# School project - Designing a fast cargo boat

Discussion in 'Boat Design' started by Krautern, Dec 2, 2014.

1. Joined: Oct 2014
Posts: 343
Likes: 5, Points: 0
Location: Italy

### WindRafSenior Member

Krautern,
for answer to your questions is essential to know the engine power; there is much difference in the geometry of a hull with little power and more power

2. Joined: Sep 2011
Posts: 6,737
Likes: 491, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

More than a question of more or less power is a question of the volume and weight of the engine. Also very important to know the same data for the battery that will power the motor.
There are many outstanding questions. For example,
• Should I be hollow hull or may be solid polystyrene?
• Must meet any requirement boat for stability, freeboard, ...?
Here are some ideas:
• An exhaustive list of items and equipment of the ship and their weights.
• Start with the size of the winning boat in previous tests and try to improve its dimensions. Very important to analyze in depth the winning boat.
• There should be enough space to place the containers on deck.
• From there, with the length of 0.9 m, calculate the beam and draft producing less wetted surface.
• Depending on the engine and the height of the propeller shaft would have to calculate the required minimum depth, so that the propeller working at the proper depth.

3. Joined: Dec 2014
Posts: 47
Likes: 0, Points: 6, Legacy Rep: 10
Location: USA

### graywolfJunior Member

From what I see, the main constraint is going to be those drink boxes. They are going to limit the narrowness of the beam. With that constraint, you will want the hull as narrow and deep draft as possible, giving that bottom plate as long an arm as possible so the boat does not capsize. Within those constraints you will want the lines as fair as possible to enhance the speed.

In the real world, you would probably be designing the hull to carry the maxim cargo possible within that 90 meter length rather than for speed, but here your instructor has set speed as the deciding factor.

In the above I made an assumption, that assumption is that the motor provided is not powerful enough to plane the boat. If it is, the tradeoffs become somewhat different.

4. Joined: Jun 2010
Posts: 983
Likes: 32, Points: 28, Legacy Rep: 300
Location: Australia

### NoEyeDeerSenior Member

If stability is problematic, making the hull narrow and deep is the opposite of what you want. What you will want is initial stability, which is best provided by a slight increase in beam.

In any case, there would be no point in making the hull too deep, since this will just increase wetted surface.

5. Joined: Sep 2011
Posts: 6,737
Likes: 491, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

The OP says that the boat must carry 3 kg of steel on the bottom, which will give enough initial stability, although the breadth is lower than normal.
It will be necessary to find the combination, breadth-draft, which generates the least wet surface.
I would put the minimum breadth that will promote the "containers" on deck. That would lead to a breadth of about 125 mm.

6. Joined: Sep 2009
Posts: 5,804
Likes: 369, Points: 93, Legacy Rep: 2489
Location: North of Cuba

### hoytedowCarbon Based Life Form

7. Joined: Dec 2014
Posts: 7
Likes: 0, Points: 0, Legacy Rep: 10
Location: Norway

### KrauternJunior Member

WindRaf, NoEyeDeer and TANSL:
I will try to find out some information about the battery and motor

Hoytedow:
Looks like our teacher got the idea from that contest. Donâ€™t think our class will participate tho.

Again thanks for all the answers!

8. Joined: Dec 2014
Posts: 7
Likes: 0, Points: 0, Legacy Rep: 10
Location: Norway

### KrauternJunior Member

Our teacher said that the boats normally reaches a speed of 3knopt. The battery`s power is 7,2V.

9. Joined: Mar 2007
Posts: 1,046
Likes: 72, Points: 48, Legacy Rep: 361
Location: Maryland

### BMcFSenior Member

oh. Well, heck.....

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.