New Project -- Mohan Singh Tumba Replacement

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katyrow
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New Project -- Mohan Singh Tumba Replacement

Post by katyrow » Mon Jul 18, 2016 6:13 pm

This is a 1950s Mohan Singh. Someone had done an awful job repairing the tumba before I got it. There was basically no original gourd material left, so I have removed completely what was there. I want to build a tumba from scratch and am wondering if anyone has attempted this before. I've thought about fiberglass or maybe carbon fiber. The other option might be to build a balsa wood structure and then clad it with balsa. Any thoughts on this? Thx.
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katyrow
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Re: New Project -- Mohan Singh Tumba Replacement

Post by katyrow » Sat Jul 23, 2016 12:29 am

Decided to try balsa wood. Most of the frame is done. Will need to clad and finish it after that. No idea how it will sound, but it's solid and very light weight.
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Lars
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Re: New Project -- Mohan Singh Tumba Replacement

Post by Lars » Sat Jul 23, 2016 1:17 am

Looks fine, you would have had to cut the gourd anyway to get it to fit right given how the structure was. Quite a job!

Lars
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Greg
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Re: New Project -- Mohan Singh Tumba Replacement

Post by Greg » Sat Jul 23, 2016 12:23 pm

Great project....nice start. You could of course have made the gourd a different shape if you wanted, not sure what shape...but p'raps better to stay with the traditional.

Have you thought about covering your frame in papier mache? Not sure if you could bridge the spaces, but with big enough pieces of paper initially it could work. I imagine the end result would be as strong as a gourd if you used enough layers and as lightweight, also easily shaped, sanded and painted.

Just an idea....

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katyrow
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Re: New Project -- Mohan Singh Tumba Replacement

Post by katyrow » Sat Jul 23, 2016 6:59 pm

Thanks Greg! The Rajah Electric Zeetars from the '60s had paper mache gourds. I did think about that, but plan to try balsa because I think it might be lighter in weight and it seems to resonates in a way that is similar to spruce used on some guitar tops. I'm guessing that paper mache was good for the Zeetars because they had steel strings with magnetic pickups and weren't really acoustic instruments. I'll be interested to see what this sounds like because the tabli under both bridges will be physically connected to every area of the "gourd," instead of the tabli meeting the gourd on just the perimeter. I'm hoping that it has the same effect as a violin sound post or the block connecting the top to the back in a semi-acoustic guitar. Or maybe it will be similar to having a thicker tabli.

RobertMaya
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Re: New Project -- Mohan Singh Tumba Replacement

Post by RobertMaya » Sun Jul 24, 2016 12:35 am

Hmm...

My only concern is that the internal braces/structure thingies would hinder complete resonance, as opposed to a completely empty gourd. Carbon fiber would be an expensive alternative, as you would need 2 - 4 (prob closer to 3, 4 for strength) layers of 2X2 twill (this loose pattern conforms to curves much better). You could just throw in a block of foam, carve it to toomba size, then vacuum bag some carbon fiber on it.

I built a rudra veena toomba using paper miche and resin, so kinda familiar with this stuff (but nobody read my post on the Rudraveena Build Advice thread, so I'm sad).


Best of luck on the restoration!

Rob

katyrow
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Re: New Project -- Mohan Singh Tumba Replacement

Post by katyrow » Sun Jul 24, 2016 3:18 am

RobertMaya wrote: My only concern is that the internal braces/structure thingies would hinder complete resonance, as opposed to a completely empty gourd.
Agreed. It might be a muffled mess for that reason. I'm no expert, but I understand that this has to do with the volume of air in the chamber as well as how the chamber is segmented. On other other hand, I have sitars that are too resonant for my taste, and others that are boomy, which I assume is because the tumba is either too large or too open, or the tabli is too thin and not well-dampened. I think that this is a luck-of-the-draw kind of thing having to do with all of the aspects of the instrument, so I've got my fingers crossed that is will one work out.

RobertMaya
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Re: New Project -- Mohan Singh Tumba Replacement

Post by RobertMaya » Sun Jul 24, 2016 6:40 am

Well on the other hand, you could use this balsa structure as a skeleton, steam/bend/fix the outer toomba shape, add the varnish/laquer, and remove the inner scaffolding after the outside has structural integrity. That would give you a nice hollow chamber. If you'd like to use a composite as reinforcement, I'd recommend carbon; fiberglass is too floppy (hence the prevalence of carbon violins over fiberglass violins). It is more expensive though, but with balsa making up most of the gourd you'd greatly reduce the cost.

Keep us posted!

Cheers,
Rob

katyrow
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Re: New Project -- Mohan Singh Tumba Replacement

Post by katyrow » Sun Aug 21, 2016 12:49 am

Balsa gourd is finally done. I don't even want to think about how much time I've got in this project. The sitar sounds great though.
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desh
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Re: New Project -- Mohan Singh Tumba Replacement

Post by desh » Sun Aug 21, 2016 3:18 pm

Congrats on a job well done! The sitar looks fantastic. A few questions:

Did you end up covering the balsa frame also with balsa?
If so, how did you bend the balsa to get it so rounded?
If not, what did you end up using?
How is the strength and weight of your new toomba compared to a traditional gourd?

Thanks
Desh!

Bakersbites786
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Re: New Project -- Mohan Singh Tumba Replacement

Post by Bakersbites786 » Sun Aug 21, 2016 5:14 pm

Hi
A job really well done!!
Plz share more info regarding the finished product. I have an old Teak Rikki Ram (white badge with gold lettering) that needs a new tumba. Was thinking of sending it to Sher Mohammed and sons because they use similar soft wood tumba construction which I like the sound of.
Thanks.

katyrow
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Re: New Project -- Mohan Singh Tumba Replacement

Post by katyrow » Sun Aug 21, 2016 5:35 pm

desh wrote:Did you end up covering the balsa frame also with balsa?
If so, how did you bend the balsa to get it so rounded?
If not, what did you end up using?
How is the strength and weight of your new toomba compared to a traditional gourd?
Thanks Desh! Yes, the entire tumba is balsa. After making the frame, I cut the balsa in short strips, maybe three or four inches long and an inch wide, and glued them to the frame one at a time. Had to fill in a lot of little spaces with odd shapes. It took a long time. Cut against the grain, the strips bent easily along the grain and stayed in place with painter's tape while the glue dried. Had to do it in pretty small sections at a time. It's probably a little stronger than a natural gourd because of the frame. No noticeable difference in weight. The balsa gourd might be slightly lighter.

I have another one of these sitars in original condition from the same era. It may be the best sounding sitar I own in the upper register. The one in original condition has a brighter and more focused sound. The one with the balsa gourd has a rounder and more woody sound. I like it better than the one in original condition in the lower register. A lot of this difference, though, is probably due to the the tabli. The sitar in original condition has a considerably smaller one. And, of course, the jawari is different, the new gourd hasn't settled in, and so on.
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katyrow
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Re: New Project -- Mohan Singh Tumba Replacement

Post by katyrow » Sun Aug 21, 2016 6:03 pm

Bakersbites786 wrote: Plz share more info regarding the finished product.
A couple of more thoughts in addition to the above. The sitar in original condition is louder, brighter, punchier, and has greater dynamic range. The balsa tumba is warmer, has more mid-range frequency content, a growlier lower end, and better sustain.

Bakersbites786
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Re: New Project -- Mohan Singh Tumba Replacement

Post by Bakersbites786 » Mon Aug 22, 2016 3:09 pm

Thank U for your feed back!
Guys in Lahore do something every similar but without the bracing.

I also find their sitars do produce an amazing mid section sound as you described but would say they are relatively loader than sitars from India also very lightweight judging from the two I once owned.

Thanks

Bakersbites786
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Re: New Project -- Mohan Singh Tumba Replacement

Post by Bakersbites786 » Mon Aug 22, 2016 3:12 pm

I will post some pictures of their tumba construction as soon I have them.

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