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[DBS88]

Quite unexpectedly I was offered the chance to buy a partially started model boat kit of a tug called Imara, it was an impulse buy, in the heat of the moment, literally I went out in the morning knowing nothing about the boat or model, and by lunchtime in the back of my car was a box of bits. I took it on as winter project, I asked my friend John to help with the build. Most of the parts for the kit were present, the hull had been fitted with prop shafts rudder, servo and decking. The model has a steam boiler and two vee twin steam engines. Our first decision has been to build the Imara Kit as Perseverance. After about a year Imara became Perseverance and spent the rest of her working life as Perseverance The first task was to obtain plans and instructions for the Imara Kit, they were obtained quickly from contacts in other clubs and here on the forum (Thank you Martin and Martin). For my sins I have never built a model boat before, I have renovated a couple and have some knowledge of model steam, so I am truly grateful to John for agreeing to work with me on this project. This is very much a learning exercise for both of us and we will share with you our dilemmas, mistakes and hopefully some successes as well. It's always a risk taking on a job that has been started by someone else, so our next decision was to undo some of the work and and start again. Here are photos of the model and the steam plant as it was when I collected it and lastly the real Perseverance to give you an idea of what we are aiming to achieve.

[SteamboatPhil]

Great purchase Dave, a nice project, you will I hope keep us with the restoration 

[Neil]

I remember 15 or more years ago answering an add in Model boats mag for a steam plant, a cheddar boiler, ceramic burner, gas tank and 2 x twin cylinder puffin engines all tubed up in copper with the other necesarry plumbing ready to go.

So I drove over from blackpool to leeds and went with my £500 quid asking price and put it on the table for the gentleman as the  thing was so beautiful to me that my eyes were nearly popping out on stalks. I put it all in a box and stood to go out when he said " just a minute, you have forgotten something".
He disappeared in to the next room and came back with a partly built but full kit of the Imara converted to the Perseverance with the closed wheelhouse, plonked it on the table and said, this is yours as it goes with the steam plant.

you never get that lucky in modelling more than once.

I did finish the model in the end and it won best in class at the Blackpool show around 2008/9 but at the time had never got the plant steaming although I did have it certificated for pressure safety. And at that same show a certain model kit manufacturer of modern lifeboats made a bid on the model and I left with two kits of his 12th scale lifeboats. A good deal considering what I had paid for it only months before.

I built boats faster in those days.........but your model just reminder me of it and what she would have looked like had I got her steaming.........wonder if the owner after our deal still has her.

[DBS88]

Phil and Neil, thank you for your kind feedback. The steam plant that came already installed in Perseverance comprises of Two Vee Twin double acting oscillating engines, PM Research No 8 Engines, each with a 1/2 inch bore ad 3/4 inch stroke. Each engine has a single control valve that selects forwards/reverse and controls the engine speed (these were not set to be used). The boiler that supplies the steam is a MacSteam 3 1/2 inch boiler, gas is supplied from a refillable MacSteam gas tank and the exhaust steam exits via a homemade oil separator then out via the chimney. When ehe steam plant was checked over and fired up, the boiler was fine and the engines turned over beautifully. so all positive. The problems with the existing layout are accessing the two engines to oil them, removing the steam plant to service it and the way the throttle was set up meant both engines operated at the same time and speed but only in forwards. The decision was therefore made to remove all the steam plant, increase the access space, then reinstall the steam plant on a new base board – more about this in later updates. Here are photos showing the engines and steam plant

[rhavrane]

Bonjour Dave,Great project indeed 

Several remarks:
   - These steam machines are 8 cm3 each ==> with this small boiler, you will have a small autonomy, a pump could be an option to increase it.
  - Twin machines are great for manouverablity ==> I would kindly suggest you to install a servo for each of them, this means two inverters.
  - I would kindly suggest you to install a safety gasvalve and a gas regulator.
And last but not the least, where is the whistle  ?

[Colin Bishop]

Twin machines are great for manouverablity ==> I would kindly suggest you to install a servo for each of them, this means two inverters.

Yes, you need independent engine control. I built the original review model for Model Boats magazine which was electrically propelled and it does not respond to the rudder. This is why a single screw version of the kit was subsequently offered.

Colin

[nemesis]

You are certainly going in at the deep end for a first model, I wish you all the luck. nemesis

[Geoff]

As an observation, as you are temporarily removing the steam plant my I counsel that you lag the boiler as this will reduce internal heat and make it a little more efficient. With an internal plant you will need a lot of ventilation so in the superstructure, every door, porthole, hatch etc should be open to admit air. It may also be a good idea to use a small computer fan to duct air into the boiler room, it does no harm. I have two models with internal installation and use a fan on both to assist.


Lovely looking miodel and great purchase.


Cheers


Geoff

[Geoff]

Also lag all the steam lines from the boiler to the engines to reduce condensation and reduction of steam pressure. I also assume you will remove the gas tank from the model to re-fill it as gas is havier than air and will ignite in the bildges.


Cheers


Geoff

[DBS88]

Thank you all for your feedback.
Raphael yes when I started I was concerned about the boiler being able to cope with both these large powerful engines, and yes they will be installed correctly, each with its own servo, so each engine can be independently controlled for speed, forwards and reverse. A radio controlled gas cut off valve will definitely be added, and when the model is proven I will consider the additions of a pump and a whistle.
Colin, you raise an interesting point about not responding to the rudder, I have heard that this can be an issue, depending on whether the props are turning into the centre of the boat, sucking the rear of the boat down, or the props turning outwards, so the rear of the boat rides on the prop wash, do you know which way the model was set up? I know very little about this and will have the props rotating inwards to start with.
Geoff, most definitely will lag the boiler, have not done this before, so will learn a lot from the experience, will also make sure that the hatches provide air and also a release for the heat and humidity, will look at lagging ht pipes and the gas tank will be removable.


When reviewing the steam plant multiple problems were identified so I disassembled the whole plant so that it can be reinstalled with in an improved layout that will take into account the points raised. In effect it will be a complete new installation, albeit with parts that have been previously used. Here is a link to a video of the steam plant running before I removed it.
https://youtu.be/BEllvAAbEaE?si=-AAMt_chMJxUTKib

Other problems with the steam plant are as follows: there is not enough space to lubricate the engines, the steam plant is integrated into the boat, it is not removable. The gas burner boils the water in the water level, so a protective screen is necessary. The engines and boiler are all placed higher in the boat than necessary, so I will try to place them as low as possible, closer to the bottom of the boat. I'm afraid of having a higher weight, I know that the superstructure and accessories will have a lot of weight at the top, so I want heavy objects to be as low as possible to promote stability.
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[Colin Bishop]

My review model was set up with the props turning outwards. Changing to inward turning might help with steering by directing the ahead thrust across the rudder more but you would have to experiment unless another member can comment on this.

Colin

[rhavrane]

Bonjour Colin,
I asked myself the same question for my boats equipped with 2 propeller shafts so I went for a walk in ports and I noticed that the work boats were rather supra divergent (right propeller turning in the direction of the needles of a watch) while the speed boats were super convergent.
Example : https://youtu.be/CagA7tJTPrs

[Colin Bishop]

It is never simple. But waterflow against an inclined rudder is certain to have a turning effect even if the model is at rest. If the waterflow is being pushed away from the rudder then the rudder will be less or non effective and will only work once the boat is moving forward.

You can see this with paddle steamers.The rudder only begins to take effect when the ship is in motion. When I was aboard ps Waverley in Portsmouth Harbour some years ago, the vessel needed a workboat pushing on the bow to turn the ship towards the harbour entrance as  without that assistance the rudder would have not been sufficient to safely turn the ship round even in the full width of the harbour.

The best configurations tend to be models with single screws and rudder or twin screws and rudders.

Colin

[rhavrane]

Bonjour Colin,
This is why having two independant machines / propellers is really helpful.

I also have paddle boats and one of them has one machine for each wheel : https://youtu.be/SnXPs3sGdN8 and https://youtu.be/qLmOZyA-yKQ

[DBS88]

Great feedback on the direction of rotation for the props, I suspect I will have to try both in and outwards rotation to find which works best for this model, unless someone with an Imara can confirm in or out rotation works best.


With the engines removed from the boat, I got a good look at them, I had not seen them before. Both engines were bolted to a piece of wood, I removed the engines for cleaning and checking. The engines are the PM Research No 8 V Twin Steam Engine which is an oscillating v twin engine with forward, reverse, and speed control capabilities via a single servo operated lever for radio control, so one servo controls Stop, Go Forward, Reverse and the engine speed in both directions. The engine has a cast bronze base and frames, oilite bronze sleeve bearings on the crank shaft and piston rod. The crank pin bearings are machined from solid bronze which run on a ground pin. It also has a precision ground stainless steel piston rod with O ring seals. The lightweight aluminum cylinders are hard anodized to give you long wear. The crankshaft is 3/16" diameter precision ground stainless steel. The steam inlet and outlet are both threaded 3/16-40. Bore 13mm - 1/2 inch Stroke 19mm - 3/4 inch Twin Cylinder Double Acting Height: 63 mm - 2-1/2 inches Width: 112mm - 4-1/2 inches Length: 80mm - 3-1/8 inches. These are powerful and potentially steam hungry engines.

[rhavrane]

Bonjour David,

I have compared my PM Research machine to two other 8 cc and it is not consuming more steam than the others : https://youtu.be/Uw4GUNGqvME
It’s a very torquey machine with excellent value for money 

[DBS88]

Raphael, Thank you for the link to the video steam test of the engine.



Everyone has there own way of doing things and I have seen a large number of steam plant installations now, what seems to work well from a maintenance and testing perspective is to have the complete steam plant (engines, boiler, oil separator, gas tank, water tank, servos etc) all on a single base that can be lifted from the hull easily. This was not the case with this project, so decided to change the layout so that it would all go on one board and to also increase the area of the access so that the steam plant would lift in and out of the hull easily. The first step was to create a cardboard template upon which to test different layouts for the steam plant – as a result, the boiler has been turned round with the gas and oil separator tanks being placed side by side. The base board was then cut from waterproof ply and for the area where the engines would sit, a raised wall was created to confine water and steam oil residue, preventing it from running loose in the bottom of the hull. The board was painted with a heat resistant paint since the boiler will be operating at about 160C  Here are some photos of the work in progress.

[rhavrane]

Bonjour David,
Smart job indeed and unfortunately, not possible for all the boats, easy for an open launch but impossible for my cargos built originally for electric motors.

Steam purists used to say "a steam boat should be build around its plant, not the opposite" 

[Geoff]

Looking good. I would counsel you make the retaining walls on the engine bed plate higher as oscillating engines do make a mess!


Cheers


Geoff

[DBS88]

Geoff and Raphael, thank you both, I agree oscillating engines can be messy and it's not possible to build steam plants on removable trays for all models.


Having seen inside many models, it appears that modellers spend hours making the outside of their model look wonderful and less time on the areas that are not seen, so I will try to make the inside of this model as neat and tidy to look at as the outside. With the engine, boiler and other parts sat on the bench, the hull was basically empty so I washed the inside, dried it and sprayed it white with a heat and oil resistant paint. At the same time the deck openings were increased in size so that the whole steam plant can be removed by just disconnecting the prop shafts. My friend John made a neat job of cutting out the deck and making watertight doors that would open to allow the stream plant to be removed. However, between us, we made a mistake, we got the size of the opening and doors wrong, they were too small so the steam plant base caught the sides of the opening. I therefore cut the opening even bigger, we therefore needed another plan to cover the opening that was visible on the decking. Here are photos of the white inside with the first openings, the third photo shows the engines sat on the new baseboard together with the new bigger deck openings.

[1967Brutus]

Great feedback on the direction of rotation for the props, I suspect I will have to try both in and outwards rotation to find which works best for this model, unless someone with an Imara can confirm in or out rotation works best.

General thought in full size ship design is that outward turning props is best for manouvering, since both wheel effects are supposed to assist in the turn. Shape of the aftship has significant influence on how strong this effect is, but that is pretty unpredictable.
Inward turning props in ahead direction push the wake down and is claimed to have a better efficiency.

Converging or diverging propshafts also affect how the ship responds, where diverging shafts (props wider apart than the engines) reduces the turning effect of the props, and converging shafts increase this effect.

In general, anything that improves "long distance efficiency" (inward turning props, diverging shafts, single rudder) reduces manouverability and vice versa.

At least that is how it was taught to me in nautical college (quite a while ago), which admittedly was not an education in ship design...

For total disclosure, I have no idea how this would scale down to model size.

[Colin Bishop]

For total disclosure, I have no idea how this would scale down to model size.

Good point, but all too often with models it is a case of 'suck it and see'.

You would think that modern full size propeller design might have been largely perfected by now but there is  a report in the current issue of Ships Monthly magazine where fitting new propeller blades to a Baltic Ferry is expected to give a 13% increase in efficiency. Clearly there is still a lot to be learned.

If the full size version is still subject to so many variables, the model boating scene is even worse. Leaving aside the competitive model power boat racing where there is a lot of development, the scale side is much less clear. There is a vast range of propellers available but it remains very uncertain which one might be right for your boat. Most of them will work OK and for forward thrust any deficiencies can be overcome by a few more volts through the motor or opening the steam regulator a bit further. The loss of efficiency is not usually significant in the average sailing session. I found with one of my models that substituting a four blade prop for a three blade one gave a useful speed increase with negligible effect on sailing time. It was just more efficient.

When it comes to manoeuvrability there is no substitute for a model boat than directing the waterflow onto the rudder to kick the stern round. The alternative for twin screw boats is 'tank steering' whereby the motors are controlled independently but, although convenient for close quarters manoeuvrability, this can be quite a clumsy way of steering a boat around the pond. Mixers can sometimes offer a halfway house.

There is no need to overthink these things. For ahead thrust it doesn't much matter whether the props or inward or outward turning, but when it comes to steering (without tank steering) the key factor is the prop waterflow over the rudder(s) as it is this which determines steering characteristics.

Colin

[Neil]

General thought in full size ship design is that outward turning props is best for manouvering, since both wheel effects are supposed to assist in the turn. S

That is why all British RNLI Lifeboats from the age of twin screws and indeed twin screw pilot boats have all been outward turning props on forward motion, giving them great manouvreability at the scene of a casualty.

[DBS88]

The discussion about the direction of turning for the props, with people being willing to share their experiences, shows the strength of a forum like this, thank you. So I guess now might be a good time to discuss props!
As this is a steam powered model, the slower the props turn, the less steam(water) is used and the longer the model can stay on the water. So with this in mind and with the knowledge that we are supplying steam to two large steam engines the decision to invest in two larger dia 4 blade steam props was made. The idea was to improve performance with two larger dia Propshop steam props to replace the props that came with the model. The 80mm props will help achieve the same speed with lower rpm and save steam, there by extending run times – at least thats the theory! The new props with 80mm dia and 1 to 1.5 pitch mean each revolution (in theory) moves the boat 120 mm through the water. The old props are 75mm dia and 1 to 1 pitch so one revolution moves the model 75mm. If nothing else, the new props look fabulous.

[Neil]

i swear by Propshop gear............beautifully made and perfectly ballanced too.