Careening your Day Sailer is a relatively easy one person operation that allows you to work on the boat's bottom, remove the centerboard, or work inside the centerboard trunk. I have a 1986 Precision made DS I with a deck stepped mast. I have seen no undue stress on the mast, the mast step or any other fittings while careening my boat, and think that it might work for most small boats.
Careening does create a hazardous situation since the boat is up on edge and could come crashing down without warning if something fails. If you choose to use this method, please be careful.
I have done this enough that I'm comfortably cautious when my boat is careened. This is the method that works for me:
First I remove my boat from the trailer by driving a pry bar into the ground about 10' behind the boat in a grassy area of the back yard. I run a rope around the pry bar and fasten it to the stern cleats. Remove all straps, and other ties holding the boat on the trailer. Then drive forward very slowly. The rope holds the stern stationary while the trailer slides out from under the boat. A tilt trailer helps ease the boat onto the ground.
Once the boat is resting on the ground, raise the mast and attach the forestay and the shrouds. You'll use a rope hoisted to the hounds (where the shrouds attach to the mast) to gain leverage from the mast to tip the boat on it's side. My rope is about 50' long. Tie a large loop around the mast above the spreaders using a bowline. The loop will slide up the mast increasing the lever arm length. Attach the main halyard shackle to the loop, hoist the loop up to the hounds , and cleat off the halyard. Be sure the loop is at the hounds since the shrouds support the load on the mast. Pull the pry bar out of the ground and move it perpendicular to the boat about 30' - 40' away. The pry bar will be the place where I tie off the rope when I have the boat careened on it's side. Pound it back into the ground - be sure it is very secure and that the top leans slightly away from the boat. This will help prevent the rope from slipping up the bar. A convenient fence post, tree or other solid object would also work as a ground anchor to tie off the rope. Just be sure that your rope, your knot and your ground anchor are secure - your health and your boat will depend on it.
Pull the rope perpendicular to the boat toward the ground anchor and the boat will start to roll up on it's side. When you get it raised into the position that you want, tie the rope off to the pry bar/ground anchor. Be sure to not pull the boat all the way over. It really doesn't take much strength to tip the boat on it's side due to the large amount of leverage gained by using the mast. The boat may tend to pivot a little as it starts to come up on it's side, and you could tie off the stern to something if it becomes a problem. When I finish working on one side of the hull, I lower the boat, spin it 180 degrees, then tip it up to expose the other side.
It might be prudent to rig a couple safety lines (if possible) to insure that the boat doesn't come crashing down. I always lower mine when I'm done working on it and keep kids, pets and everyone else away when it's careened.
This is an easy way to tip your boat on it's side to work on the hull, remove the centerboard, or clean exotic species out of your centerboard trunk before trailering to the next site. I've even seen a picture of a 17 -20' boat careened at the water's edge for hull work.
Just be careful and stay safe.
Lee