# Slipway launching calculations

Discussion in 'Hydrodynamics and Aerodynamics' started by athvas, Mar 6, 2013.

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### athvasSenior Member

Could anybody having launching calculation of slipway (sample calculation). or any website links which demonstrates launching calculations plz share

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### gonzoSenior Member

What are you trying to calculate?

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### athvasSenior Member

To know how launching calculations are carried out for slipway launching.
1)Moment of buoyancy required for stern lift .
2)Min tide required for stern lift
3)Min tide required for bow lift
4) launching draft.

How these calculations are carried out for a vessel (any sample calculation for study purpose)

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### jehardimanSenior Member

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### gonzoSenior Member

All you need to know is the draft of the vessel. When the tide rises to give you that depth of water, the vessel is floating.

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### TANSLSenior Member

And what happens in those seas where there are no tides?
Athvas is talking about launching a ships in a slipway. This process requires complicated calculations and has nothing to do with putting a ship afloat. (I apologize if my English is not correct. Technicians, however, will understand me perfectly)

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### gonzoSenior Member

His question in post#3 numbers 2&3 are about tides. I think he is overthinking the calculations.

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### TANSLSenior Member

Yes Gonzo, you're right, but when you say "All you need to know is the draft of the vessel", what draft do you mean, what condition, what trim, at what point of the length .....?
It's more complicated than just wait for the tide reaches a certain level (draft)

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### jehardimanSenior Member

Not really. In an end launch, depending on the ship and the ways, if the water is too low you could break her back or damage the way ends. Conversely, if the water is too high compared to the way slope you could crush the fore poppet and hole her. However, unless this is a class exercise, way launchings should be left in the hands of experienced people as there are a lot of other things that can go wrong besides just way loadings (c.f. Principessa Jolanda).

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Indeed. One condition that is often overlooked, but must be checked is the GM in various locations as the vessel slides down the slipways or greasy ways. There are times where given the right conditions, the GM can become negative and thus the vessel capsizes.

The calculations for launching are straight fwd, I've done more than I can shake a stick at. It is just methodical process which you must follow and obtain the correct accurate data of your slips way, angles tides and hydrostatics of the vessel being launched.

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### TANSLSenior Member

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### jehardimanSenior Member

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### gonzoSenior Member

Unless the slipway is not standard, there shouldn't be any major problem. The usual method of launching sideways takes care of the problem of the stern hitting the bottom or the bow getting crushed.

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Can you define what is "not standard" please..

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### TANSLSenior Member

Why? ???? The ship, does not has stern, nor bow, in that case?

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