# Help with design first steps?

Discussion in 'Boat Design' started by voodoo92, May 25, 2014.

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### voodoo92Junior Member

Hi there im wanting to start designing a 5.5-6 mtr bow rider for construction in a few years after i finish my apprenticeship. Im after all the basic kind of guidelines and formulas to get on the right track. I have done a few drawings of lines plan development at tafe a few years ago and have procured for myse;f some lead weights and fairing battons for the processs.
Any of the small things that are often looked ever would be awesome. At the moment im after a supposed formula for determining the length and width of a keel flat from the length of the boat. im looking at around 2.3/2.5 mtr beam and 4mm aluminium plate construction. Thanks for anyones help.

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### rwatsonSenior Member

Your apprenticeship in aluminium welding I presume ?

You either then have another 4 years as a naval architect, or you just go out and buy some plans,

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### Eric SponbergSenior Member

Hi Adam--Voodoo92--Welcome to the forum. I am going to give you some advice, and please don't take it the wrong way. You are to be commended for knowing when to ask questions, and I trust your curiosity will lead to a better understanding of how boats are designed and built.

To answer your question, there is no "supposed formula for determining the length and width of a keel flat from the length of the boat." The length and width of a keel flat, if you have one, are determined by many things, not the least of which are the shape of the hull and the sizes and shapes of the internal structural members which are conceived in the depths of your own mind. That is, it is determined by whatever you want to make it--it's up to you, the designer, to choose. You have to make the decisions about those things, and you will have experience, knowledge, and engineering tools to help you determine what the final size and shapes are--of everything. It's the design and engineering process, filtered through the mind of the designer, that determines how things are shaped and built.

I think what RWatson is trying to say in his advice is that you will need a bit more experience in design to figure out stuff like this. Just be aware that there are no magic formulas for design. The key word here is "magic"--there are formulas for design, but they are often overided by the whim of the designer. There are engineering formulas, but those are different. And usually, there is no one formula that gives the final answer--there are many formulas that are used to arrive at a solution for whatever the device is at hand. The judicious and talented designer will have more success at using those formulas to his or her advantage than the person who does not understand this.

So my advice to you is--there are not magic formulas, but keep asking the questions and studying. The more you know, the easier it will be to make design and engineering decisions.

I wrote an opinion article about this three years ago in Professional Boatbuilder magazine. I attach it below.

Good luck on your design.

Eric

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### Mr EfficiencySenior Member

I think anyone with a ghost of a chance of designing a successful boat will have a keen eye for differences between existing designs, I am surprised that many people standing in front of two boats can't identify even obvious differences between the two. If they all look the same, "like Chinamen" ( they probably say the same of Europeans ) you won't likely be designing a worthwhile boat.

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### Leo LazauskasSenior Member

As a student of naval architecture.

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### Ad HocNaval Architect

Nicely said Eric. Sadly over the heads of many.

To follow on from Eric's article....add another 5-10 years to that 4 you noted before one can become a "professional" engineer as a C.Eng.

But even then one is still just at the "beginning"....

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### Mr EfficiencySenior Member

You don't need to be a NA to design a simple boat like what the OP is talking about. The best performing smaller planing boats I had direct experience of, few were the work of professional designers, most were conceived by people with a great amount of practical experience on the water. Equally though, some of the worst boats probably were not the work of NA's either. But to lack either formal training, or the informal "knack" honed by observation and experience, the chances of producing something that will compare favourably with an off-the-shelf professional design is miniscule.

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### PARYacht Designer/Builder

Welcome to the forum.

Agreed (somewhat), but the OP hasn't any experience, practical or other wise (my assumption) to offer anything to the proposition.

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### Mr EfficiencySenior Member

There is no formula for happiness, or keel flats, that I know of.

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### voodoo92Junior Member

wow thanks for all the great replies. first of all im a 3rd year aluminium boat builder (cert 3 in marine craft construction). Ive been building mostly 24-35mtr boats all my vast career haha, like ferries, currently doing 3 24mtr qld police patrol boats, weve done a coast guard boat, many refits, both cosmetic and structural. Im currently doing a 10 mtr barge that looks nothing like a barge. it has twin outboards and a simple side console, plug welded checkerplate deck, boarding ramp for an atv and a small crane. supposidly reaching speeds of 35 knts..? Im always asking all the annoying questions that may seem silly at the time but to me all information is valuable. Im not one to do a cheap or crappy job and want my boat to be as good as it can, design and construction. The most experience im really had with small craft was yesterday when i had a whole hour at the sanctuary cove boat show. so much time haha but had to leave really early because of my 7 month old.
Im passionate about what i do and only buy the best tools. Ive got my own mig welder that cost a fare chunk of money but it pays for itself so im happy with that
so thats a quick run down about me. thank you

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### daiquiriEngineering and Design

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### rwatsonSenior Member

Just a question on that book- how come the softcover versions are \$500, and the hardcovers around \$15 ?

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### daiquiriEngineering and Design

And what do you say about the one at the bottom of the page?

I guess that I would rather opt for a hardcover...

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