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I'm toying with the idea of 10mm foamcore on a PSE frame. How well would the foamcore cope with under-baseboard point motors?

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Not very well is the short answer.

 

You can't screw into it.

 

What you have to do is glue some ply or plastic to it then screw/bolt to the plastic/ply.

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Not very well is the short answer.

 

You can't screw into it.

 

What you have to do is glue some ply or plastic to it then screw/bolt to the plastic/ply.

 

I've built a couple of boards using extruded foam and have also had to glue hardboard patches to the underside

to accommodate wiring connections and so on. It's no real drawback though - just means that it pays off to

glue the necessary bits the day before you want to screw into them. I think the benefits of lightweight

construction far outweigh the minor additional hassles compared to using wood.

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I'm toying with the idea of 10mm foamcore on a PSE frame. How well would the foamcore cope with under-baseboard point motors?

 

I used 10mm foamboard on top of Brilliant Baseboards frame and had a lot of problems with it not staying flat. Particularly once I glued cork sheet for the trackbed. I had to rip it all out and replaced with 10mm MDF, although now I wish I'd used marine ply, just because of the weight really. Cheers, Nick

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I'm toying with the idea of 10mm foamcore on a PSE frame. How well would the foamcore cope with under-baseboard point motors?

Gluing Tortoise motors to the underside of baseboards is far from new. Gluing velcro to the underside, then velcro-ing the Tortoise, is also a known route to success. Do a small trial patch and see how it turns out!

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Have you tried using Foamex? it's a compressed PVC board in 3, 5, & 10mm thickness - cut it with a craft knife, and you can sand it, screw into it, etc. It's used by sign board writers/manufactures. I scrounge off-cuts from our local sign makers. Cost nothing as hey throw away pieces too small for their use. or pieces they have spoilt.

Might not suit your purpose, but well worth having a play with.

 

Shaun.

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I used 10mm foamboard on top of Brilliant Baseboards frame and had a lot of problems with it not staying flat. Particularly once I glued cork sheet for the trackbed. I had to rip it all out and replaced with 10mm MDF, although now I wish I'd used marine ply, just because of the weight really. Cheers, Nick

 

Yes, cork sheet glued to foamboard with PVA leads to severe warping, even if all is weighted flat for a couple of days whilst drying. See herefor a picture :(

 

Nick

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Yes, cork sheet glued to foamboard with PVA leads to severe warping, even if all is weighted flat for a couple of days whilst drying. See herefor a picture sad.gif

 

Yup that's exactly it! I had other problems too, it seemed to sag between the supports after a while. All in all not a good experience! I think the warping is to do with uneven lamination, ie, if you put cork on both sides of the foamboard it wouldn't warp, but obviously that's not practical. I've been using 3mm foamboard clad in plasticard for my goods shed though and that's been fine.

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Yup that's exactly it! I had other problems too, it seemed to sag between the supports after a while. All in all not a good experience! I think the warping is to do with uneven lamination, ie, if you put cork on both sides of the foamboard it wouldn't warp, but obviously that's not practical. I've been using 3mm foamboard clad in plasticard for my goods shed though and that's been fine.

I think the cork expands when it is dampened by coating in PVA. After all, it's this expansion that makes cork a good seal for wine bottles :) Later, it tries to return to its original size and whilst well-braced plywood may be able to resist the pull, foamboard can't. As you say, laminating with plasticard is fine. You're right also about the sagging, too. My embankment section didn't break away from the supports but ended up with an undulating surface between them.

 

Nick

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I think the cork expands when it is dampened by coating in PVA. After all, it's this expansion that makes cork a good seal for wine bottles https://www.rmweb.co.uk/community/uploads/emoticons/default_smile3.gif Later, it tries to return to its original size and whilst well-braced plywood may be able to resist the pull, foamboard can't. As you say, laminating with plasticard is fine. You're right also about the sagging, too. My embankment section didn't break away from the supports but ended up with an undulating surface between them.

 

Nick

 

I think there's more to it than the cork expanding. I've had exactly the same warping problem when laminating sheets of foamboard together with PVA.

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I think there's more to it than the cork expanding. I've had exactly the same warping problem when laminating sheets of foamboard together with PVA.

 

Interesting ;) Is this with large areas? I've only done this with strips of foamboard no more than 40mm wide laminated to larger sheets. There certainly was a tendency to warp, but nothing that couldn't be prevented by letting it dry for twelve hours or so between bricks to hold it flat. The warping with cork seems to happen later over a period of days.

 

Nick

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Interesting Is this with large areas? I've only done this with strips of foamboard no more than 40mm wide laminated to larger sheets.

 

I was laminating strips 70-100mm wide together as track bases and gluing them to a flat base; but the width wouldn't have been an issue as the longitudinal warping was much more pronounced than any transverse warping (which wasn't noticeable). They were glued under weights, although not seriously heavy ones.

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I'm reading this thread with interest since I've made a small foamcore baseboard with success and am now thinking about a bigger one.

 

now-you-dont.jpg

 

Lots of layers here: a braced 10mm foam board base inspired by Chris Nevard's Catcott Burtle board, with a 50mm slab of Styrofoam on top of that for surface relief, then a 3mm MDF trackbed and finally some 3mm cork before the track. No issues with warping - the braced board was very strong and square and the Styrofoam probably helps a bit as well. The MDF provides a flat surface to mount trackside items to, and you can just about screw into it if you're careful.

 

There are more pics here in case they're useful.

 

One tip I've seen several times for foamboard, as mentioned above, is to always do the same thing to both sides where possible.

 

Will

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Yes, cork sheet glued to foamboard with PVA leads to severe warping, even if all is weighted flat for a couple of days whilst drying. See herefor a picture ../../../public/style_emoticons/default/sad.gif

 

Nick

 

Hi Nick,

Im reading these threads with interest as Im building a layout in a relatively new house loft. Ive deliberately picked a foamboard base to save weight and was about to PVA my 2mm cork matting on top of the 20mm foamboard sheeting when I came across your discussions. Am I likely to have a setback I wonder? Please can you or anyone else shed any more light on what they think has happened here. It would seem that the cork has shrunk and pulled the foam with it at a different rate. What environment were the failures in (i.e. loft, house, garage?) and what mix of PVA was used to achieve the bond? – was the faomboard sealed with a PVA mix before hand ? Im hopeful a PVA mix can be achieved that would stop this happening. Also how long after the intial bonding did this occur ?

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Well, I'm no expert in building baseboards and am really just at the experimenting stage. The warping that I and others reported above does seem fairly consistent, though. Will's example with the layer of MDF under the cork seems to confirm that cork is fine when it is glued to anything reasonably stiff. As he suggested, gluing the MDF onto 50mm styrofoam also increased the stiffness. My particular example has since been stripped down and the foamboard has been replaced. I then laid the track directly on this and then ballasted it. That was six months ago and there has been no warping so I'm happy to continue that particular micro layout without any cork. The PVA I used was a general purpose type for builders, somewhat more dilute than the wood glue types, and all was done indoors.

 

IIRC there have been discussions on here of various types of foam underlays as an alternative to cork.

 

Nick

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What I would try is gluing a balancing sheet of strong paper (brown parcel paper would perhaps be good) to the underside. Kitchen worktop manufacturers have to do this to prevent worktops from deforming when they glue the top surface to the core.

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Is this not just an example of why plywood is made in odd numbers of layers. The two materials have different expansion characteristics and so the cork layer is simply distorted by the foamboard? I'm not sure that just adding a third material (or even third layer of the same material) would work - it took many years of experimentation to get ply wood to the strength it now has.

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Cork is probably good for wine bottles, but it (IMO) belongs in the same skool-of-thought as "2x1 and Sundeala" for baseboards...but each to his own I guess.....

I'm inclined to agree, Mickey. When I returned to modelling about four years ago after a thirty year layoff I had this distant memory of track always being laid on cork, so that's what I did. Since then, I've been trying various types of lightweight board construction and am happy to say that I think I've weaned myself off cork :)

 

Nick

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What I would try is gluing a balancing sheet of strong paper (brown parcel paper would perhaps be good) to the underside...

Bang on. It is basic materials science that a laminated structure has to be balanced for stability. It is the adhesive that exerts most of the force, so make it symmetrical with an identical application of the adhesive on both surfaces. That's why plywood has an odd number of laminations, resulting in an even number of adhesive layers, and thus symmetrical forces: always seal both sides of plywood with the same agent.

 

It does get more complicated than this when significantly different materials are laminated together. Experiment is necessary in advance of construction with the potential combination to be used, surprisingly often the brown paper glued on to the back face does the job well enough.

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I'm currently working on a 1900x500mm foamboard layout - similar construction to the teeny tiny one I posted above, but deeper. Again I laminated a thin MDF skin to the top, no cork this time, it sounds like I may have got lucky with my recipe last time as well!

 

index.php?app=core&module=attach&section=attach&attach_rel_module=blogentry&attach_id=116040

(The top isn't stuck down in this picture, and I've cut out a fair bit inside the loop to save weight. See these blog posts for more...)

 

One thing which seems to be a big structural help and I didn't mention above: I skin the outer sides of the board (like profile boards) with the 3mm MDF as well, bonding it to the track bed layer as well as the foamboard. This makes the whole assembly quite a bit stiffer - with just the foamboard it's possible to get a few mm of deflection over the length of the board if you support it at the ends and press down in the middle, With the MDF skin, not really.

 

I've also just checked the board over for warping where the MDF and foam are laminated - so far as I can see, it's all flat except where the friction fit cross bracing was a bit too big and the original foamboard structure bowed out a little. The top doesn't appear to have any waviness at all. Certainly as good as or better than anything I've done in timber, although that may not be saying much... I'll report back if it does anything banana-ey or otherwise untoward.

 

Cheers,

 

Will

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A question about the general strength of foamcore/board...

 

I'm planning to build a diorama using the shed base from the Cornerstone Diesel House, and it needs to be secured to hold it flat. The base is a 243mm x 421mm in injection moulding. Would a well braced foamboard base have the strength to hold this, and is glueing with impact adhesive to the outside OK? If not, would the self adhesive backed foamboard likely have the strength to hold the parts on? There's not a massive amount of warping, probably not even 1.5mm along the whole length.

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I have used two layers of 25mm thick foamboard glued together with PVA and then glued this on top of 25mm x 50mm softwood framing. The track and solenoid positions under turnout tie bars was then marked onto the foamboard then a slot in the top layer cut to take a suitably length of 25mm x 50mm softwood block that has an elongated hole in the centre for the solenoid arm to fit through once the turnout is mounted above with a slightly smaller hole in the lower foamboard sheet. The softwood block then rests in the hole whilst the PVA glue around it sets.

 

Cork was then laid over the foamboard using PVA glue and the track glued down to the cork.

 

For holding wiring in place I used the self adhesive plastic pads that cable ties pass through but used a bit of PVA glue rather than just rely on the self adhesive pad. Both Squires and Maplins sell these if I remember correctly.

 

This layout is now 5 years old and has done quite a few shows with no movement in the cork foamboard or the timber blocks that the SEEP solenoids have been fixed to.

 

Ian

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As already mentioned above, and although by no means a surefire recipe for success in itself, a basic rule for laminating anything is to maintain an Odd Number of material layers.

 

Hope this helps.

 

regards

Stewart

Edited by 45157

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