# Drag Force ?

Discussion in 'Hydrodynamics and Aerodynamics' started by panther13, Apr 13, 2013.

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### panther13New Member

What is the average drag force for a catamaran boat?

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### jonrSenior Member

42, but the units vary based on lots of things.

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### FMSSenior Member

A 16' hobie cat or a 65' motor yacht catamaran? You need to provide a specific and detailed question to get any reasonable answer.

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### panther13New Member

This is a school project. We were asked to design a shallow water solar / electric boat capable to carry from 10 to 15 people with 1' of draft. We are planning to use a catamaran 26’ long and 9.5 width with two sponsons ( 30 ‘’ wide each ) . We are planning to use to Torqueedo electric motors 48 V each. I was trying to run some simulations using solid work and it gives me 422 lbf of drag force. I have no experience working with boats, but I think that is a big number for a drag force value.what do u think ? Thank You for ur help?

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### Leo LazauskasSenior Member

If you have the time, Michlet might give you some reasonable estimates for
the total resistance.
Be aware that the wave resistance can be very significant in shallow water
when the depth-based Froude number is close to 1.0. That Froude number is

Fh = U/sqrt(g*h)

where
U is speed (in m/s)
g is gravitational acceleration (about 9.81 m/s/s)
and h is water depth (in metres).

Michlet is free and is available at:
http://www.boatdesign.net/forums/design-software/michlet-9-30-released-46533.html

There is also a paper on solar-powered multihulls that might help you at:

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### quequenSenior Member

This spreadsheet may help with the critical depth determination and Fh

#### Attached Files:

• ###### Depth Froude Number.xls
File size:
87.5 KB
Views:
387

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### jehardimanSenior Member

A cat may not be what you need given the design criteria. It will be difficult to get the required burden in a power efficient hull with only 1' draft. Cats are very load inefficient.

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