bill a wrote:
there's 231 cubic inches per gallon of water and a gallon of water
weighs 8.35 pounds
As someone else suggested, I would use two lengths of the lighter weight
PVC (used
for yard drainage and a similar product with holes is used for
foundation drainage).
They are only about $5 for 10' and the common pvc cements in the
plumbing department
make a reliable seal. Each 10' length would lift about 53 pounds.
If you want to get really high tech, rig up a valve system to flood the
tubes (to launch the
kayak) and a simple air pump to force the water out and lift the kayak
out of the water.
A commercial version of this is called a hydrahoist.
bill

If my hubby heard this suggestion, he would require $200 worth of
electronics to operate the valves ) I'm thinking about bevening one
end of the "rails" so the kayak slides on and a couple of rope handles
to push off. Looks good on paper )