For a larger portable bench, there is no doubt in my mind that the Moravian workbench is the way to go. My failed attempt of last year helped me to better appreciate what a truly great design it is. Watch this brief video of Will Myers assembling it in 60 seconds. Very stable too. Amazing. Not something I could make in a day, though, and somewhat larger than I had in mind.
I had just one day to build something compact that could be clamped to a picnic table. This isn't as farfetched as it may sound; you may remember Chris Schwarz's "milkman's workbench" from a few years ago, although it isn't tall enough and I didn't want any vises on mine. Most picnic tables are 30" high, I like to work at 36", so I had in mind something about 6" tall and around 16"x36". Standing at my Nicholson workbench thinking about this, it struck me that a scaled-down version of it without legs would fill the bill nicely. I had some dry 2x6s on hand, so that's what I made. As you can see, it fastens to the picnic table with c-clamps, although there a variety of ways to clamp it down:
With the clock ticking, I wondered what to do about a vise. I knew that I wanted a Moxon to sit on top, just as I use at home, but I wanted a considerably smaller version. I had an old one that used F-clamps sitting on the shelf, so the first thing I did was cut it down to 16". I didn't want to use F-clamps, but looking around the shop I had a brainstorm (possibly because I had seen it somewhere before but I can't remember). I picked up a wooden handscrew, sawed the screws in half in the middle where the threads change direction, then cut the jaw on either side of the barrel nuts. These became the twin screws for my vise:
Using the barrel nuts allows the jaws to skew and it was very fast to construct:
It works much better than I expected, though it does only accommodate workpieces up to 6/4 and it is 12" between the screws, but that's enough for a portable vise in my opinion. Of course it can be used directly on the picnic table if I choose but I generally like to use it on top of the bench so I can stand straight when I saw.
I didn't have a lot of time left and I still had to figure out what to do about tool storage, so I salvaged the "drawer" from the previous version of the portable workbench and used some scrap pieces of plywood from the trailer project to make a case for it:
The three pieces stow away for travel in a compact space. All in all, it works quite well and I'm not sure I could have done a lot better in one day.