Check out this trailer

Take a look at this.......

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_7769_7769

This version has 12-inch wheels.
Don't buy the version with 8-inch wheels.

The pictured trailer is entirely bolt-together.
The "tongue" of the trailer is too short for our (kayakers) uses.

For about $30 you can get a 2-1/2 x 2-1/2 square aluminum extrusion, which is an exact-size replacement for what you need, and you can cut it from the supplied (about 25-feet) length to get what you need (so the noses of boats clear the rear of the car as it makes a tight turn).   This aluminum extrusion, you can get most cheaply at Alcon Metals....Doolittle Drive....San Leandro.

This trailer is very light, about 160 pounds...and this is VERY important.
For example, there's a fishing ramp I go to often out near Locke at a State Park called "Delta Meadows Park."     This ramp is gravel, is very steep, and it is absolutely all my two-wheel-drive (Toyota Corolla) vehicle can do (traction-wise) to pull my little trailer up that ramp.    !!!!!!     Yes...exclamation points...!!!....

And another argument for a LIGHT trailer.   I was once backing down a road that was steep and gravel and so narrow that when I let my trailer get out of line I couldn't make the "correction" without bringing my front wheels off the road-sholder.    So with the light trailer I was able to just walk around to the rear, pick the thing (mostly) bodily up....and carry/bounce/shuffle the wheels back into allignment.

I bought a "Contracters Lock Box" and put it on the trailer.......it's been a wonderful improvement, in that it gives me a weathertight lockable storage space for my stuff.

Judd

Nice trailer, Judd. I completely agree that light is the way to go.
How do you secure the kayak on that trailer?

Gandoderma........I put my boat on it's chyme, roped against the side of the contracters lock-box.   I put my wife's Ocean Kayak on top of the box.   Note that I've put Eye-Bolts at all four corners of the Lock Box lid.    My wife's kayak secures to those eye-bolts.....meaning that with her boat in place and tied down, I can still unlock the box and lift the lid (with her boat still on the lid) and get access to the contents of the box.

You can see the wooden strips that I bolted to the lock-box as standoffs between the box and the boat.    Previously the boats were chafing through to the paint, creating bare spots where rust would take over.

Judd