Bridge positioning & Gluing?

TheDudeAbides

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I have a preslotted fretboard installed on my tenor with a theoretical scale length of 431.8mm. StewMac's calculator says I should compensate by +2.548mm and put the saddle at 434.348mm. I've seen compensation recommendations online from 2 to 2.5mm, does StewMac' calculator of just a hair over 2.5 sound right? (I'm used to intonating electric guitars where I can adjust this stuff with a screw after installation, so looking to double check my numbers)

As for gluing the bridge, is there a reason folks use long C clamps instead of a go-bar deck? I'd obviously need to raise the deck, or use shorter go-bars, but if I were to simply support the neck and secure the body so it doesn't move, the go-bars seem like a much simpler way of gluing the bridge on. However every book and website I've read seem to use C clamps, so I assume there's some advantage to the clamps that I am missing?
 

dofthesea

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Do not use your go bar deck. it will put pressure on the top which could break or create problems with top and bracing. The versions I've used are a Vacuum clamp and long C clamps with cauls. I prefer a vacuum clamp setup as its so easy once you do it your ask yourself why would I do it any other way. But then a lot of builders in their early stages don't have a vacuum setup.
 

John Colter

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StewMac's figures are not wrong but you can ignore the three decimal places - just round them up.

I would not recommend applying downward pressure on the unsupported front of the uke while gluing the bridge. If you can slip something inside, between the bridge plate and the back, I guess you could use go-bars.
 

Coast_Ukulele

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i was one of those folks in the beginning where i didn’t have a vacuum clamp and i just could not find the right c clamps. all the ones i got were just not fitting my ‘ukulele correctly. so for the first 5 ukes i built i used my gobar deck with a light enough pressure (i do a string through bridge). i didn’t run into any issues doing this, but it did freak me out so i invested in the vacuum and never looked back.

long story longer, in the beginning you don’t always have all the right fancy tools to get the job done in the best ways, i had to work with what i had and still somehow made some nice ‘ukuleles. I then kept investing as i went along and now have more tools to do things a little better.

it’s exciting how accurate you want to get with your measurements! i think any of those numbers you mentioned will work out well. the thickness of the saddle will also allow you to adjust intonation too.
 
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TheDudeAbides

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Do not use your go bar deck. it will put pressure on the top which could break or create problems with top and bracing. The versions I've used are a Vacuum clamp and long C clamps with cauls. I prefer a vacuum clamp setup as its so easy once you do it your ask yourself why would I do it any other way. But then a lot of builders in their early stages don't have a vacuum setup.
Thank you, will scrap the go-bars idea.

I don't have a vacuum setup so I'll be looking into either purchasing or building some clamps
 

TheDudeAbides

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StewMac's figures are not wrong but you can ignore the three decimal places - just round them up.

I would not recommend applying downward pressure on the unsupported front of the uke while gluing the bridge. If you can slip something inside, between the bridge plate and the back, I guess you could use go-bars.
Perfect, I'll aim for just shy of the 434.5 mark on my ruler and call it good 😉.

And you all talked me out of the go-bars deck idea
 

dofthesea

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I would venture to guess that the Dude Abides has an engineering background? I've never seen a relative newbie so worried about dimensions lol Anyhoot good on you for taking it to the next level as a beginner. Compensation is approximately 2mm for most builders. You also have quite a bit of play in how you shape the saddle to compensate.
 

TheDudeAbides

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i was one of those folks in the beginning where i didn’t have a vacuum clamp and i just could not find the right c clamps. all the ones i got were just not fitting my ‘ukulele correctly. so for the first 5 ukes i built i used my gobar deck with a light enough pressure (i do a string through bridge). i didn’t run into any issues doing this, but it did freak me out so i invested in the vacuum and never looked back.

long story longer, in the beginning you don’t always have all the right fancy tools to get the job done in the best ways, i had to work with what i had and still somehow made some nice ‘ukuleles. I then kept investing as i went along and now have more tools to do things a little better.

it’s exciting how accurate you want to get with your measurements! i think any of those numbers you mentioned will work out well. the thickness of the saddle will also allow you to adjust intonation too.
Good to know, and I'm not sure a vaccum press is in my future for this particular build, but have added that tool to my wish list for the future 😁
 

TheDudeAbides

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I would venture to guess that the Dude Abides has an engineering background? I've never seen a relative newbie so worried about dimensions lol Anyhoot good on you for taking it to the next level as a beginner. Compensation is approximately 2mm for most builders. You also have quite a bit of play in how you shape the saddle to compensate.
Lol, well I do have "engineer" in my job title, but I'm an IT guy so probably not the type of engineer you are thinking of 😉

My big concern here is from experience intonating individual strings in an electric guitar and how very small changes impact it, and the fact I have to file a saddle to do that on an Uke which gives me less leeway than I have on most electric guitar bridges, as well as no easy way to reverse it if I go too far.

But, on the other hand, this is also how I started building furniture too, and after a few years eventually moved to story sticks and a pair of dividers. I may get there with Ukes one day too, but until I get more comfortable will stick with measurements that can be easily verifiable.
 

Benros

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Any suggestions where to get a vacuum pump with the right frame for a ukuele bridge? Or did you built it yourself?
 

Kekani

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Any suggestions where to get a vacuum pump with the right frame for a ukuele bridge? Or did you built it yourself?
This isn't the latest version, but still works.

 

Pegasus Guitars

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This isn't the latest version, but still works.

Guess I'm the outcast here. I have a good vacuum pump that I mostly use for laminating curly wood onto lap steel bodies or making binding/purfling laminates. I have tried it for bridges and find it to be a complete hassle. A dedicated shop made bridge clamp,simolar to the one Stew-Mac sells for guitars, is easy to use, easy to do cleanup, and works very good. It requires only 1 light weight cam clamp. Unless you have some other use for a vacuum, and there are many good uses for one, I would not recommend buying one just to do bridges. No need.
 

Kekani

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Guess I'm the outcast here. I have a good vacuum pump that I mostly use for laminating curly wood onto lap steel bodies or making binding/purfling laminates. I have tried it for bridges and find it to be a complete hassle. A dedicated shop made bridge clamp,simolar to the one Stew-Mac sells for guitars, is easy to use, easy to do cleanup, and works very good. It requires only 1 light weight cam clamp. Unless you have some other use for a vacuum, and there are many good uses for one, I would not recommend buying one just to do bridges. No need.
I got rid of my gobar deck a while ago. I now vacuum clamp top and back braces (got that from Joe at Kanilea) and some fretboard inlays if they're glued with HHG or epoxy.

I too used a one clamp method a la SMD, but much prefer vacuum clamping bridges with HHG. Fun science stuff, I guess.

And I agree, not worth it, unless its worth it.
 

TheDudeAbides

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Hmm, all excellent suggestions, though I think I'm going to hold off on any more expensive stuff from those wonderful luthier supply websites for now.

It looks like harbor freight has some 5.5" throat clamps that'll work as long as I'm careful not to ding the sound board.

Though on the other hand, any reason I couldn't just mix up a small batch of hot hide glue and apply hand pressure for about 60 seconds to let it harden? I know rubbed joints are almost instant but I'm not sure I could position the bridge accurately with a rubbed joint, and I believe hide glue only has a 1 minute clamp time anyway, though I've never tested it that short either.....
 

lakesideglenn

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All of the StewMac clamps are too big for a soprano…any suggestions from you builders out there? I have a Pohaku sop that needs the bridge reglued. I’m looking to buy, not make clamps.
 

sequoia

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There are classical guitars builders that don't clamp at all but just hold down the bridge for a couple minutes and let the glue do the work. They swear clamps are unnecessary. I'm not one of those people. For tenors I use a 5" c-clamp I got a long time ago from SMD. Works great but probably too big for sopranos and probably concerts too. $28 bucks. Don't over clamp. I use just one and lightly clamp the wings with cam clamps. I've had to try and recover some of my bridge glue downs and I can attest those things are on there like the hammers of Hell I glue with TiteBond I but hide glue works just fine. I'm told.
 

TheDudeAbides

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There are classical guitars builders that don't clamp at all but just hold down the bridge for a couple minutes and let the glue do the work. They swear clamps are unnecessary. I'm not one of those people. For tenors I use a 5" c-clamp I got a long time ago from SMD. Works great but probably too big for sopranos and probably concerts too. $28 bucks. Don't over clamp. I use just one and lightly clamp the wings with cam clamps. I've had to try and recover some of my bridge glue downs and I can attest those things are on there like the hammers of Hell I glue with TiteBond I but hide glue works just fine. I'm told.
Working on a tenor, and can grab get cheapo Chinese 5" clamps for about $5, so in thinking I'll go that route. Though I may craft my own version of StewMacs caul with the 2 outer screws so I only need 1 clamp through the sound hole.

Looking into hide glue and the clampless technique some more, and it is mainly for rubbed joints, and I want to correctly position the bridge, not rub it and have it positioned wherever it grabs. I've also seen some general strength tests that recommend clamping HHG 4 to 6 hours for joints that will be stressed. The hold in place for 2 minutes should work but may not be as strong, so I'm opting for a clamp. Though I may still HHG it as those pesky classical guitar guys seem to prefer it for bridges over PVA and I have a couple bags of glue in the garage already anyway.
 

dofthesea

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I got rid of my gobar deck a while ago. I now vacuum clamp top and back braces (got that from Joe at Kanilea) and some fretboard inlays if they're glued with HHG or epoxy.

I too used a one clamp method a la SMD, but much prefer vacuum clamping bridges with HHG. Fun science stuff, I guess.

And I agree, not worth it, unless its worth it.
Can you please show a pic of your vacuum clamp set up for tops and backs?