Boat rocks back and forth like a see-saw?

[Winter Dragon]

ie. The front lowers 3-4 blocks below the water line while the back lifts 3-4 block above, then vice-veras.

Does anyone know what causes this and how to fix it? Is it a center of gravity issue? I've been at this for 2 days adding weight <here>, removing it <there> ... no matter where I put the extra mass the ship refuses to stop oscillating up and down at opposite ends.

[Chrozayis]

you could try jet stabilisers

[Discohydra]

If you increase the surface area that your boat takes on the curface of the water (read: from a bird's eye view, increase the amount of boat you see by adding to it), you'll increase the angular drag across the z plane, which will stabilize your boat.

[Winter Dragon]

After a few more days at this I have noticed the following:

The rocking motion seems to be perpetual based, like no amount of external forces applied to it can stop it. I tried hundreds of jet stabilizers and they had zero effect, changing the surface area didn't work, and no amount of weight added anywhere reduced the rocking or leveled the boat out which one would expect ballast to do.

The rocking apears to be influenced by two things:

1. Length of the boat. (The longer the boat is, the more it rocks up and down.)
2. Block count. (There is a minimum block count required in order to reduce or stop the rocking, and this is based on the length.)

The second factor is linked to the first, meaning a shorter boat needs a lesser minimum block count to stabilize than a longer one.

ie. One of my boats is 92 blocks long and needs a minimum block count of 5,020 to stabilize.
ie. Another of my boats is 262 blocks long and has a block count of 12,758. It rocks very slightly up and down (about 0.25 blocks above or below the water line each end) but above 13,500 block count it doesn't rock at all.

This is not ideal because higher block counts affect performance, but it's the only way I've found to fix the issue. That, or just don't build any boats more than 30 blocks long.

[Chrozayis]

does your boat have an engine? it needs one to use jet stabiliers

[khaz]

Use something other than an all light weight alloy (all alloy builds float like balsa wood). Using either mixed wood/metal/alloy, wood/metal or all metal with airpumps will improve stability. Lead blocks can also help, but the main one is use alloy for planes, not boats :)