Displacement Calculation

There are several formulae you can use, and you really should learn them. You should probably also learn quite a bit more before you think about building a 50 footer, just to keep yourself out of trouble. If you're this lost about basic displacement calculations, you're well and truly lost.

The usual formulae for displacement are Simpson's, Trapezoidal and Tchebycheff's. Look them up.

Simpson's is the most accurate. Trapezoidal is accurate enough for a lot of things. Tchebycheff's is very handy for quick checks if doing things manually, and is often surprisingly close to the other two. You should know all three and understand how to use them. It's not hard. I could do it in my early teens, before calculators were common and before PC's were even invented.

 

Soloman1970, you can also calculate the displacement, using AutoCAD, without even a multiplication with an accuracy greater than with Simpson, trapezes, etc.. As you have AutoCAD, if you want, I can explain how to do that. But, of course, previously you must draw frames and the longitudinal profile of your boat.

 

I think it's reasonable to assume, he's not using software to design this yacht, other wise the displacement question would be answered. We'll just have to wait until he joins the discussion again.

 

The OP has a design, by which it appears to be a set of lines. If he did the scantlings, adding all the weights is tedious but simple. Otherwise, he does not have a design but a concept drawing of something that could be designed and built.

 

In reply to my post # 4, the OP said he had, or was going to do, some plans in AutoCAD. So I offer him the opportunity to perform some calculations with this program. I gather, from his initial question, he has no software for naval architecture calculations and, I guess, do not know much of this discipline. So I offer assistance but we can go as far as he is willing to learn, and be able to. For now, the first steps, draw transversal sections and calculate the volume at various drafts, are relatively simple. It can be done just by knowing AutoCAD commands.

 

I don't see this post. The OP Made 2 contributions to this thread and in neither of them was any mentioning of computer generated plans (unless you've been communicating in some other fashion). Even the most primitive software package, that can handle typical 50' yacht shapes, would provide displacement figures, so (again) it's reasonable to assume he's hand drawing and only has a basic GA, with exceedingly limited hydro understanding, hence the displacement at drawn WL question.

 

Gonzo
All the designers seem to overlook the fact that Solomon already stated the displacement at 21k plus 9k ballast or 30k pounds
As you stated
We know what Solomon wants, the DWL, the depth the boat would sit at to displace the 30k
Translation says to calculate the volumes at various depth of immersion and eventually he would get to the depth at which the volume of water in cubic feet equals 30,000 divided
62.5 prox(salt or freshwater)
But in order to get to a design DWL, Solomon needs to know the CG and the centre of buoyancy to see if the boat would sit level
Solomon
Send your boats info to a qualified naval architect to get these calculations done so you know where the DWL will be/ or should be
Rather than spend thousand of dollars and thousands of hours hoping that you get what you want. OR buy a set of plans whose designer has not only had a successful result but also dealt with the strength issue focal points of the mast and keel