Roofing material?

[Paul D Peterson]

Gentlemen, what do you like to use for roofing on a box van? I have two scratchbuilt boxcars with arched roofs ready for a final, exterior roof (they have an under-roof of wood). I originally thought to apply a covering of thin plastic card. Then I stumbled upon a reference in Peter Jones to using cardstock soaked in white glue--I assume he means something akin to "Elmer's" school glue here in the States--and wondered if that might be a better option. I'm not keen on wood-to-plastic bonds as a general rule; wood-to-card sounds promising, having done it with success in smaller scales, but I wonder whether the result is really robust enough for typical use outdoors. Any suggestions? What works best for you?

[IanT]

I'm not familiar with "Elmer's" School Glue Paul - but I suspect that Peter Jones would have been referring to some form of PVA adhesive.

There is a popular brand over here called 'Evo-Stick Wood Adhesive' which comes in interior and exterior versions and it could well be that. PVA is white whilst in glue/liquid form - but hardens to a clear gloss. You can also bulk buy PVA from DIY outlets over here (useful for larger surfaces - scenery etc) but I generally use the 'Evo' for wood myself (just the ordinary kind - which comes in a green plastic bottle).

The card could work (although I'm sure Cabbage will recommend Plasticard) as once glued and painted it will become quite hard and fairly durable. It probably depends on how exposed the edges and ends/corners of your roof might be. If there is a very large edge 'overhang' or the corners stick out - then both plastic and card could get damaged in transit or handling. If so, you might have to consider using something a bit more robust (one of the softer metals for instance).

But normally I would think card would be OK. I have an old (1/2" scale) NE Van & it's just got a simple curved roof (no wooden support underneath) which is about 2.5 mm thick card and it's still in one piece - after I'm not sure how many years.

Regards,

Ian T

[John Candy]

My preference is for metal.

I use either aluminium or brass, shaped using slip-rolls plus final "massaging" with the fingers to get a good fit.

Benefits :-
1) Requires no reinforcement to prevent sagging.
2) Does not need to be so thick as to look "clunky".
3) Withstands knocks which would break off the corners of plastic/resin materials.
4) If a hot cinder lands on it (from a passing "live steamer") you will not have a hole in the roof!

Very thick (120thou) pre-formed styrene sheet is used in the GRS kits which requires no reinforcement but you try shaping it at home without a vacuum forming machine! You could try laminating thinner sheets but it usually distorts, sooner or later.
You could try a wooden former immersed in boiling water which may work (or even a former placed in a hot oven) and it may be that Ralph (famous for his kitchen table recipes) has tried these techniques.

Regards,
John.

[blagdon]

For my three 'Brandbright' Toads, I have used handkerchief linen 'glued' on with aero-modelling dope. This on the wooden strip planking I use makes for a very strong roof, and allows the wooden roof strips to be initially held in place with fine pins while the glue dries. Others have used aircraft silk or tissue paper with this form of construction.

This assumes you want to reproduce the canvas covered type of roof.

Ian the Gauge '3' Pirate.

[IanT]

Or (once the collars & cuffs are worn) a plain cotton shirt will give a good length of material from the back too Paul. The rest will tear up for cleaning rags - great for wiping down the lathe and oily hands etc.

Do check with household management first though and don't (mistakenly) use your son's shirts. Even though well worn, it might be his favorite one.

Ian T

[Ted Sadler]

In the past I got good results with the glued-on cloth technique described above. However, it pays to check how well your chosen paint goes over it before you commit to the actual models. 'White glues' like PVA can induce a mottled finish (it's sometimes called 'crocodile skin effect') in the final paint layer that isn't easy to get rid of, even after several coats of paint. School glues contain some PVA but are mixed with permanently water-soluble resins to make them easily removable by washing. Aeromodellers solvent-based dope is usually good at sticking the cloth to the roof and is water-resistant, or you can even used diluted paint as the adhesive.

I've never had good experiences trying to soften plastic sheets in either hot water or a low oven. They always went wrinkly after a while. The wooden roof former I had so carefully planed into the correct arc profile went banana-shaped after heating 2 or 3 times. Sigh.

Regards, Ted

[MikeWilliams]

Just a comment about mottled finish to roofs.  Having re-roofed a real carriage exactly as it would have been done when new - with unproofed canvas and white lead paint, I can state that the surface is not smooth.  A steel roof would be different and may well have been smooth until rust took hold, but not a real canvas roof.  For that reason I deliberately try to create a rough or mottled finish!

Also, when some roofs were described as "white" when new - white lead is more cream than white, so don't overdo it.

Mike

[Paul D Peterson]

Many thanks to all who replied! I'm glad I asked about "white glue"; I haven't used PVA before, but it definately sounds worth checking out. I'm intrigued by the suggestion to use actual cloth, and think I'll try that, though not with the PVA (thanks for the warning about mottling). Household management won't mind--I have one or two frayed old shirts that I'm sure she would prefer to see on the roof of a boxcar and no longer on my back.

I would like to ask John, or anyone else who has used metal roofing, how they attach it. Some combination of adhesive and tiny nails? I've been thinking about using metal roofing on a structure project, but again this is uncharted territory for me. I imagine it must hold up wonderfully well in the garden.

Cheers,
Paul

[John Candy]

I would like to ask John, or anyone else who has used metal roofing, how they attach it.

Paul,

I use two-part epoxy resin which is strong, a gap-filler and retains a small degree of flexibility which prevents joints cracking. It is VERY strong; try pulling the joint apart and the joined components will fail before the  joint breaks.

Regards,
John.