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First Things First

Lets start with a little background information on the boat itself. A few years ago, Brian who owns and runs Mobile Marine Models was approached with a challenge. I draw your attention to those marine training places where people are taught to drive supertankers and the like? Basically is a scale model of the tanker and accommodates two men and weighs roughly 5 tons. Well, a certain training company wanted a fleet of scale tugs with enough power to shove these tankers around, like in the real world...

The FT-X was born and is one of these products that isnt really advertised as its more for commercial use given its an absolute monster. I am aware of a fisherman up in Scotland who uses two of these things to trawl a decent size net on a small scale fishing operation!

A 1/24th scale tug, certainly of this size is generally unheard of unless it was completely scratch built. The only exception I know of is my Model Slipway tug, which is quite small and is sadly no longer in production.

The total ballast needed in this boat so im told, is roughly 50KG all in. That proves a huge engineering task in itself moving the thing around - albeit half of the weight could be removed with batteries.

 

Starting The Build

The bottle on the rear deck or seen in the photos is a big 5 Litre one to show size comparison.

The bow thruster itself has a diameter of 30mm. These were installed during construction of the boat by MMM.

These are the drive motors. The are best run on 24volts and appear to be similar to ones used on mobility scooters. Plenty of torque which is what a tug needs.

Some of the the other running gear. The prop shafts themselves are a solid 8mm (which again is unusual - given the biggest is normally 6mm) all made by MMM. The kort nozzles are 90mm diameter.

The props are casted by the prop shop and are a small fortune (£100 for the pair). Prop shop props are generally known as the best on the market.

The first job was to install the running gear. An age was spent carefully marking out where holes should be made. You cant really rely on the shape of the hull itself as for example, on the inside, the thickness varies only slightly but could throw the kort out - hence the little jig assembled to keep both korts on the same vertical and horizontal plane so to speak..

The assembly was glued into place with 2 hour epoxy and left to set overnight. The kort assembly was then fibre glassed into place for extra security. At this stage they would have to be cut out of they needed to be removed - measure lots of times and cut once!

Couplings are needed to connect the shaft of the motor to the prop shaft which turns the prop. Getting 8mm couplings in the model world is seemingly impossible, given the largest is 6mm for the standard m6 shafts which you see on large lifeboats etc. MMM make their own safety couplings which is essentially a piece of hose, some turned brass and these are connected with 1mm dia brass rod. The idea is that if the prop were to become fowled, then the coupling would break instead of the motor receiving a lot of stall currant. I absolutely cannot stand them, however its proven very difficult to get hold of commercially available ones and so these will have to do.

The FT-X really is best used with 90mm korts, however the bottom of the nozzle sticks well below the keel. This doesn't make sense to me and whilst the korts would need a big knock to hurt them, I felt it best to try and eliminate the issue by deepening the keel. This was done by rough cutting some 3/4" solid oak into shape and then scribing the outline. This was then cut down further and fettled with a sander. Fibre glass filler was used to secure the oak to the keel and once set, normal car body filler was used to fill in the gaps to achieve a nice finish.

And finally all smooth with a quick coat of halfords primer to show any hi/low areas.

Ok so this is where things start to get serious. Annoyingly I feel the shafts are a little to short as the motors and mount practically sit on the bottom of the hull with no apparent easy solution to secure them. A belt drive could be used (as i had to in my other tug) however I have slippage issues and its generally not very good. The shafts should be as close to the same horizontal plane as the waterline is, however its simply not possible in this boat without radical work. The angle of the shafts affect attitude of the boat in the water under a lot of power. 

I found some right angle brackets laying around and decided this would be the way forward. I chocked the motor assembly (which must weigh 7-8kg) so the shafts are in line and marked out drilling holes. M4 nuts and bolts were used to secure the angled mounts to the motor mount.

When satisfied everything was perfect, the fibreglass filler was applied under and other the brackets to secure them to the hull.

The aft part of the prop shaft requires fixing to the hull to ensure there is no vibration. MMM supply a white metal casting for this, however at first I didn't want to use it. Instead I wanted to make my own A-Frame which would in theory provide more lateral support, but with the awkward sizes of shaft casing used versus the sizes of brass tube available, I struggled to get something which would slide over the shaft. I wasn't prepared to braise the bare shaft onto some flat sheet brass - which would then be bent to form a V shape and secure inside the hull, due to the temperatures involved and how the temperature affects the brass. A standard blow torch with normal propane will melt brass of this thickness quite easily and taking the brass to red hot which is when the braising rod is introduced to join the surfaces, its metallurgical structure changes making it very easy to bend.

I decided to just go with the white metal fitting for ease. It had roughly 0.5mm play over the shaft which allowed me to use metal epoxy to secure it to the shaft using a rotation of shaft method to ensure the epoxy was spread inside. Once dry and solid, some PVA was used to dress the seam and blend all in together.

Holes where then drilled into the hull along the centre line of each prop where the support bracket would stick through. This was then fibre glassed to the bottom of the hull along with the shafts themselves.

The opening was then filled with car body filler, sanded and then given a quick coat of red.

The external part of the shafts can be secured using normal car body filler, the insides were secured using fibreglass as this makes for easier sanding. The area was given a quick paint and a few blotches were present which were then dealt with by some squadron green.

Annoyingly the props seem to hang roughly 1mm off centre - not a lot but when the kort turns over the prop, they practically touch which is not good. Luckily it only seems to be a vertical issues rather than horizontal and so the issue can be resolved by simply using a washer or two to space the kort lower.

Whilst I decide upon other options for the boat and design an electrical bus system, I set my mind to the wheelhouse, one of the feature points of the model when complete.

As you see, this is the bog standard moulding for the wheelhouse - which is fine, however it makes life difficult to detail it.

The idea is to have a fully lit interior with all the usual electrical panels etc. The wheelhouse therefore has to be a modular type of system which simply fits together and I for one cannot be bothered to fiddle around with plasticard trying to make it fit. Im getting into Autocad and basic 3d modelling to help with boat boats. 3D Printing is the next step. I set about designing a decent and accurate looking wheelhouse in google sketchup.

The panels were then placed into turbocad (an easier version of autocad). They need to be orientated to the 'top' plane which then allows for them to be laser cut or water jetted which is the plan. At this stage, the vendor in which I plan to use for the cutting, seemingly cannot see the drawings on his software (yet i've sent things to him before and its been fine).

There's still an awful lot to think about - working radars, working nav mast lights on separate circuits for different towing lengths etc, interior lighting, exterior lighting, crew figures (got a really neat idea for this one) internal 3d parts such as the captains chairs, all wiring must be hidden or what is shown, must be scale.

Anyway, we will pick up the wheelhouse parts at a later stage of the build.

I must cast my mind to other things. I want some sort of Dynamic Positioning System in the boat - it allows the vessel to be precisely controlled or mainted at a set position at sea. This on real vessels usually has its own operator and can achieve marvellous things. For this build, a rasperberry Pi would probably be the way forward. A gps sensor and I might even try to throw in a depth guage. This is going to take some doing and a lot of help from others. Luckily, the gps and sounder are the only things that need to be installed at this stage, as the rest can be added at a later date. All motors are controlled with their own speed controllers. I know others who have integrated their Pi's into model boats so its clearly achievable.

This may sit as just a dream but I will endeavor to incorporate as much technology in this tug as possible.

 

 

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©Dan Walker