Monohull thruster placement

[Joao Fonseca]

I have decided to go for a challenge myself and build a RC boat (with the help of a friend) for leisure and improve my knowledge about boating.
I have however a simple question yet not intuitive for me... the ideal position for placing 2x Thrusters which will power the boat and make it possible to do the steering.

The boat has a deep V monohull and the hull length is 50" - picture attached.
I have selected these thrusters to power the boat: T200 Thruster

In the attached picture I have set the center of mass in ~30% of the hull's length (yellow line). Distance shown is measured at this location. Seems reasonable to use 2x T200 with the shown distance between them? Or better to place the thrusters in the stern? Any help would be much appreciated as the next step is to drill the holes to place the thrusters support.


Thank you in advance,

João Fonseca

 

[rhomodel]

As I read the spec of the truster it will be a trolling boat, not a speedboat. Is that what you envision?

 

[Steve White]

Probably set it up so you can adjust depth and do a bit of testing. For a start, the top of the thruster pods should be below the bottom of the V to prevent cavitation. And yes, probably trolling speed.

 

[LohringMiller]

Even more fun is a jet drive. See my article at namba.com/content/library/propwash/2021/October/8/ A twin setup running 2 4S power plants might be about the right size. From my smaller boats performance, you should get a really maneuverable, fairly fast boat. Three units would be even better. The drives should be grouped together near the centerline to keep the pickup submerged. See

Lohring Miller

 

[john v]

i would think the drag from those thrusters would be high, a trolling speed for sure

 

[Joao Fonseca]

Many thanks for all of your contribution.
Yes this boat is aimed to be a trolling boat, not a speedboat at all. Just cruising around and do some autonomous missions.

 

[rhomodel]

Then it doesn't matter where you place them, as long as they are submerged. Your boat won't get on plane so I wouldn't worry a lot about the CG as well.

 

[Joao Fonseca]

Yes they will be submerged.
I was worried about maintaining the CG (according to the attached file I found online) since each thruster weights 344g and, for instance, if I place them at the stern probably it will be more challenging to get the CG right. However there are plenty of boat where the thrusters are placed near the stern...

 

[rhomodel]

The CG is important if your boat is in planing phase: the lift of water and air needs to be in balance with gravity so that it glides over water without flipping. But as you will not reach a speed that will push / lift the boat out of the water the CG will not be critical. It will only have an effect how the water line will be. As the boat will be electric you can then easy shift the batteries around to get the desired looks when the boat is idle in water..

 

[Joao Fonseca]

Thanks for the information, makes sense!
However in choppy waters I guess having the CG shifted more forward would have a favourable effect in terms of stability.
My choice of the T200 thruster is related to the fact that is suitable to salty water whereas having a motor inside and a drive shaft outside running a propeller will require much maintenance in the long run.

 

[Steve White]

^^^ Optimal CG would be neutral or slightly aft of neutral, definitely not forward of neutral.

 

[Joao Fonseca]

In terms of stabilization, seems that is preferable to have a fin installed on the hull at the bottom. Do you advise to get a fin installed? Something like this:
https://www.thingiverse.com/thing:2417793

 

[Joao Fonseca]

Any help please?

 

[Christian Lucas]

Hi, the fin belong to the water you are runing the boat. With lots of debris it is okay in a pool you need no.
One of the fastes monohull modelboats has it´s surcaface propellers mount far outside like you want to place the truster. This give a lot of stabilisation against rolling in axis. But it need synchron running propellers for smooth straight running . This twin propeller driven boat was very efficancy as it reached close 100 mph with much less power than the record setting monohull with a single in the mittle placed propeller. 1/3 less close speed 98 mph to 100 mph of the record boat. The last record boat has close in the middle placed twin corntra running propellers.

Happy Amps Christian

 

[Joao Fonseca]

Many thanks for the information, make sense!
Thanks for sharing the pics!

 

[Joao Fonseca]

Well unfortunately seems that my friend can't finish this boat (due to high priorities in his life) project so I have to look elsewhere to get a boat with potential to do some autonomous missions on the sea.
I've searched the web for ready available boats (1m+ long) but the prices are way too high and I'd need to add the cost for 2x thrusters...
Is there anyone who have better alternatives or who can build me a suitable platform?

Attached is one candidate that I'm looking for.

Thank you!

 

[RobertDoak]

Why not just make a pontoon style boat with a flat deck....super cheap and simple..