Submitted: 08-01-2008 by kozmikarl
I can't comment on J carriers because I don't use them, but perhaps I should. The design weakness with Thule is the square bars, which only becomes a problem on curved roofs, but as the roof curves so must cradles cant away from each other, reducing contact between boat hull and cradle to inside edges. The cradle faces are absurdly small to start with; this rotational deviation from level makes it even smaller. Couple that with Thule's comically inadequate détente angle fixing clamp (for holding the saddle in the shape of your boat hull) and for support you are probably better off using foam blocks. So J carriers may work better on a curved roof, if I can lift that high. I've seen some people use them for composite boats so it might be OK.
Don't get me wrong. I use Thule racks and locks and cradles and locking cable and straps… the whole kit. That's because security and convenience and bicycles and protecting the roof of my car are also important, and because I started with a used Thule rack, gradually accumulating a closet full of proprietary extrapolations and substitutions as needs changed. And it does work. It all works. It's just that every single bit of it is clumsily engineered and imprecisely manufactured, requiring brute force as well as wiggling and finagling to get it just right. Some parts fit loosely, some tightly, some are robust and some flimsy. Every change, every adjustment to a Thule rack is a project and a series of compromises. Admittedly, I change things around a lot, but as familiar as I've become with my rack, I still spend an inordinate amount of time getting all the parts straight and tight and solid before I reach for my boats.
If I had it to do over I would definitely get Yakima, which has different problems but at least it acts like the parts were all designed by the same team, and round bars are simply stronger.
Please, whatever you use, tie down the bow and stern. It doesn't matter how many times you haven't and nothing bad happened. It doesn't matter how little it shifts in the wind. It doesn't matter that you're 15 minutes from home and only driving on pavement. The point is that if a strap breaks you could easily kill someone in a following car. I read somewhere that no boat is ready to drive away until it has 6 lines on it: two each across the midsection, triangulated from the bow and triangulated from the stern. Take it to heart.
Also, poke holes in dead tennis balls and jam them on the ends of your bars. It will keep your passengers from clonking themselves, not just because they are softer and rounder than factory caps, they are bright. It's easy to lose track of exactly where black-on-black bar ends are in space, even when you're looking for them; it's hard to overlook glowing lime-green spheres. You'll have to replace them each year as they fade; remove the factory caps beforehand so you won't pull them off inside the tennis balls.