Stepped hull, a different thread, and book recommendations

[curtis73]

In preparing to build a Glen-L thunderbolt, I'm planning on using a couple hull upgrades. I absolutely love the deck and plan of the Thunderbolt, but the hull is a shallow vee designed for all out speed. Speed won't be my main concern. I will gladly give up 10 mph to get a little better handling and ride qualities.

I'm thinking about adding longitudinal strakes and have seen many new sport/performance/bowrider boats with stepped hulls. Is it just to help compensate for their portly displacement, or would it be something I should include?

Also, (so I can quit asking you nice folks dumb questions) I'm looking for a good resource that will answer questions like:

what are the elements of hull design? What's the definition of a strake? What do steps accomplish? benefits? drawbacks?

For now I'm only concentrating on single hulls, in particular, vee designs, but the book can include others.

My problem is that I know what most of them do (using common sense) but don't know where to put them, when to use them, or what they're called.

what are the elements of hull design? What's the definition of a strake?

These links are a start, though you probably want something more in-depth and maybe somone else will have some better links (there is no easy single source I'm afraid, else the universities would be in trouble):

Glen-L Glossary of Boatbuilding & Boating Terms
http://www.glen-l.com/resources/glossary.html

BoatTalk Nautical Dictionary
http://www.boattalk.com/dictionary/

Nautical Terminology
http://www.dynagen.co.za/eugene/hulls/terms.html

[Jeff]

Adding a step or steps will aerate the hull thus reducing drag a little and also it will add stern lift so the boat will be able to get onto plane faster and also without the bow sticking up in the air for so long.

Keep in mind that although since this is a one-off project you might be able to visually copy common step designed in use today (esp. the two-step which is so common now), you will also be taking a risk to do so. Even with a lot of time spent doing calculations, I believe it is still a trial and error process, so if you add feature x to hull y, you may or may not be happy with the results. While it's not all important that you get the best performance, as a goal of simply 'better performance' would probably be acceptable for a one-off project, there may be side effects that you can not anticipate.

Of course, while I warn you that there is risk involved and it will not necessarily be as easy as you think, I do like the idea of building a boat which is truly unique and customized for my needs rather than building it 100% off the plans. But just remember that once you deviate, nothing is guaranteed, tested, or proven.

[Jeff]

As far as a general resource, take a look at some of the books in our book list: http://boatdesign.net/directory/books/ or http://boatdesign.net/books/

For example:

Understanding Boat Design by Ted Brewer
http://boatdesign.net/cgi-bin/bdn/jump.pl?ID=206

(You can also get an idea of what this book will be like by visiting Ted Brewer's web site and specifically http://www.tedbrewer.com/yachtdesign.html)

Designing Power & Sail by Arthur Edmunds
http://boatdesign.net/cgi-bin/bdn/jump.pl?ID=191

Yacht Designing and Planning : For Yachtsmen, Students, and Amateurs by Howard I. Chapelle
http://boatdesign.net/cgi-bin/bdn/jump.pl?ID=207

Preliminary Design of Boats and Ships (I don't know anything about this one, but I've seen it recommended)
http://boatdesign.net/cgi-bin/bdn/jump.pl?ID=363

Also:
Boat Data Book by Ian Nicolson
http://boatdesign.net/cgi-bin/bdn/jump.pl?ID=210

The Elements of Boat Strength: for Builders, Designers, and Owners by Dave Gerr.
http://boatdesign.net/cgi-bin/bdn/jump.pl?ID=517

Note that these books all help with a general background and overall understanding of yacht design, but do not specifically address some of the cutting edge things like step design.

[Polarity]

I'd like to add one more to that - not specifically for Curtis but for anyone who wants a from absolute basics explanation of design terminology, what all those TLA's (Three Letter Acronyms) mean and how to apply them along with some examples, I can thouroughly reccomend "The art science and magic of cruising boat design" by Danny Greene.

Paul

[Jimboat]

I'd like to reiterate Jeff's comment that steps can improve performance, but should be designed for the specific hull's application. Using a step design from one boat on a hull of a differenct design or setup or application, will probably not give similar performance results - and may make it worse.

Hull weight distribution, deadrise and strake positioning will influence the results of the steps - as, of course, will the step design itself.

Here's another book reference: "Secrets of Tunnel Boat Design" - it's mainly for tunnel boats, but also includes vee-bottom hull discussions and bottom design discussions are still applicable.

http://boatdesign.net/cgi-bin/bdn/jump.pl?ID=1769

[curtis73]

You are all great with info. I had been searching on barnesandnoble.com and Amazon and found several inappropriate books. I went to B&N today and looked at a few of them. They were all nice, but were mostly a pictoral history and a few plans.

I agree with what you all are saying about deviation from designs. As a Car nut, I'm of the mindset that autos' factory engineering is rarely optimal, only cheapest and easiest. While I may try to apply this attitude to boat crafting, I understand that these boat plans don't have to be sourced out to the lowest bidder so those rules don't apply. Cars seem to have predictable parameters: increase caster in the alignment = better high speed stability. Lower center of gravity = better handling. It may be true that the Glen-L design is not optimal for my desires, but I'm certainly not a boat engineer. I can tune a small block with my eyes closed, but I don't know the rules of hull design ...yet My game is always to find out the facts and then build what I want. This just may take longer. Oh well, I'm 28 so that gives me about 80 years to finish the project.

It looks like steps are not something I need. Speed and planing won't be a problem with a dry hull weight of 700 lbs and 270-ish hp. I'll need to slow it down if anything.

Thanks to all and keep suggesting. I'm never offended in the presence of masters.

[Jimboat]

We NEVER need to slow down a boat!!!

/Jimboat
AeroMarine Research