6mm or 9mm ply

Discussion of model railway baseboard design and construction
zigzag
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6mm or 9mm ply

Postby zigzag » Thu Apr 18, 2013 3:56 pm

Im about to embark upon my first baseboard construction, softwood frame and ply top.

What are the pros & cons of 6mm vs 9mm ply, is the extra thickness and thus rigidity worth it for the extra weight?

Steve Hill
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Re: 6mm or 9mm ply

Postby Steve Hill » Thu Apr 18, 2013 4:54 pm

Do you intend to move the layout much once you've built it? If not the extra weight is a non-issue, and you may prefer the extra strength. (I actually use 12mm ply). Using thinner ply probably means putting cross-braces closer together, so the weight saving is less than you think, and the more cross-braces you have the more care you need to take about where e.g. point motors go.

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Bufferstop
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Re: 6mm or 9mm ply

Postby Bufferstop » Thu Apr 18, 2013 5:19 pm

I used 6mm ply throughout apart from the ends which were going to take the alignment dowels and coachbolts which I made from an offcut of 12mm. The thicker ply adds little extra strength ask an aircraft designer. An inch square PAR (planed all round) batten joining the top and sides will hold it rigid. I put in 2 crosspieces in a 6ft x 2ft board. My test for solidarity is to put the board down on a flat surface, put a 10kilo weight borrowed from my son's exercise kit in the centre and try to lift it by one corner. If it doesn't flex it's passed. If I was designing the same thing for a portable layout I'd use the same materials but keep the lengths down to between 3 and 4 feet, makes it easier to get in and out of cars.

If you want real lightweight, Kingspan rigid insulation, sheeted over top and sides with 4mm ply is exceedingly light and really rigid, but it won't take anyone leaning on it. I built a layout that way which sat on top of bookshelves around the room but had to be put away when the room was needed for guests. A 12 X 8 L-shaped layout it all packed away into a double wardrobe with the stock boxes on the top shelves.
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b308
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Re: 6mm or 9mm ply

Postby b308 » Thu Apr 18, 2013 6:12 pm

With ply baseboards it's more about structure than weight, as Bufferstop says correctly constructed 6mm ply will give you a solid board... Personally I tend to favour 9mm round the outside and 6mm for the track base and framework.

AlunKimber
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Re: 6mm or 9mm ply

Postby AlunKimber » Thu Apr 18, 2013 7:57 pm

I use 6 mm ply for the main baseboard (top AND bottom), with 9mm ply for the edges and 4 mm for the intermediate bracing. As is said already, it's the structure not the weight that brings strength.

noel
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Re: 6mm or 9mm ply

Postby noel » Thu May 02, 2013 4:45 am

+

9mm for egg-box, and 4mm for top.

Use a straight fence on the 9mm ply to ensure true cuts

+

peak experience
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Re: 6mm or 9mm ply

Postby peak experience » Tue May 28, 2013 2:00 pm

if you are using below the board peco point motors, use 9mm as the screws protrude through the top of 6mm.

CF-FZG
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Re: 6mm or 9mm ply

Postby CF-FZG » Sun Sep 08, 2013 9:28 pm

peak experience wrote:if you are using below the board peco point motors, use 9mm as the screws protrude through the top of 6mm.


Or use shorter screws :D
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RAFHAAA96
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Re: 6mm or 9mm ply

Postby RAFHAAA96 » Thu Mar 13, 2014 4:47 pm

b308 wrote:With ply baseboards it's more about structure than weight, as Bufferstop says correctly constructed 6mm ply will give you a solid board... Personally I tend to favour 9mm round the outside and 6mm for the track base and framework.


My plan for a future garage sized layout intends to use 9mm framing with a 4mm bottom closure and a 6mm open frame track bed. (drawn up using the very easy to use free Sketchup-Make for the tree wood bits and the simply splendid and also free Scarm software for the trackwork visualisation bits)
The reason for the closed bottom is:
1) to give strength and
2) to keep the beasties out
and using a 6mm rather than 9mm track bed for gives more flexibility for changing levels, although the obvious plan is for all track to be level and the terrain to do the up & down bits.
I would like to know how people mechanically work the gradient transition to avoid loco jacking at the top and bottom of a slope, whilst avoiding adverse camber on any adjacent curves.
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Catweasel
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Re: 6mm or 9mm ply

Postby Catweasel » Thu Apr 03, 2014 10:18 am

Baseboard 1.JPG
Baseboard 1.JPG (48.43 KiB) Viewed 3185 times


For Fosdyke Yard,I built 2 baseboards. Each one is 1030 x 600 mm. Frame is 70 x 18 softwood with a 6 mm ply top. It seems to be a pretty sturdy design and is light. Although it looks bent in the photo,the sides are straight.There are 2 blocks on the bottom in the photo which the second board sits on. Its held in place with 2 dowels and over centre catches and rests on 3 trestles.

Mark1963
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Re: 6mm Frame flex’s

Postby Mark1963 » Fri May 04, 2018 10:39 am

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?
D8074D62-9482-465B-8AFB-F7BAEE75A647.jpeg

B0511687-3C0F-41C7-B222-E921EF25BBF7.jpeg

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Bufferstop
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Re: 6mm or 9mm ply

Postby Bufferstop » Fri May 04, 2018 12:27 pm

RAFHAAA96 wrote:I would like to know how people mechanically work the gradient transition to avoid loco jacking at the top and bottom of a slope, whilst avoiding adverse camber on any adjacent curves.


With great difficulty. Very gradual transition curve in the vertical, only on straight track. Trackbeds for parallel tracks laid independently and for curves tilted in on one axis at a time. If you are going to have multiple gradients rigid chassis must be restricted to 4 wheels, even then some degree of vertical movement of one axle is desirable. The traditional "rabbit warren" 009 layout is a nightmare to get acceptable spiral curves, I suspect it was only the enormous treads and flanges that ever allowed them to work. This isn't just a problem for modellers, when it comes to getting locos on and off road trailers, a ramp up to a flat deck is deprecated, a ramp to a sloping deck is better and a dropped roadway to the end of a siding is preferred. The NRM has very strict guidelines on the abruptness of changes of gradient they will permit their locos to use.
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Ex-Pat
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Re: 6mm or 9mm ply

Postby Ex-Pat » Fri May 04, 2018 12:28 pm

I have experience only of 3.6mm ply, but the cross-supports are far more comprehensive than your structure, and I get no warping or flexing.

I would suggest you put in further bracing/supports.

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RAFHAAA96
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Re: 6mm or 9mm ply

Postby RAFHAAA96 » Sat May 05, 2018 8:59 am

@mark1963
You can really stiffen your 4x4 board by putting another sheet on the bottom rather than the top.
Think how stiff the hollow door contruction is in your house. You could even mimic the door’s cardboard core but its not necessary on a board that size.
If you need to wire point motors or a track bus then obviously add the lower skin after the wiring has proven reliable.
Rob
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Bufferstop
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Re: 6mm or 9mm ply

Postby Bufferstop » Sat May 05, 2018 10:28 am

RAFHAAA96 wrote:@mark1963
Think how stiff the hollow door contruction is

The first time I heard of this type of construction was a competition to design a layout to fit on a 6'6"x2'6" door. It's possible to cut them in half and hinge them, you need a batten as thick as the framing of the door. Pull out or compress the filling far enough to insert the batten between the sheets then glue and pin it in place. If you want to attach hinges, fit them to the undisturbed edges.
Flush panel doors may work out a bit expensive, but a site where they are re-modelling a building may be a good source for little or no cost.
Store revampings amaze me, what happens to all those solid if slightly work worn counters, display stands etc. that go into the skip.
Perhaps one amongst us is a shopfitter and could enlighten us. :)
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