Jump to content
Maestronet Forums

Recommended Posts

I've recently been inspired to design and make a new viola. I thought it might be fun to post some of my progress pics to anybody who might be interested...

Here's a picture of the plate I joined last week for the viola back.

 

I slightly undercut the notches you see to be about halfway up the full thickness of the plate so as to even out the pressure on the seam when I clamp.

 

post-24834-0-49644000-1456949699_thumb.jpg

Link to comment
Share on other sites

I took some liberty in drawing up a full template in AutoCad. The full template design is not anywhere near symmetrical. The C-bouts are 2.5 mm's out of center from the upper and lower bouts, and the upper and lower bouts aren't much better. The treble C-bout corners are about 5 mm closer together than the bass side.

 

Here's a picture of the completed template I made out of 6061 Aluminum, and the form, with blocks attached:

 

I've also included a picture of the outline, overlayed with a mirror image of the same outline so you can better see the asymmetry.

 

 

post-24834-0-93430200-1456950497_thumb.jpg

Viola Outline.pdf

Link to comment
Share on other sites

As I designed the template, I wanted the volume in front of the mensure/sound post area to be equal to the volume behind the mensure/sound post area. Using AutoCad made it easy to check my work.

 

Correct me if I'm wrong, but I seem to recall that some of the data from the Strad/Guarneri ct scans that they've done, have shown this relationship. I'll let you know how it turns out!

Link to comment
Share on other sites

It's very loosely based off of the Andrea Guarneri, Conte Vitale. It's a bit smaller, as I want the completed viola to be right at/under 16". I also messed with the bout sizing to get it closer in volume behind and in front of the bridge like I mentioned in my previous post. Call me crazy. I know.

Link to comment
Share on other sites

Here are the ribs I'm going to use. I use a toothed Lie Nielson block plane to bring them close to thickness, and then a cabinet scraper (parallel to the flame for that ripply goodness) to finish them off. I use a flashlight as a quick way to see that I've gotten (most of) the tool marks out.

 

Also, scraping goes a LOT better for me with these two tools: Alberti sander and carbide burnisher. No luthier should be without.

   

(edit) I forgot to mention that one of my ribs doesn't match. I think it's close enough, and it's what I had. *Shrugs

post-24834-0-10094800-1456953276_thumb.jpg

post-24834-0-46600100-1456953290_thumb.jpg

post-24834-0-03555400-1456953383_thumb.jpg

post-24834-0-67673300-1456953406_thumb.jpg

Link to comment
Share on other sites

Here's a pic of the C-bouts bent and glued/clamped in place. I know my method isn't traditional, but it works for me and I like the results. It's pretty fast and simple.

 

Also, I had trouble finding a bending iron that I liked. I really wanted to get a Gewa/Aehnelt, but they're so expensive and their customer service there is non-existent for those of us on this side of the pond.

 

I got the ebay special and I LOVE it. Digital temperature control and read-out, and the curve works well. I mounted it on a couple of joined 2x4's for easier clamping to my bench.

 

post-24834-0-47987300-1456953815_thumb.jpg

post-24834-0-38474800-1456954044_thumb.jpg

Link to comment
Share on other sites

As I designed the template, I wanted the volume in front of the mensure/sound post area to be equal to the volume behind the mensure/sound post area. Using AutoCad made it easy to check my work.

 

Correct me if I'm wrong, but I seem to recall that some of the data from the Strad/Guarneri ct scans that they've done, have shown this relationship. I'll let you know how it turns out!

 

This is the "balanced chi" that Steve Sirr thinks is a big deal.  Personally, I think it's just a random coincidence that you might find if you're looking for such things.  There is nothing further in the acoustic/structural theory to indicate that it matters.

 

Also, the scans where this seemed to be true are violins.  I suspect that violas, especially the larger ones, would not have a "balanced chi", due to the relatively larger lower bout.

Link to comment
Share on other sites

'' Many authors mentioned that the bridge position divides the top in two parts of equal weight... it does not happen in general, even with Strad tops, It is a violin myth, ''
~ Maginni violas were designed that way. The ex-Coates 1610 has a stop of 207mm exactly half the body length. Of course Strad didn't do that with violins. 

David,
You have a very nice workshop set up with expensive tools. 
Your work looks to be excellent. 
Conte Vitale is sadly one of the most common ones people copy. 
It works well to play, but the archings are quite hard to pull off, the edge work is so thin on the original.
Dilworth wrote an article about that viola for the Strad, have a look for it.
  
That C bout clamping block method is the prescribed one at Newark, 
and as I said to P.Bowers 22 years ago, it doesn't work. Sure, some people insist on 
doing exactly what they were told, but it really doesn't work effectively. 
The clamping forces are not directed to the glue line, but into the middle of the c bout, 
and if you are doing corner shapes like Da Salo it will work even less well. 
If you've made it work, then fine. I'd suggest using the dowels and string method. 

Have fun. 



 

Link to comment
Share on other sites

'' Many authors mentioned that the bridge position divides the top in two parts of equal weight... it does not happen in general, even with Strad tops, It is a violin myth, ''

~ Maginni violas were designed that way. The ex-Coates 1610 has a stop of 207mm exactly half the body length. Of course Strad didn't do that with violins. 

David,

You have a very nice workshop set up with expensive tools. 

Your work looks to be excellent. 

Conte Vitale is sadly one of the most common ones people copy. 

It works well to play, but the archings are quite hard to pull off, the edge work is so thin on the original.

Dilworth wrote an article about that viola for the Strad, have a look for it.

  

That C bout clamping block method is the prescribed one at Newark, 

and as I said to P.Bowers 22 years ago, it doesn't work. Sure, some people insist on 

doing exactly what they were told, but it really doesn't work effectively. 

The clamping forces are not directed to the glue line, but into the middle of the c bout, 

and if you are doing corner shapes like Da Salo it will work even less well. 

If you've made it work, then fine. I'd suggest using the dowels and string method. 

Have fun. 

[/quote

Ben,

Manfio said devided by weight not length.

Link to comment
Share on other sites

I like the idea of drawing one's own patterns.  Especially with violas.  I tend to make the upper bouts slightly smaller as I have short fingers and want to keep the string length slightly short.  I realize that this makes the strings have a little less tension.  One sometimes needs a harder-tone C-string or perhaps even steel-cable strings. 

 

The method of clamping into the C-bout is the best I have seen,  It minimizes the perimeter and therefore pushes the rib onto the surface of the mould everywhere,  including the glue joint.  There should be no objection to closing the glue joint at the blocks.  The forces derive from a stress-strain tensor consideration anyway.  Intuition about forces is not always correct.  I don't glue until the rib has shrunk for a couple of days for drying after the bending process. 

Link to comment
Share on other sites

"...   That C bout clamping block method is the prescribed one at Newark, 
and as I said to P.Bowers 22 years ago, it doesn't work. Sure, some people insist on 
doing exactly what they were told, but it really doesn't work effectively. 
The clamping forces are not directed to the glue line, but into the middle of the c bout, 
and if you are doing corner shapes like Da Salo it will work even less well. 
If you've made it work, then fine. I'd suggest using the dowels and string method. ...."

 

It works just fine  if you add ridges (very small steps) to the slant sides of the trapezoid.  This is easily done with a bandsaw.  Then the trapezoidal block can 'lock' on the rib and only one central clamp is needed.  Also you can adjust for more pressure by sanding the rib if it is not square.

post-24376-0-13183500-1457024078_thumb.jpg

Link to comment
Share on other sites

I disagree with John above, and i bet he hasn't even tried the dowel and string method. 

I found both methods work well properly applied..... daSalo corners might not work so well with the wedge method, but for getting Strad ribs up tight to the form it works great. the big trick is trimming the ribs to the best length , to long and the ribs fold in the corners , to short and the wedge  bottoms out. The up side is there is no need for carefully fit the cauls needed for the log and dog method using strings . My wedges have little steps cut into the sides to grip the ribs ,they help control the force vectors. That said I have come to prefer the log and dog ...Rope on a stick method , given it's efficiency and simplicity I  mainly enjoy it's historical connections over any real practical reasons. A romantic at heart.... 

Link to comment
Share on other sites

Thanks for all of your comments! This is a fun project and I enjoy hearing everything that you all have to say.

 

Regarding the C-bout clamping method, I have also used the the dowel and string method on a number of instruments and have gotten what I believe to be good results. I'm not worried too much about where the clamping force is exerted (with the wedge method) because I've found it's been sufficient for me to get a good "squeeze out," on the joint with the block, as long as I've fit the maple very well. 

 

As far as what is traditional.. I'm not trying to make an exact copy or even model. I'm just doing a little experimenting and showing one way that it could be done. : )

 

Looking forward to hearing more!

Link to comment
Share on other sites

You're right! the proper length of rib is crucial! The step previous is me trimming the rib until about 1mm of wood is extending from the block with just hand pressure applied.

 

 I like using two clamps because I find that I can adjust clamping pressure from one side to the other based on what is happening as I'm applying pressure. Also, if my blocks aren't quite square (I'm trying to get away from doing everything terribly precise) I can adjust pressure up or down on one side or the other.

It's easy enough to trim the ends of a rib at a slight angle if you need to as well to get the right set-up.

Link to comment
Share on other sites

Trimmed the blocks, and fit the upper and lower bouts this morning.

 

I use an incannel gouge for most of the wood removal, careful not to exit the cut at the edge of the maple, to avoid chipping. I make it ever so slightly concave at the leading edge, and then use a file to refine it to almost flat. When I then glue the ribs on, it closes up nice and tight.

post-24834-0-47461300-1457024867_thumb.jpg

post-24834-0-50333300-1457024888_thumb.jpg

Link to comment
Share on other sites

Many authors mentioned that the bridge position divides the top in two parts of equal weight... it does not happen in general, even with Strad tops, It is a violin myth,

 

What about instruments with the conical hole in the center of the back, does anyone know if the plate balances there? I've been wanting to experiment with graduating a plate to balance on a spike that would fit such a hole, but can't bring myself to drill an unsightly hole in the center of the back.

Link to comment
Share on other sites

I just use a low-angle block plane to trim the rib miters. 

 

 

I'm interested if anyone has a good technique to being able to get the ribs convex from top to bottom. I've seen this effect on some nice Cremonese instruments, and have heard others talk about this phenomenon as being desireable.

 

Interestingly enough, using the wedge clamp method on the c-bouts can get this effect, but I often find that the ribs for the upper and lower bouts always end up a little bit concave with my current construction methods. 

 

I scraped the ribs a for a bit and was able to reshape some portions of them to a convex shape without too much loss of thickness.

post-24834-0-18984600-1457106779_thumb.jpg

post-24834-0-93514100-1457106795_thumb.jpg

Link to comment
Share on other sites

 

I'm interested if anyone has a good technique to being able to get the ribs convex from top to bottom. I've seen this effect on some nice Cremonese instruments, and have heard others talk about this phenomenon as being desireable.

 

Desirable for what?

 

I speculate that 300 years can do a lot to 1mm thick wood.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.



×
×
  • Create New...