GIGO principle or mistake in workshop documentation process organization.
In computer science, garbage in, garbage out (GIGO) is where flawed, or nonsense input data produces nonsense output or "garbage".
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“What about hull surface?” is a typical question when Subcontractor signing contract for production of the hull workshop documentation.
“Don’t worry we have it and we will deliver it to you” is it a typical answer from the Customer.
Customer think he delivered hull surface and expect good workshop documentation in according to the time schedule. If Subcontractor is smart enough he will check hull surface carefully before making model and explain to Customer that is not good enough for workshop in case of some problems. Sometimes after such discussion sides of the contract agree that preliminary surface is not good enough for production and need to be faired for production. It will take some time and some more money for that, but this is normal situation.
GIGO principle starts when initial surface uses for production of the workshop documentation. Customer point that he has a good surface, because it’s look’s good in some shaded pictures, and Subcontractor can’t explain the problem correctly. Simply the Customer think that Subcontractor just want to get some more money. Then modeling of workshop documentation started. Usually it’s work quite well in parallel mid-body area, where surfaces are not complicated. Packages for some units can be deliver to the Customer already before the Subcontractor facing in problems in fore and aft ship areas. Especially it is often happened when Subcontractor try to model shell plates. Bad hull shape, gaps between surface patches and other problems make it not possible. Finally, Customer understand a problem, but when a lot of time lost and delivery behind of schedule. Then final surface fairing need to be done in short time, with a lot more limitations, when some units already start with production. Usually it cost more money.
In most worst situation Customer will get same surface, he gave to Subcontractor, in metal.
Very often we have such requests when it’s almost to late, and delivery time was “yesterday”. It happens because of misunderstanding what kind of surface need to be done for production. Quite many designers use different hull surface modeling programs on initial stage of design. In general, it is just hull surface idea, which can be used for making drawings and calculations, but more correct surface need to be done for production.
In our practice almost, all preliminary surfaces not suitable for production. It is easy to avoid this problem, if someone check hull surface, but in real life it’s happened again and again.