Fixed mandolin bridge compensation.

[Bryan Bear]

I am making a flat top mandolin that will have a pinless glued bridge. I don’t know much about mandolins but I suspect that with the 14 inch scale, compensation/intonation will be an issue. If this were a floating bride, I would just start with a saddle surface shaped to get the 4 courses close then locate the bridge testing intonation as I go and do any fine tuning on the “saddle” that may be needed. Since I have to glue the bridge down before I string it up, I’m a bit nervous about locating it. On a guitar I have a fair idea of how much longer (than desired scale length) to make the e strings and can file the saddle if needed. Can someone offer me a little help? Ideally, if someone could suggest a ballpark length for each course beyond the 14 inch scale that would be great! If not, how much further back should each of the outside courses be and about how much offset is typical in a compensated mandolin bridge? I haven’t made the bridge yet, so I can build in an angled saddle slot like a guitar or I could use a thicker/wider compensated saddle (but how thick should I go?).

[Steve Senseney]

I have a side question--

The tension on 8 strings is fairly significant. If you use a pinless bridge, are you making it extra big to avoid glue failure?

[Mark Swanson]

I don't want to knock your idea, but I might as well toss in my thoughts on flat topped mandolins, of which I have made many.
Steve is right, that is a lot of tension on a small top. Not only will you need a big bridge with eight string-through holes for the pinless part (and here the area between the strings will be small, with 8 strings in it- a recipe for disaster) but you'll also need heavy bracing. Big bridge with heavy bracing on a very small top.
This did not seem like a winning idea to me, so when I designed the mandolins I build I use a floating bridge and tailpiece, and I don't worry about having a super-high bridge. The strings are 3/4" above the top at the bridge. This means my neck angle does not need to be that huge, and I leave the fingerboard elevated above the top too so that also cuts down on the neck angle. So the break angle over the saddle is not that extreme, but still allows good down-force to drive the top. Since there isn't a terribly high down-force I don't have to brace it heavily, and it makes a loud little mandolin.

[Clay Schaeffer]

hi Bryan,
You could use the holes in the pinless bridge to provide downbearing but carry the strings back to a tailpiece. This wuuld allow you to use lighter bracing. If you slot the bridge after it is glued down you can use temporary saddles to find the required compensation for the strings .

[Mark Swanson]

That's another way to do it. It would also allow you a smaller bridge. And you may not need to glue it down, at least you may be able to try it out before gluing it down to find the right spot.
But if you are going to a tailpiece anyway, then a little extra neck angle and you wouldn't need any holes through at all and your bridge can be smaller yet.

[Michael Lewis]

The compensation for intonation will vary with the string gauges and sometimes from brand to brand due to larger or smaller core wire in the wrapped strings.

I concur with the opinions offered. One other approach is to use one string per course. Good luck.

[Clay Schaeffer]

I just finished building 40 stick dulcimers. They are kind of like long necked flat topped single strung mandolins, with one string missing . I used a very simple construction and a floating bridge with the strings carried over the end to nails in the end block. With formica bodies and about 3 hours labor in each one they are designed for the low end of lutherie.

[Bryan Bear]

Thanks all for the comments and advice. The box is braced and closed already. I had a general idea of how I wanted to approach the bracing and talked to Mario who has made a similar beast with pinless bridge for one of the challenges here. I was comforted to find out his bracing was very similar to what I had planned. The box feels and sounds about right to me (for whatever that is worth) and the planned bridge will have sufficient footprint; I’m not too worried about it not holding. The actual design of the bridge has me a bit worried – I’m not 100% sure I can pull it off (is that a poorly placed cliché or what) and have it look good, but time will tell. I think I will make the bridge (with an approximately shaped saddle) and use a temporary tailpiece set-up to locate it in the white. Then finalize the saddle shape “on location.”