What type of 4-8 metre hull for speed around 30-35 knots in calm water?

[nqb12179]

I am looking for a hull series which is suit for calm sea.

Thank you

 

[nqb12179]

What type of hull is suit for speed around 30-35 knots in calm water?

How do you know what type of hull is the best and suit for the range of speed?
1. Displacement
2. Semi-displacement
3. Planning

 

[tom28571]

You have some wishes that are incompatible. Any small monohull that is going anything near 20mph is planing. What are you planning? Semi displacement speeds depend on length among other things but such a hull is not all suitable for what you are asking.

 

[nqb12179]

Thank you so much.
If I reduce the speed of the small ship to around 20knots and length is 8 m.
Which type of hull and any series will suggest?

 

[Mr Efficiency]

In the absence of further information, you choose a planing hull for that speed range. And needing only to operate on calm water ( not even the wakes of other boats ?) makes it that much easier to satisfy that kind of cruising speed requirement.

 

[PAR]

This thread and the other thread have way too little information, about your desires and needs. There's no such thing as a semi plane boat doing 30 knots, except possibly a Nimitz class aircraft carrier (actually not). Maybe it would be better to better describe what you're looking to do, besides 30 knots in a calm sea. The more information about you needs, the better you can refine the various designs available. Simply put, there's no "ideal" or "best" boat - just ones that fit a difficult to address set of decisions, in regard to several (read many) often conflicting factors.

 

[nqb12179]

Actually, my desire is to design a motor boat which is for four to five people.
The range of speed will be more than 20.
That why I think 8m would be comfortably enough.

 

[Mr Efficiency]

Speed is now down to 20 knots ? I like it, you are flexible !
I think you need to speak about what the purpose of the boat is, to get any meaningful input from these nice people.

 

[nqb12179]

It is gonna be my family boat where the stability supposes to be sufficient enough and the speed is not too low. We have five people. The hull material will be fibreglass. There is not gonna be a large amount of superstructure weight.

 

[PAR]

Save a lot of headache and buy a set of plans in the size and general hull configuration you need, then add the aesthetic and styling touches to make it yours. Based on your questions, you have an awful lot to learn about yacht design and engineering why bother with this, when you can simply make a proven design "yours" for much less effort and the assurance it'll float with the decks facing up on launch day. Lastly, a 24' boat isn't a small project, frankly as a home built, it's a fairly large build. Many hundreds of man hours to complete, not to mention equipment and propulsion systems. It would be much faster to find a used boat, strip it back and add the styling clues and equipment you want. You'll be on the water in a fraction of the time and money, with a custom boat. Simply, a 24' yacht wouldn't be a reasonable first project and it's a lot more work then might seem at the moment. This isn't to say it can't be done, as it has, but it's very rare.

 

[SukiSolo]

You could do a lot worse than getting hold of one of these beasts! Depending upon intended use. The f/glass should still be pretty good on a fair few of them despite the age.

http://www.broads.org.uk/wiki/index...aph&photo=K1_5472&style=RIL&returnpath=notset

Those hulls make little wash at low speed so ideal on rivers and smooth water but can motor when pushed. Not sure what the top speed is but I have witnessed them chasing planing powerboats on the Thames, no slouch.

A somewhat period shot of one planing.

http://www.classicboat.co.uk/buying-and-chartering/bushells/

 

[TANSL]

Perhaps a multihull, swath, hydrofoil?. Not easy to give advice knowing only the speed.

 

[rxcomposite]

Speed is relative. Perhaps a displacement hull for a VLCC, a semi displacement hull cruise ship, or a kitchen table for planing.

 

[NavalSArtichoke]

Speed is relative. Perhaps a displacement hull for a VLCC, a semi displacement hull cruise ship, or a kitchen table for planing.

Not many 30-knot VLCCs, and even cruise ships are cutting back from liner speeds to save on fuel costs. Still, speed is an important factor in setting the other factors in a ship design, particularly length, but it's not the only factor.

 

[TANSL]

I can not imagine that the length of a vessel is a direct function of speed. Of course, for the same displacement, a greater relationship L/B may result in a faster boat but I think that, in general, the length of the boat is deduced by many other parameters.