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I am not sure about anything now i am trying to make a ship float.

Searching over internet i found some ship dimensions but i cant find any mass only displacement which i cannot quite conver to mass i am not sure if i should divide that bu surface area or what or what and or what.

so i found something has 120 tons so i decided to use that as my ship mass ok im using SI.

120 000 is our mass

i just lost contact with earth and i dont know anything:

i assume these as ship dimensions

//model overall size
		float length = 41.85;
		float span = 23.75;
		float height = 27.5;
//hull size for physics
		float hull_length = 23.0175;
		float hull_height = 5.5;
		float hull_span = 9.5;

now i am confused coz the volume of the hull is 1202.664375 m^3

and the mass is 120 000 kg

dens of sea water = 1.0270

then the overall equation if ship hull was fully submerged in water is:

BUOYANCY_FOCE = 9.81 * 1.0270 * 1202.664375

WEIGHT_FORCE = 9.81 * 120000;

anyway in any case weight > buoyancy so how the hell is that supposed to float?

maybe i screwed something maybe the weight is way too big but i am unable to find anything btw those dimensions of ship are a mean of a big brig and frigate dims.

additionally i did a screenshot where i place 8 boxes that simulate the hull they fit the hull size the problem is about way too weak buoyant force

Density of water is 1kg per liter.

A liter is 0.1m*0.1m*0.1m = 0.001m³

You have to multiply the water density by a factor of 1000

well i am not quite sure about my overall physics (if eveyrthing is correct)

but it seems not

(still didint multiple buoyant force by 1000)

first of all the exact values i get

accel = resulting_force_on_ship / ship_mass;
vel = vel + accel * time;
pos = pos + vel * time;

i decided to make a video out of crappy slow emulatori am not sure if i even should post it here since it doesnt show what is happening. basically ship is constantly swinging between air and water, it goes some meters below water then pops several meters above after some time amplitude becomes bigger and it shoots way far up the sky etc. [i could record it with other phone but i am unable to charge its battery ahue )

Well there should be an equilibrium as long as the ship wont sink. Are you correctly calculating the boyancy force based on how much of the ships volume is below sea level?

This is in essence a very elaborate mass-spring oscillator, but if you add some kind of damping or friction between hull and water, it should come to rest at an equilibrium - it should float.

Cheers, Mike

yes i have somewhere an error maybe in the cutting function, because as far as i reckon volume calculation works fine so its either the problem of calculating the base area of tetrahedron that gives NaN or the function that slices set of trangles,

anyway even when i 'disposed' of all nans and i place ship below water line i still get gravity vector bigger than buoyancy

that just doesnt make any sense

Gravity = m * g;

Buoyancy = g * q * V; <-- still i dont get why should i multiple density by 1000 shouldnt i use g/cm^3 denisty

q * V < m

so gravity always wins

120 000 = m

q = 1.027

g = 9.81

anyways:

i did the video with sea water desnity as kg/m^3

like you may see in that vid it starts to bounce and amplitude over time gets larger, i am not sure how can i dumpt that or i dont know what i am doing wrong

Volume below the waterline on hull converted to weight of water THAT volume displaces...

That has to (minimally) offset the total weight of the boat to stay afloat.

Hulls are usally designed that when they tilt, a greater volume becomes 'below the water line' on the side in the direction of the tilt so that the buoyance force on that side increases and works against the tilt (righting the boat). This is designed side to side and front to back. Likewise the rest center of mass is placed below the waterline so that rocking motions are dampened (and increased (ie- ballast at the lowest possible point) if the boat is to be subjected to large external forces as from waves.

Just be glad you aren't doing realistic physics on a submarine (with its variable buoyancy) and control plane surfaces

well forgive me but i dont understand first of all i dont udnerstand what titlt means.

second thing you are talking about

i dont know how to relate that to:

where green boxes are my hull parts

main thing i dont understand is

a greater volume becomes 'below the water line' on the side in the direction of the tilt i m unable to translate that to my language i jsut dont know what ur saying.

every such thing just makes no sense i was tought that if we throw a 1 ton stone from the height of 1000 km and appyl formula Q = mg;

well forgive me but i dont understand first of all i dont udnerstand what titlt means.

still i dont get why should i multiple density by 1000 shouldnt i use g/cm^3 denisty

You are using meters and kilograms everywhere else. So stick to the same units, otherwise you will get wrong results.

The problem is that there is no damping in your formulae. Water is very dense and so it slows down moving objects.

The force that does this is known as drag.

https://en.wikipedia.org/wiki/Drag_(physics)

Drag is denpendent on velocity. A simple formula that calculates the drag force for a moving object is:

F = -v/|v| * (D * v²)

Where D is the drag coefficient (some arbitrary number that you have to find through experimentation) and |v| is the magnitude of the volicity.