# Determining yacht particulars

Discussion in 'Boat Design' started by Laranjo123, Aug 12, 2011.

1. ### Laranjo123Previous Member

I would like to ask. Are there any formula in determining the length,breadth, depth of a motor yacht. or you any ratio values?..

2. Joined: Nov 2003
Posts: 19,133
Likes: 494, Points: 93, Legacy Rep: 3967
Location: Eustis, FL

### PARYacht Designer/Builder

3. Joined: Aug 2011
Posts: 2
Likes: 1, Points: 0, Legacy Rep: 15
Location: United Stated

### braumabNew Member

That's a tough question to limit down ...

I did a little bit of research for you to make sure my answer wasn't wasting your time. I found that http://en.wikipedia.org/wiki/List_of_motor_yachts_by_length will give your lengths for just about any size you could probably want.

That's an interesting site I found. Anyway, for power vessels, the formula is length x breadth x depth over 100 x .67

...And for sailing vessels it is: length x breadth x depth over 100 x .50

1 person likes this.
4. Joined: Dec 2001
Posts: 2,474
Likes: 117, Points: 63, Legacy Rep: 1728
Location: Oriental, NC

### tom28571Senior Member

That sounds like it might be a broad sweep at the prismatic coefficient. Not sure what it would be good for though.

1 person likes this.
5. ### Laranjo123Previous Member

Gee thx though

Question guys? Are you all naval architects?

6. Joined: Oct 2008
Posts: 1,913
Likes: 73, Points: 48, Legacy Rep: 739
Location: New Orleans

### StumbleSenior Member

What you asked were what the formulas are to tell you how long a boat should be. Reality doesn't work like that.

You tell the designer what you want, and a price point and he determines the length based upon experience, comparable vessels, price, and a whole host of other criteria to determin what boat would work out well for you.

7. Joined: Nov 2003
Posts: 19,133
Likes: 494, Points: 93, Legacy Rep: 3967
Location: Eustis, FL

### PARYacht Designer/Builder

Sorry to be so flip Laranjo, but your question is so broad in scope, it's a bit like asking to know what the formulas are used to design a red car.

8. ### Laranjo123Previous Member

actually your right mr. par merchants ships have their own ratios. Unlike this yachts.\ In my own thinking i knew that this yachts doesn't have any ratios i mean it depends on how will be the owner wants his/her yacht to be like this like that. you are all right. This means my last bet is to get the info specs of the existing vessels and make a ratios out of them... ( correct me if i'm wrong?..)..

9. Joined: Mar 2009
Posts: 1,426
Likes: 66, Points: 58, Legacy Rep: 680
Location: europe

\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
these are the ratios

10. Joined: Oct 2008
Posts: 1,913
Likes: 73, Points: 48, Legacy Rep: 739
Location: New Orleans

### StumbleSenior Member

I am not sure what ratios you are thinking of, or what they might tell you. Private boats run anywhere from 12 to 900 foot. Obviously there are more of the former than the latter and the richest people tend to have the biggest boats.

Within size ranges there are relationships between length and width, or depth, but only generally since a lot is driven by the specific design and intended use of the boat.

11. Joined: Nov 2003
Posts: 19,133
Likes: 494, Points: 93, Legacy Rep: 3967
Location: Eustis, FL

### PARYacht Designer/Builder

Making ratios for yourself is a noble if fruitless venture. They will not help you in any regard other then rational comparison. In other words you'd have to have several "qualifiers" to make any ratio list useful. By this I mean, lets say you're looking for an average beam/length ratio for a 30' sailboat. Well if you just take the B/L from the first 50 sailboats you encounter, it's not going to account for many "modifiers", such as triangular stern racers or relatively balanced ended CCA era yachts. The results of this B/L ratio homogenization would be meaningless. On the other hand if you subdivided the B/L list into specific categories, such as all out racers, racer/cruisers, cruiser/racers, light cruisers, medium cruisers, heavy cruisers, working craft, etc. then you'd have a marginal set of B/L ratios to work with, under it's specific category.

Laranjo, it might be more helpful if you just told us what you are attempting to do and/or ask a specific question(s).

12. ### Laranjo123Previous Member

All i want to know is are there any possible info about the ratios that are being used in yacht desinging?...Cause in my thesis what i've used was my parentship's ratios.... O__O

13. Joined: May 2010
Posts: 232
Likes: 20, Points: 18, Legacy Rep: 192
Location: New Zealand

### JRDSenior Member

Read through Eric Sponbergs lecture notes on this site from a couple of years ago, he has analysed quite a number of critical ratios relevant to yacht design and how they relate to performance and safety. I dont think this is related to parentship data as such, but makes a very interesting read for the would be amatuer designer. (like me)

Larrson Elliason book gives a bunch of compatitive graphs showing ranges of relative dimensions and ratios which pertain to scale up/scale down of designs. As their perfromance writings focus on the delft models for drag etc, their book may be of interest.

I agree with PAR in that you will get better answers if you can share what you are trying to acheive in more than one line of text.
It may be a language thing, but your questions give me the impresion that you are a student that cant be arsed doing his research so jumps on the net every 5 minutes to ask questions, then assumes a correct answer from whoever will reply. Im sure thats not the case, but as a student of a proffesional engineering discepline you could consider making a bit more effort with your questions. You would not be employed for long sending out communications like that, if you worked in a real design office.

14. ### Laranjo123Previous Member

I see thx mr.JRD what you mean is i should detail my questions right?...

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.