# determining distance between catamaran hulls

Discussion in 'Boat Design' started by Thai, Mar 29, 2006.

1. Joined: Nov 2004
Posts: 27
Likes: 0, Points: 0, Legacy Rep: 10
Location: VietNam

### ThaiJunior Member

Hi everybody!
Now I want to build a catamaran. But I don't know formula to calculate distance between two hull. Could you guide or show doccument for this issue
Thanhk
B.V.Thai
HochiMinh City - Viet Nam

2. Joined: Jan 2004
Posts: 19
Likes: 0, Points: 0, Legacy Rep: 10
Location: Warialda Australia

### wingsailsKim Prentis

There is no set formula that I am aware of, it depends on how stable you want it to be and how much of a problem being too wide is eg on a trailer behind a car.
Years ago width was 1/2 of length, but now wider boat are more popular.
That is only the start of your problems though, take advice and think things through trying to imagine how it will all come together.

3. Joined: Oct 2005
Posts: 49
Likes: 2, Points: 0, Legacy Rep: 28
Location: Egypt

### HishamMarine engineer

be care the larger span the larger bending moment

4. Joined: Nov 2004
Posts: 27
Likes: 0, Points: 0, Legacy Rep: 10
Location: VietNam

### ThaiJunior Member

I agree with Hisham. This distance keep eye on bending moment and shear force effect vertical wave. So I want a detail formula. Could everybody help me ?, Thank
B.V.Thai
HochiMinh City - Viet Nam

5. Joined: May 2005
Posts: 442
Likes: 8, Points: 18, Legacy Rep: 58
Location: Hawaii

### JonathanColeimagineer

The width of a catamaran depends on many things. What kind of speeds you travel, what kind of sea and wave conditions you regularly expect, what the length is, etc.

Catamarans create diverging waves between the hulls . These waves can interfere with and sometimes assist the forward movement of the boat. This depends on many other design issues including the symmetry or lack of it in the hull design, the fineness of the bow in pushing through the water, the angle of the bow to the waterplane, and the speed that the hull is moving.

At some speed the waves actually can assist the movement of the boat by something called constructive interference. There is no set formula because all of the catamarn hull design characteristics effect the wave interference.

I think the most common point of view among experienced designers is wider is better than narrower. The wider the better, until you start getting so wide that you can't find a berth for the boat.

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.