Finding a suitable model

[Morten BertheussenParticipant @mortenbertheussen92508]

Hi my name is Morten Bertheussen and I am currently studying to become an automation Engineer. For my bachelor assignment, my groups are going to make an indoor system for dynamic positioning. For this project, we will need a boat model, preferably one with installed thrusters, but I cannot seem to find a suitable one online. I was hoping maybe someone in this community could help.

The model should preferably look like a platform supply vessel, but this is not mandatory. What is mandatory though is the ability to control the vessel on multiple axes, which means a minimum requirement of a bow thruster and a main propulsion system, but the more the merrier.

The model does not need a control system since were going to make this from scratch, but we won’t exclude because of this.

PS: The tank the boat is going to be used in is 4m*1.5m long so the try and keep the size of the vessel as small as possible.

Best regards

Morten Bertheussen

[Morten BertheussenParticipant @mortenbertheussen92508]

Dynamic positioning system

[ashley needhamParticipant @ashleyneedham69188]

Morten. That is a difficult brief. You may be better off making a very simple semi-scale model, as it is not the quality of the model that is on display, but your systems. I know you would want to simply buy one, but for the purposes of your assignment, having a hull like this would be so much easier. Making something suitable should not require any effort at all. A hull could be made from 4 pieces, 3 bits for a stepped deck and 5 bits for a box cabin. A few fittings, purchased online, just stuck on after painting would furnish you with all you want.

​By making a very simple stand-off scale type with a flat bottom, you will have loads of room to fit your gear, and as you say, the more the merrier as far as propulsion systems go, and there will be no stability issues or anything else to contend with. The entire deck can be made to lift off for maximum access, as water tightness will not be an issue on a test tank. Fitting any drive system would be childs play, without having to contend with limited access or making holes in cambered and curved surfaces. Depends how much you want to spend but all sorts of goodies are available, including Voith Schneider propulsion units… one at either end of the hull would furnish you with the most comprehensive and sophisticated arrangement to demonstrate hydrodynamic positioning. Cut a round hole in the bottom of your flat hull bottom and glue in…..then there are Schottel units, very easy to fit, cheaper….

​Likely someone could knock up a simple drawing for this on a CAD program, or indeed, a fag packet.

​Ashley

​Ashley

[Morten BertheussenParticipant @mortenbertheussen92508]

I just want to inform you that I have read you response and will formulate an answer over the weekend. I’m a little bogged down right now with creating a spreadsheet. Thanks for the reply and I will come back to you later.

Best regards

Morten Berteussen

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by ashley needham on 22/10/2016 11:41:29:

Morten. That is a difficult brief. You may be better off making a very simple semi-scale model, as it is not the quality of the model that is on display, but your systems. I know you would want to simply buy one, but for the purposes of your assignment, having a hull like this would be so much easier. Making something suitable should not require any effort at all. A hull could be made from 4 pieces, 3 bits for a stepped deck and 5 bits for a box cabin. A few fittings, purchased online, just stuck on after painting would furnish you with all you want.

​By making a very simple stand-off scale type with a flat bottom, you will have loads of room to fit your gear, and as you say, the more the merrier as far as propulsion systems go, and there will be no stability issues or anything else to contend with. The entire deck can be made to lift off for maximum access, as water tightness will not be an issue on a test tank. Fitting any drive system would be childs play, without having to contend with limited access or making holes in cambered and curved surfaces. Depends how much you want to spend but all sorts of goodies are available, including Voith Schneider propulsion units… one at either end of the hull would furnish you with the most comprehensive and sophisticated arrangement to demonstrate hydrodynamic positioning. Cut a round hole in the bottom of your flat hull bottom and glue in…..then there are Schottel units, very easy to fit, cheaper….

​Likely someone could knock up a simple drawing for this on a CAD program, or indeed, a fag packet.

​Ashley

​Ashley

 

In fact, a rectangular box would work perfectly well – I assume there is no need for the boat to travel through waves at speed?

For propulsion, you might like to consider small brushless motors running underwater. This is not an ideal way to treat motors, but they will survive quite well if immersed temporarily and dried afterwards. Things like this are quite cheap, and could simply be mounted on a strut going down from each corner of the box. **LINK**

 

Another possibility is to use pumped water-jets – which means you don't need to buy propellers or any other gear! Simply mount several small aquarium submersible pumps under the box and point each one in a different direction. Here are some cheap ones: **LINK**

I assume that most of your control electronics and power supply will not be in the 'boat' but will be at the side of the tank feeding through umbilical cables… 

Edited By Dodgy Geezer on 22/10/2016 17:41:54

[Paul TParticipant @pault84577]

Morten

The solution to your problem is fairly straightforward as a fishing bait boat would, with the addition of a few small water jets make a very stable and highly responsive platform.

However, and as you probably know any dynamic positioning system depends heavily upon the shape, size and weight of the machine in question and the conditions under which the machine is to operate so any answer that we supply will ultimately be akin to shooting in the dark.

Have you tried looking at the systems being used in oil/gas exploration or even some of the experimental naval projects?

Paul

Edited By Paul T on 22/10/2016 18:42:46

[Morten BertheussenParticipant @mortenbertheussen92508]

Posted by Dodgy Geezer on 22/10/2016 16:52:09:

Posted by ashley needham on 22/10/2016 11:41:29:

Morten. That is a difficult brief. You may be better off making a very simple semi-scale model, as it is not the quality of the model that is on display, but your systems. I know you would want to simply buy one, but for the purposes of your assignment, having a hull like this would be so much easier. Making something suitable should not require any effort at all. A hull could be made from 4 pieces, 3 bits for a stepped deck and 5 bits for a box cabin. A few fittings, purchased online, just stuck on after painting would furnish you with all you want.

​By making a very simple stand-off scale type with a flat bottom, you will have loads of room to fit your gear, and as you say, the more the merrier as far as propulsion systems go, and there will be no stability issues or anything else to contend with. The entire deck can be made to lift off for maximum access, as water tightness will not be an issue on a test tank. Fitting any drive system would be childs play, without having to contend with limited access or making holes in cambered and curved surfaces. Depends how much you want to spend but all sorts of goodies are available, including Voith Schneider propulsion units… one at either end of the hull would furnish you with the most comprehensive and sophisticated arrangement to demonstrate hydrodynamic positioning. Cut a round hole in the bottom of your flat hull bottom and glue in…..then there are Schottel units, very easy to fit, cheaper….

​Likely someone could knock up a simple drawing for this on a CAD program, or indeed, a fag packet.

​Ashley

​Ashley

In fact, a rectangular box would work perfectly well – I assume there is no need for the boat to travel through waves at speed?

For propulsion, you might like to consider small brushless motors running underwater. This is not an ideal way to treat motors, but they will survive quite well if immersed temporarily and dried afterwards. Things like this are quite cheap, and could simply be mounted on a strut going down from each corner of the box. **LINK**

Another possibility is to use pumped water-jets – which means you don't need to buy propellers or any other gear! Simply mount several small aquarium submersible pumps under the box and point each one in a different direction. Here are some cheap ones: **LINK**

I assume that most of your control electronics and power supply will not be in the 'boat' but will be at the side of the tank feeding through umbilical cables…

Edited By Dodgy Geezer on 22/10/2016 17:41:54

The minimum requirements for bachelor to be considered a success is:

• Buy or design a boat model with enough thrusters to complete the dynamic positioning.
• Design an indoor positioning system which will substitute GPS.
• Create an IMO DP class 1 system for dynamical positioning.

Although the assignment doesn’t explicitly exclude using a box as a boat, the idea is to use this project for educational purposes, both for automation engineers and nautical engineers. For that purpose a boat with a real hull is preferable. On a side note we plan on letting the user control the boat from point A to point B using coordinates or a joystick so the boat needs to be responsive which I cannot imagine a square box is.

Keep in mind that we are not alone on this project. The university has both resources and people with expertise to us out when our knowledge is not enough.

TL;DR

We need help finding a boat model with enough thrusters to dynamically position and move the boat inside a grid. Money is not unlimited but the budget is quite extensive.

[Morten BertheussenParticipant @mortenbertheussen92508]

Posted by Paul T on 22/10/2016 18:22:06:

Morten

The solution to your problem is fairly straightforward as a fishing bait boat would, with the addition of a few small water jets make a very stable and highly responsive platform.

However, and as you probably know any dynamic positioning system depends heavily upon the shape, size and weight of the machine in question and the conditions under which the machine is to operate so any answer that we supply will ultimately be akin to shooting in the dark.

Have you tried looking at the systems being used in oil/gas exploration or even some of the experimental naval projects?

Paul

Edited By Paul T on 22/10/2016 18:42:46

The group i am in already have some knowledge about DP from an operators perspective. We do know about the math involved and we know it's quite extensive, perhaps even beyond our capability. If so, I imagine we can rely on help from the university considering this assignment in reality goes beyond the scope of automation engineers.

That said, we plan on contacting Kongsberg (the company that created dynamic positioning) when we have accumulated enough questions.

[Colin BishopModerator @colinbishop34627]

I don't think you are likely to 'find' a boat with those characteristics, you will have to make one to some extent. You could start off with a readymade hull of approximately the type you are looking for. These usually come with plans from which you could make a simplified superstructure. You could then fit a variety of propulsion units from steerable korts to Voith Scneiders plus bow thrusters etc. as you wish. If the budget stretches to it you could purchase more than one hull and try different combinations. Some possible starting points are listed below.

Colin

**LINK**

**LINK**

**LINK**

**LINK**

[ashley needhamParticipant @ashleyneedham69188]

This is a bit of a chicken/egg situation.

​Some facts need to be established first before any decisions can be made, first amongst them is the type and number of drive/thrust units to be provided and if they are to be representative of current full size vessels. Having decided that, then the size of the boat needs to be defined. I know the pool is small, but all that is required is some shifting about and standing stationary, so the boat could be a bit larger than at first assumed.

​There will, having just said it is a small pool, be considerable currents set in motion by using all these thrusters, and it may be found that the control system may not cope with these unrepresentative currents.

​Something like this…would be so easy to simplify and make, and look stunning in the yellow colour with decal-detail added, really easy.. Ashley

https://www.bing.com/images/search?q=oil+rig+support+vessels&view=detailv2&&id=0F9AB8B63E841172BE946680FA81A22F0DB9CA7F&selectedIndex=86&ccid=HPAaIIx2&simid=608021375789830022&thid=OIP.M1cf01a208c76c3dd952248f8afa201f0o0&ajaxhist=0

[Paul TParticipant @pault84577]

I've been thinking about this and to me this shape of hull is ideal for dynamic positioning, take the guy and chair off and you have a perfect circular hull. Add four water jets at equidistant points around the hull and you have a great test bed for a prototype dynamic positioning system.

Edited By Paul T on 23/10/2016 18:37:59

[Dodgy Geezer 1Participant @dodgygeezer1]

It is often a good idea when considering engineering projects to put some ball-park data down which will drive you towards the choices you are going to have to make.

If we have a fixed tank of 12×1.5m and you want to manoeuvre a hull in this, the maximum size for one which rotates on its own axis is going to be about 1×0.25m. One which actually turns is going to be about 0.5×0.15m.

From this we can estimate that the hull is going to displace somewhere between 20kg and 2kg. This gives you your first decision point – what weight is the onboard kit going to be, and hence what power do you need the thrusters to be? If weight is going to be a problem you have the option of having the batteries out of the boat and power fed via an umbilical, but I suspect that this will interfere with the movement of the hull a bit. I suggest that lighter is better…

I (well, I would, wouldn't I!) am inclined to suggest this hull – a Thames Lighter. **LINK** Simple to make, a bit more sophisticated than a box, but readily variable to any size. Here are the plans http://eezebilt.tk/lighterplan.pdf – double the size and make it in ply will result in a 0.75m hull able to carry heavy weights.

I would then buy 7 of these cheap submersible pumps  **LINK** and mount them on the bottom of the hull (which is conveniently flat.

Two at the back for propulsion, one at the front for reverse. Two at each side pointing outwards, front and back, for sideways motion. There is no need for any rudder or steerable thruster, or any rotating part going through the hull. The pumps are entirely self-enclosed, so there is no need to plumb them in – they just sit under the water and produce thrust when activated.

Two at the back plus one of the front ones will produce a forward turn. two opposite sides, front and back, makes the ship rotate on its own axis. Two side ones on the same side moves it bodily sideways.

12v of Nimh batteries in the hull would provide adequate power, and would not be very heavy. I estimate that hull complete with propulsion at 1kg, giving you at least 2kg for onboard equipment, so long as it is distributed suitably. It won't be very fast, which is a benefit in a limited size tank, though you could always add more thrusters at the back to speed it up. It would be quite draggy underwater, which again is an advantage for a hull which needs to keep position.

This approach lets you add, remove or alter the thrust position and angle of any of the thrusters, and compare different underwater configurations quite easily, which might be useful for experiment….

 

Edited By Dodgy Geezer on 23/10/2016 23:31:55

[ashley needhamParticipant @ashleyneedham69188]

I think collectively we have given a good range of possibilities to fit the bill.
​It is up to the project team to sift through this and narrow down the choices and/or provide more definite criteria for the build.

Ashley

[Morten BertheussenParticipant @mortenbertheussen92508]

All your input has been valuable for us and we want to thank all of you for spending your personal time on us. We have a lot of options to consider and therefore, we will take a break from this thread to consider our options. We will come back later to either update you on our progress or perhaps ask a few more questions.

Thanks for your time and we’ll see you later. =)

Best regards

Morten Bertheussen

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