FoamCore plywood sandwich baseboard - Any ideas

[Junctionmad]

HI ,Im investigating if its possible to build baseboards that are of foam core construction, my idea, was plywood panel epoxied to PVC foam or a cheaper version of Nomex.  Then a balancer plywood would be expoxied to the base of the foam.   Th eidea is to move away from the 2"x1" plus ply conventional base board.  Baseboard would be 2' - 3' by 6' and then would be supported on an " under frame , trestle type arrangement .  The foam Im thinking of is this http://www.easycomposites.co.uk/products/core-materials/EasyCell75-Closed-Cell-PVC-Foam-Core.aspx, in 25mm form, 

 

alternatively thin MDF instead of plywood, again two sides epoxied to the foam core, to provide "balance"

 

There have been one or two threads here on RM, but just looking for peoples view and advice 

[BR60103]

Mr Mad:

I wonder if this is like the extruded polystyrene (a.k.a. Styrofoam et al) that we use over here; not foam core, just pure foam.

I made a layout of this for my wife's O gauge.  I made a frame of 1x2 with a lip on the lower edge. I put small strips across every 15" or so. The foam I used was 2" thick. The layout is 2 4'x8' sections.

There are no cuts into the foam, but I built a bit up using more foam. The track (Lionel) is held in position with large headed pins to restrict horizontal movement only.

I use the foam for scenic sections on my own OO layout but don't use it for situations that require screws. The track and roadbed are glued down with Woodland Scenics products, either their Foam Glue or Scenic Cement.

I like to carve it with a hot wire cutter. There's less mess than with a saw or even a knife.

 

We also have a product that we call "foam core" that is 1/4" of foam inside 2 sheets of card.

[DavidB-AU]

This may be of interest re sandwich baseboards. These use expanded polystyrene foam (white foam) but foamcore would probably work too.

 

https://sites.google.com/a/nscale.org.au/convention2015/program/Sandwich_and_Spline_Baseboards.pdf

 

Cheers

David

[Stubby47]

Do you intend to cut through the baseboard ( for point motors, wiring etc ?).

 

If not, you might want to consider an internal door as a baseboard.

 

If so, you could still use a door, with added sides for protection for the underside electrics.

 

HTH

 

Stu

[DCB]

The foam looks horribly expensive £50 for less than 6X4.  I used an internal door a part of a baseboard, lt is light, but pins don't go in easily  and everything has to be surface mounted, wiring, point motors etc, and it was very difficult to keep the track level at the ends where the track passed over the internal framing.  Personally I think the whole foam sandwich concept is flawed, a 2X1 framed baseboard with a Sundela board or similar top and a plywood bottom is a much better concept, especially for a portable layout, in that the bottom can be held with a few countersunk screws and can hide all the wiring, point motors etc.

[Crewlisle]

The five baseboards of my 2.6M x 2.3M 00 gauge layout Crewlisle are built on 15mm Sundela with 50mm x 25mm stiffening.   The downside with this is that it requires stiffening about 300mm centres requiring almost twice as much stiffening as 6mm plywood.   The corners were screwed, glued & dovetailed; cross-halving joints where the stiffening crossed; pinned & glued where the stiffening met the outside framing & pinned & glued to the Sundela.  Make sure that the framework is allowed to dry flat (weighted down on a flat surface if necessary) before pinning the top surface to it.

 

The big advantage is that they are extremely light, strong, easy to insert track pins & cut openings for point motors, etc..  Any part of the baseboards can be handled without fear of it ‘breaking’ off or distorting the baseboard.  I have inclines which are all securely glued & screwed to the main baseboards  & I can vouch for the strength as they were built 40 years ago & have been transported to many exhibitions without any damage or distortion.

 

6mm plywood is just as light as Sundela with less stiffening but you may probably get more noise/vibration.  ‘Foam board’ is probably the modern solution but the downside is that it is expensive & thicker than Sundela.  Do not use MDF bonded to  ‘Foam board’ as it is not very strong, heavy & absorbs too much moisture.  If you have to bond anything to it, use 3 or 5mm ply.  PVA woodworking glue (eg Evostik Resin W) would probably be a cheaper & better solution than epoxy.

[hayfield]

There was a chap at the St Albans show with very thin foam cored baseboards with wafer thin ply skins. Ever so strong and light. I think he may have been a last minute stand in, so a mail to the Chilterm Model Railway Assocation may result with a good lead.

 

http://www.cmra.org.uk/diary.html

[bgman]

A similar product was used as the basis for Gordon and Maggie Gravitt's exhibition layout Pempoul and seems to survive the rigours of exhibitions.

There are numerous videos on YouTube showing the layout dating back at least 4/5 years which may be testament to its suitability.

[Oakydoke]

The use of extruded foam (pink or blue foam) for baseboards is a popular choice in America and quite a few people here in the UK have used this method. Generally the method used is not like the OP is proposing, but rather the slab of foam is either supported on an open framework, or solid base (e.g. Ply), or sandwiched within an outer framework of protective thin ply around the sides.

The second of those gives a lightweight but rigid board, ideal for portable or exhibition layouts. There have been a few examples shown on this forum.

[David Bigcheeseplant]

We had a meeting at our club on Friday regarding foam baseboards, the member who will be building them brought along a few samples he had made to test thickness and adhesive.

 

Our plan is to use blue foam between two 3mm plywood sheets. the test pieces were 25mm and 50mm foam although there seems to be very little difference between the two in weight the 50mm is available in larger sheets as our boards will be five foot long the 50mm is easier for our needs.

 

As for glue the test pieces were clamped together I think with a PVA which was easy to pull apart even after clamping till the glue went off. The best adhesive was a resin casimite, which was impossible to part. The plan is to laminate the board in a  veneer press as (the member who is building them has one in his workshop.)

 

Recesses were routed in to the foam which gave very clean edges, further tests will be carried out in the next few weeks but the results so far seem really good.

 

David

[hayfield]

Back to the demonstration at St Albans, the boards were about 1" thick foam and from memory high quality 1 mm ply, Whilst the components were very fragile on their own, once glued became extreme strong. High performance glue was mentioned. For larger boards thicker ply may be a better choice as the layout in construction was from memory 2 mm scale and boards kept quite small, designed to fit into large plastic containers

 

Would make a very good thread of use to many from various scales 

[David Bigcheeseplant]

We may have some examples of our foam baseboards at Railex on the club stand if people are interested.

[Izzy]

The foam looks horribly expensive £50 for less than 6X4.  I used an internal door a part of a baseboard, lt is light, but pins don't go in easily  and everything has to be surface mounted, wiring, point motors etc, and it was very difficult to keep the track level at the ends where the track passed over the internal framing.  Personally I think the whole foam sandwich concept is flawed, a 2X1 framed baseboard with a Sundela board or similar top and a plywood bottom is a much better concept, especially for a portable layout, in that the bottom can be held with a few countersunk screws and can hide all the wiring, point motors etc.

Whether the basic concept is flawed very much depends on what you want I believe. Needing small, light, and easily portable boards I have experimented in recent years with using firstly artists mount board glued into layers, and lately a sandwich of mount board and 5mm foamcore board. Yes, it can be expensive, but then so can decent quality birch ply these days, and the layouts I have built have been about half the weight of ply based ones.

 

Needing just a cutting board, craft knife, straight edge, and pva, construction is clean and easy, no messy sawdust etc, so it can be carried out indoors, in the warm and dry. Useful for those living in flats/apartments and not having anywhere outdoors such as a shed/garage to use. It's true these were for 2mm layouts, but the size would be equally viable for 4mm at least, the largest boards to date being 50"×16".

 

Izzy

[sp1]

This has got me thinking : my local RC model shop sells sheets of depron 1000x 700mm in 3mm (at £4)or 6mm at £6 - sandwiched between mountboard or 4mm ply (of which I have lots) I think this would be strong enough for a 4mm layout, and would be more economical on a ply or even softwood frame?

[Junctionmad]

Thanks so far at 50 quid per 6x4 I don't think it's that expensive . I got my idea from the marine construction world , I don't think styro foam is good enough and as it's open cell it will absorb water nor is it designed to be structural.

 

As for sandwich doors. No I really don't think these are much use. Too little internal stifening , low quality construction. It's also a sound box. My experience with other panels suggests that PVC structural foam will produce a far quieter baseboard then other methods. I can dril and secure items to both sides. And route slots etc throug the foam

 

The epoxy is marine grade laminating epoxy, much more watery then the twin tubes stuff.

 

There has to be a better way then 2 x 1 and sundela. I was 15 when I last used that stuff

 

I'm going to make a few test panels with different materials and see how it goes

[davetheroad]

I used a sandwich of 3 layers of 50mm blue extruded foam. Somewhat over engineered but I had plenty of the stuff. There is no wood cladding or bracing of any kind as the boards are for a permanent layout. They don't flex at all and even take screws to lock them together (not self tapping ones).

 

i was using Kato Unitrack with points that had built in motors so all that was needed was to dig small trenches in the surface for the wiring.

[AndyID]

Could there be a problem with warping caused by differential expansion between the foam and the ply skins due to changes in humidity and/or temperature? Might be something to watch for.

[Junctionmad]

I used a sandwich of 3 layers of 50mm blue extruded foam. Somewhat over engineered but I had plenty of the stuff. There is no wood cladding or bracing of any kind as the boards are for a permanent layout. They don't flex at all and even take screws to lock them together (not self tapping ones).

 

i was using Kato Unitrack with points that had built in motors so all that was needed was to dig small trenches in the surface for the wiring.

interesting, the blue foam , you are in the US I suspect, is a DOW foam, high density expanded polystyrene. ( or is it polyurethane )  I'd still feel more comfortable with  ply skins bonded as this adds a lot of rigidity 

Could there be a problem with warping caused by differential expansion between the foam and the ply skins due to changes in humidity and/or temperature? Might be something to watch for.

thats the idea of the balancer ply bonded on the underside 

[AndyID]

interesting, the blue foam , you are in the US I suspect, is a DOW foam, high density expanded polystyrene. ( or is it polyurethane )  I'd still feel more comfortable with  ply skins bonded as this adds a lot of rigidity 

 

thats the idea of the balancer ply bonded on the underside

It sort of sounds a bit like an I-beam. Under load, the top surface is typically in compression and the bottom is in tension. The web really only maintains the distance between the top and bottom (that's a slight exaggeration, but it is the basic principle.)

 

With an I-beam, the coefficients of expansion of top, bottom, and web are all the same. I'm not sure what might happen if the web had a different coefficient of expansion. I don't know the answer, but it might be something to take into account.

[PatB]

It sort of sounds a bit like an I-beam. Under load, the top surface is typically in compression and the bottom is in tension. The web really only maintains the distance between the top and bottom (that's a slight exaggeration, but it is the basic principle.)

 

With an I-beam, the coefficients of expansion of top, bottom, and web are all the same. I'm not sure what might happen if the web had a different coefficient of expansion. I don't know the answer, but it might be something to take into account.

 

Fabricated I and box beams with natural timber flanges and plywood webs are common in wooden building construction. It's reasonable to assume that the expansion coefficients of the two materials are at least somewhat different and they seem to work OK. Whether the dimensional tolerances in the structure of a large building would be acceptable for the baseboard of, say, a P4 model railway, though, I wouldn't like to say.

[AndyID]

Fabricated I and box beams with natural timber flanges and plywood webs are common in wooden building construction. It's reasonable to assume that the expansion coefficients of the two materials are at least somewhat different and they seem to work OK. Whether the dimensional tolerances in the structure of a large building would be acceptable for the baseboard of, say, a P4 model railway, though, I wouldn't like to say.

 

Differential expansion probably won't be a problem, but it's always worth looking for any potential "gotchas" when trying something new.

 

One thing to careful about would be heating. A heat source under the baseboard could heat and expand the bottom skin while the foam is preventing the heat from getting to the top skin. That would produce some amount of sag, but I've no idea if it would be enough to cause any real problems. There might be a similar concern about overhead lighting.

[ScottW]

HI ,Im investigating if its possible to build baseboards that are of foam core construction, my idea, was plywood panel epoxied to PVC foam or a cheaper version of Nomex.  Then a balancer plywood would be expoxied to the base of the foam.   Th eidea is to move away from the 2"x1" plus ply conventional base board.  Baseboard would be 2' - 3' by 6' and then would be supported on an " under frame , trestle type arrangement .  The foam Im thinking of is this http://www.easycomposites.co.uk/products/core-materials/EasyCell75-Closed-Cell-PVC-Foam-Core.aspx, in 25mm form, 

 

alternatively thin MDF instead of plywood, again two sides epoxied to the foam core, to provide "balance"

 

There have been one or two threads here on RM, but just looking for peoples view and advice 

 

Maurice Hopper has been documenting his method of baseboard construction in his blog. His first posting on the subject starts here-

 

http://www.rmweb.co.uk/community/index.php?/blog/1391/entry-15121-dutch-p87-baseboards/

 

 

Scott

 

 

[Junctionmad]

Im familiar with foam core in marine construction and it has been used to produce furniture panels that are very light but very strong.  The key is to bond the foam to the skins to produce in effect an i-beam 

 

from purely subjective reasoning and experience of marine panels, I would believe this is superior to sundela / plus framing, and I suspect is far less likely to warp.

 

I suppose the proof is in the eating  

[1BCamden]

hi Junctionmad,

I am planning a large layout (eleven plus baseboards) and am definitely going down the extruded polystyrene route. In Australia its a FOAMEX product called 'Styroboard XPS extruded polystyrene' it is produced in 2400 X 600 sheets, of various thicknesses. I intend to use this product with 3mm MDF framing/laminating sections, edging, plus upper and lower skins as required.

This is not a cost exercise, it's about weight and durability, while delivering high stiffness and workability. Noise reduction will hopefully be a side benefit.

The sandwich concept is not my design basis, more a case of depth of material rigidly bonded to a vertical box section/arrangement, the upper and lower skins are primarily for encasement. With each of the eleven or so baseboards (2400 X 1000 X 120) include provision for all the items to; stand, and display the layout, therefore a timber arrangement as you stated was never going to be a practical option.

 

The bonding, laminations design will be the challenge, while below board switch drives etc will be generally straightforward.

 

best regards

Stanley

[davetheroad]

I have a 4 feet section of baseboard that has to be lifted out to allow access to the operating well. With extruded polystyrene i can lift it with one hand even although it is 6 inches thick.