Is it necessary to repair a crack?

[HonketyHank]

I have a very basic question. Is it always necessary to repair cracks in the soundboard? The question occurs to me because of my recent acquisition of an old, beat up, cracked waldzither that just happens to sound pretty nice after being cleaned up and restrung. I see two gaping cracks in the soundboard, two systems of related smaller cracks in the back and a crack or two in the ribs. The bracing in this thing would be suitable for a battering ram and the top and back are firmly attached to same. One top brace runs pretty close to right under the bridge. I don't hear any buzzes, except bass strings on fretboard due to slightly low bridge. I don't detect much if any movement when I push on either side of the cracks.

It is strung up fairly tight using plain old EJ74 strings at 18.5 inch scale to achieve D-A-E-B tuning plus a big fat .059" string for a low G (for a total of nine strings).

I got some photos and will attach.

This instrument is ~110 years old and appears to have been used, abused, then hung up in a coal cellar for a half century.

A video of me showing it off is here https://www.youtube.com/watch?v=0RiMdxCq_Mw (starting at the 1:07 mark).

So the question is: do I really need to have those big cracks in the top repaired? Will the instrument sound 'better' if repaired? Will it fall apart if not? I strongly suspect it will last longer than I will whether or not it is repaired, so maybe this is just a question about whether it will sound even better than it does now.

Two pix of sound board plus one of back, all with flash. Note that the 'gouge' marked in blue is almost certainly a crack. These are hi-def, so you can blow them up by clicking on them.

[pops1]

Hank, You could leave the cracks, but then it will be prone to get dirt into the cracks. I wouldn't try and close these cracks, as you say there is bracing underneath. Putting in a spline would be the tried and true way, but I wouldn't do that either. I have been repairing cracks by using plane shavings inserted into the crack dry and as tight as I can make them fit and still get into the crack. I then wick HHG into the crack with the shaving. It really does a nice job of sealing the crack, keeping it clean and making the top solid again. Should you want to in the future you could always put in a spline, but it's really not needed. I have had repairs with shavings out there for years now and they work well, are less noticeable, and less invasive. For very thin cracks such as the back where it is too narrow to insert a shaving I sometimes use glue and dust and rub it into the crack. It does the same thing and keeps it clean and surprisingly strong.

[rcc56]

Cracks have a way of growing if they are not repaired.

[Tavy]

It'll sound better and last longer if they're all properly repaired, just my 2c.

Love those old waldzithers though A Boehm?

[DavidKOS]

Another vote for yes, fix it before it gets worse.

[Ivan Kelsall]

If it was mine,i'd have a good luthier take a look at it. A repair to stabilise it might be all that's required ie. pops1's idea. Only by taking a look inside can you find out if the original bracings are doing their job,or have come loose,allowing the cracks to spread.

Apart from that,putting it 'right' once more would give me immense satisfaction, & prolong the life of the instrument itself,
Ivan

[Jeff Mando]

OTOH, it has taken 110 years for the cracks to get this bad......might be another 110 before it flies apart! Just sayin'

[fscotte]

I build two f-shape cracks into my soundboards. Doesnt seem to bother the tone or structural stability.

[John Kelly]

I am guessing that the big crack in the first picture has developed over time and only stopped because it has reached the rosette, which might be holding its progress now. I'd have them attended to.

[bernabe]

Very close to the string line on all those cracks with one being under the bridge. This is the most vulnerable area due to downward bridge pressure and longitudinal compression. Unless there are cleats already under neath, its most likely going to get worse, imo.

[sunburst]

The info I have gathered from this:
The instrument is old.
The instrument is over-braced.
The top cracks go the full length of the top from edge purfling to rosette purfling.

My conclusion about the top cracks:
How can they "get worse" when they already go as far as they can? The top cracks cannot easily be closed because of the bracing, so the only good way to repair them is with well-fit splints/splines.
The presence of "battering ram" bracing makes the structure solid while making closing of the cracks nearly impossible.
The structure of the instrument seems to be holding up fine.
I don't think it is "necessary" to repair the top cracks. The soundness and stability of the instrument will probably hold up if left as is. It is relatively difficult to fit splines well enough to restore structural strength, compared to simply gluing tight cracks.
I don't think the sound would improve noticeably if repaired.

The back cracks look like they could be closed and glued, but I'm only looking at images on a computer monitor. After evaluating them in hand I might conclude that they are worth repairing.

Bottom line:
It is nearly never a bad thing to repair damage, but in this case I doubt that there would be improvement in sound or structure, so repairing the cracks is not "necessary".

[DavidKOS]

Bottom line:
It is nearly never a bad thing to repair damage, but in this case I doubt that there would be improvement in sound or structure, so repairing the cracks is not "necessary".

Good points, but when an instrument is this old and in this condition, the glue becomes brittle and iffy, the bracing could break next, and so on.

Sure it might stay in the same condition for a long time. It's a gamble.

[Phil Goodson]

For what it's worth, my recent story:

A little over a year ago, I bought an 8 year old very nice instrument with a known small tight crack in the top. It had lived in the southwestern U.S. in a very dry area and had been very stable for years with no progression of the ~1 inch crack. Advice was that it was unlikely to change, given its dry history.

I played it in NC and all went well. Well, .... until this year when we had an unusual period of VERY dry weather, rel humidity sometimes dipping below 10% in my den. Once the humidity got below 35% I started keeping the instrument in its case with humidifier except when playing, but the crack began to lengthen by a few millimeters and I contacted the luthier.

At that point, he recommended repair and that's happening now. With a little luck, that will hold it till my descendants have to watch over it.