F hole twist what is the cause ??

[Rickbcnu]

Double Bass
I have a question that I keep getting different answers to in regards to the top and bottom of the F hole on the sound post side, twisting in on the top and out on the bottom.
Can anyone tell me the cause of this ??

Thanks

[littlebill]

This might not answer your question since yours is on the sound post side but about 1/3 of the bass bar had separated from the top when my bass had that happening with the F hole on the other side. I found out when I took it to a good luthier trying to find out why I couldn't get any volume and that is the first thing he checked. It had been going on for a while and if I had waited much longer, the top could have caved in. It is a bit costly since the top has to be removed to glue the bass bar back on but once it was back to together and everything settled down, the repair made a world of difference in the volume as well as the tone.
I would get it checked out soon, good luck.

[uprightben]

I don't know if what you are describing is as severe as what littlebill went through, let's hope not. There are many possible causes for distortions around the f holes, since you are describing only your treble side distorting you might want to see if your sound post is too long and thus pushing the table out. This is easily fixed by a good luthier, but don't delay as it can cause damage. Of course, there could be a million other causes, but if you bass bar and sound post are sound, there's not much to be done about it.

*disclaimer: I am not a luthier!

[Rickbcnu]

I spoke with a repair person and was told that because it was a new bass the wood would move alittle? I had an older cheaper plywood bass and the f holes were perfect.
This bass is a plywood bass also with a maple lamanate and I don't think it would be moving but I could be wrong. Looking for other opinions.

[Monkey]

My 1945 Kay has a similar distortion around both f-holes. The bass side is only very slightly distorted, but the north end of the treble f-hole has sunk in about 1/4 inch. The south end of that f-hole sticks out a tiny bit.

I was worried about it and ask my luthier. He said he had seen it before on Kays. He said it seemed stable and that I shouldn't worry about it. I dont think it has changed in the 24 years that I have owned the bass.

[Matthew Tucker]

It's pretty common. it depends where your soundpost is and the width of the bridge blank and the thickness of the top etc. As the bridge is pressing down with some force on an area just north of the sound post, it's not surprising that the upper treble f hole tab will tend to sink a little. (This same effect happens in fiddles, and some makers purposely "lift" the FF hole tab a little bit with a wedge during the glueing to counteract the tendency.)

I think, as long as it is not getting progressively worse, it's probably OK. Check that the bridge is properly centred between the FFs and that the sound post isn't too far south from the bridge foot.

[KSB - Ken Smith]

Also, as Matt just mentioned about the Bridge size, measure the inner distance of the upper F-hole eye openings. The Bridge should be similar to this and maybe just a bit wider if the Bassbar is up against the edge of the upper eye on that side. The E-foot of the bridge should be centered over the bass bar as well.

If they ( F-eyes) measure say 6" (inside), then the other bridge feet should measure 6-6 1/4" but this depends on the bassbar placement. Even though it's a Ply Bass and not carved, the measurements should still be correct.

If the Bridge is too wide, it will push the G-side F-hole down on the inside edge. If the Bridge is too narrow, you are loosing some depth and spread of sound on your Bass.

Also, those end tabs on the FFs have nothing to hold them in place unless they are attached like some older Basses have been made. See the 'attached' examples below;


On this Bass here the Bridge is too wide as you can see the feet overlapping the upper eyes. I have already trimmed some wood off the outer feet but after the Bass is restored it will get a Bridge with a narrower feet spacing;


When a bass is over 200 years old, you don't want the wrong sized Bridge on it. With years and years of previous distress, old cracks can be opened up by excess pressure on the Top like seen here. Also, the good news is that it can still be fixed when the Bass is restored. It is best though not to chance fate and fit the correct sized Bridge in the first place.