Need advice on hull

[fbeytell]

Hi
I am a beginner builder. I am also a draughtsman by trade.

I am going to build a speed boat. I would like to know if there is any specific rules that I need to know about v shaped hulls. Should it be a specific degree/angle? Is there maybe a formula for working out the hull? The boat is going to be 20'. I do not want to spend all that money and the design is wrong.

Could some one please help, it’s difficult to get the right info.

Thanks
Francois

[yokebutt]

Franny,

There is a lot to designing a boat, I think you'll be much better off with a design from a reputable designer instead of trying to do it yourself the first time. Have a look in the directory of this site, you have a decent chance of finding a local designer in SA.

[fbeytell]

Thanks for the reply.

I have some what of experience in boat building. I worked 4 years for a company that builds Catamarans.

I will go and check out the directory.
I just need help on the hull design. I am just looking for the perfect shape for the type of boat I want to build. Both Speed and Comfort.

Thanks Again.
Francois

[tom28571]

This request comes up often, way too often. How to answer truthfully and tactfully is very difficult. I am sorry to say that your wish for an easy answer that can be given on the internet is impossible for anyone here to give.

(I just need help on the hull design. I am just looking for the perfect shape for the type of boat I want to build. Both Speed and Comfort.)

Those here that have spent long hours over years to try to learn enough to do what you want in a few sentences must feel insulted that such knowlege can be gained so easily. Here are a couple sources that can get you started.

Dave Gerr - The Nature of Boats

Ted Brewer - A basic look at design but I forget the title

The Ideal Series - A series of articles published by Motor Boating many years ago that may rarely be available.

Peter DuCane - High Speed Small Craft

Lindsay Lord - Naval Architecture of Planing Hulls

Larsson an Eliasson - Principles of Yacht Design

Numerous articles in publications like Professional Boatbuilder

If you just want a good runabout, study the plans and offerings in Woodenboat's catalog and ads in the back of WB. Some are better than others for what you want but opinions differ, even among the knowlegeable.

If this were not true maybe there would not be so many bad boats around.

[Tim B]

I agree with Tom. Some of us spend years studying to learn how to start approaching the design. You're effectively asking for at least three or four years of someone's life in a single post. I'ts not going to happen.

There is however, a number of formulae to help with hull design, and I could just reproduce them. It wouldn't do much good though, as you wouldn't have a clue what to do with them.

Boats (power or sail), don't come down to formulae at the end of the day, they come down to skill in designing. Skill takes time to learn, very few designers got it right on their very first attempt. There is only one way to automate the design of a boat. Employ a designer.

Tim B.

[monrosm@shrewsb]

Tim and Tom are right about not being able to just gain a massive amount of information in a few sentences. However it depends what you want to use your boat for. If you intend it to perform to high standards and be able to go out in all weather you are going to need to look and learn alot about hull shapes/sizes and lots of other things.
But the boat you want to build sounds more like a recreational craft used for fun and enjoyment. So what you need to do before you just jump in to building a hull is make a list of things and conditions your boat will have to deal with. There is no set angle of chine or dead rise for a boat. It depends on alot of factors and not just the length of it. You also need to consider the weight, size , hp and type of engine you are going to power it with, this can be the key as to weather your boat actually works as a boat. If you can provide us with more information as to the specifications of the boat you want to build im sure people (including me) would be happy to help.
Stefan Monro

[fbeytell]

You are right but I dint not mean to let it sound like that.

I have been looking to start a project for quite a while now.
I have allot of fiberglass and carpentry experience.
It is hard to get the right info to get started.

I guess I won’t know how if I don’t try.
I have drawn a couple of cad plans for the project.
I am going to stick with my design and see the outcome.
It is worth the try and I won’t get the knowledge and experience if I don’t start.

Thanks I will post questions if or rather when I get stuck.

Thanks again!
Francois

[FAST FRED]

"I am going to stick with my design and see the outcome.
It is worth the try and I won’t get the knowledge and experience if I don’t start."


If the knowledge you are looking for is to be a boat designer , a very steep learning curve and lots of poor outcomes , as you learn , awaits.

If you want the experience of building your own boat and having it operate normally , get a PRO designer , or plan on a decade or two of poor outcomes.

A simple look at the hundreds of abject failures from major mfg will show the problems of a design by computer (and cost), rather than trained , experienced NA.

FAST FRED

[fbeytell]

Hi Fast Fred

Where I am situated in South Africa, you will not find a pro designer.
Let me ask you then this if I purchase plans for a boat, just for the hull would that be stupid. I am a designer but for a totally different field. This Project is more of a father son type of deal. I don’t want do build boats for a life, that’s why I asked for some help.

I don’t know if you got cad or something that can view dxf or dwg files.
If you got time maybe you can have a look at my plans and tell me you personal opinion. I am not an Expert but will appreciate an expert’s opinion.

Thanks
Francois

[ted655]

Might be a few nuggets of gold here for you.
http://home.clara.net/gmatkin/therules.htm

[tom28571]

The books by Lord, Brewer and Gerr I listed above are all available from www.abebooks.com .

I consider Gerr and Brewer extremely helpfull for a beginner to even choose to buy a plan among the various offerings. Lord is expensive but of great value for designing. DuCane is very good but even more expensive on Amazon.com.

Even the more basic books by Brewer and Gerr will give you far more information than you are ever going to get here.

[Scott Carter]

Fbeytell -
Newbie to newbie, just build it. BUT! Do your homeowrk first. These books that have been offered as references are industry accepted becasue they really do provide a lot of good, understandable information re. design. I know I'll get some good-natured eye rolls from our PRO colleagues in this forum, but you can read through them all (the books, not the colleagues), pick out what applies and then, if you use your head, end up with a boat that floats, runs around pretty good, and probably won't meet most of your expectations anyway because it's a boat.
Some of the authors of these books point out what I've (as an inexpeienced designer with a brain) come to appreciate and take advantage of: use the designs of existing, proven boats, change what you want to change knowing that there WILL be consequences (some good, some bad) and then build it. This isn't at all about what you call yourself. "I'm a draughtsman", "I'm a Naval Architect", "I'm a guy with an idea". It's about using your head and learning from others' experience and then gaining your own. It doesn't matter whether you read it in a book, learn from your own experience or pay someone to tell you or draw it for you. In the end, if you and your son build it you will have learned along the way and your second one will be better. There's lots of bad boats out there, sure, and just one of the reasons for this is because EVERY designer has to start somewhere. That doesn't mean that just because it's your first design that it's going to be a bad one, it just means that no-one is immune to poor design.
Tom28571 hit the nail on the head. This forum is great for specific questions like "what kind of glue" or "isn't this a beautiful boat". But what you're asking for you'll have to pay for, and I'm not talking about South African $$. I mean pay for it in the time you'll spend reading and learning, asking specific questions, studying existing lines and reading reviews of the performance of that particular boat to see what features you admire. Then again, NA's need to eat too, and there are some really cool designs out there that have been around a while and you can be pretty confident in the seaworthiness of their design so you can focus on the seaworthiness of its construction.
Good luck, I think it's a cool thing you and your son are doing.
Scott

[rayaldridge]

Originally Posted by Scott Carter

Fbeytell -

Some of the authors of these books point out what I've (as an inexpeienced designer with a brain) come to appreciate and take advantage of: use the designs of existing, proven boats, change what you want to change knowing that there WILL be consequences (some good, some bad) and then build it.

Scott

I think there's a lot of wisdom here, even for professional designers. A lot of the pioneers of multihull design, for example, acquired their expertise by imitating a guru, and then, as they acquired experience, diverging from that beginning. Piver and Brown come to mind, though the pupil soon reached a point where his designs were far superior to his teacher's.

For an amateur designer, it's almost a necessity to learn by imitation, at least if you want your first efforts to be usable. I'm currently building a tiny open-hull catamaran to my own design, but my design owes a lot to T.F. Jones, who in turn owes a lot to Wharram. Much of the detail in the construction is lifted from designs published in Jones' books. The hulls, however, look like miniaturized versions of Woods' Janus design, though I arrived at the shape before I knew about the Janus design. Still, it was reassuring to discover that a competent designer had come up with a similar form, and that it worked. I'm taking my sailplan from Michalak, and my construction method from Glen-L.

If it's a disaster, I'll have a lot of people to blame-- another advantage.

[fbeytell]

I read thru all of your posts and want to thank you for your advice.
I have ordered a couple of books and I can’t wait. I think I am more excited then my son.

I have learned that there is match more to design in naval architecture than meets the eye.
I am going to wait just a little longer before I just jump in, I want to do my homework 100 times if must. I am confident that this project will be a success. Maybe not the best boat out there but surly one of the most appreciated one alongside my family and me.

I will keep every body informed on what is happening.

I hope one day I would also be able to sit in your chair and look back at the trials, disasters and success and give my knowledge to some newbie.

After all that’s what’s keeping the art of boat building alive.

Francois

[tom28571]

Francois,

I'll bet you will find the study and revelations along the way at least as enjoyable as the building and use of your boats. Yeah, boat(s) since there will be more than one.

Good luck,

Tom