Hello everybody. I have a plywood baseboard 9mm thick. 122cm by 76cm and looking for wood for a frame.
Can you recommend what thickness the wood should be. Obviously I want rigidity but don't want too heavy a baseboard. Would 2.5 cm be thick enough. ?
By thickness do you mean depth (i.e. vertically) or horizontally with the thin face at the top and bottom?
If you want stiffness as well as strength and keep the weight down then use deep sides made of thin material and cross-brace. You could even use more 9 mm ply for the frame. Square section strip, say 15 mm x 15 mm would make useful blocks for reinforcing the joints.
Take a look the way laser cut baseboard kits are made. The fancy tongue-in-slot construction adds some strength, but mostly it is for convenience allowing the builder to assemble them accurately with the minimum of hassle and tools. Diagonal cross bracing adds torsional stiffness.
I'm of the opinion that the 'traditional' 2x1 construction is too heavy, probably too strong and insufficiently stiff and the bracing would be better if it was thinner but deeper - I've used 70 mm, but it depends on the length.
I've used much thinner ply (B&Q's 'finest' (cheapest) that I thought was 6 mm but was actually rather less). It is remarkably strong and stiff but is noisy as I effectively made a cigar box guitar body or cajon!
Hi, Jane - welcome to the forum! We hope you'll find us friendly and helpful - there's lots of ideas, advice and experience here so don't be afraid to ask.
Obviously you have 'plans ' - we look forward to hearing about them in due course. Photos during the build are always welcome.
David.
When I wrote thickness I meant width rather than depth . So how wide should the braces be ?
I was also planning on screwing them to the baseboard as well as using wood glue.3
To certain extent it depends on what you intend to do with your layout,if its just for home or taking out to exhibitions,i tend to stick to 3/8 ply with 2"x1" frames as my layouts are primarily for exhibition use so have to contend with large changes in temperature not to mention bouncing up and down in the back of a Land Rover going down a farm track.Andy
Quote from: Jane Bourne on July 12, 2021, 13:20
When I wrote thickness I meant width rather than depth . So how wide should the braces be ?
I was also planning on screwing them to the baseboard as well as using wood glue.3
If you are gluing (definitely a good idea I think) then the screws are there mainly to hold the pieces together in the right place and provide some clamping. I think then it is how thin the wood can be without the screws splitting it. If the right size pilot holes can be drilled then the wood can be quite thin.
With my small baseboards (the largest is 1200 mm x 600 mm) I glued them and used small panel pins just to stop the bits of wood sliding and didn't hammer them in fully so they could be pulled out again when the glue dried.
With laser cut boards the tab in slot construction does much the same though it also increases the gluing surface area.
On my boards I achieved a similar effect by laminating the sides from two thin pieces of ply, stepped so there was an internal L-shaped corner that the top was glued into. The outer pieces could double as front and side profile boards and backscene.
Quote from: Jane Bourne on July 12, 2021, 10:22
Hello everybody. I have a plywood baseboard 9mm thick. 122cm by 76cm and looking for wood for a frame.
Can you recommend what thickness the wood should be. Obviously I want rigidity but don't want too heavy a baseboard. Would 2.5 cm be thick enough. ?
*
May I very politely say that your question reminds me of the old joke about the aristocratic gentleman on his horse seeking directions from one whom he considers to be a humble countryman. Given the intended destination the countryman suggests that the gentleman is starting from the wrong place.
Whilst a baseboard of 1.22m x 0.76m (10sqft) is not small, I would think that using 9mm thick ply for the top surface is overkill by a very significant amount. This will greatly and unnecessarily contribute to the weight.
As Andy Cundick has already said, it is important to consider how portable you wish the project to be. If it is hoped that it can be taken out of the home to exhibitions my remarks below are pertinent. If not they can perhaps be ignored.
*****
Some years ago I constructed the baseboard for my "Pynton Tramway Co" (RM, June 2013, pp. 484-487, and film taken at various exhibitions to be found on the web) which as very slightly smaller than you intend at 1.22m x 0.69m. The top surface was 6mm ply (nominal - in reality about 5.5mm thick) and therefore a third lighter than 9mm ply.
You speak of a "frame" for your baseboard. The crucial matter here is not the thickness of the material but the depth as it acts as a beam. For my baseboard the framing around the outside was again 5.5mm thick plywood but 9ins deep. In strict terms this was far more than necessary, but gave considerable protection to Tortoise point motors and wiring under the baseboard, and allowed for an inset control panel of generous proportions.
In addition to that frame there was also one centrally square and two diagonal braces under the baseboard. These were also 5.5mm ply, only 4ins deep, and to reduce weight had large diameter holes cut out of the length down the centre line.
If you persist with your 9mm ply and added a frame around the outside it may still be inclined to slightly twist across the surface. The bracing (especially the diagonals) of my baseboard were specifically designed to avoid that situation.
*****
Many years ago I built a pair of 3ft x 2ft baseboards and did use 9mm plywood. I learnt from that experience that such heavyweight construction was unnecessary. I then used (nominal) 6mm ply for my next six layouts including the one mentioned above.
Mindful (as I have got older - I am now in my 70s) of the weight issue of exhibition layouts, for my most recently completed project the "Pyn Valley Railway" (RM, November 2018, pp.917-921, and filmed at various exhibitions on the web) I experimented successfully with lighter materials.
The baseboard area is 43ins x 18ins (1.09m x 0.46m = 0.5sqm), the framing and bracing (one central and two diagonal as above) are all 3mm ply, and the top surface 5mm foamcore board.
*****
All of the above said, I wish you well with this project.
CP
Quote from: Andy Cundick on July 12, 2021, 14:40
To certain extent it depends on what you intend to do with your layout,if its just for home or taking out to exhibitions,i tend to stick to 3/8 ply with 2"x1" frames as my layouts are primarily for exhibition use so have to contend with large changes in temperature not to mention bouncing up and down in the back of a Land Rover going down a farm track.Andy
Thank you for your reply 😀
Quote from: GraemeD on July 12, 2021, 15:00
Quote from: Jane Bourne on July 12, 2021, 13:20
When I wrote thickness I meant width rather than depth . So how wide should the braces be ?
I was also planning on screwing them to the baseboard as well as using wood glue.3
If you are gluing (definitely a good idea I think) then the screws are there mainly to hold the pieces together in the right place and provide some clamping. I think then it is how thin the wood can be without the screws splitting it. If the right size pilot holes can be drilled then the wood can be quite thin.
With my small baseboards (the largest is 1200 mm x 600 mm) I glued them and used small panel pins just to stop the bits of wood sliding and didn't hammer them in fully so they could be pulled out again when the glue dried.
With laser cut boards the tab in slot construction does much the same though it also increases the gluing surface area.
On my boards I achieved a similar effect by laminating the sides from two thin pieces of ply, stepped so there was an internal L-shaped corner that the top was glued into. The outer pieces could double as front and side profile boards and backscene.
Thank you for your reply 😀
CP,
Your reply was detailed and interesting - thank you.
You mentioned experimenting with foambord as a surface for a layout. I tried this out a while ago, with a 5mm foamboard top and 3 ins x 1/2 ins sides. There were two cross braces, both foamboard. The board was 33 ins x 9 ins so quite small, very light and adequately stiff, although in retrospect duaginal braces would have probably been an advantage.
However I found the board amplified the noise of the locos to a very great extent. I wonder if you had this problem and if you found a solution. The track was glued directly to the foamboard.
Frank
I've been using 6mm ply for the surface, 9mm for the outside edges (4 ins, 100mm deep) and 6mm for the cross bracing for ages, no issues.
Another thought if you want to keep weight down is not to have a solid board on top, just where its needed, such as track bed and for buildings.
Quote from: Frank on July 15, 2021, 17:57
CP,
Your reply was detailed and interesting - thank you.
You mentioned experimenting with foambord as a surface for a layout. I tried this out a while ago, with a 5mm foamboard top and 3 ins x 1/2 ins sides. There were two cross braces, both foamboard. The board was 33 ins x 9 ins so quite small, very light and adequately stiff, although in retrospect duaginal braces would have probably been an advantage.
However I found the board amplified the noise of the locos to a very great extent. I wonder if you had this problem and if you found a solution. The track was glued directly to the foamboard.
Frank
*
Frank
An interesting and valid question. Thank you.
My earlier layouts with a top surface of 6mm plywood, also had 3mm thick cork sheet under the track which was pinned in place. It was then further fixed by the glue used for the ballast.
In the case of the "Pyn Valley Railway" with the top surface of 5mm foamcore board, I glued the track straight onto it (no pins), and then as before the ballast was glued down.
I had not previously given any thought to the matter of sound amplification. Now that you ask the question I can only say I have not been aware of any difference, especially in the context of the usual levels of general noise in a typical exhibition setting.
That said, on the one hand my instinctive expectation would be that foamcore board would be less amplifying of sound than plywood. On the other I do not question your experience and observation.
CP
Quote from: Frank on July 15, 2021, 17:57
CP,
Your reply was detailed and interesting - thank you.
You mentioned experimenting with foambord as a surface for a layout. I tried this out a while ago, with a 5mm foamboard top and 3 ins x 1/2 ins sides. There were two cross braces, both foamboard. The board was 33 ins x 9 ins so quite small, very light and adequately stiff, although in retrospect duaginal braces would have probably been an advantage.
However I found the board amplified the noise of the locos to a very great extent. I wonder if you had this problem and if you found a solution. The track was glued directly to the foamboard.
Frank
Yes, the construction does make a very effective sound box. Adding track underlay may help a bit but another thing that should not add much weight that might work is adding some wadding underneath in the cavity which is effectively what there is in cars. Essentially 'put a sock in it' (it works for my banjo!). Seriously though, something like polyester wadding might help as improvised acoustic wadding.
In one of his books Iain Rice suggests expanding builder's spray foam but that could be messy. I think the idea is to carve away any foam that expands beyond the exposed surface of the framework.
Another thing that could be tried is gluing more bracing pieces in. It will reduce the vibrating area and increase surface stiffness and the resonant frequency.
The framing for the last set of baseboards I made were made of 4mm ply formed in to girders, 4 ins deep and kept 0.75 ins apart by blocks of wood 4 ins deep x 0.75 ins wide by 2 ins long. The 4mm ply was glued and screwed to the block and each gider then became part of a rectangle 3ft by 18 ins.
Each board then had a 4mm ply baseboard surface attached to the top surface of the blocks, on top of which 8mm thick medium density was laminated using glue. (Medium density balsa wood is light, but much denser and harder than the stuff we normally think of as balsa wood.)
These boards don't have any cross bracing and have shown no signs of warping in 8 years of use going to and from exhibtions.
Julian