Sean Couch’s Bench

[Sean Couch]

I got the bass bar in and to its final shape. The top plate is still a bit hefty at 78g with an M5 of 370Hz. The back is at 110g and 372Hz. I am going to move on with these numbers and if it needs improvement when it is complete, I’ll pop the top and work on it more, maybe.

 

[Sean Couch]

On 7/13/2024 at 4:51 AM, Davide Sora said:

It's a bit heavy, but I know of at least a couple of Guadagninis with that density, so I'd say the possibility that something good could come out of it is there.

Right on, I hope she sounds decent when completed. I won’t be able to tell if it sounds good or not, but I can find help in that area.

[Sean Couch]

On 7/13/2024 at 9:14 AM, MikeC said:

You could remove a little wood from the flat area around the end blocks but that wouldn't reduce weight very much, only a little bit probably.   I think that's called the Sacconi plateau.  

If you look at CT scans of Stradivari violins the arch is very flat in that area over the blocks but I think that has more to do with the recurve of the arching rather than an actual plateau all the way across on the inside.  

But I have not seen good enough images of the inside of a Strad to form a good opinion on that.  

I am thinking about doing that. I can’t see how it can hurt as long as I don’t weaken the neck area. Even if it only saves a gram, it’s still a gram lighter.

Last night I was pondering reducing the height of the bass bar in the f-hole area to take out more weight and try to get my M5 down to around 350Hz. I don’t know if that would help or hinder.

[resonant]

On 7/19/2024 at 12:25 AM, Sean Couch said:

I got the bass bar in and to its final shape. The top plate is still a bit hefty at 78g with an M5 of 370Hz. The back is at 110g and 372Hz. I am going to move on with these numbers and if it needs improvement when it is complete, I’ll pop the top and work on it more, maybe.

 

The bass bar has too large a plateau to my eye, could just be the picture. Based on the very little I know the bass bar should start curving down almost immediately from the highest point, for instance http://www.makingtheviolin.com/Building/Front/Bass bar/6.svg

Then again there are probably different schools of thought as there always are.

How was your experience fitting the bass bar? Perhaps I was using bad chalk but I found it almost useless and really hard to clean off. And how did you clamp it?

[Sean Couch]

5 hours ago, resonant said:

The bass bar has too large a plateau to my eye, could just be the picture. Based on the very little I know the bass bar should start curving down almost immediately from the highest point, for instance http://www.makingtheviolin.com/Building/Front/Bass bar/6.svg

Then again there are probably different schools of thought as there always are.

How was your experience fitting the bass bar? Perhaps I was using bad chalk but I found it almost useless and really hard to clean off. And how did you clamp it?

For the bass bar shape I watched the videos from Davide Sora and tried to mimic the shape he uses. I did notice that it is different than what is called out in the “Making the Violin” manual.

I clamped it with 5 clamps that I got off of eBay. They came from China, but the set was only about $50 with shipping. They seemed to work ok.

The chalk fitting wasn’t bad. I used regular old black board chalk that I got from the dollar store. I didn’t use anything special. It highlighted the high spots fairly well, but I did have to apply more chalk quite often. Probably after every 2 or 3 fittings. It was a slow process for me, but everything I do takes a while. I think it took me about 4 hours to cut, plane to thickness, chalk fit, and glue in the base bar.

[Davide Sora]

On 7/20/2024 at 5:09 PM, Sean Couch said:

For the bass bar shape I watched the videos from Davide Sora and tried to mimic the shape he uses. I did notice that it is different than what is called out in the “Making the Violin” manual.

I clamped it with 5 clamps that I got off of eBay. They came from China, but the set was only about $50 with shipping. They seemed to work ok.

The chalk fitting wasn’t bad. I used regular old black board chalk that I got from the dollar store. I didn’t use anything special. It highlighted the high spots fairly well, but I did have to apply more chalk quite often. Probably after every 2 or 3 fittings. It was a slow process for me, but everything I do takes a while. I think it took me about 4 hours to cut, plane to thickness, chalk fit, and glue in the base bar.

4 hours for the whole operation is more than reasonable, I would say in line with my times. I know of some luthiers (inexperienced, but already graduated from the school) who take a couple of days for the bassbar. I suspect it's more a matter of personal insecurity in pursuing hyper-precision...

Regarding the bassbar, I don't think that minimal differences in the shape of the central part make a real difference, as long as mass and stiffness are appropriate. I consider the end parts more important, which for me must guarantee a certain flexibility (not too high and rigid). The "strange" shape of the central part of my bassbar in my idea is functional to concentrate a greater mass in the center with more flexibility at the ends, especially the upper one. The displacement of the central mass downwards (under the bridge) always in my head should minimize the wolves. However, I have never done serious experiments to validate this hypothesis, and I don't think anyone has ever done them. When it comes to bassbars, it's more a matter of opinion than fact, something like "what works in our violins is fine".

[Sean Couch]

1 hour ago, Davide Sora said:

4 hours for the whole operation is more than reasonable, I would say in line with my times. I know of some luthiers (inexperienced, but already graduated from the school) who take a couple of days for the bassbar. I suspect it's more a matter of personal insecurity in pursuing hyper-precision...

Regarding the bassbar, I don't think that minimal differences in the shape of the central part make a real difference, as long as mass and stiffness are appropriate. I consider the end parts more important, which for me must guarantee a certain flexibility (not too high and rigid). The "strange" shape of the central part of my bassbar in my idea is functional to concentrate a greater mass in the center with more flexibility at the ends, especially the upper one. The displacement of the central mass downwards (under the bridge) always in my head should minimize the wolves. However, I have never done serious experiments to validate this hypothesis, and I don't think anyone has ever done them. When it comes to bassbars, it's more a matter of opinion than fact, something like "what works in our violins is fine".

Shortly after my last comment, I grabbed a screen shot from one of your videos that is similar to the picture you posted, and spent some time identifying possible areas that I can tweak. I think I am going to take out some material in the area where it transitions from the max height in the center. I would like to have a steeper transition like yours, and plus it will also remove some weight from my portly top.

The 4 hours was for getting the bass bar glued in. I think I spent another 4 hours shaping it, so about 8 hours work total. I’m going to be back in the shop tomorrow to dink with the bass bar and start rounding the plate edges. I was going to hold off on assembling the sound box and start working on the neck and scroll, but I think getting the body put together will be a nice milestone.

Your bass bar shape theory makes sense to me, it sounds quite logical. The hardest part about being completely green is not knowing what is right, or acceptable, or how any of the changes will affect the sound. I reckon I won’t know until I have made a few violins and can hopefully start to understand.

[resonant]

Since you are approaching this point, have you decided when you are going to install the neck? By which I mean, will you glue the top and back first and then fit the neck, or glue just the top and fit the back after the neck is in?

I had glued top and back when I fitted the neck, and although I had a relatively straightforward experience doing this, I decided for the 2nd violin I will try fitting the neck with just the top in place for a hopefully even easier experience.

[Sean Couch]

I have seen where people have glued just the top and then put in the neck. I think it was just a day or two ago that I watched some videos on it. I think they were by Maestro Kimon on YouTube. It looks like it would give better access to working the area with only the top in place. I will have to give it some more thought on which way I am going to proceed, but I am leaning towards putting the back and top on before setting the neck.

[Davide Sora]

10 hours ago, Sean Couch said:

Shortly after my last comment, I grabbed a screen shot from one of your videos that is similar to the picture you posted, and spent some time identifying possible areas that I can tweak. I think I am going to take out some material in the area where it transitions from the max height in the center. I would like to have a steeper transition like yours, and plus it will also remove some weight from my portly top.

When I shape my bassbars, I start with the central "straight" area slightly longer than the F-holes, then I progressively reduce it according to the needs of that top and bassbar. I take the length of the f-holes as a reference, but sometimes (although rarely) I end up with the "straight" part shorter than the f-holes, usually about the same length. One of the main parameters that I consider is the weight of the bassbar between 4.5g max and 4g min. Another is the M5 of the top between F and F# (roughly 350 to 370 Hz). However, there may be variations in these parameters depending on the situation and the personal choices of each luthier, it's hard to establish absolute standards.

[Davide Sora]

4 minutes ago, Sean Couch said:

I have seen where people have glued just the top and then put in the neck. I think it was just a day or two ago that I watched some videos on it. I think they were by Maestro Kimon on YouTube. It looks like it would give better access to working the area with only the top in place. I will have to give it some more thought on which way I am going to proceed, but I am leaning towards putting the back and top on before setting the neck.

My two cents on this is that with just the top glued the frame is too flexible and most likely twisted to get accurate measurements, and when you glue the back you could easily change the measurements you set during neck setting. I admit that I have never tried, but if I were to try a different way, I think I would go for setting the neck on the ribs still on the form, without either the top or the back glued. Anyway, I don't think I will ever do it, being a fan of the accuracy of the measurements I believe that the only way is with the finished, and stable, body.

 

[resonant]

1 hour ago, Davide Sora said:

My two cents on this is that with just the top glued the frame is too flexible and most likely twisted to get accurate measurements, and when you glue the back you could easily change the measurements you set during neck setting. I admit that I have never tried, but if I were to try a different way, I think I would go for setting the neck on the ribs still on the form, without either the top or the back glued. Anyway, I don't think I will ever do it, being a fan of the accuracy of the measurements I believe that the only way is with the finished, and stable, body.

 

Good point. Maybe I'll stick with fitting the neck to the closed body.

I'll just add that I underestimated how much the presence of the glue would change my measurements, and I ended up having to remove the neck while the glue was still wet, clean off the glue and start again. 

[Sean Couch]

1 hour ago, Davide Sora said:

When I shape my bassbars, I start with the central "straight" area slightly longer than the F-holes, then I progressively reduce it according to the needs of that top and bassbar. I take the length of the f-holes as a reference, but sometimes (although rarely) I end up with the "straight" part shorter than the f-holes, usually about the same length. One of the main parameters that I consider is the weight of the bassbar between 4.5g max and 4g min. Another is the M5 of the top between F and F# (roughly 350 to 370 Hz). However, there may be variations in these parameters depending on the situation and the personal choices of each luthier, it's hard to establish absolute standards.

Yes, I don't think there can be a “standard” when dealing with so many variables. That is where experience and intuition take over to get the best out of any particular instrument. I watched a video, I think from Edgar Russ, where he had a guest who produced violins through CNC machining. The guest stated that he can get to within 97% of what a good luthier can do, but there is no way to mechanically replicate what can be done by hand. I don’t know how accurate those claims are, but I think it gives insight into how human handwork is still better than 100% machine made.

Once I realized I had a weight issue with my top, I figured I would take out as much material as I could while keeping the M5 above 300Hz. Then with the bass bar, target 350Hz. I hit the first part of that, but then when I was shaping the top of the bass bar, I hit the 370Hz and stopped. My bar is about one gram heavy so hopefully by reshaping the transition area, I can drop that gram and get to close to the 350Hz.

[Sean Couch]

2 hours ago, Davide Sora said:

My two cents on this is that with just the top glued the frame is too flexible and most likely twisted to get accurate measurements, and when you glue the back you could easily change the measurements you set during neck setting. I admit that I have never tried, but if I were to try a different way, I think I would go for setting the neck on the ribs still on the form, without either the top or the back glued. Anyway, I don't think I will ever do it, being a fan of the accuracy of the measurements I believe that the only way is with the finished, and stable, body.

 

Very good points. In the video I watched, Kimon left the rib garland attached to the mold while setting and gluing the neck. He also only put in the belly side linings leaving the back open to make removing the mould easier.

With his method it might keep the dimensions more stable while setting the neck, but then I would be worried about changing the profile when installing the linings on the back. I’ll probably go with the traditional method, but it is fun to ponder the possibilities. This is where I think a collapsible form could really shine.

[Davide Sora]

1 hour ago, Sean Couch said:

Once I realized I had a weight issue with my top, I figured I would take out as much material as I could while keeping the M5 above 300Hz. Then with the bass bar, target 350Hz. I hit the first part of that, but then when I was shaping the top of the bass bar, I hit the 370Hz and stopped. My bar is about one gram heavy so hopefully by reshaping the transition area, I can drop that gram and get to close to the 350Hz.

Keep in mind that I don't worry about getting to precise frequencies, any frequency between 350 and 370 (and I would extend between 345 and 375 Hz) would be fine. I only think of it as an index of mass/stiffness ratio, not a true tuning, which doesn't matter to me.

[Davide Sora]

59 minutes ago, Sean Couch said:

Very good points. In the video I watched, Kimon left the rib garland attached to the mold while setting and gluing the neck. He also only put in the belly side linings leaving the back open to make removing the mould easier.

With his method it might keep the dimensions more stable while setting the neck, but then I would be worried about changing the profile when installing the linings on the back. I’ll probably go with the traditional method, but it is fun to ponder the possibilities. This is where I think a collapsible form could really shine.

I believe that every system can be made to work with due care and experience. But be sure you have thought about the whole chain of events that will lead you to the finished violin with the correct measurements, if you neglect any of them the problems will be there to remind you for next time.

Each luthier should optimize his "chain of events" from the beginning to the end of the violin construction according to his preferences and priorities (e.g. accuracy, working time, respect for tradition or not, etc.), a path that lasts years and leads to inevitable differences between the work of one luthier and another.

[Sean Couch]

2 hours ago, Davide Sora said:

Keep in mind that I don't worry about getting to precise frequencies, any frequency between 350 and 370 (and I would extend between 345 and 375 Hz) would be fine. I only think of it as an index of mass/stiffness ratio, not a true tuning, which doesn't matter to me.

I took away some material from the bass bar, and in the upper and lower bouts near the top and bottom blocks. At the top, I left the line straight and on the bottom, I contoured it like you do on the back plate (the thing that Mike C. mentioned a few days ago). I didn’t take off much in the contour area but I was able to move my 0.5mm offset glue line a mm or so.

My top plate seems to have gained weight after sitting for a few days. It was at 78.4 and today it was at 78.6g today. The humidity has been pretty constant at around 45%. I only mention that because it skews my new numbers.

Now my top plate is at 77.5g and 359Hz. I decided to stop there and move on. It is in the range that you mention and I am not tied to any particular number. I don’t want to become fixated on plate frequencies as the “golden rule,” I would prefer to use them as a guide like you.

 

2 hours ago, Davide Sora said:

I believe that every system can be made to work with due care and experience. But be sure you have thought about the whole chain of events that will lead you to the finished violin with the correct measurements, if you neglect any of them the problems will be there to remind you for next time.

Each luthier should optimize his "chain of events" from the beginning to the end of the violin construction according to his preferences and priorities (e.g. accuracy, working time, respect for tradition or not, etc.), a path that lasts years and leads to inevitable differences between the work of one luthier and another.

 

Yes, I agree 100%. Everyone will develop their own processes and order of operations that works the best for them. I already have some ideas rolling around in my head on how to improve the process for me. I’m sure it is nothing revolutionary, but different than how I see other makers doing things. 

I am keeping a log of “Important Violin Notes” for future use so I can look back and hopefully not repeat the mistakes I have made on this one. My first item on the list is “watch your corner lengths.” 

[PawelP]

4 hours ago, Sean Couch said:

Once I realized I had a weight issue with my top, I figured I would take out as much material as I could while keeping the M5 above 300Hz. Then with the bass bar, target 350Hz. I hit the first part of that, but then when I was shaping the top of the bass bar, I hit the 370Hz and stopped. My bar is about one gram heavy so hopefully by reshaping the transition area, I can drop that gram and get to close to the 350Hz

I used similar approach on my 1st violin, overweight plate at 350 Hz with a bass bar tuned to 370. My violin was lacking a low end, so I opened it and thinned bass bar to 350, and it helped significantly.  Curious to know how it will work for you.

Did you get a tap tone with f holes cut but without the bass bar?

[Sean Couch]

3 hours ago, PawelP said:

…Did you get a tap tone with f holes cut but without the bass bar?

I did. I looked in my notes and before putting on the casein wash, she was at 72.5g and 303Hz. That 303 was from the tuner app (gStrings) on my phone. I usually use Audacity on my Linux box. I can’t remember if I confirmed that 303 with Audacity or not.

I am glad thinning the bass bar on your violin showed good results. I am not expecting mine to sound great, but I would be happy with decent and thrilled with good.

I need to get my mom’s cheap childhood violin set up and the bow rehaired. At least then I can hopefully compare open string notes on my violin with the painted on purfling student violin that my mom used 65+ years ago. I keep telling her that she is my designated sound tester, but she ain’t having it. 

I don’t know how to play, but I am hoping to be able to at least have them both make a sound that doesn’t sound like I stepped on a cat’s tail. Lol.

[Sean Couch]

Worked on rounding the edges of the back. She is pretty much done. There are some areas that still need some attention. I will probably finalize the edges once the sound box is assembled.

 

 

[Sean Couch]

Got the top to the same stage as the back. Needs some refining when I get  the plates glued to the garland. I included a nice close up of my hacked in purfling corners. Hehe 

 

[MikeC]

I didn't notice the little gap until I zoomed in.  You could fill that in with a little bit of sawdust and glue.  

[Sean Couch]

14 hours ago, MikeC said:

I didn't notice the little gap until I zoomed in.  You could fill that in with a little bit of sawdust and glue.  

I was thinking about doing that. Would you use hot hide glue or a wood glue?

[Sean Couch]

I got the rib garland liberated from the form and got the back glued in place. Wasn’t as bad as I thought it would be. I did the “thin knife method” where you remove 4 clamps at a time and work the hhg onto the gluing surfaces with a thin blade.

[MikeC]

2 hours ago, Sean Couch said:

I was thinking about doing that. Would you use hot hide glue or a wood glue?

I wouldn't have a problem using modern wood glue for something like that, but thas just me.   And I may have done a little of that on my last build.    Only in small spots where it doesn't matter of course.  

Good job with the glue up plate to ribs!   I wasn't brave enough to try it with the thin knife last time.  Just put glue all the way around and clamped quickly.