(Question) Help me, please...(recommend waterjet and motors)

Hello dear.
It's my first time here in boatdesign.net.
I'm a really novice to boat making. And I really need expert's help.
I am going to make the following boat.

- Length : 2 m
- Hull shape : catamaran
- Hull material : FRP
- Propulsion system : Waterjet with electric motor
- Control method : Remote Control
- Speed : about 30km/h
- Usage of the boat : for Science experiment at inland water

I would very much appreciate to recommend Waterjet and motors that are suitable for making the described boats.

Thank you.

 

I think you should choose a small waterjet that fits inside the hulls. Well, I suppose you'll put one on each hull.

 

Thank you !

Thank you very much for your recommendation.
I'll check them.

 

vicmouse, have you estimated the boat resistance for the desired speed ?

 

Ah... Not yet...
I didn't think about it...
Do I need to consider something?

 

Of course, you are very novice and I do not want you to be offended but your words make me doubt that you are prepared to carry out "Science experiments". What is the real purpose of your project?

 

Welcome to the forum.

Why a convoluted configuration like this? Why not a more conventional approuch, so you can increase your opportunities for success? Simply put, a 2m cat isn't going to hold up much, unless quite distorted hull shapes are employed, defeating the advantages of a cat hull configuration. Additionally, electric jets aren't terribly efficient and a lot of energy losses can be expected, particularly at your targeted speeds, so why this choice, compaired to something much more efficient and appropriate for the speed range?

Can you post a sketch or two of your cat with a GA?

 

Vicmouse, as PAR suggests you need to know resistance to work out how much power you need to install on your model. Having said that, with a model it is easier to select the right amount of power based on trial and error.

TANSL on a side note..why the patronizing tone..a science project can be exactly what is required to give a flavour of ship design!

 

I did not mean to mock anyone at any time. It just amazes me that someone with a scientific mindset starts a project and starts asking for help with such poorly worked out ideas about what he wants or needs to do.
How can you ask for the type of motor if you do not have an idea, even if approximate, of the power needed ?. How can a scientific mind ask: "Do I need to consider something"? Frankly, it seemed patronizing to me.
I will be happy to help, within my possibilities, to vicmouse but I think he should elaborate his SOR a bit more, or consider several things, before asking for help. That is my opinion and I express it, not to annoy, but so that vicmouse can advance more and better in his project. If we knew what his scientific project is about, perhaps we could give him more accurate advice. Don't you think so?.

 

You make a lot of assumption, TANSL. What if Vicmouse does not have a scientific mindset at all and is here because they want some basic advise. If you feel patronised by this and aren't going to help, why comment at all.

 

NavArc..., you also make too many assumptions, for example, you're assuming I do not want to help and that's not true. But how many things should we assume or suppose to be able to help? Do you really think that with the data we have we could help?

 

Welcome, vicmouse.

We are very curious about the intended purpose of the science experiment.

You will, I believe, get more range and speed from gasoline powered jets than you will from electric.

Questions:

1. How much will the boat while holding the science experiment equipment weigh?

2. Will the boat have a live crew or will it be controlled remotely?

3. How far does the boat have to travel to accomplish the experiment?

4. Do you think you can reasonably expect a boat 2 meters long to reach speeds approaching 30 km/h?

5. Is that speed necessary to accomplish the experiment?