Double Bass C Extension Material Question

Victor Ruiz · May 10, 2024

Hello all! Hope you are doing well.

I've recently had the interest in making a C extension for my double bass. I've been taking measurements and studying a few different extensions I am able to find in my area as well as whatever dimensions or drawings I can find online and am fairly confident in my ability to create one since I have a fair amount of woodworking experience having worked on pipe organs and guitars a while back.

I'm wondering if anybody has used Indian Ebony as a choice of wood for the whole extension? It's less harder than the usual Gaboon Ebony that is used for most fingerboards and gates but it still seems to be a popular alternate choice for fingerboards depending on the maker/luthier. Has anybody here made an extension using it and how did it turn out for you?

Matthew Tucker · May 10, 2024

indian ebony is perfect. Good luck ... a C extension is tricky work. Don't cut the scroll!

stefaniw80401 · May 14, 2024

One of my friends, Denver luthier Ian Heggele, recently made his first extension. He first carved and fitted a prototype made from poplar. Then he repeated the process with the final material. Came out great.

Victor Ruiz · May 17, 2024

Matthew Tucker said:
indian ebony is perfect. Good luck ... a C extension is tricky work. Don't cut the scroll!

Awesome. And definitely will not be cutting it. I love the shape of my scroll too much

Victor Ruiz · May 17, 2024

Matthew Tucker said:
indian ebony is perfect. Good luck ... a C extension is tricky work. Don't cut the scroll!

Also Matthew, I took inspiration of your extension designs. The photos online have been very valuable. I have one question. In Chuck Traeger's book of bass building, he mentions the angle of the C extension fingerboard should be straight parallel with the main fingerboard. Or at least that's what I think he is trying to explain but he mentions it something like "...if you hold the string down taut around the middle of the scroll, the string should lay flat on the fingerboard." or something like that. Don't have the book with me at the moment.

I'm trying to find references to how builders go about the angle of the extension but I can't find much. One bass player on facebook messaged me saying that the fingerboards on his bass are completely parallel to each other from the main one into the extension. What are your thoughts if you don't mind sharing?

Greg Clinkingbeard · May 17, 2024

The angle should be such that when closing the gate the string isn’t pushed significantly toward the A string. As you get into it you will probably see.

robobass · May 28, 2024

I like the extension to perfectly telescope the scoop of the main board and with no step. Also, gates tend to work best on very low scoop boards. If you have excessive scoop you want to correct that before building the extension.

Victor Ruiz · May 28, 2024

robobass said:
I like the extension to perfectly telescope the scoop of the main board and with no step. Also, gates tend to work best on very low scoop boards. If you have excessive scoop you want to correct that before building the extension.

The fingerboard itself on my bass is pretty flat length-wise. Is was very well set up by a talented luthier in my area before I bought it. The step reccomendation is very helpful. Haven't understood why the step is on mine. I'll upload some pictures later of my bass setup as well as pictures of the rough mockup of the extension that I have cut out right now out of poplar before using Indian Ebony.

Victor Ruiz · May 29, 2024

Well for those of you interested, here is the progress on the extension. Been working on this for the last 3 days I think. This is currently the rough version made out of poplar so I can figure out what to expect and what tools/methods to use. All the shaping for the scroll section has been shaped with a dremel, a utility knife blade, a blade runner i grabbed from fb marketplace, and needle files.

While the scroll shaping fits my bass scroll well, it could be better. There's no side to side movement when sitting with even minimal string tension so I'm not too concerned on this but, anybody have any tips? I was trying to transfer over markings using graphite, a wet marker(on tape of course), and charcoal dust. But almost nothing transferred over even though i know certain points were making contact. I've checked other areas of the extension and nothing else is touching the scroll and preventing the scroll from making contact. It is sitting pretty securely.

Anyway, going to grab some rasps and a small block plane to work on shaping the neck of the extension and shape the fingerboard and test before grabbing Indian Ebony. Still need to drill the bath for the C string through the extension.

stefaniw80401 · May 31, 2024

Try something softer like lipstick.

robobass · Jun 1, 2024

Looking good! I like that you've left it fairly thick in the middle. There is a lot of bending force there.

Victor Ruiz · Jun 20, 2024

After quite a bit of time, fitting the actual ebony piece on and off while I have been putting on the old extension back on when I need to gig, the extension is just about done. Still need to get a steel rod for the pulley dowel and then make 3 more gates(I am short on wood so I can only make 2/3 gates needed. So for tomorrow, I will just focus on getting the D gate finished). Still may need to file down the nut a bit more. The C strings seems to feel dead at the moment but I also degreased the strings too when cleaning the entire top the other day. Currently sanded to 400 grit. But I have read pf people going all the way till 1000 or more for a good finish? May try it out next week. Otherwise, intonation for the open C and Closed E is spot on and i'm happy with it and actually proud to say that it is an extension I made.