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I was wondering if bending the sides as narrow as possible (as opposed to leaving some 1/2" or more extra width) would help against rippling, cupping and the like. I am currently trying to leave some extra if possible in order to remove some of the curling that sometimes occurs at the edges.

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Build log

I cut my sides to the final width of the tail. Then cut the back taper when I have the blocks glued in. Leaving extra sounds like just extra work to plane it off later.
How are you bending your sides? I use a hot pipe and I don't get much cupping or curling. Maybe you're using too much water?

Pipe, no water at all. I only got some curling and cupping on a few sets and i could file and sand them flat without making them paper thin but i find it *very* annoying

Recently I started to experiment with water (wipe both sides with a soaked sponge) and wrapping in alumina foil and I think it does wonders. For example I had the worst luck with a pair of very very curly maple. First piece bent dry, waist scorched deep (would not bend at lower temp). Second lower temp, I tried harder at bending it, it broke. Soaked it, broke again. Later I experimented foil on them and it worked, bent very fast and easily. Then i tried it again for a pair of Macassar (one normal the other wrapped) this time I didn't feel any improvement but it didn't do any harm either. Today I bent a set of Madagascar rosewood (which I consider a tricky wood, snaps very easily if thick, distorts if thin) and it worked like a charm. The waist bent nicely, it felt very compliant, and there was virtually zero distortion at the end.

If anyone tries this, watch that steam lurking under the foil! Gloves or wooden blocks are kind of mandatory (when dry I had no problems using just the bare hands).

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Build log

Glad someone has tried the foil idea. It can work in a fairly spectacular way. Maple has a tendency to bend very readily (using the foil method) but it can also straighten out because of the moisture/heat retention. Not so much of a problem providing you are aware of it. Rosewood seems to bend easier too but with less tendency to spring back.
As for rippling sides. I think it really is down to the individual piece of wood. I've had bad rippling from both Rosewood and Maple but I've also had many examples that were well behaved. I also suspect that sides that have a wide variation in density across their width are more prone to cupping/distortion.

Yikes! I can't imagine bending sides on a pipe with no water at all. I don't use much, but keep the area being bent (usually about 3-4" in length) moistened with a sponge dipped in water until the curve is very, very close to final shape. You can tell when all the water has left the wood because it starts to fight back. Once you get your final curve you can drive off any remaining water and the sides will take a set once cooled.

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Stay with the happy people.
--Reynolds Large

Thanks for the tip, Alexandru!
I'm gonna try foil on me next one!
Alan

On lighter color woods I would always have a soaked rag near me and wipe some water but besides scorch protection (and grain raising) it never felt like it is helping at all.

But with the foil it feels like a very different story. Bending is much faster.

Michael is right about immediate self straightening also, it happened to me yesterday on the second rosewood side were I doubled the foil. I bent the waist then did the LB. Returned to the waist, it was half straight. Heeey I thought I already completed this part?! I bend it again, then do the UB, return to check waist, again straightened. HEY WHOS MESSIN WITH ME. At this point I fixed it and ripped the foil immediately and it staid put.

On my first maple attempt I only used a 6 inches of foil or so to try waist bends and by the time it bent (matter of seconds) the steam was also gone. On the first rosewood side yesterday I only had 1 foil, bottom quickly ripped from abrasion with the pipe so no straightening.

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Build log

Have you tried the style of putting a rag or paper towel on the pipe and spritzing it with water regularly to keep it wet? Helped a lot on some flatsawn spalted maple sides I bent for my last guitar, which really didn't want to bend even when spritzed with water. The paper towel seems to pump more steam into the wood, rather than boiling it off right away.

Another thing I did was press on the contact line with a block of 2x4 to prevent it from cupping, which seemed to be effective. At least from what I can tell, cupping/rippling is a sort of self-reinforcing problem, where as soon as it ripples a little, the peaks are all in contact with the pipe and bend easily, while the dips are away from the pipe and don't bend as much, thus getting deeper. So my theory was to force the whole width to remain in contact with the pipe, so it never gets started on the cycle. It's kind of tricky manipulating the wood block while pushing with your fingertips to make the bend, though.

But then my next bending job was some eucalyptus bindings, and still took forever to get going even with the wet paper towel. It was pretty cold outside that day, though. Hopefully someday I can get my time down to where my back and knees aren't stiff by the time I'm done

Oh, and as for the original question... I trim my sides to a little wider than the tail depth before bending. I don't think it makes much difference in terms of cupping/rippling either way, and you can get free bindings from the offcuts Also, I assemble with dentellones rather than the rim first/solid mould style, so it would be pretty tricky to trim any edge curl from the soundboard side anyway.

Trimming the edge wasn't that hard, I would mark 5mm with a gouge, saw most of it then plane with a block. Still a bit tedious as it can be very easy to break it.

Anyway these last foil sides are my best yet. Virtually no ripples or edge curl, no end cupping, no below-the-wast flat area cupping. Before, the edge curl on rosewood was almost guaranteed.

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Build log

That's about as good as one could wish for.
You can also try the foil method for Bindings. I've found that it works for those as well. I tend to bend a lot of Ebony bindings and without the foil they are prone to becoming more brittle than they already are.
Just to reinforce the advice of wearing gloves. When I first tried the idea of the foil I did not wear gloves. . . ouch!