It's actually quite easy, now that I've thought about it. If you don't have a pattern in front of you and you want to crochet a single crochet ripple, then simply figure out how many stitches you want on each side of the peak, add one for the peak and two for the skipped chains at the bottom. This is your multiple. Then crochet this multiple until you have as many peaks as desired, then add three more. This formula will work for any size sc ripple, no matter how many sts you want in each peak.
For instance. Say you want 7 sc along each side. Okay, that's 14. Now you will add 3 more (one for your peak and the two you will skip at the bottom). So that's 14 + 3 = 17. 17 will be your multiple. Now say you want 10 peaks for a wrap. Your starting chain will be 17 x 10 = 170. Now you'll want to add 3 more, bringing your total to 173. So your pattern will read multiple of 17 + 3, meaning you will chain your multiple (17) as many times as you need, then add three more chains at the end.
To crochet this, you will sc in 2nd ch from hook, sk next ch, *sc in next 7 chs, 3 sc in next ch, sc in next 7 chs, sk 2 chs. Repeat from * across to the last 2 chs, sk 1 ch, sc in last ch.
Row 2 and all other rows: Ch 1, turn. Working in the BLO, sc in first sc, sk next sc, *sc in next 7 sc, 3 sc in next sc, sc in next 7 sc, sk 2 sc. Repeat from * across to the last 2 sc, sk next sc, sc in last sc.
That's all there is to it. Use a little math and pre-planning and you can make anything from a scarf to a wrap to an afghan.
Here's some starting multiples for you:
4 sc on sides: Multiple 11 + 3
5 sc on sides: Multiple 13 + 3
6 sc on sides: Multiple 15 + 3
7 sc on sides: Multiple 17 + 3
8 sc on sides: Multiple 19 + 3
9 sc on sides: Multiple 21 + 3
10 sc on sides: Multiple 23 + 3
See the pattern?