Sound Post Contact & Crazy Idea?

derft · #1 08-18-2010, 10:28 AM

Hi, As a small intro I am new to the talkbass forum. I am not a Luthier. However, I have built 5 F5 Mandolins, 3 Guitars 12 Dobros and 3 Electric basses.

I have a 1939 Kay that I have started to repair as the bassbar was loose about half way from the bottom and the top was caved in. With advice from this forum a bag of sand and some weight reformed the top and the bassbar has been re glued. After reading Mr Traeger's book I have decided to add a chalk fit spruce patch to the top on the sound post side. I am also going to add a popular patch on the back where the sound post rests. Now to my questions.

During the patch process I am thinking about making the area where the sound post meets the top and the back FLAT for easy install of the sound post and to ensure perfect contact. Am I nuts? Has any one done this before?. Thanks in advance for the advice.

George700DL · #2 08-18-2010, 10:54 AM

Quote:

Originally Posted by derft

During the patch process I am thinking about making the area where the sound post meets the top and the back FLAT for easy install of the sound post and to ensure perfect contact. Am I nuts? Has any one done this before?. Thanks in advance for the advice.

I'm not a luthier, but...

I included a pre-emptive soundpost patch in the bass I built last winter. In the spot where my soundpost goes, that area is already sort of flat-ish. The patch still follows the contours of the surrounding areas. It's not flat, but pretty close to it.

However, my soundpost patch is inlaid - I carved a spot for it in the carved top and then chalk-fitted the patch itself.

For a plywood top, Chuck Traeger recommends an entire breast patch (fitted to the surface of the plywood top), not an inlaid soundpost patch - so he basically introduces a graduation where there isn't one. Is this what you're talking about?

George

jtlownds · #3 08-18-2010, 11:10 AM

My old King Moretone had a patch on the back plate that was raised and flat for the soundpost to sit on. That was the way it came from the factory. There was, however, no patch on the front plate. Don't know why. I'm sure that there have been other basses set up the way that you describe.

derft · #4 08-18-2010, 11:13 AM

I am doing an entire breast patch. Two pieces, one on each side of the bassbar. This is to strengthen the top as it is 3 ply and I do not want it to cave again and maybe to use higher tension strings. Only the area where the sound post rest would be flat.

JJDMusic · #5 08-18-2010, 02:22 PM

You should probably remove the bass bar and fit a single breast patch in first, then later fit and glue in the bar.
Making two breast patches to sandwich the bass bar seems like a bad idea and, may not help prevent the top from sinking again.

**Matthew Tucker** · #6 08-18-2010, 05:02 PM

I know exactly what you're talking about and as far as the back is concerned I think a flat platform would be a good idea, in fact why not just install a lightweight brace across the back at that point with a flat surface? i wouldn't do it to the top, but i would install a belly-patch covering the whole area between the ffs to reinforce the sunken top, adding 3-5mm thickness in the middle and feathering out to the edges. Although you could take the bass bar off and fit a patch as JJDMusic describes, you can install a two-part patch as you describe and in my opinion, if the bass bar is good to start with, it will work as well.

PS fitting a sound post is not THAT hard, but it can be time consuming. And I don't think a flat surface really saves you all that much effort.

forester · #7 08-18-2010, 06:00 PM

+1 if you are able to reform the top,and chalk fit patches,i trust you can install the sp anywhere. i find flat (like in viola flat) more of a task to set.

and welcome...

fdeck · #8 08-18-2010, 08:36 PM

Yesterday I had the opportunity to sit next to a Shen SB-80 for a while, and naturally peered inside. There was a patch inside, on the back, going all the way across and about six inches wide. It looked like it might have been formed to the inside curvature of the back, rather than chalk fitted.

Anyway, it seemed like a decent way to spread out some of the load on the plywood back, and the bass sounded like a nice honest ply bass.

John Sprague · #9 08-19-2010, 08:26 AM

Quote:

Originally Posted by fdeck

Yesterday I had the opportunity to sit next to a Shen SB-80 for a while, and naturally peered inside. There was a patch inside, on the back, going all the way across and about six inches wide. It looked like it might have been formed to the inside curvature of the back, rather than chalk fitted.

Anyway, it seemed like a decent way to spread out some of the load on the plywood back, and the bass sounded like a nice honest ply bass.

Yes, we put an extra veneer across the back and a patch between the f-hole and bass bar of the post side of the top of the ply models to simulate graduations. These patches are formed right along with the backs and tops, with the veneers being shaped at the same time they are glued together. Arnold Schnitzer actually had a hand in sending us in that direction. Now where's that royalty check I meant to send him, I know it's here somewhere...

As to Derft's original question, it's my opinion (nearly worthless, I'm not a luthier) that one has to only ask why carved instruments of the past have not had a flat spot carved into the post areas.