Volume of a Half-Diamond For Hull Volume Displacement

[Free Pirate]

I'm trying to figure out where to put my 1290 lbs of displacement below the waterline. The boat is canoe-shaped (no transom) and V-bottomed. It's about 19.7 cubic feet of mass displacement in salt water (am I correct?).

I don't know the beam to length ratio or the draft, is it a bad idea to find it out by moving around the volume that needs to be displaced until I find something that seems to fit, and designing the freeboard up from that? Or am I on the right track? Or just a weird one?

What formula is there to calculate the volume of a v-bottomed canoe-shaped hull? (It's basically a half-diamond, a diamond being two pyramids resting on each other's bases). I can clarify what I mean with drawings if it's confusing.

I'm avoiding finding it out through Simpson's because I'm trying to get a rough, basic shape without having to measure and redraw, and also because I don't know it well enough to see if I'm doing it wrong.

Should I just use Simpson's or is there a faster way for a volume of a half-diamond?

Sorry for being new and unknowing. Your answers are helping me out a lot. Tell me if I'm asking too many questions.

[Free Pirate]

What I need to know is how to find the volume of an irregular tetrahedron.

If you put two identical irregular tetrahedrons together so that they are shaped kind of like a canoe, it will make the rough shape of the wetted surface. I need to be able to find the volume of one of them so I can find out the possible proportions between the draft, LWL, and BWL.

Is there a better way? It seems to me like 2 identical irregular tetrahedrons should be easier to find the volume of than a complex hull shape.

Please help!

[Raggi_Thor]

I suppose you have some books?
Try to figure out a waterline length, say 16 feet for a simple calculation.
What speed do you intend to cruise at?
If you plan to paddle at 4 knots or slower, go for a Cp ~ 0.5
If you want to go faster than 2x (lwl)^0.5 (faster than 8 knots) go for Cp ~ 0.7
Then you can decide an area for your midship section, or the larges section, normally a few % aft of "midship".
Area x Cp x LWL = Displacement
So if LWL = 16 , Cp = 0.5 and Displacement = 20 your section area is 2.5 square feet. For a simple V shape that could be 5 feet beam (at wl) x 1 feet draft, for example.
I suppose all this is found in any of the popular books.