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Here's Mike Conner's report and description
of his two new bridges,
along with some construction hints!

 



(On July 3rd, Mike wrote:)

Red, Just completed my first bridge this morning, and I can't believe my ears! I think everyone is a little bit conservative and sceptical when it comes to things like this. But I have to say you were 100% right! My bridge is from some curly and streaked SC maple. I need to take it off to finish sand, etc., but I really don't want to!

Tone:
I'll make some subjective comparisions, easy to do since I left the same strings on the mandolin, and these strings are getting old. Compared to the two-piece Breedlove bridge:
- The notes (tones) are better defined. You can actually tell there are 2 strings.
- The E and A treble strings are clearer and warmer sounding. Less harse - more "bell" and less "bark".
- The G bass strings are very well defined. The Breedlove bridge sounded muddy with the G and D strings, which is why I was thinking they needed to be replaced.
- Overall much more sustain, especially noticeable on the G and D since they are clearer sounding now.
- Since the wound strings are less muddy sounding, chop chords have more punch.
- With the overall better definition and sustain, cross-picked chords sound incredibly better. The individual notes cut through very nicely while the sustain keeps it from sounding "plinky".

Design details:
I made a careful tracing of the Breedlove bridge first to make sure I replicated the string spacing and arch. I also made careful measurements of the Breedlove regarding thickness and other features. The Breedlove base is 4.380" long, 0.375" thick at the bottom with a flare down to 0.250". The upper section is 0.395" thick.
I used your bridge #5 as a starting point, especially the cutout at 1/4" by 1-1/4, and the feet each at 1-1/8" long. I kept a 4" overall length, and worked from the centerline, comparing to the Breedlove bridge, to create a layout template.
The cutout is centered in the approx. 1" total height of the bridge.

The completed bridge is approx. 0.240" thick at the feet. I began a taper flare lined up with the bottom of the cutout, and the upper portion of the bridge is approx. 0.175". Overall this is thicker than your #5. I was uncomfortable with having the contact point of the feet as thin as 7/32" as you mentioned. So I chose to keep them closer to 1/4", and lighten the bridge by a more abrupt thinning, rather than a gradual taper to the top. Does this description make sense?

I kept the top portion stay a bit thicker than your #5 because I didn't want to give up all the compensation for intonation. And I figured I could always thin the bridge down if the results weren't good.

Overall this bridge was pretty easy to make, except for the tedium of fitting the feet to the top. But the results are sure worth it! I'm going to make a few more, and send a couple to my brother to test on his Breedlove Roque. My son will need a science project his year, and we talked about using mandolin bridge design for the project. He'll make some radically different choices of dimensions and materials (like a Pine bridge - now that will sound interesting!), and I'll record the results to MP3 for comparisons. Should be fun.

Thanks again for all your information and inspiration. ...



 

...here's a drawing of this bridge.

drawing of bridge specs



(On July 10th, Mike wrote:)

Here's some more info on my methods:

Resaw: The maple was originally variable in thickness from 5/8" to 13/16". I ripped to around 1-3/8" strips, then split them using a thin kerf 24T Freud ripping blade on my table saw.

Layout: I made a template using graph paper glued to poster board to make layout easier and consistant. The bridge cutout was 1-1/4" by 1/4" as you specifiied. I made two puncture marks at the center of the 1/4" holes defining the ends of the cutout and made starter holes with a finishing brad.

Bridge cutout: Make the cutouts before cutting the bridge shapes out! I used a 1/4" brad point drill bit in a hand-held drill , and a piece of plywood as a backer, for cleaner entry and exit holes. I marked the starter hole locations with nail marks, and the brad point bit very reliably hit the marks. A row of 5 holes roughs out the cutout. A sharp 1/2" chisel makes quick work of cleaning out the balance of the cutout.

Cut out profiles: I have a inexpensive scroll saw for this. Quick and surprisingly accurate.

Rough shaping: My Craftsman belt sander has seen better days, but it clamps on it's side in a Workmate really well, and with a couple of 2x4 scraps as a table I can work the blanks around to clean up the shapes. It's easy to just hit the top section on the belt to make the taper.

Rough Feet fitting: Since I want to do several bridges, I took the time to make a sanding caul using a chunk of 2x4 that I planed, filed and sanded to the same profile as my Breedlove top - I used a fitted bridge as a guide. I've attached 150 grit sandpaper with spray adhesive and can now quickly get the feet close to a good fit without using my mando as a sanding block!.

String slots: A Dremel razor saw blade is 0.012" thick and is great for starting all the slots very precisely. Just right size for the E strings, and with a slight rocking it can do the A string slots too. I have nut files (older Stew-Mac versions) for the D and G slots - but needle files and old strings can do a decent job too.

Final fit: The Frank Ford method at http://www.frets.com/FRETSPages/Luthier/Technique/Mandolin/FitBridgeFeet/fit feet.html is pretty close to what I ended up doing for the final fit. The slight hollow with a pocket knife as a scraper is really a good idea.

Finishing: Sand to 320 grit, then polish with 0000 steel wool. Apply Minwax finishing wax and let dry thoroughly, then buff. No wax on the bottom of the feet though!
 




Now, here's a scan of Mike's second bridge, with his description of it:

picture of mandolin bridge



Here's a JPG of the bridge I'm sending my brother for his Breedlove Rogue.

As scanned it is finished. It has been fitted to my Breedlove Quartz top, with the action left high (approx. 1/8" from 12th fret crown to strings - plenty of room to adjust down from there). You can't really see the curly figure too well in this scan, and the upper section is out of focus due to the taper I use.

This is the "front" or fretboard side of the bridge (G-strings on the right). The drawing I sent you is the tailpiece view - the G-strings on the left.

You might notice there is a small difference in the shape of the "legs". The E-string side has more material than the G-string side. Nothing scientific there, it's just the way I drew my original template and it worked, so I left it alone!



 


 

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