hello!

I’ll get straight into my question. Basically I have a ship hull (closed brep) that i have to calculate some stability stuff for (specifics not too important). To do this i have the ship hull itself and a cutting plane. The ship’s hull is rotated, and then the cutting plane cuts the hull shape, so that i only calculate the volume under the waterline.

The problem comes from the fact that the volume has to stay constant regardless of the rotation of the ship. I already have found a way to move the cutting plane (waterline) up and down. I however don’t have a way to find the correct height so that the underwater volume stays the same as in the upright situation.

I was trying to look for a solver that will solve for a certain input value to obtain the correct volume, but i haven’t found anything. I have also tried to make some scripts with grasshopper python with no success.

Hopefully someone has a way of solving this. Any help is greatly appreciated!

The ‘**Z-offset Solver**’ in my hydro model does exactly that using a pair of Anemone loops *(nested)* to move the hull(s) up and down to find the target volume *(displacement)*. But it takes some time and effort, it’s not “real time” feedback as you adjust pitch and roll.

http://www.islandcad.com/grasshopper/hydrostatics/

The GH code is very old now and probably needs a revisit but it’s rather complicated. It handles multihulls and the “leeward pod” shown above that touches water only when the boat is heeled - like the “safety ama” on Hawaiian sailing canoes.

The ‘**Domain Search Solver**’ is a subset of the ‘**Z-offset Solver**’ and can be adapted to solve similar goal seeking issues unrelated to volume. It systematically adjusts one value until the ‘Feedback’ value is as close to zero as possible.

**P.S.** With some additional GH and GIMP/Javascript I used that ‘**Z-offset Solver**’ to create this interactive visualization of how COB moves fore and aft as pitch goes from 4 to -4 degrees:

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Thank you! This is just the thing i am lookin for. Its getting quite late so ill take a look in the morning, but thanks for your fast reply.