I'll start the ball rolling by adding some preliminary thoughts as I am sure there will be more ideas to come.

First up it is important to realise that a rudder works in exactly the same way as an aircraft propeller by generating 'lift' at the expense of 'drag'. The shape and design of your rudder will be dependant on the use of your model and consequently whether manoeuvrability or speed is more important for you. At one extreme a speedboat will sacrifice manoeuvrability and reduce drag by having a relatively small rudder whereas a tug will sacrifice speed for the best of manoeuvrability by having a large rudder. Have a look at typical speedboat models such as a Club 500 here at:

club500slipway.com

and compare that with a model tug such as a Mobile Marine Models steam tug or a Model Slipway Envoy Class.

Your next main concern is placement. Looking at your hull you basically have two options, you can either have your prop shaft coming out of the bottom of the hull, with the rudder mounted on the bottom directly behind it, as per the Club 500 arrangement, or you could have the propeller mounted on the transom, again with the rudder mounted behind it. Unfortunately with your flat wide based transom you will have a great deal of difficulty in getting a good flow of water around the rudder so really your only options are either to have the tube exit the hull through the keel and the rudder mounted vertically behind it or an outboard on the transom with the propeller extending below the transom. I would use the Club 500 arrangement for guidance. Offset rudders are only really used in high performance boats, in your case you need the most effect so the rudder may be best mounted directly behind the propeller in the best flow of water. If you use a flat brass rudder, as used by the Club 500, you will have minimum drag and mounting it directly behind the propeller will give you maximum effect.

You haven't said what the dimensions of your model are but taking the proportions of the Club 500 and scaling them up or down should give you an idea of what size and shape of rudder you need. To meet criteria A) you do need performance as well as endurance so you should be looking for as light a construction as possible combined with the 'V' hull. If your model is fairly close to the size of a Club 500 you might want to consider buying the motor, shafting and running gear as well as the rudder unit from the manufacturer.

Anyway just some ideas to start the thinking off. Good luck with the competition!

Whilst some idea of size can be determined from the photographs you need to provide more accurate information i.e. length, width and depth of the boat before anyone can advise you.

I assume that the frames and foam are just temporary to form the hull? Otherwise you won't have enough space for all the gear and battery etc! It will be beneficial of course to have some framing to stiffen the hull, mount the deck and fix the aforementioned gear.

Have you tried the hull in water yet with the 2kg. load in place. Be interested to see how it sits in the water, both loaded and unloaded!

Chris

Edit: other posts made by others whilst making mine which have covered some of what I have said.

Edited By Chris Fellows on 21/01/2020 23:27:16

The flat transom will kill any performance* unless the boat goes fast enough to break the water flow around it. Any propeller would need to be below the hull, along with its rudder. If the prop was mounted behind the transom, it would never get clean water flow.

Racing boats generally have an offset rudder because they are only intended to turn one way. A rudder generally sits in the waterflow caused by the prop and redirects it, it doesn't need to be any bigger than the flow.

Any boat weight detracts fromits payload. I think most boat modellers would conside 5 or 6 of the frames to be surplus to requirements, although without knowing the size of the hull, it is guesswork. Guessing that a 2Kg payload + weight of whatever holds it will remove any likelyhood of going fast enough to break the transom waterflow. Probably mess with any hopes of stability, as well.

*both speed and efficiency (ie run time) will suffer.

Hi Joe

I'm intrigued by your phrase "fully autonomous boat". Presumably, this means a 'pre-programmed' motor run with rudder inputs at the predetermined turning points (approx. 90 degrees) on the lake ?

Whilst you're solving your propulsion /steering methods, it would be a good idea to get a team member up to speed on control systems eg any radio control experience would be useful….of course, you can't use radio as such but you could use Arduino (or, another microcontroller) to take the place of the radio transmitter and receiver. Arduinos can drive the rudder servo and, the motor's speed controller, and they are cheap !

You don't say if you're allowed to use GPS ? If so, this could tell the Arduino when to change course etc. You can write some simple sketches (programs) to achieve this using the 'C' programming language.

I think you'd better allow plenty of time for testing and fine tuning !!

Hope this helps,

Dave

Hi again Joe

Get your 'mechatronics' person to have a look at Arduino Starter Kits – I think it will have a lot of the bits you'll need for the fully automated bit : eg micro servo, stepper motor, breadboards, jumper leads etc. Mine cost around £29 – good value and much quicker than buying all the parts separately ! It comes with a tutorial on CD as well.

As you have 'wi-fi' coverage you could use a mobile phone for a GPS signal, although, a dedicated chip (eg an Arduino "Shield&quot would probably be lighter, more compact and easier to program.

In the Arduino IDE (development environment) he /she will find lots of pre-written code examples. You could probably pluck these out as they are and 'tailor' them for your application. I should think some of the "robotics" code (turn left /turn right etc) would give a starting point.

Good luck,

Dave