6mm or 9mm ply

[Admin4]

I am using 9mm at the moment for my fiddle yard, but that’s only because it’s what I have laying around

[MickleoverTestTrack]

Hi
I was thinking adding another 6 mm sheet on top to take flex out ?

What are your thoughts?

It depends what is causing your flex? What and where your weight is.
Is it flex in the middle of each quarter, flex across the whole thing or dipping in the middle?

If it is flexing where you lean on it to test for flex, well you might never have that weight on it in practise, nothing on a model railway is that heavy.

I think from the photos, the battens aren't sufficient. I've built a hovercraft from 4mm ply and that didn't have a problem being stood on.

I think the problem you have is that the ply top forms part of your overall torsional rigidity and 6mm is too flexible for that. An extra skin of 4 or 6mm ply would strengthen it but could introduce other problems. Probably some extra battons cossing the 4 quarters would be best.

[Roger (RJ)]

Hi
This is my first post .
I have just built a 4 x 4 board for the grand kids , using 2x1 soft wood battens with 6 mm marine ply top .
I was going to use 9mm but thought in was too heavy.
The frame is supported in the middle ie 2 foot , the top glued and screws in place .

I was bit dismayed to see the it flexed , Not a lot but would you think that it will be ok?
Idea is that it will be movable ie live in the spare room , get it out to work on, play with...
I have bought 4 Ikea legs for it to stand on ; these screw in to the plates on the corner .

Yes in hind sight 9 mm would be the better option , was thinking adding another 6 mm sheet on top to take flex out ?

What are your thoughts?

I would add more battening underneath. I wouldn't recommend more than 12 to 18 inches between battens for a 6 mm top. Also, pre-drill holes through the battens (easier to do before fitting them) for wiring to pass through.

[atnas666]

i used 12mm Oriented strand board (OSB)on mine

[Bufferstop]

It's not the thickness of the board that's letting it flex, it's the lack of depth in the bearers. Cut four pieces of 6mm or 9mm, 100mm wide to go round the outside of the board and screw and glue it to the edges, so that it forms a 100mm deep frame. Put in reinforcing blocks in the corners, and cut another piece 100mm wide to go across underneath the centre. You'll have to notch it to clear the existing battens, then add glue blocks at both sides and at intervals underneath. Keep telling yourself "it's the depth not the thickness that does it".