Cello rib wrinkles

[MJ Kwan]

I haaaate ripples along the grain in cello ribs.

 

The ribs I bent are supposedly all from the same chunk of tree, so I don't understand why some of them got the strong wrinkle and some not at all. Makes me want to blame the wood rather than my technique.

 

So I guess my question has two parts:

 

1. Looking at unbent ribs, are there any signs that can tell if one's going to be a ripple-prone rib? Is it variation in grain? Did I thickness unevenly? Does it have something to do with seasoning?

 

2. Does anyone have some technique tips to share on minimizing the ripple?

 

Photo comparing the two C-bouts below.... one has a nasty wrinkle and one does not, though they are from the same piece of wood. (This is my first cello.)

 

[Michael Doran]

It looks like your ribs are shrinking around the mold. You can minimize this by using a thicker mold and/or using less water when you bend your ribs, but I say embrace it! True the first picture is a little excessive, but I try to get my cello ribs to warp a little, and if they wrap around my mold a bit it just makes for more interesting dips and hollows for antiquing.

M

[nathan slobodkin]

Definitely more likely to happen the more water you use. Sometimes it will happen due to grain anomalies in the wood but if you  plane them thin enough and just wipe both sides with a  wet cloth or paper towel and then bend with one smooth pull around the iron  you should get better results. I use 1.6 mm thick for maple and 1.8 for willow or poplar.

[Nick Allen]

Maybe one of those double-decker cello moulds would minimize that. Is it too much ripple that you can't simply scrape it away later?

[MJ Kwan]

Thanks yall. Too much water could be it. I've been dunking and wiping off the water with my hand immediately after. Maybe I should not dunk...

 

It's hard to see in the photos, but the mould is actually pretty thick - barely got room for linings. The wrinkles seem pretty independent of the form. I agree about appreciating some mild gradual waviness over the width of the rib, but I can't embrace these isolated stripes of tight little v-shaped wrinkles... they make me think of soft-story collapses in buildings, ugh!

 

I think this is more than I'd want to scrape:

 

 

 

Also sometimes the wrinkle is indenting, not protruding (another reason why I think the issue is independent of the mould):

 

 

 

They are pretty furry looking - I'll definitely try cutting down on pre-wetting the ribs. A bunch of people at school are about to bend cello ribs. I'll suggest trying less water if they're getting wrinkles.

 

Still curious if anyone has noticed clues in the wood itself. Is a piece of wood predetermined to wrinkle in that one spot?

[Conor Russell]

I've had this happen a few times and scrapped the rib. I like wobbly cello ribs, and I'd probably scrap poplar ribs if they came out too straight, but, like you, I hate this particular kink. 

 

I think it's an anomaly in the wood. I bend ribs dry, but I have wondered if this happens more when the wood is humid. A very hot iron seems to help,  with a piece of paper between it and the rib, to stop scorching. 

 

I like thin ribs, and I line them with strips of silk from a wedding dress bought for €10 in a charity shop.

[Joaquim Azevedo Neto]

I had the same situation with ribs with different thickness. Usually the thinner section will dry first and that may cause the warping due to the difference in the wood fibers.

Edited October 17, 2020 by Joaquim Azevedo Neto