Violin Forum/Message Board Forum Index Violin Forum/Message Board
Provided by Lemuel Violins
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Repairing my cheap first cello

 
Post new topic   Reply to topic    Violin Forum/Message Board Forum Index -> Violin Making and Restoration Forum
View previous topic :: View next topic  
Author Message
whatwasithinking
Member


Joined: 26 Jan 2013
Posts: 227
Location: Washington State

PostPosted: Sun Jan 03, 2016 9:31 pm    Post subject: Repairing my cheap first cello Reply with quote

Despite having too many projects on my plate already, I finally decided I wanted to do something with my rather sad old Scott Cao cello, which had a drooping neck, a crack in the top of the back from careless handling by a child (who had a too-trusting dad), and a lot of extra weight.

This instrument was never going to get the attention it needs from an expert, so it's getting me.

The belly weighs about 640g, with bass bar in place. Thicknesses range from about 3.6 near the outside-upper bouts, and mid-lower bouts. The center section reaches 5.8 in some spots, but is mostly between 5 and 5.5. The area with the most consistently thick area is the region on each side of the bass bar. It goes up and down longitudinally from the center about 100mm, and out laterally from the bar to about 20-25mm, and is mostly 5.8mm.

The ribs are mostly 1.5mm, but reach 1.8mm in a couple of spots.

The bassbar was 28.7mm at the middle, and drops to about 16mm at the 1/4 point. That includes the thickness of the belly. And not really a very nice taper to it--kind of like a dromedary. Thickness is okay--about 10.5mm.

Looking at the varnish that was dribbled into the inside around the f holes, it seems thick--and maybe heavy. How much weight could this represent?

I don't know much about tap tones on instruments, but there sure isn't much of a ring to the wood, no matter where I tap it, except for the presence of a very low frequency vibration. Just guessing, it feels like well below 60Hz.

Suggestions, please!

Leave the graduations mostly as is? Take off the high spots, where they are close to 6mm, but leave the rest alone? Try to thin down the varnish, to remove weight? Strip it off, put a proper ground on, and refinish?

I haven't tried mode testing, or any of that sort of stuff, but have tools around, if that's worth pursuing. I hadn't planned on any of that.

I've been accused of being foolish and/or stupid before, and that's never stopped me. Hoping to have something that's playable, in the end.

Thanks!

Bob
Back to top
View user's profile Send private message
whatwasithinking
Member


Joined: 26 Jan 2013
Posts: 227
Location: Washington State

PostPosted: Mon Jan 04, 2016 3:03 pm    Post subject: Reply with quote

I know some folks here have worked on sad Chinese cellos. I welcome any suggestions.
Back to top
View user's profile Send private message
L P Reedy
Super Member


Joined: 02 Apr 2009
Posts: 271
Location: Brevard, NC

PostPosted: Mon Jan 04, 2016 6:46 pm    Post subject: Reply with quote

I don't make cellos nor work on many of them, but that hasn't stopped me from commenting. I think that 3.5 to 4 mm all over is a more normal belly thickness (Chet knows), so some careful thinning might be in order. I wouldn't worry about whether it rings when tapped. It isn't a bell, it's an amplifier. One of my better fiddles just made a dull thud when the belly was tapped.
Back to top
View user's profile Send private message
whatwasithinking
Member


Joined: 26 Jan 2013
Posts: 227
Location: Washington State

PostPosted: Mon Jan 04, 2016 7:40 pm    Post subject: Reply with quote

Yes, it seems a bit thick. Somewhere I saw some numbers Michael posted, and 5mm was the max, IIRC. This might not be the best wood, either, so I'm sure that is a consideration.

Interesting about the wood you describe. I don't think I can make it much worse than it was, but I don't want to make it too weak, either. I've read about cellos that were regraduated down to 2.5 in places, which I guess helped them vibrate on a bench, but that seems pretty extreme. Folks have already warned me not to go down that road.

I'm suspicious of the VLC (varnish-like coating) on the front. It looks pretty thick.

Thanks for the comment!

Bob
Back to top
View user's profile Send private message
L P Reedy
Super Member


Joined: 02 Apr 2009
Posts: 271
Location: Brevard, NC

PostPosted: Tue Jan 05, 2016 5:27 pm    Post subject: Reply with quote

I forgot about the varnish question. I would not do anything about that until after you get it back to playable condition, if ever. You can't really judge the thickness by inside drips. If it is original Scott Cao varnish, I would leave it alone. It is doubtful you would improve it. Also not likely that it adds more than a few grams of weight.
Back to top
View user's profile Send private message
whatwasithinking
Member


Joined: 26 Jan 2013
Posts: 227
Location: Washington State

PostPosted: Tue Jan 05, 2016 9:13 pm    Post subject: Reply with quote

Thank you. I'll leave it alone.
Back to top
View user's profile Send private message
whatwasithinking
Member


Joined: 26 Jan 2013
Posts: 227
Location: Washington State

PostPosted: Thu Feb 22, 2018 12:37 pm    Post subject: Follow up Reply with quote

Thought I’d close the loop on this project.

Regraduated the top, ending with a mode 5 frequency of 129 Hz. Didn’t change the back, which didn’t seem way out of line, thickness-wise.

Undercut the fingerboard, up to about an inch before the neck.

Shimmed the neck, increasing the overstand, and bridge height, to acceptable levels.

The weight of the top, with bass bar, went from 640g to 543g. I think the spruce used in China is somewhat heavy and stiff.

The change to the sound was stunning, and now the instrument sounds dark and warm, with good lows and a balanced spectrum. It went from being barely tolerable, and difficult to play, to being one of the better cellos I’ve played, with good responsiveness. The wolf ended up just below F natural, and is easily avoided.

Now I’m planning to do something similar to my German cello, which has a rather thick top.
Back to top
View user's profile Send private message
Dave Chandler
Super Member


Joined: 31 Oct 2007
Posts: 691
Location: Mt Mitchell in North Carolina

PostPosted: Fri Feb 23, 2018 12:12 am    Post subject: Reply with quote

Sounds like a good outcome. I personally think a heavy back has less affect than a heavy belly. Fortunately, you don't have to hold a cello under then chin, so a thick back is of less consequence. (especially on a student instrument).
_________________
Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo
Back to top
View user's profile Send private message Send e-mail Visit poster's website AIM Address
Chet Bishop
Super Member


Joined: 23 Mar 2007
Posts: 670
Location: Forest Grove, Oregon

PostPosted: Fri Feb 23, 2018 10:17 am    Post subject: Good Job! Reply with quote

This is the first I had seen this thread. Sounds as though you did a great job!
_________________
Chet Bishop
https://bluefiddles.com
https://fivestringfiddles.com
Back to top
View user's profile Send private message Visit poster's website
whatwasithinking
Member


Joined: 26 Jan 2013
Posts: 227
Location: Washington State

PostPosted: Sat Feb 24, 2018 11:31 am    Post subject: Reply with quote

Thanks, Chet. I think this was worth doing.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Violin Forum/Message Board Forum Index -> Violin Making and Restoration Forum All times are GMT - 4 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group