Ok I have drawn on the CAD program a design that will be easy to build and portable. Materials are all at HomeDept or similar store. If you want to see the design (anyone) download Google Sketchup free off the internet
http://sketchup.google.com/" onclick="window.open(this.href);return false;
Then leave me a message on this forum with your Email and I will send you the file.
Ok this is what I would do: Get 2 10' pvp pipes (1 1/2" SCD 40 or if they have it 1 1/2" SCD 80 pipe..the SCD 80 would most likely be in the electrical department) Get another piece of pipe about 4' long. Your goign to cut this into 2 pipes later.
Get rope of a size and type that if you were pulling up your kayak weight plus extra "stuff" weight the rope wouldnt hurt your hands and you could have a good grip on it. Knots in the rope could be made but this might hamper the design.
Get 2 meter keys. These are steel rods with a handle on one end and a 2 pronged "fork" on the other. They are used to open home water meters. Try to find one that has a triangle handle rather than the "T" handle but both will work.
Get strapping of some type. I would try to find military strapping about 1 1/2" wide but any tuff cloth material will work.
Get gromets. You will want to gromet the strapping around the pvp pipe. If you dont want to use gromets you just need to be able to secure the strapping around the pipe (could even tie the strapping if you wanted).
Ok, the idea is really simple. Take your 4' pvp pipe and cut it in half. Drive this pipe into the ground at the sea wall. You may (most likely) need to be a few inches away from the sea wall because of concrete over pour under the ground. This over pour will stop you from driving the pipe deep enough. Drive the pipe below the grass surface until you cannot feel it under your feet. Next cut the 2 meter keys off with a hacksaw. Cut off the 2 pronged fork. Toss away fork.
These keys and pipes in the ground are going to supply the base of your kayak elevator. Attach one rope to each end of the top of the key. Ropes need to be long enough to reach the pier on the other side and also long enough to lower down to the water at the lowest tide.
Kayak elevator will be made of the 2 10' pvp pipes and the strapping. The strapping will loop around one pipe and be secured then loop around the other pipe and be secured. I would think having the strappings 6" appart would be a reasonable distance so you will need 22 strappings of the same length. I would think that you wouldnt want the pvp pipes to get on top of the kayak while lowering the kayak (might snag on something) so mesure the width of your kayak and up about 1/2 way on both sides. Add extra for looping around the pipes and enough to secure them.
Get all of the straps on the pipes and your elevator is about done. Thread your ropes (attached to the keys) through the pipes and out the other side. To make raising and lowering easier I would join the ropes together at a point where if the tide was at its lowest you wouldnt run out of rope to lower the kayak. Then join the 2 ropes at this point and have one rope goign up to the pier. So your only pulling on one rope. From the picture the railing on the pier was above the seawall. So once you raise the elevator your kayak will be sloped toward the seawall, making loading and unloading easy.
Fully loaded your kayak will be under 100lb and from this design you should be able to easily get your kayak up and down.
Not the best with CAD programs and after drawing the design I came up with a way to make the design work better. If on the ends of the 10'pipes you attached a closed pulley and ran the rope through these on each end of the pipes instead of running the rope through the pipe the elevator would be much smoother going up and down.
Cost should be rather low. Pipe and rope should be under $25 and the strapping I dont know but couldnt be too bad. Keys might be a few bucks but I would guess under $20 each. So for less than $100 you would have a portable solution. BTW, if you dont feel comfortable with putting the two 2' pipes in the ground you could just cut the keys of at an angle so they are sharp and just push them into the ground. Problem being make sure you not going into a sprinkler pipe when you do it.