Reinforcing Foam Sheet

This section explains the important step of reinforcing (or stressed skinning) the 1″ (25mm) foam sheet to give it tensile strength on the bottom surface. The top is not such a problem as the extruded foam seems to have reasonable compressive strength.
This technique borrows from bridge building and surf board building techniques – remembering that our loading is occurring primarily from the top. You can also use it on 2″ foam to allow increased distance between the supporting battens.

I am assuming that you are not going to be walking around on the top of the layout! Having said that, I have stood on the layout by placing strategic wide pieces of plywood on distributed spacers between the tracks and close to the edges.

The technique is extremely simple – coat the bottom side with a layer of cloth glued to the the surface with PVA. You could use exotics like fibreglass or carbon fibre cloth – but we are not building a spacecraft! Just some cheap muslin cloth is what I use from a fabric shop. A tea towel may do the job. Cut it a bit oversize; coat it with a generous layer of PVA glue and squeegee it into the surface … as below.
foam-reinforcement
Reinforcing using muslin cloth and PVA glue.
Squeegee / roll/ brush the PVA so that it fully impregnates the cloth.

No hi-tech tools here! You may need to thin the PVA with water just a little to help spread it. Re-coat if doubtful.

When it is completely dry, cut around the edges with a sharp knife. The reinforced surface will be the bottom!

Then glue the sheet in place with PVA. (No, this is not an advert for Valvoline!)

The underside showing additional cross bracing, both to support the 1″ (25mm) foam and to restrict any shrinkage or expansion at right angles to the track so that the latter remains aligned where it crosses the joins. There has been no problem with track alignment or binding of the lifting panel since July 2014 even through flooding rain periods and temperatures in the room between less than 10°C and over 32°C.

The reinforced side is down (up in the photo) and and the assembly rests on a flat surface to keep the top true. I then glued the battens and all the support timbers to the bottom of the foam and to the supporting structure so no screws were needed.

Shown below is a  test run I did in 2008 when I lived at Bensville (I tend to live in places with strange names). It was a test track for both DC and DCC which fitted on the bar in our lounge room. It vaguely reflects the track layout (considerably condensed) used at Oberon in the Central West of NSW when I lived nearby at Hazelgrove. The latter was a station on the now closed/ suspended railway from Tarana to Oberon. A model of the mighty Hazelgrove station will feature on Kalrail layout (later to be re-named “Brolgan Road”).

I couldn’t resist adding this photo of Hazelgrove Station posed on a temporary diorama. Yet to be finished and weathered.

The underside of the test track shows that 1″ foam has been coated with muslin and fitted with a light weight frame. The ugly blocks on the right were added to help it fit on the bar which was a bit narrow. It is 2m long, 58cm wide and weighs 4kg. Could be made much lighter with thinner timber and no ugly blocks.

Could be a neat way to take a 2m x 1/2m layout to a display. Carry it in one hand.

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Rick Fletcher

Born in the steam era and developed an interest in railways when given a clockwork Hornby "set". Surrounded by steam when travelling to school (by train of course) and holidays were always by steam train as we had no car. How lucky was I?

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