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Has anyone fixed fiberglass sousaphones with massive cracks in the bell? Any suggestions?

I have seen King and Yamaha fiber sousaphones played live, but never had one in my hands, as these instruments are next to non-existent in my country. The ones seen were from a US army band and from a Canadian high school band respectively.

Is my impression from som ad material right, that the bodies and the bells, at least in some makes, are out of different synthetic materials?

Fiber sousaphones sold on online auctions often have chipped bell rims. Aside from the ugly visuals: can these missing parts of the rim be heard as inconsistent overtone patterns?

Klaus

bloke wrote:I certainly wouldn't mind seeing what someone else might have done successfully; I would define "success" as three years without re-cracking on at least three bells.

If the original fiberglass cracked, any repair that doesn't add strength will probably crack as easily.

If you sand off the gel coat, and then lay on layers of fiberglass with an epoxy binder (such as the West System), so that the patch is as thick as the original material, and then do this on both sides, I doubt it will crack at that spot again. But I also doubt that such a repair will be considered aesthetically acceptable.

Story: Back in college, I was in the craft shop at the student center when a guy came in with a cracked aluminum bicycle handlebar. The crack went about halfway around the bar. His solution was to drill a hole at the root of the crack to stop it from spreading. He asked my opinion (I was teaching a bicycle mechanics class there at the time), and I told him to get to carry a business card for a good reconstructive dentist with him when he rode, because chances were he'd be eating the stem at some point in the near future. He didn't like that, and insisted that the hole would stop the crack.

I asked him, "Which is stronger, a handlebar with no hole, or a handlebar with a hole?"

He knew where I was going but he was trapped, "I guess the bar without the hole."

I then asked, "Did the bar without the hole, which was stronger, fail?"

And then, "If it fails without a hole, what are the chances of it not failing with a hole, even without considering the crack?"

He bought a new handlebar.

Whether a smooth repair works or not depends on what cause the bell to chip out in the first place. If it was the inevitable twisting to mount the bell or banging into doorways, then I doubt any repair will work. If the trauma was truly a unique occurrence, then the repair will probably work. If the repair is thicker and stronger than the original material, and has sufficient overlap and adhesion, it will work (though the bell will probably break somewhere else), but it will be ugly.

But use epoxy, because you don't know what binder was used with the original. Polyester resin won't stick to sheet-mold-compound or epoxy, nor is it waterproof.

Rick "with experience making similar repairs to a fiberglass motorhome body" Denney

I've done a fair amount of marine fiberglass work and I think I know how I would do it. I wish I had a fiberglass bell to give it a try on. My school changed to metal souzies a few years ago so I don't have any victims...

Nevertheless...

I would take a coarse grinding disk and grind out about four inches either side of the crack, Right at the crack, I would grind it out paper thin and feather out to only taking it down about a 1/16th of an inch or so. Then, using marine grade epoxy or vinyl ester resin and hardener, put three or four layers of of light weight cloth over the crack, building it up so that it is thicker than the material was when you started. Use a metal roller or a squeegee built for the purpose to make sure that the resin has saturated everything and that there are no air bubbles. After it has cured overnight, use a sanding disk- about 120 grit- and a medium speed sander and grind down the excess. When you are kinda close to where you want it to be, change over to 120 grit on a hand sanding block and take it the rest of the way down. You might want to take it a little bit further down than what you want for a final level. Put a very thin layer of bondo over the work (less than a 1/16th of an inch) when finished. Sand it to where you want it, prime it with high build epoxy primer, finish sand and paint.

If you want to repeat this process on the other side of the material, grinding out some of the material you have just put in, go ahead but that probably would be overkill.

This is how it is done in the marine industry and on fiberglass bodied cars like Corvettes. It's messier than hell so use gloves and a good respirator (not a paper mask.) Grinding a ditch and sticking in wire concentrates the stress right at the wire so I'm not surprised that it didn't last. In the described method, the cracked material is actually being removed and replaced with new material. Done with care, this repair should be invisible. The repair probably is stronger than the rest of the bell. I don't think that would cause a problem, though...

Jeff "250 hrs labor making a Navy whaleboat look like a yacht" Benedict

Intersecting my Industrial Design day-job experiences with my years of playing plastic Sousaphones: probably the reason typical fiberglass repairs won't work on Sousaphones is because some (maybe many) horns are made from pressure molded glass reinforced compound plastics - not the more common fiberglass epoxy lay-up that is used for some automotive or boat making. The way the plastic molecules link together under heat and pressure during the original manufacturing processes dictate how they will (or will not) be repaired. I have noticed that some horns have a rubber-like polymer in the mix, and that can really mess with later applications of resins or other glues. Even more common fiberglass reinforced epoxies are very difficult to work with after the initial chemical curing process has happened.

Take a look at a textbook from an Industrial Plastic Materials college course - there are so many different plastic compounds to choose from! Without knowing exactly what your horn is made out of, you cannot expect to be able to successfully patch it. We had to learn how to feel, smell, cut, and even burn samples of plastic compounds to try to figure out what they were made of - it is not easy (unless you somehow have access to the exact manufacturing specifications for the particular horn.)

(and I concur with the other recent comments made while I was typing this - if you have the more repairable base materials a patch can possibly be made, but it is still a crap shoot without knowing the exact type of plastic you are working with.)

bloke wrote:That sounds like a good (albeit probably more expensive than a non-cracked bell off of eBay) solution....

Probably about $10-15 in materials, 1-2 hrs. of labor with time in between working. YMMV

David Richoux wrote:Intersecting my Industrial Design day-job experiences with my years of playing plastic Sousaphones: probably the reason typical fiberglass repairs won't work on Sousaphones is because some (maybe many) horns are made from pressure molded glass reinforced compound plastics - not the more common fiberglass epoxy lay-up that is used for some automotive or boat making.

I'll defer to your knowledge rather than my experiences. Perhaps my ideas wouldn't transfer to souzies for the reasons you mention. Constructing a fiberglass bell has intrigued me but not enough to research and give it a try.

I think I would make a mandrel, coat it with resin and then build it up with cloth, biaxial fabric and maybe carbon fiber inside. I'd build it up and then sand it to finished specs on a lathe kind of like how it is done with a metal bell. Sounds like too much work. Much easier to talk about it on TubeNet than actually doing anything...

I think Goodgigs has an easier method with his plastic tuba.

Didn't/doesn't one of the guys in the Canadian Brass have a tuba with a carbon fiber bell?

The Big Ben wrote:Didn't/doesn't one of the guys in the Canadian Brass have a tuba with a carbon fiber bell?

There are several tubas that have been made using a carbon fiber composite.

But the binder in a carbon composite is the same in hand-laid epoxy fiberglass.

David was saying the same thing as me: Most repair resins won't stick to sheet-mold compound. But epoxy will, if the gel coat is removed first.

But my point is being missed by others (except bloke). If the bell is receiving the sort of treatment routinely that causes the failure, then nothing will work in the long run. If the damage was a one-time event (such as is usually the case with boats and cars), the repair methods outlined in this thread will work. If the base material isn't strong enough, no patch will be unless it's thicker and thereforestronger than the base material. And then it will break somewhere else.

So, for an adult, an epoxy repair using stuff like the West System epoxy, applied in several layers to the original material that has been feathered, will work and probably last. That's because the mishaps that caused the failure will be a rare event with an adult. School instruments are another story.

The generator and propane compartment doors on my motorhome have weak points near the vents. Those weak points tend to crack with use. Lots of people (including me) have tried lots of repairs, but the pros, when restoring a coach, replace the door altogether. Only epoxy sticks to the SMC used by GMC, but the patch can't be stronger than the original if it's sanded down to the same thickness.

Rick "not a fan of polyester or vinyl ester resins for most things" Denney

As a guy who just in the last couple of years has had to do a couple of epoxy repairs on a couple of small issues on fiberglass souzys, an Olds and a Beuscher, I agree with Rick completely. The Olds is going to have only occasional use in Shrine band, now that I have the use of the 38K and one other guy is using the Cavalier; and outdoor concerts are usually riding on a parade trailer; so the exposure to further damage is minimal, and the patch-type epoxy repair outlined above should do for the forseeable future. Fortunately, I haven't had to deal with any major cracks, and I'm not sure that if something that untoward should happen that the horns may just get salvaged out instead of getting repaired. After doing what I could for the Beuscher, it just was to the point overall that it was sold.

The Big Ben wrote:.
snip

Didn't/doesn't one of the guys in the Canadian Brass have a tuba with a carbon fiber bell?

yes - but remember that the carbon fiber is replacing the glass fibers - not the resin that holds them together.

Because carbon fibers are much stronger than glass strands, a thinner (and hopefully more responsive, brass-like) horn can be made with that material. I suppose if they ever get enough "Bucky-Tube" molecular fibers produced to be cost effective, a super strong but thin tuba or Sousaphone bell could be made with them - no idea how good or bad it might sound! (way out of my league...)

"Epoxy" is a very generic term - there are probably thousands of variations, and that does not include the other possible fillers, pigments and even mold textures - they can all have effects on what repairs are going to work or not.

There has been so much experimentation and modification of reinforced plastics over the last 40 years or more - it would be almost impossible to determine what particular compound was used by a specific plastic Sousaphone maker in any given production series unless you had access to the manufacturing records. You can get lucky with a commercial patching kit, or not. I have been working on a beater King over the last 10 years - the strongest patch has been a micro-glass bead (tiny glass bubbles so small they look like dust) in an aerospace epoxy that was left over from a project for Lockheed. I can hit it with a hammer and nothing much happens, but it is light and the horn still sounds OK!

David Richoux wrote:

The Big Ben wrote:.
snip

Didn't/doesn't one of the guys in the Canadian Brass have a tuba with a carbon fiber bell?

yes - but remember that the carbon fiber is replacing the glass fibers - not the resin that holds them together.

That was a more rhetorical than anything else.

I understand about 'epoxy' and its varieties. I had three different kinds of resins and three hardeners as well as three or four different additives when I was doing my boat project. Not getting into the reinforcement materials or the solvents.

I believe that the Conn 36K and the 22K had Bell flares that were made from Vacuformed PVC/or ABS plastics, Mated to a fiberglass type material elbow.
Almost everyone that I have seen/played has had a discolored bell flare.(I have seen one that WAS NOT repainted that had a WHITE bell flare)
The King's and the Olds/Reynolds that I have seen and played had a single material construction from elbow through the flare.(I've sanded down a number of all of the mentioned brands before painting them)
YMMV
Dave Hayami

I am using the same technique as Bloke posted in his first post, except i am applying a short strand fiberglass body filler to it over a larger area than the crack prolly around 3-4 inches away from the crack, so far it has stood up pretty well, we shall see once they return to the hands of the children that put them in this condition....

Bondo? I know they make stuff with fibers in it, like hair. I know it's used for fiberglass repair, it might work well and it might not. I've never used it myself but I've seen it on the shelves and thought "I wonder if that'd work on a sousaphone?" Resin would also be a viable option if you want to spend some time working with it. Have fun with it!

tubatom91 wrote:Bondo?

Not recommended. Bondo uses a polyester resin filler that is neither waterproof nor strong. It works because it it applied in a very thin skin over metal--thin enough to remain flexible--and then it is painted. I have used it for filler that is loaded only in compression. such as for patching holes in floors, but not for skin structures that are loaded in bending.

The epoxy that Joe mentions should work fine, but so will any good waterproof epoxy, such as the West System materials made for boat-building. The different mixes and hardeners are to control the set time, so get the slow-setting stuff and don't worry about it.

Rick "who has a fiberglass project in the works" Denney

When the cohesion has been compromised, then a repair will be followed by a new crack. That appears to be the lesson of this thread.

One way to go would be the Jupiter-emulation and put on one of the brass bell floating around after loosing a working body.

If such brass bell has its own problems like a compromised or non-fitting collar, it still may be of help. At least in my imagination, as I haven’t ever had a fiber bell in my hands. What about cutting a broad garland out of the brass bell and glue it to the back of the fiber bell? The same brass bell might even help more than one fiber bell as the garland doesn’t necessarily have to sit along the bell rim.

Klaus

white duct tape???
isn't that in every handyman's tool kit?
k

ken k wrote:white duct tape???
isn't that in every handyman's tool kit?

No, that's silver Duck Tape

God I hate these repairs!

First, if you have a King or Jupiter, buy a new Jupiter Bell. You can get a good bell and the Jupiter fits the King, and the cost is minimal and it looks and lasts good/well.

Second - I'm going to try a different technique next time - using sheet metal (brass?) over the crack as part of the fiberglass and resin application. Try to make it stronger at the crack, with room enough in the crack for the epoxy to set against itself through the crack. Probably won't work, but I'll try anything.

Beware the Plastic bells vs. Fiberglass! Nothing fixes them, ever!

Third, eBay can also be your friend!

Replacing a chip from a Sousa bell is a heck of a lot easier to fix than a crack or large broken section. Sometimes it can work quite well!

As always... your mileage may vary...

J.c.S. (who wonders if anyone else is having weird scrolling issues in the message field!)

J.c. Sherman wrote:Beware the Plastic bells vs. Fiberglass! Nothing fixes them, ever!

With plastic such as ABS, you can use ABS cement and cement a patch. ABS cement is a solvent weld and as durable as anything.

Likewise PVC, but I'll bet they aren't PVC.

Polypropylene and polethylene can't be glued successfully because nothing sticks to them. But they can be welded if you have some filler material made of the same stuff. A big soldering iron will work as will a plastic welder that uses a low-pressure stream of very hot air. As with welding metal, the key to strength is complete penetration.

Any thermoplastic can be welded with heat. But resin-set plastics like some acrylics, epoxy and polyester fiberglass fillers are thermosets, and can't be softened with heat successfully.

Rick "who bets those non-fiber-reinforced bells are ABS because it's cheap and easy to vacuform" Denney