let's build a ship

[whswhs]

Hmmm. If we assume that Dola's Fortune is a half ellipsoid, with the full ellipsoid having a volume of 9830 cubic feet, then dividing by 4π/3 and by deck height of 9 feet gives us 261 square feet. Assuming a length:beam ratio of 5:1, we get length of 72 feet and beam of 14 feet. Multiplying 72 x 14 x 18 gives 18,144 cubic feet, or 9072 cubic feet for the lower half; that's certainly big enough to enclose 4915 cubic feet. Maybe it's TOO big . . .

[johndallman]

Originally Posted by whswhs

Multiplying 72 x 14 x 18 gives 18,144 cubic feet, or 9072 cubic feet for the lower half; that's certainly big enough to enclose 4915 cubic feet. Maybe it's TOO big . . .

It isn't. You're calculating the "Block coefficient" there, one of several numbers used to measure hull forms. Low-tech ships generally have lower block coefficients than modern ones; yours is about 0.54, which is perfectly reasonable.

[hal]

If instead of going the route you're going, you went for an approximation using a prism for the hull?

If you know the depth of your hull along with its length and breadth, you could cheat by using a prism for the main body whose depth is longer than what you need. Then calculate the volume of the prism whose depth is just the tip of the prism you don't need for your hull (thus, getting a smooth bottom). For instance, if you had a prism that measured 20 feet from the flat surface to its "ridge" line, figure out the volume of that prism. Next, figure out the volume of a prism that was 10' from its apex to its base. Subtract that smaller volume from the larger and you will have the basic hull's volume. To that, add a BEAK that is essentially a pyramid like shape to simulate its bow.

That should mostly describe an early bronze age style trireme or bireme no?

[whswhs]

Originally Posted by hal

If instead of going the route you're going, you went for an approximation using a prism for the hull?

If you know the depth of your hull along with its length and breadth, you could cheat by using a prism for the main body whose depth is longer than what you need. Then calculate the volume of the prism whose depth is just the tip of the prism you don't need for your hull (thus, getting a smooth bottom). For instance, if you had a prism that measured 20 feet from the flat surface to its "ridge" line, figure out the volume of that prism. Next, figure out the volume of a prism that was 10' from its apex to its base. Subtract that smaller volume from the larger and you will have the basic hull's volume. To that, add a BEAK that is essentially a pyramid like shape to simulate its bow.

That should mostly describe an early bronze age style trireme or bireme no?

It's possible that it would. But I can't visualize the shape you have in mind from your description. Is it a stretched four-sided pyramid, or half of a pyramid (pointed at the front, flat at the back), or something else?