Help with warped model

[Isambard Kingdom Brunel]

I have scratchbuilt the goods shed at llanfyllin, however, due to family illness and personal circumstances I have not done anything on the layout for over a year. The building is quite large it has an inside platform but the tops of the gable ends have warped.

They are made from laminated plasticard, an inner piece of 20 thou with 10thou embossed brick laminated on either side. this is then added with a decorated gable of more layers of embossed plasticard.

The roof was built as removable to enable lighting and an interior to be fitted.

 

Is there anything I can do?

 

I thought about using a hair dryer to soften it up and then add some 60thou rafters to separate the gable ends, I don't really want to fix the roof permanently, but, if thats the only way to repair my kinky building I will have to

[Barry Ten]

Could you reinforce the insides of the gables with lengths of plastic section, or even metal?

[Isambard Kingdom Brunel]

I think some L shaped plastic will give ot a bit of help, but, because it is quite a thick lamination it is very rigid, I need to straighten it first

[Barry Ten]

Could you clamp the two sides of the gable and leave it for a few days to straighten out?

[ozzyo]

 

They are made from laminated plasticard, an inner piece of 20 thou with 10thou embossed brick laminated on either side. this is then added with a decorated gable of more layers of embossed plasticard.

The roof was built as removable to enable lighting and an interior to be fitted.

Is there anything I can do?

 

 

 

I'm sorry to say but your walls are too thin. at 40 thou (1mm) this only = 3" in 4mm. Most good shed buildings would have had a thick base of about 24" with buttresses running up the walls at about 18" thick with a wall between them of about 9".  Or more.

When you look at a photo of real buildings the inset part of the wall is not for decoration, it's to use less bricks in the building of the building.

A small goods shed would be about 60' long and could involve the use of 100,000 bricks (that is a low estimate). IIRC one square yard of a single skin wall uses approx 48 bricks.

 

A house wall will be at least 12" wide using two thickness's of brick with a cavity between them and a house is not built a strong as a goods shed would have been built.

 

OzzyO.

[Isambard Kingdom Brunel]

I will take a photo, there are actually more laminations, as you say, there are buttresses and other architectural features. However I would not build a model 8mm thick. I will try to take a photo tomorrow

[Isambard Kingdom Brunel]

The Gable End

 

 

The unsupported wall

 

The unsupported wall is thinner 3-4mm thick, the gable end is 4 - 5mm thick, I have not had problembs with Station Building, Signal Box and Stables all of which are completed with the roof attached (except signal box)

The unsupported wall will bend back and I think a piece of L section Brass Section epoxy to it should get rid of that, The Gable End is not such a pronounced warp nut will be more difficult to disguise

[KalKat]

I should imagine that a bit of heat may well help.

 

As Ozzyo has pointed out, the brickwork in buildings such as goods sheds is ..... well on the 'massive' type of scale. There would be heavy brick piers each side of the doorways and a socking great big girder holding the brick courses over them. This is not meant as a criticism of your model, but rather a suggestion that if these were incorporated, they would help support the gables.

 

It is also true of the sidewalls - often the lower three feet or so would be thicker than the rest of the wall which in turn would have piers/buttresses inside as well as out. Perhaps scoring the wall might allow more possibilities in removing the warps and the piers would then hide them?

 

 

Emma

[Izzy]

The problems you have encountered are not unusual and many making model buildings have suffered these over the years. Yours is, if you will forgive me, a 'classic' case. Part of the issue is the strength of the walls which can be affected by a mix of atmospheric conditions, damp, heat etc in combination with the method of construction and the materials used. Plasticard is well known for warping like this, particularly with layered construction, and if you make, say, an enclosed wagon the considered advice is to drill a 'breather' hole in the underside to prevent the sides warping inwards due to the glue reaction. As always the more support/strength you can provide the less likely this is to happen and will probably explain why your other buildings are okay. It is worth noting that the worst reactions are where there is the least support, and allowing for camera lens distortion it seems more extreme at the bottom than at the top. Had your building been glued down after construction then the outer wall would probably hardly have warped, if at all. 

 

Once warping has occurred it isn't always possible to correct it, but I would suggest that warming the affected areas with a hair dryer and trying to 'bend' them back straight again might just work. Working the affected areas with your fingers as the warm air is blown over them. It doesn't work with card, but can with plasticard most times with a bit of luck. This needs attempting before you try adding any strengthening as otherwise it will just be fighting the existing warping rather than preventing it happening again.

 

Izzy

[TheWeatheringMan]

Hi,

 

Firstly I'm very sorry to see that you have suffered this problem with your building but also I'm the bearer of bad news.

Regretably the warping that has occurred is basically imposible to correct.

The comments made above about wall thicknesses are totally pointless as the thickness of the real thing has no bearing whatsoever on the warping of a model and making the model scale thickness will not stop warping due to what has taken place.

The comment about dampness is also rather pointless as you have stated that the model is plastic card - and plastic card is not and cannot be effected by dampness in the air - card and wood construction can and often is of course.

Clamping the parts of the model - even if you could do it - would achieve absolutely nothing as the walls have not 'bent' they have 'warped' due to changes in the plastic - and these cannot be reversed by mechanical means unless the plastic can be forced back beyond the original line - something that clamping will not achieve. As described below this action must be done 'sharply' rather than slowly over a period of time.

 

Another thing that must be remembered is that heat MUST NEVER be applied to a plastic model for the following reason.

 

The application of heat 'may' enable some straightening to be effected as the plastic will be softened. However the following should be understood. Polystyrene is what is known as a 'thermoplastic' - it is moulded by being heated from raw granules of plastic. Once moulded it is fairly stable within a defined temperature range.

However if heat is applied in an attempt to correct a problem such as yours - and it cant due to whats happened - the plastic will be destabilised and it will then want to warp due to the 'memory effect' of all thermoplastics - what this is is that the plastic will always want to return to its original form - this is why polystyrene warps in 'circular' form and if the heating continues too far the item will start to deform and try to curl up - the plastic remembers that it was once a ball (granules) and tries to return to that shape.

As you will see from the above the application of heat will cause more problems that it can solve.

 

What has happened to your model is that chemical warping has taken place due to solvent action - regrettably this is most common when laminating plastic card together as the solvent will attack the differing thicknesses at different rates and the general effect is to cause the thicker sheet to warp as yours has done.

The effect is that of a 'bi-metal' strip such as used in thermostats where differential expansion causes warping - although in this case the warping is used to operate a switch contact.

 

As you will understand from the above explanation it is also not desirable to glue further plastic sections onto the model to try and correct whats happened as you will simply set up a further warp situation between the new section and the old wall - and no, unfortunately, the new warp will not cancel the old and straighten the wall.

 

Before I offer some help based on my own many years of modelling and the mistakes I've made over time I'll offer the following that hopefully whilst not offering much for the current problem might be worth keeping in mind for the future.

 

(1)  When constructing a wall by laminating always use a matching thickness of plastic card on the other surface of the thick centre so that the moulded or embossed plastic card on the outer is balanced by a layer (moulded or smooth) on the other side. This will to a great extent balance out the solvent warping and although not totally quaranteed to prevent the warping it will reduce the chances.

 

(Added following further close study of your photos)

 

It does look as though you do have an inner 'sheet' of thinner material that would normally greatly reduce the likelihood of warping so my guess would be that one of two things have happened - firstly it could be that the thick centre sheet was of inferior quality and has reacted to the solvent used very badly and warped despite the 'double-sided' thin sheet construction - it having overcome the normal effects on one side. Regretably some of the plastic sheet sold by some traders is very much a poor quality products imported from the far east. Secondly, it could be that the solvent used was applied in too great a quantity - a common mistake I've made myself on occasions.  

 

(2)  When laminating use an adhesive with a lower solvent content. The worse is a powerful solvent such as any containing Methylene Chloride such as 'plastic weld' types. Next in line is any containing Methyl Ethyl Ketone (MEK). Traditional contact adhesives come next and lastly more modern 'non-solvent' contact adhesives. I have settled on a solvent based contact type called 'Time Bond' (there is also a brand called 'Thixofix') - these are thixotropic and thus enable a very thin layer to be painted on to the surface rather than the thick layer caused by ordinary contacts such as 'Evostick'.

(3)  If at all possible don't laminate with a thick plastic centre of plastic sheet - use instead a card layer such as a good quality board from an artist's supplier - this will make warping almost unknown but remember to still add the extra inside layer to keep the balance or its possible to get warping due to differential expansion - this by the way is known as the ' plywood trick'. Remember to that dampness considerations come into play with a card middle however.

 

Now what can be done after the event - as I've said above some of the suggested 'remedies' will cause more problems that they can solve.

What you can try is (in the hope you can dismantle the building into major components) to 'force' the walls as straight as possible by actually slightly bending the walls to stretch the concave side of the warp. Be aware that you might cause cracks in the walls but these should be easy to fill and will look realistic anyway - whatever you do don't try to glue any such crack with a solvent as I'm sure you can see what this will cause!.

Adding a metal girder section carefully in unseen places AFTER bending as above will help retain the best straightness but this must be added using an epoxy adhesive or one of the modern polyurethane  adhesives - not a solvent based contact as these do not dry rigid enough and obviously contain the undesireable solvent. Non-Solvent contacts are simply not strong enough.

Do not use wood for the above job as the action of the plastic warp is so strong that wood will simply bend.

When mounting the model to your baseboard glue a small square wood beading out of site inside the building and onto the baseboard to act as a location for the building - use PVA wood glue for this for strength and it will act as a location for the building and additionally help retain the (hopefully by now corrected) shape of the walls.

 

Lastly one comment - don't despair too much if you cant get the walls perfectly straight - old buildings often have twists and misalignments in their walls after many years of service so a bit of a twist might easily add a bit of character to your building that would be the very devil of a job to build in !!.

 

Hope the above is of interest and might help - I'm sorry I cant offer a total remedy but best wishes on improving your building.

 

 

Regards

[Barry Ten]

Weathering man - your analysis looks very comprehensive and I am sure you are correct in your findings. But it's a bit strong to label other people's suggestions as "pointless", or even "totally pointless", when they have all been offered in a spirit of friendly helpfulness. Many of us have also been modelling for years, and in the absence of the actual model to examine, we do our best to offer solutions, even if sometimes we don't have all the facts to hand. Perhaps those solutions turn out not be applicable or even sensible, but they are intended well.

[Isambard Kingdom Brunel]

Thanks very much everyone for your help.

 

When I am building the models I have used mekpak and after applying each layer of the lamination, it is laid flat with a weight on it, then it is turned over and the opposite side is laminated on.

 

Part of my problem is definieley the fact that the model was not completed, but, due to various circomstances was left on the layout.

 

It is not designed to be permanently attached. Its base will be buried in the baseboard about a centimeter.

 

\i am not too worried about the base as that wont be noticed so much once it is buried, the broblem is the leaning gable end, I will try to bend it stratight then using a brass L section epoxied to hold it steady. I was originally going to keep the roof as removable but will make it permanent once lighting etc are fixed.

 

Thanks again for everyones comprehensive answers and I shall be looking for Time Bond or Thixo fix ti use for future buildings

[TheWeatheringMan]

Hi Barry Ten,

Firstly I apologise if the way I worded my reply has caused any offence - I certainly did not mean to do so.

My main concern was to get over the point that some of the 'remedies' suggested would actually cause more harm or problems than ever and hopefully stop anyone falling into that trap.

We have recently had a good deal of correspondence on RMWeb regarding paint and/or RTR finish removal and several of the suggestions offered would, whilst sometimes part working, actually cause long term effects that would destroy a model due to unstoppable chemical actions.

It would be all too easy when trying to correct what has happened with this modellers building to do something suggested untried by another modeller that would result in far greater damage either straight away or in the longer term that's why I tried to emphasise the points of what not to do.

I'm afraid that I will however maintain that it was pointless to comment on the thickness of the walls of real buildings in connection with the warping of a model as the two are in no way related. It is a fact (due to the chemical reactions as described) that if a model were constructed to a scale thickness by the methods employed then the actions that have caused the warping would in fact be increased considerably.

Whilst this next comment is NOT aimed at anyone who has replied to this thread, its got to be said that we have seen on RMWeb some totally stupid suggestions put forward by so called modellers who say things without any knowledge or experience - suggestions that very easily could result in serious damage to a persons model or much much worse including death.

If anyone thinks that comment is over the top then I'd refer you to a comment some while ago on another thread suggesting the thinning of paint for spraying with lighter fluid. Just think of the potential results of that suggestion!!.

 

Anyway Gentleman, I sincerely apologise to you if you felt my reply - which I earnestly hoped would help the OP - has caused any offence by its wording. It is sometimes difficult when due to ones knowledge and experience one spots something that is perhaps being misunderstood and ought to be explained, not to sometimes tread on toes a little.

 

Regarding 'Time Bond' it is stocked by B & Q in most branches - hope this might help.

As to the construction of the walls of a building - as will be understood from my explanation of whats happened, it will be seen that placing a weight on to the laminated construction will not in any way prevent the warping taking place - unfortunately the chemical process will of course still take place and will simply set up considerable forces within the plastic. These forces will always work out once the weight is removed and warping will result.

 

I hope the above is of interest.

 

Regards.