Help with nauticmodel project

Hello;

I'm a student of mechanical engineering and my classmates and I would like some help to project and manufacture a nauticmodel for my college.

We must use an engine from an aeromodel with 1,5 HP and 17000 RPM and produce all other parts like the propeller, the hull and a refrigeration sistem for the engine.

I think I can find a lot of information in this forum, but if you could help me indicating internet links, books or giving any kind of information, I'll be very grateful.

One thing wich we are trying to understand now is how can we determine the maximum velocity of the boat and the consumption of fuel. We're trying to determine the shape of propeller too (with a book about fluid mechanics).

So, sorry for boring you and thanks for your attention.
Thiago

 

Nauticmodel

You might like to read the section on model propellers in my web site at www.ivorbittle.co.uk . You might also find my on-going text book of interest.

Ivor Bittle

 

Thankyou very much Ivor!

I did a fast look in your website and I think has a lot of information there.

I'll read it carefuly soon.

Thanks;
Thiago

 

You can use the linked web site to determine the drag on the hull given that the boat should easily plane if it is only a scale model:
http://illustrations.marin.ntnu.no/hydrodynamics/resistance/planing/index.html
If it is intended to carry a person then it will not plane and you will need to do drag analysis for a displacement craft. Michlet is best for this.

For the prop design, you will get a good result using JavaProp:
http://www.mh-aerotools.de/airfoils/javaprop.htm
You will need to set the options page to suit water parameters. You need to understand a little about what you are doing to get a practical result. Just ask more questions on detail you do not comprehend as they come up.

Rick W

 

Thanks Rick!

It's a small boat. We must carry just an object with 2kg.

We are trying to project the boat to reach the greater velocity than possible to win a competition.

We need to know the velocity and fuel consuption to specify the volume of the fuel tank.

I'll study the websites wich you send me to make more specific questions in this forum.

Thanks again;
Thiago

 

The boat will easily plane.

The next thing is to get the weight of the motor.

You need to know how much the motor burns at full throttle and you need to know the distance or time of operation.

The process is iterative.

You could start with a boat weight of 10kg. The speed will be impressive if the boat is properly designed.

Rick W

 

Hello again;

We had to stop with the project a little, but now we are working again.

I understood (more or less) the JavaProp and we have a good structure in the University with softwares and machines, then I think we can do a enough propeller for our job.

I would like some help to understand the website wich Rick sent to me (http://illustrations.marin.ntnu.no//hydrodynamics/resistance/planing/index.html).

These are the inputs of website:

Mdepl: is it the weigth of boat???
lcg: ok, I understood.
vcg: ok.
b: beam of planing surface (what it means???)
beta: ok.
eps: Is it the angle between the water and the boat? How can I calculate it?
a: Is it equal of vcg-[b/4(tang beta)]???
f: ok.

I will put some pictures of our project here soon.

Thanks a lot for your help;
Thiago

 

Thiago
If you place your curser over the green word figure on the sheet it shows a sketch of the boat with these details drawn on it.

Rick W

 

Thanks for your attention Rick.

I saw the sketch but I don't know how I can find the value of "eps".

Furthermore, I'm not understanding the meaning of "beam of planing surface (b)". My English is not so good...

b/2 Is the dimension shown in the picture below? Then, I just have to multiply by 2 to find b?



Thanks again;

Thiago

 

"eps" is the vertical angle of the line of thrust relative to the keel line. It will be the angle of inclination of you shaft. For the best propeller efficiency it should be only small. From a boat perspective it makes very little difference.

The b is the horizontal measurement across the width of the planing surface. The measurement you have shown would only be correct if the bottom of the hull is flat.

Rick W

 

Thank you very much Rick!

Now I understood.

Without your help with the propeller and the hull our job would be much harder.

I will put some pictures of our project soon (it is a very simple project, of course).

Thanks again;
Thiago