Eastman mandolin - assymetric top carving?

[maxr]

I've had an Eastman 305 for most of this year. It's had various upgrades between then and now including a Cumberland bridge. Before I replaced the bridge, the treble side of the bridge saddle was leaning towards the fingerboard more than the bass side, and I assumed the bridge was twisted. Interesting, another Eastman 305 owner had previously posted his instrument, showing the same bridge 'twist', as I thought. The Cumberland bridge improved the sound, so I was happy, just took it out the case and played it. Recently I changed the strings and had a look at the bridge. The bass side of the saddle is more or less at 90 degrees to the top, but the treble side is leaning towards the fingerboard relative to the top, like the original bridge saddle was and the one the other poster owned. Assuming it's unlikely that the original bridge saddle and a new Cumberland bridge saddle would twist the same, the only conclusion I can think of is that the top is carved assymetrically from one side to the other. I don't think the bridge is in any danger of falling over, and the mandolin still sounds as good for what it is.

Am I right or wrong, and could anything else be causing this?

[poul hansen]

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Am I right or wrong, and could anything else be causing this?

The top has sunk/distorted on the treble side?

[maxr]

The top has sunk/distorted on the treble side?

Thanks Poul - I had a look, and it doesn't seem to to have sunk. Maybe I'll detune, straighten the bridge as best I can and see what happens.

[NDO]

Tension is higher on the treble side…maybe when tuning it’s pulling the saddle more.

[Don Grieser]

Every time you change strings, you need to straighten the bridge saddle. Use your thumbs on each end of the saddle, with your fingers stabilizing the bridge base. A little push should straighten it up. Go easy till you figure out how much pressure it takes to straighten it. You might want to do it after changing each pair of strings at first, especially on the treble side if that's where the problem is.

[maxr]

Every time you change strings, you need to straighten the bridge saddle. Use your thumbs on each end of the saddle, with your fingers stabilizing the bridge base. A little push should straighten it up. Go easy till you figure out how much pressure it takes to straighten it. You might want to do it after changing each pair of strings at first, especially on the treble side if that's where the problem is.

Thanks Don - I slackened the strings a lot and did that, but before I could get it to the point where the treble side was dead straight up, the base of the bridge (which is vertical to the top under tension) showed less contact on the nut side than the tailpiece side. So, when I tensioned up again, string tension pulled the base flat and tipped the saddle treble side back some towards the nut, although it's visibly better and not extreme. I seem to remember someone told me that mandolin bridge screws are made to tip sideways in the bridge base to some extent, maybe that's what's happening here, but only on the treble side?

PS - why are carved top mandolin bridges not fitted so the bridge bisects the string break angle over it? That would mean tthe bridge would tip slightly towards the tailpiece. I'd guess that would even out the forces trying to tip the bridge in one direction or other, but I might be wrong.

[Don Grieser]

The bridge bases on my Heiden and Stanley are both fit so they are slightly angled toward the tailpiece. The saddles are perpendicular to the top. Maybe someone could refit the bridge base for you and that would take care of the problem.

[Mandobart]

When you got your Cumberland bridge did you fit it to your mandolin"s top? I've got quite a few fiddles and mandolins. I've never got a replacement bridge that I didn't need to fit to the instrument's top.

On fiddles the bridge is twice as high as a mandolin, so there is a much greater moment arm to apply the force of the strings against. And fiddle bridges are much thinner and weaker. On my 10 string Hardanger fiddle I had to bias the bridge to lean a couple degrees off perpendicular toward the tailpiece to offset the string tension trying to pull it over. The feet are flat on the soundboard but sanded at a slight angle to do this. The original bridge was prone to dive. Not a good thing while playing. I've never had to do a similar bias on a mandolin bridge.

[maxr]

When you got your Cumberland bridge did you fit it to your mandolin"s top?

Yes, I had a mandolin maker do it, and the bridge was pretty much vertical when fitted.

On my 10 string Hardanger fiddle I had to bias the bridge to lean a couple degrees off perpendicular toward the tailpiece to offset the string tension trying to pull it over. The feet are flat on the soundboard but sanded at a slight angle to do this. The original bridge was prone to dive. Not a good thing while playing.

Yes - Advice I've had from violin techs is that a 4/5 string violin or viola bridge should have the tailpiece side of the bridge on the bass side at right angles to the top, and that's easily checked with a business card. Sometimes that side on the treble end of the bridge will lean slightly towards the tailpiece when you've done that. Some luthiers favour thin violin bridges for acoustic reasons, which I find often take a small degree of bend even when you regularly check positioning. I've never had a violin bridge fall while playing, but I did once see a viola tailpiece gut break while being played- quite dramatic.

[Skip Kelley]

Without a picture, it's hard to tell. I would refit the bridge to the top as suggested. When I fit a bridge to the top, I put a slight lean towards the t/p. I learned this from my friend, the great Snuffy Smith. He always put a small angle to his banjo bridges. I do this on my mandolins.