I like the idea of stackers. They are simple, take up less room, and cost less money. Does one stacker given enough ropes OK for three or four sea kayaks? Do they damage glass boats?
My experience with a friend is that they work great for up to four white water boats and work fine on a single wood and a single plastic sea kayaks. It would be great to haul three boats for trips. A Camry/Impala/Taurus Accord sedan can hold the gear for three people is where I am coming from.
Haul 4 kayaks(sea or mixed) on stackers
But you do need long enough bars. Put padding on the straps for the inside boat or put plastic boats inside.
Weight too
– Last Updated: Jul-19-13 1:13 PM EST –
Sea kayaks are usually heavier than white water kayaks. And much longer. These factors can stress your rack a lot more with even 1 or 2 sea kayaks compared to 4 whitewater boats. Especially on a vehicle with under 30" of spread between the bars.
So you definitely need some well-working front and rear tie ropes. And good cushioning for the boats against the bars (not so much against the stackers and between boats).
I sometimes carry one sea kayak sideways on stackers on one side of the rack while the other is on saddles at the other side of the rack. Both feel very secure, but I have 40" spread between the bars and I carry the shorter kayak on the stackers and carry the longer one on the saddles (which are mounted on a 5 foot extension). Front + rear tie downs too.
Weight-wise, 3 sea kayaks can go near 200lb, so check if your rack system can handle that much before even thinking on how to secure them against twisting and bobbing up and down at speed...
stackers
Stackers generally come with 1 set of straps, and often not with bow/stern tie down lines. I would tie each kayak down with a separate set of straps, so would pick up more sets of straps if you are doing more than 1 kayak. I have used 1 bow/stern tie down to hold more than 1 kayak, though.
The factory cross bars are generally not nearly as strong as aftermarket ones (Yakima, Thule, etc.). If you are considering carrying more than 1 touring kayak, consider getting aftermarket cross bars.
You can carry multiple kayaks, but there is limitations. For 1 kayak, you place on one side of stacker. For 2, you place 1 each on each side of stacker. That third (and fourth) boat means you are stacking one kayak against another kayak. People who have expensive composite or wood boats may not like this, as there is a significant chance of scratches.