# Determine the draft of the hull

Discussion in 'Boat Design' started by prabs, Jun 2, 2021.

1. Joined: Mar 2020
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### prabsJunior Member

How to determine the draft of a trimaran sailboat? Length: 25 feet, Beam: 8 feet.

It has 6 stations(longitudinal) in the section view and 3 panels(vertical) in the front view. (Freeship software).

What value should I input in the draft field?

What is the ratio between draft to length or draft to beam? What is the optimum? Is there a formula for an optimum draft?

What is the draft of the ama with respect to the hull?

2. Joined: Oct 2007
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### bajansailorMarine Surveyor

Prabs, is this a college assignment that you are working on?
If so, can you copy out the full text of the assignment here please?

Re the draft - it depends on what you want from the boat, and what the statement of requirement says, and how much displacement is required..
You could have deeper draft, and no centreboard, or shallower draft, with a centreboard.

Re the draft of the ama - again this depends on your displacement. Ideally a racing trimaran would have the amas clear of the water at the load displacement but for a cruising trimaran there will probably be some immersion.

3. Joined: Mar 2020
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Location: India

### prabsJunior Member

This is not a college assignment. I would like to understand what draft needs to be specified in the input field of Freeship software along with length(25 ft) and beam(6 ft).

Number of points in the longitudinal direction: 6 (from stem to stern) (section view)
Number of points in the vertical direction: 4(3 panels) (Bow/Stern view)
Length: 25 ft
Beam: 6 ft
Draft: ?????

What is the relationship between draft to length and beam of the hull. Any ideas.

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### gonzoSenior Member

The draft is determined by the hull shape and the weight of the boat. The submerged volume (displacement) is something you need to calculate.

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