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  • Writer's pictureKeith Appleton

How to build a Model Steam Boat

This article describes some of the building process involved in creating a working model steam boat using a GRP hull (Glass Reinforced Plastic)

The following text describes building a Mainsteam Model Steam Launch from scratch

If you have a kit, then follow the kit manufacturers instructions.

Adhesives required:

  • Cyanoacrylate adhesive ("Cyano" or "Superglue")

  • PVA adhesive (preferably waterproof type) 5-minute Epoxy resin.

  • "Milliput" Epoxy Putty.

  • Masking tape .

  • Tools required:

  • Craft knife.

  • Felt tipped pen and Pencil.

  • Power hand drill - with various drill bits.

  • Razor plane.

  • Power sander.

  • Sandpaper (medium & fine grade)

  • Screwdriver.

  • 90 degree set square.

  • Small plastic spring clamps (lots of them).

A model Steam Launch is not difficult to make, but mistakes can more easily be avoided if you have a map of the construction sequence in your head before you start.


  • Assemble a suitable boat stand first - if you don't, then you may damage the hull by fouling parts sat on the workbench.

  • A stand can be made in various ways, the simplest being a couple of shaped uprights & a connecting piece between them.

  • Make cardboard templates from the hull, then draw a pencil line around the templates onto a piece of wood & cut them out.

  • Material can be plywood or for a presentation display stand - Mahogany or similar hardwood.

  • Glue & screw your stand together.

  • Place the stand on a level surface & allow the adhesive to set fully.

  • Once the adhesive has set, cut some pipe insulation foam into 4 equal lengths & slit along the pre marked line. Seat the foam padding over the top of the boat stand to prevent the hull from being scratched. Once the boat is finished, the stand can be painted & the foam or other suitable resilient material can be glued in place on the top of the stand if the stand is a lakeside runni g version. If you are building a Mahogany stand, it will look better with foam rubber sheet cut to size & stuck on the hull support rails.


  • With boat stand temporarily out of the way, place the hull upside down on the bench.

  • Propeller shaft & rudder holes in the hull:

  • At the stern end of the keel, make a mark with a felt tipped pen, for the position of the hole for the propeller shaft.

Very Important:

Make sure that the mark is in the right position before drilling the hole. The propeller does not want to either foul the underside of the hull, nor does it want stick out below the level of the keel. Take your time with this & get it right 1st time. Next, drill a small pilot hole where you placed the felt tip pen mark. Now open it out to suit the diameter of the propeller shaft.

Approach the drilling of the rudder hole on the same way. Mark the centre of the rudder mounting area with a felt tipped pen, then drill a pilot hole first in that position. Open this hole out to allow the rudder mounting bush sleeve to fit snugly. Next, place the hull the right way up on the stand that you built earlier.

Step #3

Use a wedge shaped piece of wood for the internal rudder support. Mark the centre of the top the wedge with your felt tipped pen. Drill a hole the same size as the rudder mounting bush sleeve, in the top surface of this piece of wood, parallel to the 90-degree edge.

Tip: use a bit of scrap wood to make the wedge sit level on the bench.

Step #4

Using a piece of sandpaper, roughen the area on the inside of the hull around the hole that you drilled to take the rudder mounting bush sleeve Insert the rudder mounting bush sleeve into the hull from the underneath. Apply 5-minute Epoxy resin to the area of the hull inside & around the Rudder mounting bush sleeve. Now slide the internal rudder support wedge onto the rudder mounting bush sleeve from above. You must now insert the rudder shaft itself into the rudder mounting bush sleeve from underneath & support from below, so that it prevents the rudder mounting bush sleeve from slipping out of position. At this stage it is very important to make sure that the rudder is in line with the keel centre (viewed from the rear) & that the rudder is hanging perfectly vertically. If this is the case, correct it before the 5-minute Epoxy sets hard. If the wedge does not make even contact with the hull all the way around, don't worry, as the wedge assembly will be bonded in with "Milliput" as well as soon as the 5 minute Epoxy resin sets.

When the 5-minute Epoxy has set, remove the rudder & put it in a safe place for later. If you have never used "Milliput" before, it is very important to make sure that you mix two even lengths of the putty together very thoroughly or it will not set. Please read the directions on the "Milliput" box before use. Do not be tempted to use car body filler, as a substitute for the "Milliput", as polyester based resin fillers may get hot while curing & locally distort the hull. Once mixed thoroughly, roll out 2 lengths of "Milliput" and use these as a fillet around the wedge to hull joint. "Milliput" is water- soluble until it sets, so use a drop of water to smooth it out. This part of the boat is visible when the radio control hatch is removed, so make it neat!

Step #5

The first bulkhead to fit in place is the Radio bulkhead. Place the bulkhead in position in the hull, then measure from the stern centre point to each edge of the bulkhead to make sure that it sits square in the hull. Mark the position with a felt tipped pen then remove the bulkhead. Using sandpaper, carefully roughen the inside of the hull where the bulkhead is going to be fixed.

What I do, is to pre-veneer the radio & tank bulkheads and apply a couple of coats of polyurethane varnish to the mahogany & also the reverse side for waterproofing purposes before fixing the bulkheads in place. The water tank bulkhead is also sealed on the water side by using fibreglass mat & epoxy resin. The holes for the pipes must also be pre-drilled in the right place before the bulkhead is fitted into the hull. Place the floor in place temporarily (don't forget to allow for the thickness of planking!) then mark out, remove the tank bulkhead and drill the holes about half an inch above the deck level. Once this is done, and the varnish is hard, glue the bulkhead in position on the pre marked line using "Cyano" adhesive. Once the "Cyano" has set, run some more around the joint & leave to completely cure before proceeding further. It does not matter if there are slight gaps around the edge of the bulkheads where they meet the hull, as the next step will fix that. Take 2 equal lengths of "Milliput" Epoxy putty & mix thoroughly according to directions on the box. Roll out a long length of the "Milliput" & apply all the way around the radio bulkhead - on both sides. Smooth the "Milliput" with your finger, using some water, until it is smooth & even all around the joint

Step #6

As in the previous section, fix the rear floor rib in place using exactly the same technique of measuring the distance on each side from the radio bulkhead, but before gluing in place, also measure the distance from the top of both of the hull sides & make sure that the rib sits perfectly level in the hull. Now leave the "Milliput" to set for at least 24 hours.

If you are using a reversing gearbox, then it will need to be test fitted early on,

In conjunction with the propeller shaft & steam plant in order to ensure correct transmission alignment. Any errors will put undue strain on the engine & propeller shaft bearings. Also a lot of power from the steam engine will be lost owing to friction. Take your time & get it right!

The steam plant layout in the boat needs to be determined very early on in the build, as can be seen in the photograph below.

At this point it is a good idea to float the model in the bath to see how it sits. (you won't need any "Radox" or plastic ducks at this stage!)

Lead ballast can be added where necessary, but don't forget that if you are using a human figure in the boat, the weight of the figure also needs to be taken into account.

Step #7

This next step is critical: Take all the other ribs, place them in order in the bottom of the boat, but do not glue them in place at this stage. It has been found from experience that glass fibre model boat hulls vary in dimensions slightly so a little adjustment here & there is necessary. Now measure the distance once again as before, from the top of both of the hull sides & make sure that the ribs all sit perfectly level & centrally in the hull. If you fix the floor ribs in the wrong position, then the finished floor will not be level relative to the rest of the hull - this would not be good! You will need a straight piece of wood now, in order to find the correct position of the ribs in the hull so that the floor will sit level in the bottom of the boat. When the correct positions are found, mark the position with your felt tip pen. If the odd rib is a fraction lower, this does not matter, because strips of wood can be added on top of any low ribs in order to level the floor. When you are absolutely sure that you have got everything right, fix the ribs in place with "Cyano" adhesive. Let the "Cyano" cure & try your straight edge to verify that all the floor supports are level. Once you are satisfied that all is well, use the same technique with the "Milliput" as on the first rib, to bond all the ribs into place. Let the "Milliput" fully harden before you go any further.

From the above photograph to the one below. . . . . . . . . well on the way now!

Step #8

It is now time to look at the propeller shaft.

Please note: You will by this stage need to have bought a suitable propeller. The size of the propeller needs to match the power output of your steam plant. Temporarily fit the propeller to the shaft. Push the shaft into the hole that you drilled earlier at the rear of the hull. The shaft needs to be perfectly in line with the keel. The angle of the propeller will need to be set with your steam plant fitted temporarily in place. Place the floor in the bottom of the boat. Sit the steam plant on the floor with the propeller couplings temporarily in place on the engine's crankshaft & propeller shaft. Line everything up & again, using a generous amount of "Milliput", bond the shaft in place at the rear of the hull. Make sure that you do this from the inside of the hull. Use some scrap pieces of wood to hold the shaft in place so that it cannot move. Let the "Milliput" harden overnight, without moving anything. Once the "Milliput" has set, fabricate a neat front support for the propeller shaft using a suitable piece of plywood.

Below are some more photographs of the build in various stages

Panelling the sides with 1/8 inch Mahogany. Good workmanship is essential here, as any mistakes here will be very visible!

The brass parts are all machined individually - one at a time. The bollards are the soldered into the bases. Quite a bit of work is required to make the tiller arm. It is milled from a brass bar & cleaned up with files, emery cloth, fine "wet or dry" sandpaper, then polished. The handle part is turned in the lathe & then screws into the main tiller arm. These parts are shown before being hand polished using "elbow grease"

As can be seen below, to make the coaming a lot of spring clamps are required!

The coaming is made up from 5 layers of 1/2 inch Mahogany planking. It is an extremely messy job, with glue everywhere which will need to be sanded off. Using medium viscosity Cyanoacrylate adhesive, you have to be very quick in this operation, but it is essential that you are very careful to make sure that all the individual planks are tightly glued together and in perfectly line, otherwise when you plane & sand the coaming to shape, any gaps will show. As the top of the boat is not flat but slightly concave, downward hand pressure on the planking is required as you apply each clamp. I use plenty of glue, and a lot of it ends up on my hands & T shirt ...... !

Even more clamps - I never have enough of them ...... the job is very labour intensive at this stage - tedious is a better word!

All the seating and hatch components newly varnished - (1st coat)

I hope that the above photographs & descriptions prove useful to you.

These steam launches take a long time to build to a good standard.

Any mistakes occurring late on in the build are tragic - so take great care & think before you cut & glue.


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