My ship keeps drifting

[DJ OtterPop]

I've more or less given up on designing my own air planes (might explore airships at some point though) and started building another greek styled ship. This one is pretty massive, it looks good and has decent (but unfinished) offensive capabilities.
Anywho, the issue I'm having with it is that it doesn't like moving straight forwards. Instead, it drifts to it's destination, usually with one side lifting out of the water a little and the other submerging itself, rendering the lower level of cannons unusable. It's dimensions are:
Length - 171
width - 91
height - 49 (dunno if these are important)
It has 20 large propellers on the rear, several jet stabilizers and a bunch of sideways facing small propellers. It's waterline is only the fourth-fifth block from the bottom.
Anyways, anyone know what I can do to fix this?

[rditto48801]

That's kind of tall if little of it is in the water, even if it is wide.
Is the Center of Mass (CoM) at or just below the waterline?
The closer it is to the water line, the more unstable a ship will be. It will be very unstable or otherwise capsize easily if it is at the waterline, and will simply capsize easily (or always capsize) if above the waterline.
You want the CoM as far below the waterline as possible.

You also want to keep your propulsion as close to the same level as the CoM as possible, or otherwise as balanced above/below the CoM as possible if the CoM is 'between' levels/blocks. Otherwise props could cause a ship to nose up or nose down when throttled up, or cause bow/stern thrusters to flip the ship during turns.

[DJ OtterPop]

That did help a lot with the drifting (though because it's bottom takes up the entire width of the ship it never suffered from the possibility of a flip). Unfortunately because of the ship's size, the only way I could bring the CoM down was by building a freaking massive stick hanging off the bottom of the ship, dead center. This creates a new problem where it can't go into shallow water.
Is there any way I can bring the CoM down further without making the stick longer/covering the entire underside of the ship in lead?

[Lulloser]

does it have repair tentacles inside the ship? ^^

Is it made out of Metal? If so, you could try to replace the top part of the ship to Alloy, it's way lighter but not that strong.

[DJ OtterPop]

There are a few tentacles inside the ship, yes. That doesn't matter though, because ships can only repair themselves with the bots, which it also has.
And it's made out of allow and wood, with metal covering important parts and making up the bottom layer of the ship

[Lulloser]

Well, remove the tentacles or replace them with the compact ones. The tentacles, if they don't have enough space, bug out the whole ship. Maybe not the problem, but just to be sure.

[DJ OtterPop]

They are compact ones. It was drifting before I added those anyways.

[whitefoux]

Well if you are not worrying about resources to much, try and replace a good bit of your hull with metal, this way it will cause your ship to want to sit lower due to it's weight.

Other wise what you can do is put a ballast beneath your ship at its CoM, Kind of like your stick, but make maybe 3 blocks wide x (x) long(your choice just change it up to lower CoM) by (x) deep. And make it out of metal, this way it is cheaper than coating your entire hull, while sinking your ship. However I must say 20 Large props is way overkill for this size of a ship, which is probably your largest issue, I had one roughly this size and 4 did it for me, 3 in the back and on in the front, and It maxed at about 10-12(km? been a while forgot speed measurments) If you are looking for a faster ship then you need to spend some time in creative mode(forgot its title). You just need to be aware of your CoM + the location of your props compared to the Com + the amount of thrust from each prop.

If you would like other people to take a crack at it, up load the Blueprint (or add it to the workshop) and some people may tweak it for you. Give you a better idea of how things work.

[rditto48801]

If your interior is properly broke down into multiple compartments, perhaps a few compartments should be left without air pumps, or with air pumps set to reduced capacity, to help reduce overall bouyancy a little and help lower the ship into the water a little bit, without adding extra mass.

[DJ OtterPop]

Bouyancy isn't the issue. It sits exactly where I want it to (a little too low in the back due to the heavy artillery emplacement). It's CoM is a little bit too high though :/

Anyways, here it is: the Scylla http://steamcommunity.com/sharedfiles/filedetails/?id=586506780

[Lulloser]

Okey I identified the problem, your Thrust below the ship and the rudders below the Center of Mass are causing this problem. Side Thruster and the Rudders should be on the same level as the center of mass or else the ship turns with an angle, the combination with your side thrusters right below your center of mass causes the ship to drift.

I can't think of a solution without remodeling most of the ship though.