Confession: I'm not good at Navajo 3-plying, and the notion of having to spin 1/3 more single for the same yardage goes against my lazy-grain. But Navajo 3-plying (or chain plying, as it is also called) is the best way to preserve color changes in yarns. It's good for regular variegated rovings when you want to avoid tweedifying your yarn. And it's perfect for the self-patterning rovings that are sold by Twisted Fiberarts. I've been spinning roving from Twisted, so Navajo 3-plying was my first, though reluctant, choice.
Here's the first skein of the Ravelry Colorway- it's Twisted's Cloudy blend( 60% Superwash Merino, 40% Bamboo)- the colors are green, black and pink. It should knit up as sections of green separated by pink areas bordered on both ends with black, all of the colors slightly heathered from the bamboo blend. The yarn is wonderfully soft, with a lovely satin sheen (from the bamboo), and the singles spun up beautifully even. The Bamboo keeps the merino from being as bouncy as it would be normally (or maybe that's the superwash), so the yarn is much more sleek than I expected. It's a little heavier than fingering but not quite sport weight. I'll have to experiment for needle-size (either the larger 2's- 3.0mm, or 3's). This skein is 1.7 ozs and 123 yds (look at that- I wasn't even trying for 100YPO, and I nearly got it with a 3-ply). I have 4 ozs of this roving, and I can knit a pair of socks for myself with 250 yds of fingering weight yarn, so I should have enough for a pair of socks, with some left over.
The close-up pic shows the colors best. It also shows all of my plying bloopers- my joins are wretched, and there are over-plied areas (and under-plied as well). But I'll learn as I go, and bythe last skein of this roving, my 3-plying might be barely adequate (I hope so because I have another Twisted roving on hand, 2 more on the way, and I intend to order even more).
For a Navajo 3-plying tutorial with a wonderful video, go here: http://www.yarnwench.com/php/Navajo3PlyTutorial.php