lpr5184

Amati Viola

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lpr5184   
On ‎3‎/‎26‎/‎2017 at 0:25 PM, not telling said:

 Curious why you chose to make those Amati corners shorter E. How much shorter?

When removing the upper ribs, there was some small tearout right at the point. So that's one reason and the other is...the way it looks now is more pleasing to my eye.  I  probably shortened them about 1mm.

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Will you adjust the outline to get a proportional overhang? If so, that sounds like more work than doing it over. Oh well, it probably doesn't matter.  It's only a millimeter. 

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2 minutes ago, not telling said:

Will you adjust the outline to get a proportional overhang? If so, that sounds like more work than doing it over. Oh well, it probably doesn't matter.  It's only a millimeter. 

I'm not sure I follow. If he hadn't traced the garland onto the back plate yet, there's nothing to adjust. I must be missing something.

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lpr5184   
4 hours ago, not telling said:

Will you adjust the outline to get a proportional overhang? If so, that sounds like more work than doing it over. Oh well, it probably doesn't matter.  It's only a millimeter. 

NT,  Great question. The shortened corners didn't affect either of the bout outlines outside the corner block area.  I probably took off little less than 1mm.

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MANFIO   

Yes, I like to use light wood, in general. But lutherie is a bit like cooking, a good cook will make a good dinner with the ingredients he has...

I keep notes about my violas, and that includes the weight of the plates (with archings already finished) prior to the inside scooping. If the weight is a bit above, I will leave the plates thinner.

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ctanzio   

I love it when people post pictures and discussions of often over-looked details, like corner blocks. Thanks.

Can you talk a bit about how you form the corner blocks? For example, do you have a template you place on top of a wood block and trace an outline? Then use a carefully setup band saw to cut the block with its standing sides perpendicular to the outline?

Also, I apologize if you posted this and I missed it, but what type of wood do you use for the corner blocks? Are you concerned about things like grain spacing or wood density for the corners?

 

 

 

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lpr5184   
On ‎3‎/‎27‎/‎2017 at 6:32 AM, ctanzio said:

I love it when people post pictures and discussions of often over-looked details, like corner blocks. Thanks.

Can you talk a bit about how you form the corner blocks? For example, do you have a template you place on top of a wood block and trace an outline? Then use a carefully setup band saw to cut the block with its standing sides perpendicular to the outline?

Also, I apologize if you posted this and I missed it, but what type of wood do you use for the corner blocks? Are you concerned about things like grain spacing or wood density for the corners?

 

 

 

Sure. I split the blocks to an approximate size and grain orientation. Then square the ends and glue them to the mold. I then level both sides of the blocks on a glass plate leaving them a few millimeters proud. I lay the half template on the form and trace the block outlines on both sides. (I use a half template which have all the block outlines. Or you can make individual block templates.) Once the blocks are marked. I use a spindle sander and sand the blocks up to the traced lines. The top and bottom blocks will need some extra work after the spindle sander to insure a smooth transition. The spindle sander leaves the blocks perfectly square. If you prefer you can use a gouge to trim the blocks instead of a spindle sander.

I do think that the grain orientation of the corner blocks should be angled to the point. As pictured in the diagram posted by WeeBBridges.

As far as block wood goes. I use traditional  spruce or willow. Although I have used red alder (a local wood) for the linings on a few fiddles. On this viola I am using 40 year old Sitka spruce for the blocks and linings. Personally I like medium to tight grain spacing for blocks.

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MANFIO   

I use black willow for my blocks.

I make my corners a bit shorter for a good bow clearance.

ctanzio, I wrote a corner shaping tutorial some year ago, if you google "manfio corner shaping tutorial pdf" you will find it.

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lpr5184   

I use a LN 62 for just about everything. That and one Ibex finger plane. I used to have a few other hand planes but sold them. Oh and I do have a small LN block plane. But that's it.

One thing I'm glad I bought was a toothed blade for planing the highly figured stuff.

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ctanzio   

lp and manfio, thank you for your replies. I was working blocks using templates just for the blocks.

But I base everything off an initial half template I create. It never occurred to me to tack glue oversize blocks and use that template to trace the block edges "on the form". Thanks!

 

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lpr5184   

I'll keep the clamps on overnight letting the ribs relax and the damp wood completely dry before gluing to the blocks.

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lpr5184   

It seems I am starting to document this build which was not my initial intention. I only meant to post a few photos along the way.

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ctanzio   

A worry I have when clamping wet, formed strips is the susceptibility to create a permanent compression set of the clamped surface. This usually manifests itself during varnishing or applying a transparent tone with a ground. The compressed area accepts the ground or varnish differently than the rest of the wood surface causing a visually uneven application.

Have you ever experienced this? Or do you apply the merest hint of clamping pressure to avoid the problem?

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lpr5184   
19 hours ago, ctanzio said:

A worry I have when clamping wet, formed strips is the susceptibility to create a permanent compression set of the clamped surface. This usually manifests itself during varnishing or applying a transparent tone with a ground. The compressed area accepts the ground or varnish differently than the rest of the wood surface causing a visually uneven application.

Have you ever experienced this? Or do you apply the merest hint of clamping pressure to avoid the problem?

No I haven't experienced this. I don't clamp wet ribs to the blocks. The area contacting the blocks are dry after bending when it comes off the iron. There may still be some moisture left in other areas of the rib.  Allowing some time before gluing allows any moisture in the wood to escape. So there is less chance of shrinkage and pulling away from the form.  Also allowing time before gluing takes a lot of the spring out. It's nice to see when you remove the clamps and the ribs stay in place with little or no spring. Kind of a gauge to what the garland will do when released from the form.

Sorry if I wasn't clear.

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On 3/26/2017 at 0:25 PM, not telling said:

I know that's what everyone does, Wee b., I mean, we all know everyone does it that way, but does it really matter (other than being prettier)? Is there a structural strength or a more pragmatic reason? 

Curious why you chose to make those Amati corners shorter E. How much shorter?

 

  lpr5184 said: When removing the upper ribs, there was some small tearout right at the point. So that's one reason and the other is...they way it looks now is more pleasing to my eye.  I  probably shortened them about 1mm.


not telling said:  If so, that sounds like more work than doing it over. Oh well, it probably doesn't matter.  It's only a millimeter. 

Hi not telling— Prettier is not our concern here, but maybe you question was rhetorical ;)

We can witness the  historical precedence;  in the beginning we are establishing  our working habits.

Surely this is well documented in other threads,  but basic carpentry if not basic violin 101 ?  Simple enough to execute, and any advantage we can give our instruments to survive the test of time,  future restorations and repairs.

It does not take much inspection of the photos above to see the vulnerability of the corner point to failure if you have one side flat grain the other end grain, leaving a island of soft grain. Again this more pertinent  when using the Spruce,  and more forgiving when using Willow.   (Compare this vulnerability to your purfling points in the channel of spruce and how easily it can fail.)

 

-this vector down the middle splits the differences, making it easier to control your gouge when carving the corner (flat grain vs end grain.)

-gives natural reinforcement to point of the corner with  the more dense winter growth ring

-expansion and contraction of the corner is more uniform (flat grain vs end grain,) from humidity changes and subsequent aging of the blocks and ribs over time.

Obviously the larger the 'family' instrument  the more impact.

 

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21 hours ago, lpr5184 said:

It seems I am starting to document this build which was not my initial intention. I only meant to post a few photos along the way.

 

 

 

 

 

It's a good thing.  Don't stop! :)

-Jim

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lpr5184   

Moving on to the linings...I have willow and spruce to choose from. I have linings that are quarter sawn and flat sawn. Is quarter sawn preferred over flat sawn or vice versa? What are the pros and cons when it comes to linings?   There is no mention of grain orientation in C&J book and I don't recall any threads on the subject. So for that reason I never gave it much thought before and just used what was sent to me from the supplier.

 

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lpr5184   

My thinking is since the lining is laminated to the rib there is minimal cross grain stress so I'm leaning towards quarter sawing this particular piece of wood since it has some nice tight grain spacing. My other thought is making the ribs too stiff is not good either so maybe flat sawn is better or am I over thinking this?

 

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