# Basic boat design question

Discussion in 'Boat Design' started by Solomon Chang, Jan 14, 2015.

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### Solomon ChangNew Member

Hello everyone
Please give me some guidance onto how to calculate the curve (I don't know how to call it) at the sides of the yacht as show red in the attached picture. Furthermore, how can we determine how curvy should it be.

Thank you very much!

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### DCockeySenior Member

It appears to be the sheer. The shape depends on the design - there is no simple formula to "calculate" it.

What are you trying to do? Are you a student?

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### Solomon ChangNew Member

Thank you so much. So it is the sheer. But how to determine it since there is no calculation? It would be great if you could tell me where should I start to learn it?

Yeah, I'm a student. I am learning through a book called principle of boat design.

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### TANSLSenior Member

Nobody invents a new boat. To simplify the process I'll tell you that generally you start with a boat like yours modifying her shapes to suit your preferences or what you need.

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### DCockeySenior Member

I'm not familiar with Principles of Boat Design. Is it Principles of Yacht Design? If so that book assumes the reader has some basic knowledge of boats, and concentrates on analysis rather than creating a design. Creating a design is different than analysis.

A sheer curve is usually created by drawing it, either with a pencil on paper using a spline and weights; or on a computer with design software using numerical splines.

Have you designed anything before? Have you built anything which wasn't in a kit or by following a set of directions?

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### Solomon ChangNew Member

Thank you everyone. Yeah it is yacht design, sorry. No, I haven't done any design before. I know CAD. So we just use pencil to draw without any specific calculation?

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### daiquiriEngineering and Design

Principles of yacht design explains pretty well the steps involved in designing a boat. So I would suggest you to first read and try to understand all of it, and then eventually get back here with questions which didn't find an answer in the book.
Cheers

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### DCockeySenior Member

This is a good suggestion for someone who is already familiar with the basics of design and needs to learn about the specifics yacht design theory, tradeoffs and analysis. Engineering education typically does a much better job of teaching analysis than synthesis.

Someone who is not familiar with design should become comfortable with the basic design process before wading into the details of theory, trade-offs and analysis of boat design. My recommendation is to start with a careful reading of Chapter 1 of PYD, Design Methodology. In particular starting with a set of requirements and the iterative process of the "design spiral" are critical concepts. Then read through Chapter 2, Preliminary Considerations, but do not be concerned if some of the details are not fully understood. They are covered in later chapters.

Next study Chapter 3, Hull Geometry. Learn the nomenclature definitions and become comfortable with lines drawings. You need to aim to be able to look at a lines drawing and understand the hull shape which is represented. Read the "Work Plan" page and then follow it to draw a hull shape. Select a set of preliminary dimensions and requirements but don't be too concerned about how good they are at this time. The aim is to get experience with the creative aspect of design. Either pencil and paper or CAD can be used. Then draw another hull shape and then another.

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### gonzoSenior Member

It looks like a powerboat. Depending on the overall design, you will have a range of options. The curve you pick is whatever you think looks good. It is largely a cosmetic issue.

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Looks like a plan view to me, not sheer, ..an outline of the hull on the moulded beam.

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### frank smithSenior Member

It determines itself , as it is a result of the confluence of many other considerations in the design.
Some of those being material, construction, type, and use of hull, ect.

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### keroseneSenior Member

I am with Ad Hoc here, not sheer...
The way I see it.

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### TANSLSenior Member

I find unhelpful discussion of what that curve. The OP says it is "the curve (I do not know how to call it) at the sides of the yacht". That is nobody in the world except himself can know what this curve. We should only ask him to tell us what curve is the one he wanted to define. Then review.
Meanwhile, we can tell that any curve on a boat should be "smooth".

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### PARYacht Designer/Builder

The sheer is visible in plan view, though often is called the deck or something else. It clear this OP has just finished the introduction portion of "Principles" and hasn't yet moved into chapter one. He'll need to get pottie trained first, before asking too many more questions like this. Other wise, his next post will have a profile and the question will be how to define the keel profile of bow rake or something.

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### TANSLSenior Member

The sheer is visible in plan view but so is the chine or bulwark or bilge diagonals, among others. So, with what we were?
I think what we should say is that this is not the way to start designing a boat, imo.

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