It has been said that mandolin players spend half their time tuning up and the the other half playing out of tune. I guess at this point I may be loosing some readers but I would have to say there is some element of truth in this.
Intonation on mandolins can be difficult. Poor intonation is clearly heard especially when chords are strummed. With the improved clarity of sound that modern mandolins produce it is even more obvious when a mandolin is out. However when they are in they are oh so sweet.
Since most mandolins are arch top by design the bridge position can be easily changed. This can be done by simply loosening off the middle pairs of strings and either moving the bridge forward or back to sharpen or flatten the intonation. Once the the harmonics at the 12th fret for both the EE and GG are right the middle DD and AA should also be right. The obvious advantage of this is that changes in string height or string gauge can be compensated for by moving the bridge.
Unfortunately once a bridge has been moved a few times it has the tendency to slip or drift. When this happens a quick adjustment can often make things worse. I say this from experience. It is best to quietly and carefully reset intonation.
As a maker the problem of unwanted bridge movement has been an unresolved issue. I have lost count of the number of times I have been tempted to put just a tiny drop of glue at the foot of the bridge to fix it. This would be a very short sighted thing to do. The greater friction created by more downward force in instruments with a large break angle at the bridge usually stops bridge movement. The F5 mandolin is a good example of this.The tension brought about by the downward force is what gives the F5 such a bright and projecting nature. Conversely the tension also reduces the potential for sustain and bass response.
The radiant sound board design that has evolved from my experiments does not need a big break angle as tension is built into it. Minimal break angle has meant the slip sliding bridge issue had to be addressed.
The solution which works best turns out to be very simple and effective. It is one high tensile screw which fixes the bridge onto a small flat plate. This plate is permanently attached to the sound board. The bridge can be loosened for intonation adjustments and it is the lightest bridge assembly I have designed. Also it is an easy one to change if different string setups are required.
If only I had asked the right question I may have found this solution much sooner.
To fix and unfix that is the answer.
As the pictures show it does have a counter intuitive appearance. Regardless it is a good thing to know that vigorous playing will not move it. I can not think of a name to give to this bridge design.
Are there any suggestions?