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I am in regular contact with lots of Kingston Mouldings customers though, people who collectively know plenty about the subject, and the sum total of their wisdom is largely what I'm passing on to you here.

A Thames steam launch, another example with a home built steam plant. In this case the owner chose to mount his engine in front of the boiler, with the prop shaft running underneath.

I'm not addressing the experts, just trying to provide a little general guidance for the average reasonably competent modeller who is perhaps considering splashing out on a steam plant and is simply looking forward to a bit of undemanding fun sailing.

Most of the advice that follows applies more or less equally to any steam powered model, not just those built using fibreglass hulls. Nothing too technical, just some ways of avoiding common problems, the best materials to use, how to protect the hull, that kind of thing, and the three most important things to bear in mind at the planning stage are Access, Clearances and Ventilation.

Not a lot of room to spare in this Steam picket boat. See how whole sections of deck have been made removable for good access to the machinery.

Steam powered models need good access, 'finger space' if you like around all the components, and considerably more of this than is the case with electric and other forms of propulsion. Often the whole superstructure and parts of the deck as well, will have to be made easily removable to provide adequate room.

It goes without saying that once all machinery is fired up and functioning properly, it must be possible to operate the model with all top parts and hatches securely in place. A steam gauge that can be read easily with the model in full sailing trim and ready for launching, is a useful feature for obvious reasons.

A good example of the amount of access you need to operate a steam plant. The entire superstructure lifts off in a single unit, so no fiddling around with separate items when you are ready to sail.

A few dummy runs with the steam plant sitting in the bare hull before you even begin construction, will tell you how large deck apertures should be to let you get your fingers in to perform various operations. Be realistic about this. If you try to cram too much into too small a space with inadequate access, I promise that you'll spend an awful lot of time regretting it later, so try to err on the side of caution.

As the hull measures only 980mm by 160mm, steam power wasn’t an easy matter in this Victorian steam launch, but the model performs very well in calm conditions.

Clearances. Many problems are the result of trying to squeeze too much steam plant into a space that simply isn't large enough. Newcomers often don't appreciate the sheer volume of heat that small boilers can produce, and the more cramped things are inside the hull, the worse things will be. Nothing really hot should ever be in contact the hull itself, but of course this applies just as much in the case of hulls made from wood.

At the very least, a steam pipe or burner that is too close to the hull will discolour paint on the outer surface. What we want to avoid are localised hot-spots, as fibreglass doesn't conduct heat terribly well. Both GRP and wood could be charred and damaged by a serious heat build up long before either reached the point where they started to burn.

Ventilation. It's hard to have too much of this, and it's important for two reasons. To keep the interior temperatures down, and also to feed that flame under the boiler. What you can achieve here depends to a large extent on the model's design, but it's surprising how much you can improve things by leaving some portholes, skylights, doors and windows open or unglazed, and making sure that any deck and superstructure mounted ventilators etc. are opened up as much as possible.

This picture of a steam powered TID tug shows what can be done to help with ventilation. Every one of the scale engine room vents has been opened on this model.

Gratings can often be enlarged, and even if you don't want to deviate from scale too much by cheating like this, some hatches and doorways can often be left open. Small touches of this kind often make a model look more realistic and 'lived in' too, as well as helping to let the air flow freely. And getting the hot air out is every bit as important as letting the cool air in. A thin sheet metal flue positioned over the steam plant will collect the hot gasses and steer them into the funnel. Much more effective than just letting them find their own way out, and it will perform the useful secondary function of shielding the vulnerable underside of the superstructure from excess heat. A flue of this kind should extend a little way up the funnel, and a simple construction in aluminium or soft soldered thin brass does the job beautifully.

Perhaps the most popular kind of steam powered model of all these days, is the open launch. As well as showing off the polished brass of your expensive steam engine to all and sundry, exposing the machinery neatly solves the twin problems of ventilation and access in most cases.

Plenty of room in this beamy 890mm x 280mm River Queen open launch hull, but it wouldn’t need a large and powerful steam engine to move it along at a realistic speed.

There are a couple of other details that you'll have to devote some thought to, mounting everything in the hull, and adding a certain amount of insulation around the hottest areas, but that's something I'll be saying more about in a moment. Unlike some other forms of propulsion, steam doesn't fall into the 'fit and forget' category, and you'll need to be able to remove everything from the hull from time to time for cleaning and other essential maintenance.

Perhaps the best way of achieving this is to glue fairly substantial full-length bearers made from ramin or some other hard wood to the hull bottom. The engine and boiler in one or two units can then be screwed or bolted directly onto these. This method of mounting also helps to ensure that nothing hot is in close contact with the hull itself.

Many commercially available steam plants are supplied ready-mounted on one piece metal bases. Such bases can easily be fixed to the bearers of course, but if engine and boiler are not in a single unit and space allows, it's best to make up a single metal tray, and bolt the separate units to this. As well as doing away with any need to detach steam pipes on a regular basis for maintenance, this ensures that everything remains in perfect alignment.

Bonding things like strips of wood really securely to the inside of a GRP hull isn't difficult, but like anything else there's a right way and a wrong way to go about this. The main pitfall when gluing anything to fibreglass is inadequate preparation of mating surfaces before applying the sticky stuff. You should abrade or roughen all surfaces here, the wood as well as the GRP. The best way to do this is with a small piece of fairly coarse abrasive paper, not on a block in this case, but just held in the fingers. Done this way, it's easier to get right into undulations, and any nooks and crannies. Afterwards brush and blow away any dust, then wipe with a solvent moistened rag to make doubly sure before applying adhesive.

The simplest way to line everything up properly is to screw the shaped bearers onto the underside of the tray and offer this to the hull, before doing any final trimming, to make sure everything fits nice and snugly. Then bed the whole assembly onto either epoxy glue or my own preference for this particular job, a polyester filler paste such as P-38, applied fairly generously to both hull and bearers. Press down hard enough to squeeze adhesive out at the sides. You can use a slightly moistened finger to smooth out stray blobs before the stuff hardens.

After allowing everything to set really firmly, then you can unscrew the tray. Fill any gaps around and under the bearers, and generally tidy things up with neat fillets of P-38 or epoxy glue around all the woodwork.

That just leaves the insulation problem. My childhood memories of steam powered models recall hull interiors that were a mass of bits of asbestos lagging and the like, but we don't need to use anything as life threatening as that in this day and age. Or at any rate I never did even before all the health risks associated with asbestos were fully understood, and all that's required in most cases is nothing more dangerous than heavyweight aluminium cooking foil. If this is glued to hull sides and bottom around the boiler and burner, it should reflect and spread enough heat to avoid any danger of serious overheating during normal operations.

The builder of this H.S. tug made his own twin cylinder steam plant. Being a skilled metalworker, he also made most of the superstructure from aluminium, though the more usual plywood would have worked out just as well in practice.

I expect you're asking what adhesive you should use to stick this foil to the GRP hull, and I'm not really sure what to recommend. For some time, I've been using an unlabelled tube of some thick black gungey stuff that a customer gave me, rather like car underseal for those who can remember such things. I'm sure that there are plenty of modern adhesives that will do the job quite satisfactorily. You don't want anything too permanent here, then you can replace the foil from time to time and clean up around and underneath it. This is another area that's much less of a problem with open launch type models, but even here it's often a good idea to add some foil under the boiler, and in other areas that appear vulnerable, especially around any varnished woodwork. Because radio gear and nicads won't appreciate high temperatures and hot oil and steam spraying around, you won't need reminding that such items should be as far away as possible from the hottest parts of your model's interior, but this is just common sense isn't it?

Well, I hope that I've managed to set your minds at rest. My experience has been that steam power in GRP hulls doesn't raise great problems, especially with the modern ready to run units that are available today, so happy steaming.

Drifting along on flat calm water, with the throttle just open and steam wafting from the funnel, there's nothing quite like steam power.