Baseboard thickness

[johna]

Hi

Would 6mm plywood be too thin for making a oo gauge  baseboard.? I haven't been able to get out due to Covid-19

[rab]

Most recommendations I've seen have been 9mm,

but I guess it depends how big the board is,

and how much bracing you put in it.

[brossard]

6mm is ~1/4" and I would say it is too thin.  My boards are 3/16" or ~ 9mm.  Sides and ends are 1/2" ply 4" wide.

 

 

John

[Gilbert]

My kit boards from Grainge and Hodder are 6mm but nicely laser cut, well braced and fit together very well...

I have a number of 9mm boards but find them a bit heavy...

Chris

[rab]

10 minutes ago, brossard said:

6mm is ~1/4" and I would say it is too thin.  My boards are 3/16" or ~ 9mm.  Sides and ends are 1/2" ply 4" wide.

 

John

Pedant hat on: 9mm is 3/8 not 3/16.

 

[brossard]

Ah, yes, well that's telling me.  I meant 3/8".  I'm trying to balance weight vs strength.

 

John

[Harlequin]

As far as stiffness is concerned 6mm is fine - you just need to brace it more frequently than 9mm.

 

But remember that the lesser thickness will mean that fixings such as pins, nails and screws, will have less material to bite on. If you glue things in place or can add extra material where you need it for fixing, then thickness is not an issue.

 

[DCB]

Its horrible stuff, OK if its braced at frequent intervals but it tends to splinter at the edges unless carefully sealed. I would leave it to the lazer cut folks.  If I had to use 6mm ply I would use two thicknesses, that way the upper surface could be cut away where there are no tracks to get away from that flat earth illusion many layouts convey.

[PatB]

2 hours ago, DavidCBroad said:

Its horrible stuff, OK if its braced at frequent intervals but it tends to splinter at the edges unless carefully sealed. I would leave it to the lazer cut folks.  If I had to use 6mm ply I would use two thicknesses, that way the upper surface could be cut away where there are no tracks to get away from that flat earth illusion many layouts convey.

 

Very much depends on the ply. From local suppliers, I can get everything from beautiful, hoop pine marine ply that can be used for building (1:1) aircraft, through some excellent and reasonably priced exterior grade (my preferred choice for most purposes), and supposed BS1088 marine (but if it actually is BS1088, then the BSI needs to review their standards), down to some stuff that can be pretty much guaranteed to delaminate at the edges into menacing, dagger-like splinters that will slide several inches under your skin, and, finally, some ghastly softwood rubbish that I wouldn't even light fires with, it's so terrible.

 

Decent 6mm exterior is perfectly adequate for a 00 baseboard if properly braced. I've still got a 3'6" x 4'6" unit that I built almost 20 years ago from a 6mm sheet of the abovementioned dagger producing stuff. It relies heavily on deep, box section construction and is very stiff and quite light. After being banged around by a child (it supported my daughter's Thomas layout), stood on, stored without due care and attention and subjected to extremes of temperature (it's spent the last 10 years in an old caravan, whose interior temp varies from 0 to 50 degrees C over the year), it remains flat and square. The only problem with it is that a couple of the joints have become fragile, where the PVA glue I used has begun to break down. I'm currently contemplating fixing the failing joints and using the board to build an US 0-27 micro layout to run the Marx stock I've recently started to accumulate. I'm confident that it's amply robust for the heavier models.

[Stevebr]

My last layout used 6mm ply as a top surface without any problems over its 7 years of use but my next layout will probably be 9mm to reduce the bracing

[Nearholmer]

I’m with Pat B on this. Even what the Americans call ‘door-skin ply’ is fine in a box configuration and I’d still use it now if it wasn’t for the fact that I now screw, rather than pin, track because I’m working in coarse-0, so need something for the screws to bite.

 

I built the boards for an EM model of The Dyke (near Brighton) c1987, lost interest after laying the track, put it in a shed, left it there for ten years, passed the house to my eldest daughter who totally neglected the shed, and when the shed collapsed and went for firewood about five years ago the baseboards were still solid as a rock and completely square, acting as a block of flats for many field mice.

 

Many baseboards have their strength in all the wrong places so are both heavy and weak. If you look at the likes of Ikea, they design table-tops using box-structures of very thin materials, which are light as a feather yet can support your entire Christmas dinner with confidence, so even 3mm ply would be fine for Gauge 1, if used intelligently.

Edited July 5, 2020 by Nearholmer

[Zomboid]

My board is a laser cut job made from 6mm ply. As supplied it didn't come with enough bracing so it's sagged a bit creating a roller coaster effect (and making my gutless 2-10-0 even more of a nuisance than it is on perfect track). It's in 3 segments and only the central one has an 'X' of bracing supplied - that bit is perfectly smooth, the end segments are drooping where there's nothing.

 

Now I know that, I'd happily buy the same kit again, and add a little extra diagonal bracing.

[PatB]

1 hour ago, Zomboid said:

My board is a laser cut job made from 6mm ply. As supplied it didn't come with enough bracing so it's sagged a bit creating a roller coaster effect (and making my gutless 2-10-0 even more of a nuisance than it is on perfect track). It's in 3 segments and only the central one has an 'X' of bracing supplied - that bit is perfectly smooth, the end segments are drooping where there's nothing.

 

Now I know that, I'd happily buy the same kit again, and add a little extra diagonal bracing.

Diagonals are also important in order to resist twist, if there are no full, or near full, box sections in the construction. It's where a lot of baseboards are less than optimal, being either floppy in torsion, or massively heavy to compensate for not enough material where it's actually needed. 

[Tim V]

My retired exhibition layout was built with 4mm ply, it did 39 exhibitions (would have been 40 but for snow). Very light - a pair of fully detailed boards screwed together for transport could easily be lifted by one person.

 

You just need to consider bracing and box sections.

[rab]

I assume the OP was asking about 6mm because that's all they had available, but it strikes me that if you were using 6mm hoping to save weight, the extra bracing required would negate any weight saving.

[Nearholmer]

Nope.

 

With good design, thin material used in careful structures is lighter.

 

Modern flush interior doors, Ikea tabletops,  light as feathers, but  very  rigid.

 

 

Aircraft wings.

 

Acoustic guitars.

 

 

Edited July 5, 2020 by Nearholmer

[Zomboid]

It rather depends what you use for bracing. A bit more 6mm ply would be entirely up to the job, since it is only flexible in two dimensions, so at right angles to the surface it'll be fine, and still light.

 

If you use 2x1 as the bracing material on the other hand...

[PatB]

Zomboid's mention of 2x1 reminds me of the other nice thing about plywood, of whatever thickness. Given a modicum of care in cutting, it can be made into structural members which are, and will remain indefinitely, dead straight and dimensionally stable. There's not much in the way of off the shelf timber available these days that can boast that. 

 

As an engineer, the one issue I have with cutting plywood into long, relatively narrow members is that half the plies will have their grain running at right angles to the main loads, resulting in their not doing much work and making the member heavier than it strictly needs to be. The engineering solution to this is to cut the strips of ply at 45 degrees to the sheet, or use staggeringly expensive aircraft ply which is made with the plies oriented so. That's taking things to extremes though, in structures where weight is absolutely critical, such as aircraft or very high performance boats. Even there, a great many highly effective designs do not go to such an extent, so I doubt if it could be justified for even the most lightweight baseboard. 

 

And that's probably enough overthought irrelevance for today . 

[rab]

11 hours ago, Zomboid said:

It rather depends what you use for bracing. A bit more 6mm ply would be entirely up to the job, since it is only flexible in two dimensions, so at right angles to the surface it'll be fine, and still light.

 

If you use 2x1 as the bracing material on the other hand...

I must admit I hadnt thought of that. What's the best way

to fix the ply bracing to the baseboard, glue and pin?

[Zomboid]

I'm not sure I could say what the best way is, but on my laser cut board I had an X of ply that I held on with a tin of emulsion until the glue dried. I suppose it could be pinned, but the edge of some 6mm ply is a small target.

[Nearholmer]

Yes, glue and pin.

 

You can use pieces of small section softwood as fillets at the joins, but if you get really accurate (I sometimes can, but often can’t) then you don’t even need that.

 

The ‘big thing’ is to keep everything square and keep joints under pressure while the glue hardens, which can sometimes be a bit tricky - it’s something to think about as you work out the design and order of assembly, because you really need a good sized, dependably flat surface to work on. If you watch video tutorials, people make it look easy by having huge island carpentry benches with built-in clamps etc, which not all of us are blessed with. I’ve resorted to the kitchen floor when nobody is looking, because luckily ours is dead flat, but for narrower boards I’ve now worked out an assembly routine that keeps everything square using the workmate.
 

I freely confess to being a poor carpenter, and I can make really out-of-square baseboards, with built-in warps, when using traditional methods, but find it a lot harder to do that with plywood box structures!

[Derekl]

Much helpful advice on the need for bracing above, but not much on exactly how much. Say you use a 9mm board  of 1.2 by 0.6 metres (or 4' x 2') supported around the edges, what bracing are we talking about intermediately - traditional one every 300 mm or something else? And what bracing for similar sized 6mm board? 

[Harlequin]

6 hours ago, rab said:

I must admit I hadnt thought of that. What's the best way

to fix the ply bracing to the baseboard, glue and pin?

 

I built 3 identical boards and a bridge section for a test oval using 9mm ply. All the joints in Board 1 were glued and pinned or screwed. The pins often missed and split the ply on the other side.

I gradually used less and less pinning because I realised that it was taking time, doing more damage than good, making the structure look worse and because I realised I could trust the glue.

The last part I made, the bridge section, used no pins or screws at all and it's been absolutely fine.

 

(To use glue alone your edges need to be straight and square, and just before gluing you should make sure the surfaces are clean by sanding them a bit and removing the dust. Then you needs lots of weights and or cramps to hold the parts together while the glue sets.)

 

Edited July 6, 2020 by Harlequin

[Nearholmer]

A 1200x600 board with 75 or 100 deep sides, plus one x-brace (think of the plan as the Scottish flag) will work in 6mm ply.

 

The diagonal bracing is far more useful for resisting twist than a series of cross-braces.

An even stronger structure results if you add a bottom to the box, out of which you can cut triangular openings for wiring access.

 

If you want to get a feel for the strength of such structures, try making some miniature ones from cardboard.

[NittenDormer]

I thought long and hard about this when starting my baseboards. I used a 6mm ply - softwood block spacer 6mm ply sandwich for the ends of two of my boards, but decided that they were too bendable/squeezable between the spacers. (disclaimer: could be the design, could be the workmanship). I went for 9mm ply for the verticals, but 6mm for the trackbed, as I needed an element of flexibility there. So far seems good, but nothing running yet. I'm wondering about 3mm ply sandwiched for a helix as a way of getting pieces to stick together end to end.