Just thinking/typing out loud..............
A couple/few sheets of ply wood and some pieces of round dowel rod or closet hanging rod. Ply might need to be 3/4. If you know of a house being built you might be able to borrow some sheets of sheathing/sub-flooring and use it and return it. Scratches and dings will make little or no difference to the house. Lay two or three sheets on the ground and then on top of the first sheet put the rollers and a sheet of ply on top of the rollers and start rolling. Need to feed the rollers back in front as they pop out the back and the rollers getting cadywupus and jamming can be a problem. Bearings/marbles work well but not in a field of rocks where they are lost as soon as they fall off the plywood and they can sometimes be squirrley and roll sideways to much. Anchor at each end, one to pull toward the water and one to keep it from getting away and rolling too fast/far/wrong direction.
If there is no sand and just cobble and the boat is not too awfully heavy, you might get away with plywood and grease between the sheets. It makes a mess but you don't have the BIG problem of messing with the rollers that need to be constantly fed to the front as they pop out the back and are getting crossed up and jamming.
Planks work but are squirrley and hard to keep lined up.
Perhaps you could go to Walmart /Lowe's/ Home Depot and get a few packs of the disks that people put under furniture to SLIDE it around on the floor and use them on top of the plywood. They could be fed in where the hull touched the ply or maybe attached ?glued? to a pad of plywood that is a sort of hull cradle and is lashed somehow to the hull where if touches the plywood below it. mmmmmmm..???? I like the furniture moving slide pad/cradle idea the best.
Lay the sheets of ply out ot make a runway..... borrowed ply and if the ground is unven two or three layers of 3/4 or 5/8 to make a surface that won't crack or distort under the load ( might take three layers on really rough ground ). Make a cradle that sort of fit's the hull as it will be sitting during the dragging and can be sort of secured to the hull so it will not slide out from under the boat. BEST thing is if you can drag the cradle and not the boat. Just let the boat sit on top of the cradle and go along for the ride. When you drag the boat and the cradle gets to a sticky spot the boat tends to want to slide off the cradle.
Buy a sheet or two of plywood and 2x4 to make the cradle and a few paks of slidey disks and some real sticky goop to glue the disk to the bottom of the cradle (3m-5200 fast set?) and two steel straps from the home center (hurricane straps, etc) to be attached to the crade, one to pull and one to restrain the cradel from sliding to fast/far.
Borrow 6 or 8 or 12 sheets of ply to make a double or triple thickness plywood sliding ramp. A few screws of small nails will hold the sheets in position if they are sliding around to much. Pull the screws/nails as you shift the back sheets from the back to the front while moving the load in the direction of travel. Be sure to stagger the joints of the double/triple thickness of plywood so the cradle won't tend to hang up as it would if the cracks between plywood sheets sagged/shifted when it the cradle gets close to the crack between two sheets. Keeping the runway flat is the key to smooth sliding. A few nail/screw holes and scratches/dings should not bother anyone in some sub flooring.
DRAG THE CRADLE AND NOT THE BOAT IF POSSIBLE!
Post pictures if you do it!
Last edited by sailandoar; 04-17-2006 at 10:42 AM.