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Building a fiddle using mahogany for back ribs and neck

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Nov 16, 2019 - 12:35:21 PM

alex

UK

4 posts since 11/16/2019

Hi My name is Alex I am new to this forum , Hi everyone.
I have started to build a fiddle using mahogany for the back, ribs and neck.
I know that this isn't the normal wood to use , but I have some and as it's my first I thought I could get an insight into violin building without the initial outlay of buying in expensive tone wood. I am using the violin making manual PDF as my guide
My question is to all you violin builders is... If you where to build a fiddle using mahogany as opposed to maple would you adjust the thicknesses of the ribs and back to take account of any differences in the woods and why?
Any input would be appreciated
Cheers
Alex

Nov 16, 2019 - 2:28:57 PM

916 posts since 6/26/2007

I wouldn't use mahogany myself, but if I did I would not change the rib thickness. I probably also would not change the back, unless the density is a lot different from most maple. You can use weight and flexibility of the back as you thin it as a rough guide, but I wouldn't worry too much about it. It will be somewhat different anyway.

Nov 16, 2019 - 3:07:53 PM

235 posts since 1/5/2009

The only thing you really need to worry about is the grain orientation of the back. When looking at the end grain, the grain should be vertical or close to it. If it is at an angle you will have a high chance of the back splitting when under tension.

Edited by - Fiddlemaker5224 on 11/16/2019 15:08:36

Nov 16, 2019 - 11:59:38 PM

alex

UK

4 posts since 11/16/2019

Thanks for the advice guys
I ll keep to standard thicknesses as a guide.
Carl, when looking t the back the grain direction is from top to bottom with a swirl in the middle as far as I can make out .
When looking at the end grain I can't make out a direction,there are marginal parenchyma that run roughly horizontal. Does that orientation sound ok to you?

Nov 17, 2019 - 6:55:46 AM

235 posts since 1/5/2009

I do understand your question, Yes the horizontal rays do make a difference. Mahogany is a wood that is difficult to identify the grain patterns. What your looking for is Quarter saw. The vertical grain adds strength to the Arching of the back. By giving a vertical plane of the ring wood the possibility of being shaped. Looking at the side view of the back plate, then imagine cut plane running vertical its full length. Even though the ring wood is carved making the shape of the arching, the ring wood is still one continuous growth ring.

This pattern when put under pressure from the sound post and the pulling of the neck and end block, creates three directions of force on the back. Now we add in the arching making long and short fiber lengths. This weakens the back plate greatly. Mahogany is used in many instruments as a side wood, and backs in guitars. They do great overall, I am just not sure that the forces applied in a carved back will be able to withstand the pressure.

Nov 17, 2019 - 11:02:13 AM

alex

UK

4 posts since 11/16/2019

Thanks Carl,
With that in mind do you think I should air on the side of caution when thicknessing the back, maybe adding 0.5 mm to the overall thickness profile ? Wider soundpost maybe?

Nov 17, 2019 - 11:26:13 AM

235 posts since 1/5/2009

I would start out with a thicker overall graduation. Adding area to the sound post location will detract from the overall plate frequencies.

I think starting with a 4mm over all graduation will allow you to graduate the plate to get a good sound quality. While graduating, make sure you check the flexibility often. Just be prepared to graduate the plate again, if your not to happy with the sound produced. To gain more flexibility you can thin the inside of the back plate in the upper and lower bout's under the channel next to the purfling.

I would also recommend that you do not use steel strings.

Nov 17, 2019 - 11:40:22 AM

alex

UK

4 posts since 11/16/2019

Thanks again Carl, sounds like good advice. I was prepared for a different/rubbish sounding finished instrument but I hadn't considered that the whole thing might crack in half before I've even heard her sing.
On closer inspection of the endgrain the grain does run mostly verticle so that's good but at the sametime it has quite a few swirls that I thought would look nice but might weaken it.
Only one way to find out anyway ,I'll post some pic either way when it's finished.

Nov 17, 2019 - 11:47:38 AM

235 posts since 1/5/2009

Thanks, glad I could help out.

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