RE: Stuck mast
No, I haven't really elaborated on the "water pressure mast separator" here on this forum. I did describe it on rec.Windsurfing, and the prototype was shown in an article on the Frisco Woods Windfest back in April.
What it is is a piece of reinforced rubber or plastic hose that fits the tip of the top section of your mast. Attach it to the top of the mast with a couple of good screw type hose clamps.
Before you attach the hose to the end of the mast, remove the plug from the top of the mast. This usually takes a pair of "Vice Grips" to grab the rubber or plastic plug and carefully (so you can use it again) twisting it out of the end of the mast.
Then get an ABS Plastic pipe reducer bushing that the hose also fits on the OD of the bushing. I use a couple of different bushings and hoses, for different size masts, but the bushings all reduce to 1/2 " NPT Tapered pipe threads.
Then get a garden hose adapter that screws into 1/2 " NPT threads.
Attach the hose and clamp it tightly to the tip of the mast (good to go down about 6"-12" below the tip if possible).
Then stick the other end over the plastic pipe bushing and clamp it securely.
Attach your garden hose to the end and turn on the water slowly.
In some cases the water pressue will simply push the stuck mast pieces apart.
If not, you can use the same method you used without the water pressure (i.e. flexing the mast at the joint) and the water pressure will wash out any particles of sand much more quickly.
Get the tubing and give it a try.