Last winter when it came time to flip the boat for bottom work it was the middle of winter in Finland and there was no realistic way to open the doors, carry the boat outside and flip it. Too much snow, too cold. As my workspace is fairly small, although higher, it took a lot of thinking on how I could flip the boat safely.
So here is what I did. I had my wife to help, but she ended up more a spectator, no real need but definitely good to have a spotter.
You need to tie the boat to its original building cradle with a strap. Then all you need to do is to lift from the siderail until the cradle/boat ends up in its 45 degree position.
The setup is now completely stable and you can move it sideways to give you more space.
The next step is to lift the boat up to its 90 degree position. This again requires surprisingly little strength, all you need is an average office worker. And once more the boat is perfectly stable at 90 degrees standing on its building cradle side without the side rail touching the floor.
Again, you can easily move the boat, or "walk" it sideways to allow it to flip in a smaller space. I had reserved the engine hoist to help (in picture) but not needed at all.
Next you need to add something to the floor not to scratch the boat. Tires, maybe. I used PU insulation boards, just 2 inches seemed enough. And then you just turn the boat upside down. Again, not need for a strongman.
While getting you friends together, having pizza and beer is definitely more fun, this is a way to flip the boat if you are in a hurry.
The pictures are from flipping the boat right side up. I took more pictures then.
Happy building!
Pasi