autonomous surface vessel

Hi, I'm Leonardo, a researcher from Argentina, working on an ASV design.
I'm thinking on a catamaran design with a hull length of 750mm.
The propulsion will be a T-100 thruster from bluerobotics.
I have drawing some stuff on solidworks and need some advice.
I've attached a pdf drawing and igs file (I can upload solidworks parts/assembly to google drive if it help)

Is there someone than can help me with this design?

 

Welcome to the forum. What kind of help and to what extent do you need?

 

I need some advice about dimensions/shape in general. Maybe I'm making some obvious mistake...
I would like to add a keel in front of the motor thruster, something like the attached drawing. Is that Ok? what are recommended dimensions?
I know that there would be some calculus in order to get the best shape/dimension but maybe you can give me some advice.

Thank

 

I don't know what that advice you ask for should be like because I don't know what your knowledge is. An obvious tip: you have to do all the naval architecture calculations but before that, a single drawing does not indicate anything, you must clearly and in detail establish the requirements that the artifact must meet.
I think that, with these shapes, you are going to need a much larger keel because the turning effect of such a large propeller will make the entire hull turn in the opposite direction around its longitudinal axis.
Edited July,05,2021 : The second paragraph does not make sense when it comes to a catamaran. I didn't realize it when reading the first post.

 

This ASV will be use in shallow water, like a lake or a small river. The speed needs to be in the order of 1 to 3 mts/sec. As you can see (dimensions are in mm) it is a very small vessel. It's for research purpose. I just need to have a small vessel with easy "controllavility"
My work will be to coordinate the trajectory of the vessel with a quad rotor, like this simulation:


Your tip about the keel is the kind of tip I have looking for. Do you take into account that my design is a catamaran? I mean I will have 2 hull, 400mm between each other.

What do you think about thruster dimensions vs the with and height of the stern?
is it ok of having the thruster behind the stern? I've seen some design like mine and others with the thrusters under the hull, about 100mm from the stern.

Thank!

 

First of all, you need to establish the weight of the those items you wish to use, and then the weight of the hull, for the size and duty you are proposing.
Only then will you know what size hull is possible.

 

The weight of the payload (electronics, battery, thrusters...) is 10 kg. I'm thinking on 3d print the hull and then use fiberglass and epoxy resin to waterproof the hull. 3d print software estimate 1 kg for current design. I think I will need 1 kg of fiberglass/resin so, 2kg each hull. That gives 14 Kg of weight. The volume of each hull is around 9 dm3. So, I have only 4 kg left with current design?

 

Ok..so 14kg.
But how do you arrive at 9dm3?

The waterline length will be "roughly" 700mm


The draft "roughly" = 50mm
And beam = 120mm.

So, the vol = L.B.T . Cb

The CB will be circa 0.65, looking at the shape of your hull.

So, Vol = 0.70 x 0.12 x 0.05 x 0.65 = 0.00273 m3 x density = .00273 x 1025 = 2.8kg of displacement.
Two hulls = x 2 = 5.6 kg. Total weight = 14kg..

It'll sink!

 

My opinion is blue robotics may not be great for a river situation. It is an open flooded motor and will inhale River weeds, algae, and debris into the fast spinning Armature plus the water friction resistance with the Armature spinning fast in water means that it is not an efficient design, compared to a sealed motor or a motor above water. You might need much more power than expected to get 3 m per second speed (around 7 knots?) if the hull speed concept is a consideration. If there is operation near the shoreline where there are shallow spots or shallow rocks, a keel could hang the boat up, so a different method of stabilization may be necessary? A tiny short catamaran design is hard to control precisely in river currents because the individual pontoons present unequal exposure to the water flowing by each hull. A search under large toy model boats might turn up some ideas, otherwise search for small autonomous boat designs?

Hope this helps.

 

The TO maybe was calculating a fully immersed brick LOA*BOA*Depth.
7.5 dm * 1.2 dm * 1.0 dm = 9.0 dm³

 

Yes, you are right, this design will not work on an open river. It will be use on (I'm not sure what english word) shallow water, like a lake or a "small river" (stream?). I've already get 1mt/sec with a bigger design:

maybe with a little boat I could get 2m/sec? The T100 was too little for that boat, so I would like to design a smaller one and buy two T200 truster for my other ASV. As you can see in the video, the water is "so calm". The stream (?) is bigger near the river (this stream is an "arm" of Parana river (tributary stream?). BTW I'm sorry, I'm not familiarized with english terminology about this topic.

 

yes, I've do that. My mistake!

 

Ok, this (an the others comments too) are what I was looking for! thank you very much!

I will check my weight again and will re-dimension the hull accordingly with your equations.

Now, what do you think about truster size and mounting position? and what about the keel? is it necessary? will it help on "controllability"?
Could you explain what "The CB will be circa 0.65" is it?

I'm an electronic engineer so any help from you will be much appreciate.

 

The Cb (block coefficient) is the fraction of hull volume in relation to the block volume of a surrounding rectangular block. Notice: only the immersed parts of hull and block count.
Coeficientes de forma - Wikipedia, la enciclopedia libre https://es.wikipedia.org/wiki/Coeficientes_de_forma

 

Thanks for the interesting video! Is the boat in your video controlling itself using GPS or sensors of some kind, or is a person controlling it? How does the battery get recharged when it is empty? It may be possible to go 2 meters per second, but only for a very small distance or time. An air propeller may be the best way for propulsion, because of the weeds and shallow water.