. Specifically a jumbo one. That might not get you the full diameter you need but perhaps a jumbo pool noodle inside a fabric sock with some fiberfill will get you better stiffness
A pool noodle is an excellent idea. A soft wire could be used to hold it’s shape.
The cloth needs to retain its stiffness after the stuffing (whatever it is) is removed.
Use leggings for the cloth. I assume there are some that are seamless.
Bondo (auto body filler) over the cloth will give you stiffness and hardness. You can also spray insulating foam like Great Stuff on it for more strength. It’s a difficult to spray on in a particular shape but you can easily shape it after it dries. Or build up paper mache over the cloth to make it stiff.
Wow, didn’t realize it’d been since July since I last updated.
Since then, a few developments. First, I tried using pantyhose stuffed with fiberfill, then coated with epoxy, for the tubes. It worked great for the shaping, but the insides ended up all wooly. No idea yet whether that’ll be acceptable for the sound. Then, I tried stuffing the pantyhose with sand (sawdust would probably also work), and that seemed much better all around. That’ll be what I officially put in the directions (though papier-mache is probably still the easiest option for the bell).
Second development, I discovered that my prototype had a mouse-friendly user interface. That is to say, mice ate big holes in the papier-mache (I was using flour paste as the binder) as it was sitting in the basement. I’ve since patched it up, and everything is now painted over with polyurethane clear-coat, so hopefully that will protect it. I used window screening for the framework for the patching, and that plus papier-mache might also be acceptable for the large tubes.
Third, I apparently didn’t have the right amount of thin-walled brass tubing (needed for the tuning slides), so it looks like the fourth valve will remain nonfunctional for now.
Fourth, the first and fourth valves are tighter fits than they should be. I think I’ll end up needing to tweak the design, and reprint those.
Fifth, one of the pipe bits is a little longer than expected, and so I’ll need to cut another hole in one of the boards to accommodate it (and then modify the design files, of course).
All that said, I think I can still get it put enough together to do a test blow before the end of the break.
This is an amazing project! Congratulations, just for the concept! And more for the work.
For what it is worth, my mother favoured mixing large amounts of salt to papier-maché glue (flour paste) to keep mold and insects out. Might help with rats too, but obviously must be sealed in, as salt attacts water… and a soggy tuba might be nice for an experimental jazz band, but probably has no other uses.
I’d expect salty papier-mache to be even more attractive (and hence vulnerable) to rodents.
Hey! My mum is an old wife, I don’t know if anyone should trust her tales.
FWIW, she also put lots of salt in the home-made play-dough (play-doh? Basically modelling “clay” made from flour, oil, salt, food colouring and salt - the extra salt was to prevent us kids eating it)
Anyway, back to your marvellous contraption…
Salt? The home-made stuff is often pretty much starch ‘n’ baking soda. I assume nothing bad would happen if a kid ate some.
I think my mom’s play-doh recipe included borax, too.