Results 1 to 6 of 6

Thread: Neck angle and bridge height

  1. #1

    Default Neck angle and bridge height

    Following on from my earlier thread http://www.mandolincafe.com/forum/sh...ed-bridge-body I'm again appealing for help from the very knowledgable experts on here.
    I'm nearing the end of a tenor mandola build and have run into a potential problem with the bridge height. I'm planning on using a fixed pin bridge, but when I lay a straight edge along the fingerboard - thicknessed to 6mm but not yet fretted - I get a height of 12mm at the saddle position. By the time I get the frets in and add string thickness and clearance, I think I'll be looking at a string height of about 17mm on the bottom string. Is this acceptable, or will it place too much strain on the top?
    And if so (as I reckon), what can I do about it? The neck is pulled up into position with a bolt but not yet glued on, and neither is the fingerboard.
    Would it be a good idea to reset the neck angle and place a tapered shim under the fingerboard where it joins the top?
    Click image for larger version. 

Name:	Bridge height.jpg 
Views:	245 
Size:	442.5 KB 
ID:	153888

  2. #2

    Default Re: Neck angle and bridge height

    It's been 30 years since I built my last fixed bridge instrument ( guitar) but I'll give you some rough advice from my memory. Will a 17mm total saddle height at the bridge put too much strain on the top? Well that depends on how thick you have made the top and how heavily you have braced it but for the typical flat top thickness of 2.5 - 2.8mm (.100" - 110") yes, that is way too high. You want to be in the area of say 12mm for a total height at the saddle. Say 8mm bridge thickness + 4mm saddle height. That's for a guitar. For a smaller instrument, you might want to scale that down a little. For a mandola, you could probably go with a 7mm bridge thickness and zero neck rake. That should give you a saddle height, above the bridge, of around 3 - 4mm with no need for any shims under the fingerboard extension.
    Like I said, it's been years since I've thought about fixed bridges but I think what I have said is generally correct.
    www.apitiusmandolins.com

    What is good Phaedrus? and what is not good?, need we ask anyone to tell us these things?

  3. #3

    Default Re: Neck angle and bridge height

    Thanks Oliver - that's just what I thought. This is only my second instrument, and I'm finding out the hard way that things I did at the start are having a big effect on other things I'm trying to do now. The neck angle is set by the angle of the soundboard as it falls away from the soundhole to the neck join. If I change the angle of the neck, the plane of its top surface won't match the plane of the body where they join. Not quite sure how to get round this one. I guess I could decrease the neck angle and taper the underside of the fingerboard beyond the 12th fret, but probably not enough to bring it down sufficiently.

  4. #4
    Mandolin & Mandola maker
    Join Date
    Sep 2002
    Location
    Bega NSW, Australia
    Posts
    1,425

    Default Re: Neck angle and bridge height

    I agree with Oliver, 17mm is way too high. I aim for 12-14mm on my guitars and tenor guitars, most end up around 13mm when brand new. That may change a bit as the guitar ages. Note that as you get higher string heights, you need to make a thicker bridge -> more mass on the top just where you don't want it, especially if you are using an Ebony or Rosewood bridge. More mass means the instrument will be less responsive. I use Tasmanian Blackwood for my bridges which is hard but not as dense as Ebony or Rosewood. Your problem is a little tricky to solve. You do need to reset the neck and either shim or taper the fingerboard. Either that or forget about the pin bridge and use a floating bridge and tailpiece.
    Peter Coombe - mandolins, mandolas and guitars
    http://www.petercoombe.com

  5. #5
    harvester of clams Bill McCall's Avatar
    Join Date
    Feb 2014
    Location
    Forest Grove, Oregon
    Posts
    2,775

    Default Re: Neck angle and bridge height

    I'm surprised this didn't become apparent in your full size elevation drawing. You did make one, right? Obviously it would have been simpler to compare your parts to 'known good' ones at that time to determine if you were on the right track.

    I've seen this before, except the neck angle was too low, and the bridge a little short.
    Not all the clams are at the beach

    Arrow Manouche
    Arrow Jazzbo
    Arrow G
    Clark 2 point
    Gibson F5L
    Gibson A-4
    Ratliff CountryBoy A

  6. #6

    Default Re: Neck angle and bridge height

    Ok, I know where I went wrong - back when I sanded the rim on my radius dish. But still wondering what is the best way to go. Given that the guy I'm making it for would prefer a floating bridge anyway, I'm tempted to scrap the top and replace it with one braced properly for a floating bridge.

Tags for this Thread

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •