I've owned a number of kayak transport carts in the past. I had a folding kind with large inflatable wheels placed close to the center of the boat which was great for travelling over a long distance - most of the boat's weight is placed on the cart so it's nearly effortless to pull. But over rough terrain or when going over sidewalk curbs, these foldable carts are prone to collapsing - bam, you come to a grinding halt. I've tried straps, rope, placement on either side of the cockpit to minimize the collapsing - at some point the cart will collapse no matter what you do (if someone has a magic solution I'm all ears). Similar carts that are non-folding made of a one-piece metal frame won't collapse but are bulky and some cost over $100. I had a very small stern-mounted cart that came with only one cross strap. I was able to hook the strap under my deck lines to minimize the risk of it slipping around but it wasn't bomb-proof. It was so small I could fit it in my day hatch, but it wasn't big enough to go over rocky terrain. At one point I even resorted to using a modified boogie-board that I carved into a narrow "sled", which worked great, was incredibly light weight, and could be stored in the boat - until it disintegrated from being dragged across the rocks/pavement too many times.
This cart - the Quantum Engineering Stern Wheels Cart - is available from REI (haven't seen it for sale elsewhere). It is a stern or bow mounted cart, so the boat is a heavier carry than with some carts. But the key (KEY!) is that it has two straps and a hook that grabs the cockpit coaming. It WILL NOT slip off while you're pulling the boat no matter what terrain you traverse and no matter what direction (pushing or pulling the boat) you're moving. FINALLY, a cart that stays on no matter what. It also has quick-release buckles on both straps so it is installed and removed quickly. AND (ta da), the entire cart fits in a 10" Romany hatch if you squeeze it a bit. No folding or dismantling.
There are definitely things to improve on this cart. It's shape is one, the rounded base appears made for the central keel of plastic, recreational sit-on-top kayaks - it doesn't fit well on the hull of a typical sea kayak. Plus the cart should only cost $40 or so, but costs $80 - way more than it should. The wheels are on a narrow axle and are small/hard so it doesn't roll efficiently - you're dragging the boat more than rolling it easily. So long transports would be tough. But it works for shorter distances and won't come off!
Pros:
- Won't Slip Off!
- Easy to install and remove - quick release buckles- No need to inflate tires (hard rubber).
- Fits in 10" hatch
- Few bits to rust - mostly plastic
Cons:
- pulling boat is more effort than center-mounted carts
- round shape of base does not fit sea kayak hulls nicely
- expensive for what you get
- wheels are small, narrow, and hard
- wheels are small, narrow, and hard
Extra Thought: These days, when paddling in a group I try to offer and ask for a hand to move boats from the cars to the launch. After years of huffing it myself, some back issues made double-carries a wise plan and this was drilled home to me when I worked for Atlantic Kayak Tours. We staffed many trips and hauled many boats so it was essential really to have two-people-per boat. No shame in asking for a hand. Also, I've never owned a carbon/kevlar boat and have tended to own heavy-layup British boats that seem to be a few pounds heavier then their American counterparts. For solo paddling, I decided at some point that I'd had enough wear-and-tear on my body - so moved to using carts as often as I can.