Jump to content

Ply sag


shaung75
 Share

Recommended Posts

I've now reached the stage where I'm installing posts and I'm wondering what should the maximum distance je between posts to prevent sag with 18mm ply? At the minute I'm on tight (3rd/4th) bends so the posts are fairly close, but i've got some long straights in my proposed layout. I was hoping 1.2m would be fine so that I can get away with a post at either end and one in the middle of the board. What are your thoughts from experience?

Cheers

S

Link to comment
Share on other sites

Hi Shaun I have used 18mm ply as a track base, for no other reason than I acquired over 20 8x4 sheets of the stuff from a nearby building site that they were going to burn! And all for the price of asking! Anyway, I digress, you will need to build it on a framework of some sort or it WILL sag no matter what. If you trawl through my posts and look for "Indoor Outdoor Layout" it's on page 17 you will see some pic's of our layout before the ply was put down, showing the framework that I constructed first, it's built from 3x3 posts and 3x1 and 1 1/8 runners these are imperial measurements as I am old ok :lol: I have most likely over engineered the framework but I'd sooner have it too strong than not strong enough,.............you can actually walk on on it if you should need to!

Having said all that it's been outside now since 2012 and we have quite a few dips! some of which we have repaired some not!

You will find running outside is just like the real thing you are always maintaining the track in one form or another. :)

Link to comment
Share on other sites

If you skimp on the base now, you might cry later on.

Its worth getting it right once, some kind of structure under the plyboard, and then weather proof paint on the plyboard.

my 'structure' - http://i.imgur.com/2TK4Qkc.jpg

how is your final track going to look? Is it going to be on posts raised above ground, or will you add soil under the layout for some scenery?

(edit - is this a test layout or the main one built to last?)

Edited by Guest
Link to comment
Share on other sites

I've no experience of using posts to support the baseboards but if it were me (and apologies in advance because I do tend to over-engineer things) I would be inclined to provide additional bracing to the underside of the plywood along it's length to help prevent any sagging. With additional bracing then I would think posts spaced 1.2 metres apart would be fine. I personally wouldn't rely solely on the posts to provide adequate support - in fact I would imagine it wouldn't be too long before the plywood sagged without some form of additional bracing. Some strip timber or narrow lengths of plywood along the two edges of the baseboard should be sufficient although maybe even something just along the centreline if your boards are only narrow?

Link to comment
Share on other sites

I'd agree with the others you're going to need a couple of battons running the length of the board and I'd say at least 2inch depth from the board downwards even at 4ft (1220mm) spacing. If you don't you'll have railway like Brunel's earliest!!!

Link to comment
Share on other sites

Hi Shawn. 2" × 1" slatelats screwed on edge to your posts should be ok. Its very cheap to buy from a builders merchants and strong too. It's tanalised so should cope well and will no doubt be shielded from our lovely climate with roofing felt or whatever you decide to cover your baseboards in. I'm inclined to agree with Mick et al that your ply should be supported along its length or it will DEFINITELY sag. A little time spent now will save a LOT of trouble later mate. Regards. Mark

Link to comment
Share on other sites

Thanks for the replies chaps, appreciate it. So that's settled then, a sub-structure will be incorporated into the build. I have a fair amount of 38x63x2400mm studwork left over from the office conversion so I'll use that - I doubt the boards are going to be more than 120mm in most places so I'll use it down the centreline as Mick suggested. Cheers. Shaun

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...