Making a boat go faster

[Ottomic]

I'm assuming this is an age old question, but for all intents and purposes I'm asking for input on making a specific boat go faster. Allow me to explain:

I've made a multipurpose, monohull tanker with capacity of 5k liters. It runs on a single engine and two propellers at a top speed of 8.5 m/s in calm water.

https://steamcommunity.com/sharedfiles/filedetails/?id=1756935287

This is fine, but then I started working on a faster passenger oriented ship. I made it on a trimaran design, and it runs two engines with one propeller each at a top speed of about 12 m/s in calm water.

https://steamcommunity.com/sharedfiles/filedetails/?id=1756935685

Now, I'm going to assume that there would be some diminishing returns on adding more engines, but on single engine trials it turns out its top speed is about 7.5, lower than a monohull that's usually half deep in water. I imagined the lower drag of the trimaran design would help, but it seems to make matters worse.

Both designs run on naturally aspirated diesels that share one system for cooling and air and one system for exhaust and coolant out. In the case of the trimaran design, both engines share the same fuel line.

Now, faced with this situation, what would you suggest for me to do in order to improve top speed? Any input would be greatly appreciated.

[Teamkiller]

More engines - more speed. Small engine: small rotor ratio should be 1:1 for best perfomance. It is also a good thing to utilase gearboxes to keep engine RPS at about 3-5 for best perfomance.

1 fuel line (and 1 exhast line) for 8 small engines works fine for my larger ship.

Check my compact design with 4 engines (goes up to 120+ km/h (>30 m/s) - it is extremley overpowered and ustable) and automatic gear shift

https://steamcommunity.com/workshop/filedetails/?id=1746311016

[THX-11-38]

For greater speed you have to apply more moving force or to reduce drag forces.
As you've noticed, hull shape affects ship's drag. Try hydrofoil, it works pretty ok in-game.

[Urgedpanda]

try to make the ship lighter no matter what so hydrofoils can work better

[Ra-Ra-Rasputin]

Not sure why this thread was necro'd, but hydrofoils aren't always the answer, and hydrofoils are, at any rate, less boats and more their own specific thing. You can't hydrofoil a tanker, and a hydrofoil can never work as a tug or pull any kind of cargo, plus they absolutely require calm seas. (though, so do speedboats, admittedly)

General concepts of making a fast boat are as follows:

Controlled planing to reduce the surface area in direct contact with water to reduce drag. (not possible in larger and heavier boats, obviously)

The geometry of the hull gliding along the water's surface.
The design of the bottom of the hull.
The positioning of the propellers.
And finally, powertrain.



The first one is relatively self explanatory, so it can be skipped.

The geometry of the hull and the design of the bottom:

You'd be generally speaking correct: A multi-wedged hull is generally speaking a less drag-inducing solution than a monohull, with one specific exception:

A bracket-shape hull [ is specifically designed to force the ship to keep in line and to minimize the effect such as bow-waves, currents and to double up the effectiveness of rudder steering while also having the effect of giving redundancy in case one side becomes damaged. This is a very stable hull design, but it does not reduce drag.

It should also be noted that an old-style deep-dragging keel-stabilized hull, while stable and robust (offering significant protection to the propellor for one) is extremely draggy, as among other things it forces the boat to squeeze down against the water's surface.

So what's the solution? Weight-balanced flat-bottom hull in a larger ship, almost any system in a medium sized ship, and streamlined planing monohull or bi-hull in a speedboat.




The positioning of the propellers:

"At the back, right?" Not always. The section before is relevant, so if you're here, at least skim it.

If you're looking for the ship to plane, i.e. in a speedboat, the power delivery system should be designed so that it is lifting up the bow of your boat or ship to reduce drag against the water.

"So why not at the back?" you might ask, well, let's take that flat-bottom as an example. It's on a heavy boat so it won't be lifting itself off to plane. What will happen instead is that instead of a flat bottom, you're now significantly increasing the drag of the hull bottom by exposing more geometry toward water gliding against it, forcing water to work around the now inclined hull design.

There is still a way to do rear-mounted propellors, generally you balance out the effect by either angling the propellor (i.e. with a fixed alignment rotor) so that it provides strictly forward thrust without trying to force the ship to plane, or by adjusting the alignment of the hull with fins. Both work, and with a tilt sensor it should be relatively easy to set up.

However, keep in mind that this does have a cost. Diverting the power output with angling or fins means that some of the power is lost. There are ways to go about it. You could have a main propellor 1/3rds from the keel of the ship with 2 smaller propellors near the bow balancing out the thrust. This kind of reversed-tricycle design also has the added benefit of allowing power shifting of the fore props to assist in turning.

There's no clear and easy answer for this. Try different designs.




Finally... the powertrain:

All large ships anywhere are diesel-electric. This either means that they have a hybrid drive where there is at least one diesel assist motor riding along the main power drive with larger diesel engines running huge generators to have the main power be supplied at most times.

In Stormworks this is a more complex system to make, as the electric motors have already lost a significant amount of power output by the time the batteries are around 80%, so you have to basically operate like you only have access to a portion of your battery capacity. That just generally speaking means that you have to separate other electricity using systems away from motor-running batteries. This can be easily done in a single power network by using relay switches between separate networks and still have all generation in one place.

So, what's the benefit? Significant number of things, actually. You need to run generators anyway for other systems. Every gearbox reduces the power output of an engine, and engines work most efficiently when they're sitting at a stable RPM value. Stable RPM value is hard to achieve when you have a heavy load to move and need to swap around gears and deal with changing conditions. Electric motors have linear power output and do not need any gearboxes to give out the maximum amount of rotations for any load.

Sure, electric motor systems are heavy, but heavy ships are already massively heavy, so it's not really a problem.



Think that answers the question?