I know this question was probably asked a 1000 times before but...

[Sailing4Life]

... I intend to ask anyway

Hey all, I've recently begun to design a jacht, This vessel's overall length is 9 meters.... I've made some drawings in AutoCAD and made some calculations as well... However I'm stuck... I don't know how to figure out where the main waterline's gonna be. I bielieve that I need to know the Yacht's mass for my calculations.

So - the question is : How can I calculate the hull's mass ?
I already have all the hull's dimension-data, and area data (square meters) plus the hull's <hmmmm don't know that word in english but the unit is m^3>

heheh

P.S. Please forgive me for my english, it's not my first language and I'm fully aware of it.

[fede]

If i'm not wrong you should start from some datas that you should keep in mind when you start a yacht design,displacement is one of these things,give a look on some brochures of boats that might be similar to the one you are trying to design for dimensions,kind of hull and performance and see what's the displacement (light and not)... then it's up to you to decide what your boat displacement should be, than you will have to calculate how much volume you need underwater to keep your X tons boat floating ex,if you decide your boat should have 6 tons displ. the volume under salt water should be 5.85 (6/1.025 where 1.025 is the specific weight of salt water) than you might decide you want a different shape underwater (wider and less immersion) that gives you the same volume, so you start all over again,only to find out at the end that the yacht that was supposeed to weight 6 tons actually weight 7 and the w.l. is 20 cm underwater because too much material was used here and there....but I'm just a novice...someone with more experience might give you a better picture!
English is not my first lenguage as well...so pardon me too.

[Tim B]

fede,

You're dead right, it is worth noting that in fresh water, 1 ton takes 1 cubic meter displacement (handy rule of thumb)

In general,

If you can obtain a surface area (total surface area of hull and deck) then it is possible to make an estimate of weight if you know which structure you are likely to use. that is to say, you can calculate the "shell weight" (ie. hull with deck and no more). One can usually estimate the weight of the keel and rig, and then assign a maximum weight for the interior, and add a factor for the mechanics, rope, etc. This will give you a rough idea of displacement. Otherwise, you will have to take an estimate from existing boats. More critical perhaps than the displacement, is the Centre of Gravity (downwards force) and the Centre of Bouyancy (upwards force) the C of G acts at the centre of volume of the structure, and the C of B acts at the centre of immersed volume. Don't get these two mixed up.

Best of Luck

Tim B.

www.marinedesign.tk

[Tim B]

nb, it may be worth building a small section of the hull structure and weighing it. This is quite a job, though, and you should be sure of the structure to use first.

[ars-technica]

Originally Posted by Sailing4Life

... I intend to ask anyway

Hey all, I've recently begun to design a jacht, This vessel's overall length is 9 meters.... I've made some drawings in AutoCAD and made some calculations as well... However I'm stuck... I don't know how to figure out where the main waterline's gonna be. I bielieve that I need to know the Yacht's mass for my calculations.

So - the question is : How can I calculate the hull's mass ?
I already have all the hull's dimension-data, and area data (square meters) plus the hull's <hmmmm don't know that word in english but the unit is m^3>

heheh

P.S. Please forgive me for my english, it's not my first language and I'm fully aware of it.

to determine the the hull weight you had to consider laminate thickness and structure thckness, if you don't have this data the best way to have a stime of weight is to view approximate it to hull of similar dimension already constructed

[gonzo]

Hull and deck weight are the easy parts. All the interior, hardware, machinery, anchor and chain, water, fuel, etc. take much more time. The waterline will change depending on where the center of gravity is too. That means that you need to calculate that also. It is not really difficult, but tedious.

[PAR]

Ahhh . . . center of masses . . . you're going to love it . . .

[Thunderhead19]

Well, one thing I learned right at the beginning, was that yacht design is an iterative process. I feel that you have to design a hull with the waterline in mind, do your displacement calculation and curve of areas, do a preliminary design, do a preliminary weights estimate based on all the data you can lay your hands on with respect to structure, machinery, nuts bolts paint, electrical etc... do a your weight distribution curve and calculate total mass and moments. Then go right back to the beginning and modify your hull to deal with the weights so that your waterline is again where it should be......Do this over and over again for as many cycles as it takes to have everything agree. Then you're on your way to developing your construction and machinery intallation drawings. At some point, you'll probably make the discovery that something has to be moved again, and you'll be right back at square one. Have fun!!!! ha ha ha ha ha!

[djwkd]

Originally Posted by Sailing4Life

<hmmmm don't know that word in english but the unit is m^3>

heheh

Metres cubed i think you mean.

[RANCHI OTTO]

For deck and hull weight try with this...
Foe detailed weight list have a look an the spreadsheet...