Designing and building small tunnel hull powerboat

[Maciek]

Dear Friends,
Looking for help and advices to design and build small tunnel hull powerboat, 2 seater, powered by 130 hp, Yamaha, 2 stroke, 4 cylinder outboard. I'm not trying to reinvent the wheel, but can't find on the market this kind of boat in size for my particular engine. This kind of boats usually come quite larger, for the engines at least 300hp and up, length 18' to 23' and seats for 4-5 persons. What I plan to build would be much smaller and lighter. Still not sure about dimensions and this would be may first question. What would be the smallest length for my engine?
13' - 14' feet?
Second question would be what technic to use during construction?
Build traditional way, using wood and marine plywood and cover with glass laminate, use divinycell foam sheets with glass laminate, or coosa boards joined with epoxy and reinforce with fiberglass?
I have all the needed power tools, equipment and experience to go either way. Also plan to use carbon fiber for reinforcement, if necessary.
Any help, comments and advices will be highly appreciated.

Below attached pictures of this kind of boats which I plan to scale down to work with my engine.

 

[jehardiman]

Welcome to the forum.
In the upper right there is a search function. It can be really helpful.

I am looking for a book on building a Propeller tunnel https://www.boatdesign.net/threads/i-am-looking-for-a-book-on-building-a-propeller-tunnel.68248/#post-948853

Edit: BTW, the photos you show are not a tunnel drive, but an OB "pickle-fork" cat. Totally different critter.

Power Catamaran Design Information https://www.boatdesign.net/threads/power-catamaran-design-information.67919/

https://repository.lib.fit.edu/bitstream/handle/11141/798/Asapana, Srikanth, Resistance prediction ....pdf?sequence=1&isAllowed=y

(Remember: you always read papers for the references, often more good is in those)

 

[Maciek]

jehardiman, I know that: "In the upper right there is a search function. It can be really helpful"
Unfortunately, none of the articles you found there and quoted, answer any of my 2 questions.
Attached pictures of 3 boats in my post was found online, searching Google for "tunnel hulls". That's how they call them, not my invention, but you know better...
In the future, if they are questions you have no idea how to answer, stay away from my post.
And now, let's get to the original subject. Looking for practical answer to my specific questions, not doctor's thesis, lol...

 

[BlueBell]

Looking for practical answer to my specific questions

Best advice I can give you, given the very limited info you've provided (and your attitude) is don't design and build your own boat.
So, both your pending questions are easily answered right there, if you can't find a proven design that meets your needs, don't build it.
Simple really. Best of luck. Post pictures of your progress.

Cheers!

 

[gonzo]

I agree. Designing a high performance boat without experience and engineering background will most likely result in failure. However, if you are really resolved to do it, be prepared to build a few failures before you succeed.

 

[jehardiman]

jehardiman, I know that: "In the upper right there is a search function. It can be really helpful"
Unfortunately, none of the articles you found there and quoted, answer any of my 2 questions.
Attached pictures of 3 boats in my post was found online, searching Google for "tunnel hulls". That's how they call them, not my invention, but you know better...
In the future, if they are questions you have no idea how to answer, stay away from my post.
And now, let's get to the original subject. Looking for practical answer to my specific questions, not doctor's thesis, lol...

Yeah, I know that many are intimidated when approaching modern high-speed small boat design because they are unsure on the nomenclature. Often they don't even know the question to ask, or how to ask it. I try to be helpful and point them to the proper papers that will guide future questions, because I know that Naval Architecture is one of the few remaining guild systems...i.e. you have to do your apprenticeship to learn what everything means.

But BlueBell and Gonzo have it right. A lot of people spent a lot of time, money, and hurt in learning how to design a small, high-speed, asymmetrical catamaran. You can take the historical method of just adding horsepower until failure, or you can read the papers of those who studied it. The choice is yours. I will say that most small boats are designed by people who have years of experience in successes and failures. Again, the choice is yours; you can spend years and money doing all the groundwork, or you can study the papers. What you are not going to get on this forum is a manufacturer who has spent hundreds of thousand of dollars to tell you how to cheat them out of their development. Really, the doctor's thesis is cheaper.

 

[Ike]

Some bad news. You're going to run aground on regulations if you insist on putting 130 hp outboard on a 13 to 14 foot boat. At that length the boat, even though a tunnel hull, will probably never meet the definition in the Federal Regulations of a multihull. With people, gear and outboard on board it will be a monohull, that is if you draw a waterline around it, it will be one continuous circle, not two. Monohulls are required to meet the Federal HP regulations. On this type of boat, the max HP would probably be 40 HP. see Safe Horsepower For Small Boats Under 13 feet. https://newboatbuilders.com/pages/hp2.html . Frankly it reminds me of a bunch of boats made in the 80's by half a dozen boat companies. Even Mercury made one which I tried out at their testing facility in Oshkosh WI. Fun boat. It had a Merc 35 if I remember correctly. Went like a scalded cat. Was really freaky in the turns. Anyway if it were a true multihull it would be exempted from the HP regs but to be that you'd have to make it longer and wider.

 

[fallguy]

I don't know of any designs, but building from foam is a general no go. Foam is not a good idea in small boats and a general worse idea in small, high powered boats. The hull to hullsides and hullsides to deck interfaces require special construction.

I won't double down a lot on the hp being too high, but finding a boat that small rated for 130hp will be pretty difficult.

 

[Jimboat]

check out info here:
https://aeromarineresearch.com/

 

[Maciek]

Wow, must be a lot of lawyers on this forum, but I was looking for technical answers for my technical questions, not a legal advice...
Thanks to knowledgeable peoples on the worldwide net, who are not afraid to share the technical knowledge, already got answers to my specific questions. Now looking for the source of the supplies of some materials which I don't have in stock. Fortunately, not very long list...

 

[Jimboat]

Check out here for design questions


Tunnel Boats, Vee Hulls and Performance Powerboat Design https://www.aeromarineresearch.com/