bkwood

Saving the mold

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I should have mastered this by now. I am ready to remove the garland from around the mold on my 6th violin (which is going to be a five string). Each time before I have ended up cutting it out, or using a collapsible form I made. I made a new mold for this violin, telling myself I wouldn't be timid about getting it off this time. And yet, I can't seem to do it. The ends don't want to clear the linings.

Is there a trick?

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Did you glue both sets of linings on?  Usually people only glue one set of linings if they are not using a collapsible form.  I have heard of people gluing both sets on a non collapsible and then just flexing the rib garland around to remove the form.  In the case of the one set of linings/non collapsible form scenario, the back is already glued on. 

 

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I simply flex mine untill it yields me my form. It's pretty nerve wracking, buy think of it this way, the wood should give well before before any glue joints do while flexing it around. Don't be afraid to muscle it just a bit. 

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Gotta get the corners out beyond the shoulders first, then the end blocks will move north and south to clear the linings. Helps to do a bit of rough removal of stock inside the corner blocks as well, but not actually needed. 

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26 minutes ago, Nick Allen said:

OP, are your blocks partially trimmed at this point?

Thanks everybody. I do have linings on both sides. I've always done that because it seems to me it sets the shape better that way. I haven't trimmed my blocks any yet. That's a good idea. And keep my nerve. Back to it.

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40 minutes ago, Nick Allen said:

I simply flex mine untill it yields me my form. It's pretty nerve wracking, buy think of it this way, the wood should give well before before any glue joints do while flexing it around. Don't be afraid to muscle it just a bit. 

That's what worries me, the wood (not the glue) giving way in a manner that I won't be happy with. ;)

I really don't want to send new instruments out the door which already have repairs to breaks in the wood.

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12 minutes ago, bkwood said:

Thanks everybody. I do have linings on both sides. I've always done that because it seems to me it sets the shape better that way.

It probably does, but the top Cremonese makers didn't seem to be overly concerned about that. Looks like they were fine tracing the top and back outlines from distorted rib assemblies.

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The only trick is to split the inside wood of corner blocks, widen the ribs just enough to clear the edges of the form at the housing of  corner blocks , so that they can move upward and allow the linings near the top block to clear the form.

They are only two-millimeter enlargements, just the thickness of the linings, not a big deal at all.

Of course unless your ribs have accidentally glued to the form, in which case the next time it will be better to remember to put soap or paraffin on the form to avoid it.

It must always be done!!! :);)

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12 hours ago, bkwood said:

Success! Thanks again. And the David Sora video was good.

Well done, it wsn't that bad was it?

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17 hours ago, Davide Sora said:
 

The only trick is to split the inside wood of corner blocks, widen the ribs just enough to clear the edges of the form at the housing of  corner blocks , so that they can move upward and allow the linings near the top block to clear the form.

 

They are only two-millimeter enlargements, just the thickness of the linings, not a big deal at all.

 

Of course unless your ribs have accidentally glued to the form, in which case the next time it will be better to remember to put soap or paraffin on the form to avoid it.

 
It must always be done!!! :);)

Davide,  do you trim the inner edges of the linings before or after you remove from the form?     I'm working on my first build,  your videos are very helpful.

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8 hours ago, MikeC said:

Davide,  do you trim the inner edges of the linings before or after you remove from the form?     I'm working on my first build,  your videos are very helpful.

I trim the inner edges of the linings near the top block on top side only and near the bottom block on back side only, to facilitate the extraction of the form.

This way, once the ribs are free from the form,  I can scrape away the dry glue residues close to the linings more easily without damaging their edges, and I can trim all the rest of linings with better visibility of the work.

 
However, judging by marks left on the original forms, it is quite likely that Stradivari would do it with ribs still on the form, or more likely some apprentices did the job for him, just to keep them busy in downtimes.

 

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On 11/13/2017 at 10:32 AM, bkwood said:

I should have mastered this by now. I am ready to remove the garland from around the mold on my 6th violin (which is going to be a five string). Each time before I have ended up cutting it out, or using a collapsible form I made. I made a new mold for this violin, telling myself I wouldn't be timid about getting it off this time. And yet, I can't seem to do it. The ends don't want to clear the linings.

Is there a trick?

I use a full-thickness mould,   and yes,  I found a trick for myself.   When the blocks are glued in,  cut from the outline partially into the block  (band saw).  When it is time to remove the assembly,  drill a 3/8 hole into each corner block and at the corners of the end blocks.   Then use a saber saw to cut from this hole to the mould.   You can leave just a few mm of the block,  and then you will be able to spring the thing out at each corner.   After corners are released,  you have plenty of slack to get the end blocks.

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1 hour ago, Johnmasters said:

I use a full-thickness mould,   and yes,  I found a trick for myself.   When the blocks are glued in,  cut from the outline partially into the block  (band saw).  When it is time to remove the assembly,  drill a 3/8 hole into each corner block and at the corners of the end blocks.   Then use a saber saw to cut from this hole to the mould.   You can leave just a few mm of the block,  and then you will be able to spring the thing out at each corner.   After corners are released,  you have plenty of slack to get the end blocks.

By full thickness do you mean as thick as the ribs are wide?

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