attaching back to ribs while on the form??


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I know several of you including David Burgess attach the back to the ribs while it is still on the form. This sounds like a good way to keep everything more symmetrical so I am going to try this method on the two ribsets I have on the forms now.

I have always done the other way of installing the linings on one side removing the form and installing the ribs on the other side, trimming the blocks and then attaching the back.

I have a couple of simple questions...

Trimming the blocks while attached to the back???

How do you do this with out scarring the back with the gouge?

Removing the form???

Of course to remove the form with out the back attached requires a lite tap to break the blocks free from the form, but if the back is already in place do you risk breaking the back loose as well?

I know these are really elementary questions but "experience is something you gain right after you realize you needed it"!

It is much easier to ask the question than find out that I needed one little bit of info about the time the ribs crack or some other " oh S#^*" moment!

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I trim the blocks while the ribcage is on the form, the parts of the blocks that are glued to the form will be trimed after the form removal with gouges and chisels.

After glueing the back, to remove it from the form, I tap the blocks and corner blocks with a hammer to unglue them from the form, then - with the mold facing down - I tap the ribcage against a flat surface to take off the mold and glue the top linings immediatly.

Some problems that may occur:

1 - if some part of yor ribs got glued to the form, it may be difficult to remove it, and you may even break the ribs;

2 - Some parts of the back/rib garland joint may get loose due to the tapping.

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I rub my form with paraffin to keep glue from sticking in the areas where I might possibly have some excess glue.

YOu trim the block while they are still on the form?? It seems that if you use a chisel or gouge to trim the blocks the thickness of the tool will force the blocks out away from the form and break them loose from the back??

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You'll end up with some minor gouge marks on the back. How prominent they are depends on how much control you have.

The way I remove my form is a little different from Manfios. I hook my fingers in the holes in the form, and push down on the blocks with my thumbs, wiggling each end of the form up a little at a time.

I've never had a back come loose from the ribs when removing the form.

Once in a while, a small piece broken from the form, or some glue residue will "key" the parts together, and I have to go between the form and block with a palette knife to get the form to come out easily.

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This method obviously works to great effect given the great results

of David and Manfio and others I know who use it...but.......it

 feels a bit complicated to me.....( as I guess any method one

does not use would)...OK  you get the back glued on fast and

accurate but then all is wobbly again.....Do those using this

method  put in linings and then take a rib outline to make the

front or do you hope the structure you have will conform to the

shape you aim at on the ready made front? The structure will be a

bit wobbly and vulnerable also as you true the rib gluing

surface??? It feels a bit uncontrolled and Cremonese to

me!......

My basic method is different.. I glue both sets of linings in on

the mold. Everything is nicely rigid so I can quickly true/shape

 the rib/plate gluing surfaces on a large rubbing boards

(80/120grit on 6X4 MDF) refining further if need be.

I pop these off the mold without stressing them (mold shape allows

this). To glue ribs to plates I pre clamp and lift of clamps

inserting glue with pallet knife and re clamping  in 4

stages on a violin. Everything goes where it is meant to allowing

as much accuracy or deliberate inaccuracy as required.

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I glue the lining of the back and make the linings of the top, that I leave in the mold but unglued. Then I lightly glue the back to the rib cage just in the block's regions (with a thick piece of paper betwen to make further unglueing easy) to cut the overhand and shape the corners. Then I do the same with the top. Then I pin the top and back, so that they will turn back to the same place when I want. I unglue the top and back and purfle both back and top. When I remove the form my top is already done and I'll glue it in 2 or 3 hours, there is almost no time for distortion, and the pins will help me in the alignement.

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quote:


Originally posted by:
Melving

Do those using this method put in linings and then take a rib outline to make the

front or do you hope the structure you have will conform to the

shape you aim at on the ready made front? The structure will be a

bit wobbly and vulnerable also as you true the rib gluing

surface??? It feels a bit uncontrolled and Cremonese to

me!......


I'd take the outline for the front from the ribs while they are still on the mold. If linings are fit on the mold, and glued in shortly after the the mold is removed, shape doesn't change much. Cellos take some pushing and pulling, but that happens with any method, I think.

I true both rib surfaces while still on the mold. Upper linings glued in after mold removal are brought flush to the ribs with a plane.

I don't represent that this method is better than any other; I'm just saying what I do. If you like significant asymmetry which varies with every instrument, this probably isn't the best method.

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One of the reasons I thought I would try this method is because it seems to be a way to eliminate the asymmetry. The only way I will know if I like this method is to try it.

How do you trim up you linings on the back or do you leave them square?

David, you say you trace the outline of the front while it is still on the mold...what would be the down side of drawing the outline after the mold is removed and the linings glued in? Obviously as I have already stated the purpose for me is to try to eliminate asymmetry as much as possible. Everybody has there likes and dislikes and for me the asymmetry thing makes me nuts!

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Does anyone else use a two part mold, with a space between the halves, which is spanned by steel straps? I remove the straps (held by stove bolts and T-nuts), then the two halves collapse toward the center, making them easy to remove individually.

Once the mold is out, I reassemble it with the steel straps, and it is back to its original shape and quite rigid.

Because I can do this, I install all my linings while in the mold, and carve as much of the block as is accessible, just to avoid the damage Barry mentioned. Right now I happen to like the idea of gluing the front first, as it allows fitting the neck absolutely flush with the back surface of the block, without having the button in the way. (got the idea from the late great David Rubio) But I may change that practice again.

Once one plate is glued, I have not noticed ANY floppiness when the mold is removed. I have (once) had a rib break because it was glued to the mold, and I was too dense to see what the "hangup" was, so I kept pulling 'til I broke it. (sigh...)

I trim my linings before I glue either plate on, and (obviously) before removing the mold. After the mold is out, I do the final scraping and clean-up.

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Gluing the back to the rib garland while it is still on the mold is a great way to ensure the garland shape follows the outline of the back perfectly, though I prefer to have access from either side while I carve the linings down. I glue both sets of linings on while the ribs are on the mold, and ease the garland off the mold when done. As said, I like the extra access offered to trim the linings with this method. In the past I have had a problem with aligning the ribs when gluing the back on, but adopted a method I saw somewhere that uses a garland support. I dry-clamped the garland to the back and manipulated it into place, then lightly glued the garland support to hold it's shape. It worked very well.

v043.jpg

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quote:


Originally posted by:
David Burgess
You'll end up

with some minor gouge marks on the back. How prominent they are

depends on how much control you have.
[/img]

You might find this pic backs what you are saying.

"http://www.flickr.com/photos/21263760@N05/2355951193/sizes/o/in/photostream/">

Gouge marks

I would just add that the amount of control spent might vary with

the amount of time available.

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