I'm getting ready to start building my HO layout and need advice on the thickness of the plywood that would be practical for my layout.
The layout will be a cookie cutter type with L girder benchwork. All along I have planned to use 1/2 inch plywood for the sub roadbed. But now that the time is here I'm questioning whether or not I should use 3/4 inch?
The layout will be in an E shape 15' X 20'. It will have a lower level for staging. To get to the lower level the trains will run around a double track that will be attached to 6" wide plywood. It is this plywood that I'm in question of.
I know the experts here have already gone through this dilemma and have reasons for using one over the other. Please chime in and let me know your reasons for either.
Thanks in advance for your guidance.
Bill
Go with the 1/2". Most people don't realize just how storng 1/2" of plywood can be. If supported properly (every 24") it will hold 300-400 lbs easy.
It will not warp...maybe if you soaked it in water for a few weeks, but even 3/4" will do that.
It is lighter and easier to move.
If the risers under the descending tracks are 12 inches apart 1/2 inch ply would probably suffice. Rather than use cork roadbed, I plan to use sheet cork in double track width and glued to the plywood. It won't be ballasted so it should be very quiet. Defiitely, don't lay the track right on the plywood.
In my last layout with L-girder and 16 inch spaced girders, I used half inch ply, BUT I glued 1 x 2 (actualy 3/4 x 1 1/2) wood beams under the center of each span with elmer's glue. I used adjustable C clamps to hold them firm whuile the glue set. No sag whatever. I had plenty of scrap wood left from the bench work construction so it was free.
Unless you are modeling No 1 gauge Live Steam 1/2" ply will be fine.
-George
"And the sons of Pullman porters and the sons of engineers ride their father's magic carpet made of steel..."
Even 1/2" is unecessarily thick with HO and smaller scales.
You could get by with 3/8" of a quality brand and 15" spans with no difficulty. The thicker it is, the more plwood costs and the heavier it is. It also costs more to cover and to cut, and takes more energy, to boot.
I firmly believe that if your benchwork is constructed well and with good material, your roadbed of cookie-cutter style need not be as thick as 1/2" unless you find you must span between risers that are perhaps 24" or more.
My
Bill54 wrote: The layout will be a cookie cutter type with L girder benchwork. I have planned to use 1/2 inch plywood for the sub roadbed. I'm questioning whether or not I should use 3/4 inch? ... the trains will run around track that will be attached to 6" wide plywood. It is this plywood that I'm in question of.
Our club has a minimum sub-roadbed width of 4" and we therefore require 3/4". The maxium span is 20". That is probably over engineered, but we assume eventually, for some reason, people (and big people at that) will be leaning on the track.
Texas Zepher wrote: Bill54 wrote: The layout will be a cookie cutter type with L girder benchwork. I have planned to use 1/2 inch plywood for the sub roadbed. I'm questioning whether or not I should use 3/4 inch? ... the trains will run around track that will be attached to 6" wide plywood. It is this plywood that I'm in question of. The answer is in the distance between the cross members of the L-girder. 1/2" should easily support a 6" wide strip for distances up to 20" or so. I would cut a strip and test it out. See how much flex there is versus how much flex you want it to have. Our club has a minimum sub-roadbed width of 4" and we therefore require 3/4". The maxium span is 20". That is probably over engineered, but we assume eventually, for some reason, people (and big people at that) will be leaning on the track.
Another thing to keep in mind when selecting your ply for cookie cutter approach, is, even a quality 5 ply in 1/2" may not be strong enough for turns. Any plywood is strongest when ripped with the grain, as you cut it for a radius, especially smaller 18-22", the risers for support should be much closer for stability. I would not recommend that you allow any ply to have surface graining pass the 45 degree (1/4 of the turn). If you feel that many splices throughout the turn are not stable enough, you can laminate the subroadbed and alternate the seams. In this method 2 layers of 3/8 is very strong. Many when building helixes do so w/ great success.
Modeling B&O- Chessie Bob K. www.ssmrc.org
Risers will be between 12 and 16 inch so what I'm listening to is that the 1/2 inch plywood will be sufficient for my layout.
I hope to get some pictures on soon.
Thanks again everyone.
bogp40 wrote: Texas Zepher wrote: Bill54 wrote: The layout will be a cookie cutter type with L girder benchwork. I have planned to use 1/2 inch plywood for the sub roadbed. I'm questioning whether or not I should use 3/4 inch? ... the trains will run around track that will be attached to 6" wide plywood. It is this plywood that I'm in question of. The answer is in the distance between the cross members of the L-girder. 1/2" should easily support a 6" wide strip for distances up to 20" or so. I would cut a strip and test it out. See how much flex there is versus how much flex you want it to have. Our club has a minimum sub-roadbed width of 4" and we therefore require 3/4". The maxium span is 20". That is probably over engineered, but we assume eventually, for some reason, people (and big people at that) will be leaning on the track.Another thing to keep in mind when selecting your ply for cookie cutter approach, is, even a quality 5 ply in 1/2" may not be strong enough for turns. Any plywood is strongest when ripped with the grain, as you cut it for a radius, especially smaller 18-22", the risers for support should be much closer for stability. I would not recommend that you allow any ply to have surface graining pass the 45 degree (1/4 of the turn). If you feel that many splices throughout the turn are not stable enough, you can laminate the subroadbed and alternate the seams. In this method 2 layers of 3/8 is very strong. Many when building helixes do so w/ great success.
There is no "grain" to plywood. Plywood is made of layers of thin wood that has been peeled off a log and laminated with alternating layers perpendicular to each other. That all said, I agree that 1/2" is sufficient up to 24" support centers, as long as it is a good grade of plywood, such as B/C fir. Do NOT buy the cheap pine CDX that is sold at Home Depot, Lowes etc. Pine has a bad habit of warping, and being harder than fir is harder to nail. B, the smooth top surface, is free of knots & voids & will not give you problems with the cork, C, the poorer grade, had knots & voids that will make an uneven base for your cork. The couple of dollars difference between the grades is more than worth it, in the ease of working, and less tendancy of warping. A little over 40 years as a carpenter/cabinetmaker taught me this. Good Luck!
Ivenhen, Thanks for picking up on the "graining". In lay terms this is the only way to describe the strength factored into the ply. Of coarse ply has no grain, but is strongest when the orientation of the outer plys are not crosscut. As you mention the interior plys may have voids also showing that the outer plys(even though plugged or boat patched) will afford the most strength.
I can't agree more about the poor quality of the ply whether pine or fir at HD and Lowes. A quality lumber supplier will have a better product and generally is very little more in price, than the so called "premium" varieties from a home center.
Actually, there IS a grain to plywood - a double grain (it goes two directions). In five-ply plywood, generally three run lengthwise with the panel and two run width-wise.
Structurally, the weakest direction in five-ply plywood is around 55 degrees off the top and bottom layer grain direction (that's the 3-ply grain. In seven ply sheets, the weakest direction is about 51 degrees off the top grain direction). The sheet will flex easier along that line than in any other direction. It isn't enough to make a major impact on subroadbed, however...
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
Terry
Luckily there are several lumber yards near here other than Home Depot, Lowes and 84 Lumber. I'll check them out this weekend to see what their prices and inventory looks like.
The better grades of plywood help, but 24 inch supports are iffy for half inch ply, 12 inch is good, 16 inches is not as good as twelve. Better 5/8 ths, and make sure the board is not warped, they don't get straighter with time. Do use the 5 ply, it is much better to work with. And use fresh, sharp, fine tooth saw blades.
Good luck and enjoy.
Tilden wrote: The better grades of plywood help, but 24 inch supports are iffy for half inch ply, 12 inch is good, 16 inches is not as good as twelve. Better 5/8 ths, and make sure the board is not warped, they don't get straighter with time...
The better grades of plywood help, but 24 inch supports are iffy for half inch ply, 12 inch is good, 16 inches is not as good as twelve. Better 5/8 ths, and make sure the board is not warped, they don't get straighter with time...
I don't see how you can say this. If you support 3/8" plywood that is in a strip 3" wide between two risers set 24" apart and place an HO Challenger so that its couplers are equidistant from the riser centres, you will get something like 1/32" deflection downward. This heavy engine will deflect the centre of the span so little because of its overall weight distribution, much of which is within 6-8" of the risers. That is where there is most resistance to bending, within 6" of either side of the risers. So, saying that 1/2" 5-ply should not occupy spans greater than 24" is overkill.
In the case of a smaller engine, say a light Mikado, the deflection will be much the same for all the obvious reasons. Now add all the scenery, the strips and tape or paper, the plaster, or the glued foam, and fix it to the plywood. Your roadbed will be now supported to the extent that you will get effectively zero (0) flex over such spans.
I've used 3/8" ply with 24 inch risers and it warped and sagged. Now, a better grade may have helped....some. I simply don't think it is worth it to use anything less than 5 ply 1/2 inch board, better 5/8 inch if you would have any 24 inch spans. The three ply board tends to be soft and subject to deflection and twisting.
Just an opinion.
Tilden
You are going to get many different answers to your question based upon the personal experiences of the many modelers answering your question. And most of the info will be correct from what they are doing.
Plywood is very strong, stronger than boards of the same thickness, that as why they use laminated beams in home construction that eliminate the use of support columns in the basements or large rooms on any level of the homes.
So the questions is, what do I need? The shorter the width from the wall, ie 12" vs 30", the thinner the plywood you can use within reason. If you had a 12" width, 1/2" plywood would perform very well. At 30", 1/2" will perform well "if" you place supports undernieth at appropriate spacings, not so much for breakage strength, but for elimination of sagging under weight, or, moisture causing swelling or shrinkage when too dry.
Many people will tell you that 3/4" or even 5/8" is overkill. Are they wrong? No. But if money were not an issue, or, I had 3/4 or 5/8" hanging around from other home projects, you bet I would use it? Why? Because I "know" I would never have a problem with that thickness unless my location was prone to a heck of lot of moisture, and I mean a lot!!
It is all common sense, the thicker the plywood, the stronger the base, the less problems that you could have. Probability of a problem is whole different ballgame, and you can cut those odds by using more supports on thinner plywood.
A deflection of 1/32 is a change of over .030. And people wonder why their trains break apart because of misaligned couplers. Run that loco over that spot in hot humid weather and cold weather for the next five years and then let's look at the deflection.
I once acquired a used bare top 2' x 4' module with a top of ½" plywood. I started to lay my track on it and wondered why my turnout would not lay flat from the edge of the module... guess what, the top was bowed in and no signs of water damage on it. A perfectly square and true box had at least ¼" of deflection down in the top in the first 8" of the center length of the module. I have 5/8" supported every 24" that is sagging on a 30" wide module. Because of that I use only ¾".
Do what you want but I don't have any warping roadbed or trains breaking apart because of undulating roadbed on my modules. It may be overkill but 4 years down the road you won't be wishing you did use the better stuff or braced the thinner plywood every 12-14".
I used 3/4" plywood on my layout for three reasons:
1. Peace of mind. You're going to invest $100's, of not $1,000's in materials on the layout, not to mention years of work on it, and pinch pennies for $50 or so and HOPE you didn't cut yourself too thin? Unless you plan on moving your layout around towm weekly, go for the most robust design you think you'd ever need, and then step it up further an additional notch, and sleep comfortably for the next 30 years.
2. Overkill in strength. I wanted to be able to climb on the layout and not have things move. If you have track on risers ANY vertical deflection of the base will kill you, as it'll be magnified 100 fold. I've found myself shimming the track with pieces of paper to get the final alignment perfect. If your layout is sagging even 0.10" you'll see it in the running of your trains.
3. Sound control. Heavy boards transmit les sound than thin and lightweight boards. If you want a quiet layout you generally need to build a solid layout.
That's my $0.02.
Mark in Utah
Mark, Thanks for reminding me about overkill. I usually do exactly that, overkill most everything such as pulling a 24 ft, 5,000 lb camper with a 1 ton, Ford F350 4x4 dually when a standard 1/2 ton would suffice.
I suppose the difference in the cost clouded my judgement. I believe 1/2" would "suffice" but I'd be wondering whether I did the right thing or not.
3/4" it is.
Thanks again everyone
Now let's look at the downside of oversized materials in construction:
1. Cutting. You have to cut all that overly-thick plywood. 3/4-inch plywood is much harder to cut than 1/2-inch plywood, meaning more dollars wasted on worn out saw blades, and time wasted on making the cuts, since it takes longer to cut the thicker material. If you're building table tops, that's not a consideration, but it you're using the cookie-cutter moethod or cutting roadbed strips to fit, extra time will start to add up.
2. Weight. One average-strength man can handle a sheet or 1/2 plywood without a whole lot of grunting and straining. He can not easily handle a 3/4" sheet of plywood. It can be done, of course, but an arm in a sling from a strained elbow, one week in bed because of strained back, or damaged equipment (perhaps including locos, rolling stock and structures) because you couldn't hold onto the plywood and wound up dropping it onto the layout will add a whole lot to your model railroading fun, won't it? Simple to just get a friend to help lift the plywood sheet to the table to cut it or install it or whatever, but now you're working around someone else's schedule along with your own.
3. Cost. If you're building a layout larger than 5X10 feet or so, the cost of the over-thick plywood will begin to add up. $50 extra will buy you maybe three or four sheets of 3/4" plywood instead of 1/2" plywood. If you layout will wind up using more than that, you'll wind up wasting even more money.
4. Peace of Mind. Maybe this applies to me only because I'm a structural / mechanical engineer, but my peace of mind comes from knowing I've done the job right, not from building airplanes out of lead sheeting, so to speak. Because of my background I know I can use the lighter material and have a sound structure. But without being a structural engineer, maybe that doesn't apply.
But that's just my perspective on the subject. Certainly using 3/4 inch plywood will not be a detriment to your construction, unless you decide you can get away with fewer risers and a less-solid benchwork as a result. Then you might actually create more problems for yourself than if you'd gone with 1/2 plywood.
To each his/her own.
I've always had good experiences with 3/8" plywood. I like to use supports at least every 12 inches, and my layouts are around-the-wall types were the benchwork never exceeds 24" depth.
Most modelers massively overbuild their benchwork. I did that too but quickly realised that for my style of layout I didn't need to. My first layouts were built like a tank and I had a terrible time building them and taking them apart later. And as said by Brunton, overbuilding results in difficult handling, excessive weight and you pay too much. Lumber and plywood nowadays is awfully expensive, and I've chucked away a fortune in wood when I had to move or made changes to the layout. My benchwork now is much more economical yet still very strong.
HO scale trains are not that heavy and if there is a need to climb onto the benchwork, than the design needs a re-evaluation. Maybe add an access opening or something similar to improve access.
Nowadays I don't even use plywood anymore, just the blue/pink extruded foam on top of L-girder.
Frank
We are working on a club layout in HO and have used 3/4 inch MDF. It is a little heavy but very stable. The cuts are very crisp with no jagged edges. Perhaps a little expensive, but we have found it to be worth the difference.
Tom
3/4" plywoood is the best to use it is much stronger than 1/2". I have built two large lay outs with 3/4" and have found it worth the extra money.
Pete Ward
petew78039@aol.com