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Double Bass Top back seem separation help/options.

Ruckus_Instrmts

Ruckus_Instrmts

Jan 5, 2010
533
34
NEO
#1
Hi I'm looking for advice on how to go about repairing the seam separations occuring to my cel..l... lets call it a mini-bass. In the pictures you'll see the worst of the separations. I'm not trying to treat this mini-bass as some million dollar strad, but also don't want to have to repair the same spots year after year.
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As I said this is the worst of the separations. There are a couple other spots but no where near the size of the one pictured.

What now? :help:
 
#2
Seam separation is common and normal, especially with a new instrument. Think of those seams as a "safety valve". You want them to pop open if warping and stressing happens. Otherwise you'd have cracks in the top to deal with.

This is an inexpensive fix at your local luthier. It would be cheaper to take it to a pro than to buy the hide glue, a glue pot, and clamps for a DIY project.
 
#3
DallasStrings said:
Seam separation is common and normal, especially with a new instrument. Think of those seams as a "safety valve". You want them to pop open if warping and stressing happens. Otherwise you'd have cracks in the top to deal with.

This is an inexpensive fix at your local luthier. It would be cheaper to take it to a pro than to buy the hide glue, a glue pot, and clamps for a DIY project.
Click to expand...

Thanks for the response, was hoping you would chime in. Glad to hear its a normal/common problem. Makes sense seeing as how it came from Chicago all the way to central FL. Funny you mention cracks in the top, as there is one(sound post side) and the repair is obvious.

I'm more then capable of doing the work myself, have plenty of tools, and would rather enjoy taking on the project.
Is there an article on such a repair?
 
#6
Yes.

Since I suppose the luthier has to take down your soundpost anyway, to do the repair, then he or she can set it back up properly for you. But it could also possibly damage your cello in that orientation. What think the luthiers?

Note that I've also got a cello, rather old and many-times-repaired.
 
#7
I assumed the soundpost issue was to be added to the list when he brought it into a luthier.. If you're a bound and determined DIY'er, I'd suggest adjusting the post so that it's parallel with the back of the bridge, directly behind the middle of the bridge foot opposite the bass bar, and about one and a half times the width of the post itself behind the bridge foot. This is a good starting point from which you can adjust to tweak the tone quality.
 
#9
bigolbassguy said:
Have you removed the tension from the strings? It might be a good idea before your skewed soundpost does any damage.
Click to expand...

Yeah, and knock the sound post down while you're at it! Pointy sound post corners and spruce tops don't really go well together... :)
 
#10
bigolbassguy said:
Have you removed the tension from the strings? It might be a good idea before your skewed soundpost does any damage.
Click to expand...
Yes, the strings are sitting loosely on the cello, with just enough tension to hold them in the slots on the bridge.

DallasStrings said:
I assumed the soundpost issue was to be added to the list when he brought it into a luthier.. If you're a bound and determined DIY'er, I'd suggest adjusting the post so that it's parallel with the back of the bridge, directly behind the middle of the bridge foot opposite the bass bar, and about one and a half times the width of the post itself behind the bridge foot. This is a good starting point from which you can adjust to tweak the tone quality.
Click to expand...
I'm bound and determined because I'm a poor college student and the cello was basically given to me. I love playing(or at least attempting to play) the instrument, and I'm sure I would benefit from understanding the construction and inner workings of it. I figure if I can maintain/repair aircraft I can maintain/repair anything. :smug:

Jake deVilliers said:
Yeah, and knock the sound post down while you're at it! Pointy sound post corners and spruce tops don't really go well together... :)
Click to expand...
Thank you, I'll mess with the sound post today. Following Invalid Link Removed step by step article.
 
#11
Jake deVilliers said:
Yeah, and knock the sound post down while you're at it! Pointy sound post corners and spruce tops don't really go well together... :)
Click to expand...

...especially if you're clamping things. It's not just the pointy parts. The post is also longer in that orientation - bad combo.

Don't adjust the soundpost unless you just want the practice. Take Jake's advice - knock it out and remove it. As a mechanic, I'm going to assume you have something to fish it out with. It's pretty annoying when it's rolls around in there :)

ps - Checked out your link. contrary to popular belief - the soundpost does not transmit the vibrations from the top to the back. (I heard Yo-Yo Ma fueling this myth just a couple of days ago... anyway... he's wrong.) It's a focal point that works in conjunction with the bridge feet, allowing some control over the way vibrations radiate. Almost all of the vibrations from the top travel down the sides to the back.
 
#13
Ruckus_Instrmts said:
Ok so how do I fix the seams?

Does this just involve wicking in some fresh hide glue and lightly clamping it?
Should the old glue be cleaned out?
Click to expand...

Carefully clean out the old glue. Use a thin, round-ended blade to apply the fresh stuff. Clamp until the glue just squeezes out and clean up the excess right away with plain water. Use a weak solution - should be oily-feeling when rubbed between your fingers. It sets up quickly, so a lot of people like to heat up the area with a blow-dryer to increase working time. Your glue should be abt 150 degrees, I think. I use an old Hold Heet pot - so my glue is always the same temp.

Don't just take my word for it though. Ask a pro if you can - because I'm not one. :hiding:
 
#17
Alright Guys, I have to thank you for all your help, go ahead and give yourselves a nice pat on the back(just don't break your arm doing it). The cello is back up and running at full speed. And heres how I did it. You'll notice I did all this on my kitchen counter, and before you demote me to a "Kitchen Hacker" understand that I'm in central florida and at this time of the year the heat index goes up in the hundreds. Not to mention the MC%. So the garage/shop is not the place to work on cellos.

This first pic shows the gluing process. I used my stove to heat a small sauce pan filled with enough water to just float a small ramekin in which the glue was heated. I tested my stove and the small burner set on 2 kept the water bath at exactly 140-145 degrees. I used a small chisel edge oil painter's brush and a .0025 feeler gauge to work the glue into the joint and then clamped them with spool clamps. I made the spool clamps from threaded rod, a 1 1/2" poplar dowel, washers and wing nuts. Also used the timer feature on my microwave(set to 90 seconds) to make sure my speed was good. Non-skid padding helps to keep the instrument from moving around.
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After all the seams were fixed the sound post was next. I made my own sound post tools from 10 gauge copper wire twisted together and formed the same shape of the setting tools used by professionals. Did some practice setting before I glued up the seams to get the hang of it. This final set took me a good hour to get it were I wanted it.
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Not too shabby, eh? Although I did manage to ding up the finish around the f hole a little. Whats the best way to fix that?
 

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