# How to make hull calculations for a small motorboat (walleye boat)?

Discussion in 'Boat Design' started by Bemboo, Apr 26, 2020.

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### BembooJunior Member

Hi everyone,
I am a mechanical engineer but I have a great passion for boats. and I would like to build a small one (walleye boat) the same style as Crestliner, Lund...... I want to do it for myself but in case it will work, I would like to work as a builder.
I started to study the fabrication (types of aluminum, welding, DC...) and I have no problem with all these.
My problem is with the design, so I started to study hydrostatics and stability (Ship Hydrostatics and Stability By Adrian Biran, Ruben Lopez Pulido) first chapter was great I understood a lot about Geometry for Naval Architects. but the second chapter it was like Houston we have a problem, I need to repeat all Algebra II and Trigonometry to understand what he talking about.
I am lost and I don't know is that correct what I am studying or should I study another book? especially all the calculations are about big ships. I need advice to know what exactly should I study to make a hull calculation for a small motorboat.
Also, I started to practice on Rhinoceros and it's going well.

P.N : I can't study this in University or Institute. I am in Poland and I don't speak polish. So I have to study by myself with books.

Thanks for the help and looking forward to hearing from you.

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### Mr EfficiencySenior Member

Well, the easiest way would be to work from readily available plans, but before anything, establishing the requirements that you want to be met, by the boat. For example, the conditions it will be exposed to, in terms of water smoothness, distances travelled, loads carried, type of fishing and many more.

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### BembooJunior Member

It will be for fishing, like the one in the picture, and will use in lakes.

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### Mr EfficiencySenior Member

There are sure to be plans to suit, available at reasonable cost. But you need to fine down your requirements, do you need speed, and how much, for example, what is the budget, also has to be set.

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### BembooJunior Member

Boat length will be 17 to 20 feet, speed I think 50 MPH, Person Capacity like 4,5. Hull shape will be Deep V or Modified-V. I will build it myself so the budget without the engine will be from 10 to 15.000€

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### Mr EfficiencySenior Member

50 mph top speed ? Is the lake big enough to need that sort of speed ? And big enough to get choppy enough to justify a deep vee, which will not be as steady at rest as a lesser veed boat ?

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### BembooJunior Member

Lakes are big here, speed can be changed as well as the rest. I just need to know what exactly should I study to build one like this.

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### Mr EfficiencySenior Member

Why do you want to start from first principles, and not from existing plans? It could take half a lifetime to become au fait with all the nuances of even a particular sector of boat design. Then there are the skills of construction to become adept at. It's not like making a kid's cubby-house. To arrive at something as fit for purpose, as a tried and proven design, is no small task.

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### BembooJunior Member

So what you suggest to start with. to have the knowledge to build a 20-foot motorboat? I really love this field and I want to do it. I already finished 3 books talking about aluminum boats.

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### Mr EfficiencySenior Member

Have you looked at designs on the market ? Or aluminum kit boat suppliers ?

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### ondarvrSenior Member

The aluminum walleye boats are a compromise of what the ultimate design the designer desired, and what can be formed with aluminum at a reasonable cost.

The composite versions are more of a representation of the goal for the hull. It doesn't mean it was right for everybody, just it can be formed in composites much easier.

Most of these walleye hulls sort of follow the normal aluminum hull design with a few minor tweaks in hopes of making it more friendly for the intended use.

You could get an idea of what works by looking at the specs from aluminum walleye boats you like.

Many small boats of this type don't start out with doing the calculations, they start with what someone feels is right, then get fine tuned in the real world from there.

And many aluminum walleye hulls aren't dedicated walleye hulls, its just a hull the company already makes that's close enough. Then the interior layout is set up for walleye.

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### BembooJunior Member

You are right, I thought before to copy a boat, but I am not sure about the weight and the stability and how it will react in water and what is the best Engine HP chose. I want to learn when I use Deeb V or Modified-V. the relation between Hull Length and Beam. a general idea about Planing hull. Where can I study these??

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### ondarvrSenior Member

Do you want to make a boat(s) or study hull design?

I ask that because studying hull design and understanding it in detail is a long term goal.

If you just want to build this type of boat you can use dimensions that are already being used in the market.

And whatever you do, the first hull, once you start using it, will be changed.

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### BembooJunior Member

Will do as you said. Thanks for the advice.

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