GR Bass AT-112H – Structural Reliability Issue

[Jeff Scott]

think OP's photos show very well that it's really a structural problem: it's almost impossible to keep this material together firmly with all the vibrations a bass cab has to endure.
If you design a car to beat world records, you want it to be as reliable as possible but it will always be more fragile than a familly car.

 

[JazznFunk]

Can't tell but did the weave actually break or are we seeing compromise in the interfaces between dissimilar materials? I'm wondering if this is something we can wrestle back into shape with clamps, epoxies (Western Systems), and internal reinforcements & bracing. The velcro grille mount separation is particularly disturbing and may very well be representative of the balance.

We've got tons of boat repair guys here who COULD tackle the project but at a hefty cost. I'd check in with @Bruce Johnson first...not necessarily a cab guy but knows his way around epoxies, glue-ups, TOS, etc.

Riis

Good question, and point taken. My assumption is that there was some sort of impact which might have caused it to happen. If it's a separation of pieces which are not part of the carbon fiber panels and are only attached, then as long as the resin and weave aren't compromised, it's a whole other ballgame in terms of repair.

 

[JazznFunk]

F1/auto racing guy here:

That's a misleading video in terms of discussions of carbon fiber strength/resiliency. The experimental uprights on Buemi's car failed, and they were made of titanium/aluminum alloys, not carbon fiber. The upper and lower A-arms are usually made of carbon-wrapped steel. They did not fail in that accident. There are a lot of parts on a modern F1 and IndyCar that are totally made from carbon fiber, Kevlar, etc for sure though. Tub, bodywork, wings, etc. Key structural points are usually carbon-wrapped metals of some sort.

 

[JazznFunk]

Carbon Fiber cabs are not design for easy life, they are like race cars.

Not necessarily. As long as the carbon fiber resin/weave is not broken, it will last longer than any of us will be alive. It's impervious to environmental issues as long as it's not structurally compromised by physical damage. There is a lifespan for every single part in a race car because of the forces to which it's subjected, and certain parts are 'lifed out' after X number of miles, but even cars which have been in heavy crashes where every other damaged part is replaced can be rebuilt if the core carbon fiber safety cell/tub is not damaged. Having spent quite a bit of time around IndyCar paddocks in my life, you'd be surprised at the cars which are still good to go despite having been in several incidents. If the tub shows any signs of a crack or any sort of compromise, it is retired. They are often scanned via X-Rays and other measures to find hairline or invisible cracks too.

All of that being said - a bass cabinet will NEVER be subjected to the same impact or vibrational forces that a race car is. There is no reason, as long as the panels/components are fitted together well, that a carbon fiber bass cabinet would have any less of a lifespan than another cab of a different material.

 

[Jeff Scott]

F1/auto racing guy here:

That's a misleading video in terms of discussions of carbon fiber strength/resiliency. The experimental uprights on Buemi's car failed, and they were made of titanium/aluminum alloys, not carbon fiber. The upper and lower A-arms are usually made of carbon-wrapped steel. They did not fail in that accident. There are a lot of parts on a modern F1 and IndyCar that are totally made from carbon fiber, Kevlar, etc for sure though. Tub, bodywork, wings, etc. Key structural points are usually carbon-wrapped metals of some sort.

I agree, but it's still a "fun" video to watch.

 

[JazznFunk]

I agree, but it's still a "fun" video to watch.

I remember when it happened! That was insane.

 

[Zooberwerx]

Good question, and point taken. My assumption is that there was some sort of impact which might have caused it to happen. If it's a separation of pieces which are not part of the carbon fiber panels and are only attached, then as long as the resin and weave aren't compromised, it's a whole other ballgame in terms of repair.

Yeah, I saw that dab of adhesive on the velcro block and kind of wonder if this was the same level of integrity applied to every joint t/o the enclosure? Given the ease at which it separated, I'd be half-tempted to "finish the job" and re-build from the sneakers-up like a flat kit.

Riis

 

[JazznFunk]

Yeah, I saw that dab of adhesive on the velcro block and kind of wonder if this was the same level of integrity applied to every joint t/o the enclosure? Given the ease at which it separated, I'd be half-tempted to "finish the job" and re-build from the sneakers-up like a flat kit.

Riis

You read my mind. If the cab is made from 5 or 6 completely separate panels that are then bonded together and secured at the corners and at other points there's a lot that could go wrong if it's not done properly. Now, if 5 panels of the cab are formed as one complete piece (leaving one opening in the front) and then fired in an autoclave, where there are no seams at all, and the only opening is in the front where the speakers, etc are then installed, that's a whole different ballgame. That would be an incredibly strong and durable cab with no seams to bond, but also a lot more expensive to produce most likely.

 

[matthewbrown]

I bought the same model cab about a year ago. I don't gig with it more than 3-4 times a month, and I keep it in a padded bag when not in use. One advantage of the light weight is that you can move it quite carefully. I'm 67, and I'm hoping that it will outlast my ability to carry it, but perhaps I'm being too optimistic. I'm 67, and I'm hoping that it will outlast my ability to carry it, but perhaps I'm being too optimistic. Perhaps I'll have to save it for those gigs that 1) require more output and 2) are UPSTAIRS with no elevator!

 

[gil_mor]

Exactly what I was going to mention. Even though his region (Talent, Oregon) isn’t known for humidity fluctuations, sometimes the room where it’s stored may have dampness issues. I know. I used to live in a house that had humidity issues in one room. I was going to ask the OP if the cab showed any signs of previous repairs in those trouble spots.

While humidity doesn't go crazy high/low here, maybe temparture has something to do with it.
The inside of my car can get pretty toasty. Perhaps over time the uneven heating caused it to warp?
I sometime leave gear (not basses) in the car between shows/practices but never had an issue.

When I got the cab it was in the mintiest of mints condition. No issues whatsoever. It must have happend in the last year.

Can't tell but did the weave actually break or are we seeing compromise in the interfaces between dissimilar materials? I'm wondering if this is something we can wrestle back into shape with clamps, epoxies (Western Systems), and internal reinforcements & bracing. The velcro grille mount separation is particularly disturbing and may very well be representative of the balance.

We've got tons of boat repair guys here who COULD tackle the project but at a hefty cost. I'd check in with @Bruce Johnson first...not necessarily a cab guy but knows his way around epoxies, glue-ups, TOS, etc.

Riis

This is what GR told me about the possibilty of fixing it (initially, they thought it was possible):

I have reviewed the photos together with our technician, and technically it would be possible to glue the structure again. However, the chances of achieving a stable and lasting result are extremely low.

In one of the photos, we can clearly see that the internal foam is tearing apart, which means that a large amount of two-component glue would be required. Even then, the curve would no longer close perfectly, making the whole structure unstable.

Unfortunately, the only way to fully restore the cabinet to 100% is to completely replace the structure.

Since they are the one's who built it, I'll take their word for it.

I bought the same model cab about a year ago. I don't gig with it more than 3-4 times a month, and I keep it in a padded bag when not in use. One advantage of the light weight is that you can move it quite carefully. I'm 67, and I'm hoping that it will outlast my ability to carry it, but perhaps I'm being too optimistic. I'm 67, and I'm hoping that it will outlast my ability to carry it, but perhaps I'm being too optimistic. Perhaps I'll have to save it for those gigs that 1) require more output and 2) are UPSTAIRS with no elevator!

I think using it for those situations is an exclent idea. Stairs and no elevtor is the reason I bought mine.

 

[Pep]

I'm 67, and I'm hoping that it will outlast my ability to carry it, but perhaps I'm being too optimistic. I'm 67, and I'm hoping that it will outlast my ability to carry it, but perhaps I'm being too optimistic.

Matthew,
You’re starting to worry me. You repeated yourself and you’re only 67.

 

[MCF]

Honestly folks. There is a lot in this thread which is a little less than accurate. One could make carbon fibre cabs that you could stand an elephant on if needed.
To my mind the big challenge with CF cabs is building them down to an acceptable price. The materials can be as solid as you like. You know the sort of thing, cheap, light, strong, pick any two.

As ever, the engineering is a question of compromise and learning. If this is a cab they built five or 6 years ago then its probably not built the way they make the things now. I'd need to see the thing to give a serious opinion on what went wrong, even as an amateur boat builder with carbon, but on the face of it this looks as if it could be a design issue with that particular product as they were making it 5 or 6 years ago. Rubbishing the entire concept because of a failure of one particular implementation isn't really rational thinking. Don't get me wrong, I think there are serious challenges in putting together a roadworthy CF cabinet, but they are mainly about affordability.

Yep.

CF revolutionized my other hobby, fly fishing. And look what the technology did for cycling. Quality CF fly rods are exppesive. And some cyclists pay what many of us pay for cars. CF is amazing tech. And evolving. But it isn’t cheap. I applaud the effort to bring it to bass cabs. Not everyone wants to play through tiny DI boxes. They will get better. It will take time. And players willing to pay the premium to finance the evolving tech.

 

[Zooberwerx]

While humidity doesn't go crazy high/low here, maybe temparture has something to do with it.
The inside of my car can get pretty toasty. Perhaps over time the uneven heating caused it to warp?
I sometime leave gear (not basses) in the car between shows/practices but never had an issue.

When I got the cab it was in the mintiest of mints condition. No issues whatsoever. It must have happend in the last year.


This is what GR told me about the possibilty of fixing it (initially, they thought it was possible):


Since they are the one's who built it, I'll take their word for it.


I think using it for those situations is an exclent idea. Stairs and no elevtor is the reason I bought mine.

GR's response pretty much sums it up...go for the discounted plywood cab. The foam scenario smacks of the Status all-composite sandwich. They start with a foam structure (...like the stuff florists use?!?) and then wrap from there.

Sorry this happened. Don't care that it's out-of-warranty, secondhand, stolen, etc., the fact it suffered this level of non-traumatic failure makes me a little uneasy. I've had bad experiences with PUR foam in medical equipment.

Riis

 

[matthewbrown]

Matthew,
You’re starting sorry me. You repeated yourself and you’re only 67.

Editing too fast among way too many interruptions. Sorry!

 

[agedhorse]

Composite-foam core is very difficult to work with, it's hard to make inexpensive connections between panels and wrapping the panels to integrate into a single structure is expensive.

 

[JimChjones]

While humidity doesn't go crazy high/low here, maybe temparture has something to do with it.
The inside of my car can get pretty toasty. Perhaps over time the uneven heating caused it to warp?

Very unlikely IME. Whilst there are things that can go wrong with some resin systems if they get badly cooked (mostly early wet layup ones) I cannot see that they would be significant used for a cab. I might be a bit more concerned if there was structural wood in the mix, but even then not very worried.

From what I can see in the photos my first guess would be that it got one hell of a thump from just the wrong angle. If I'm right about that the same impact would have done a ply cab no good at all either. It might just be bad luck. If it were mine I would repair it, but I don't have to cost my time. One of the considerations, too, is aesthetics. I would run carbon unidirectionals over the area that's failed and make it twice as strong as before, but you'd lose the nice weave appearance. That is one of the material limitations - you can almost endlessly repair lower stressed carbon fabrications, but making them look as if they haven't been patched up is quite another game. We amateur boat builders tend not to clear coat our carbon: paint and filler hides all sorts of sins!

 

[Pep]

Editing too fast among way too many interruptions. Sorry!

No apology necessary. I’ve done it a couple of times myself.

 

[JamesGrant]

I'd love to know where you got the corners.

Invalid Link Removed

 

[eniac]

Matthew,
You’re starting to worry me. You repeated yourself and you’re only 67.

I'm older than he is. He did it intentionally for me, in case I didn't get it the first time.

 

[Relsom]

The fragility of the AT line has me hanging on to my Shuttles at least for now. Admittedly, I've dumped a boatload of $$ on 2 pieces that I'm hoping will last as long as I need them to. An AT 212Slim ACT arrived with a busted corner and piece of the trim. I bought it used and the trim damage doesn't appear to extend into any of the structure, so I'm not worried about that....yet. GR is sending me a few corners to keep me in spares, so thanks to them for willing to take care of a 2nd hand piece like that.
With the broken corner removed, you can see the internal foam core. I'm wondering, does anyone know how these cabs are actually constructed? How thick are these panels, how are they held together, is there any bracing? I'm not going to take it apart to investigate these curiosities....I'm afraid of the hardware stripping out and don't want to risk it. I will say that the unit sounds fantastic. No complaints in that regard. I haven't had the chance to take the Cube 800 Combo out of the house yet. So far though, it's flawless and has a warranty, so some piece of mind.