poplar vs. plywood

[tom mann]

Six years ago, I bought some pieces of 1x2 poplar.  These have been out in my garage (temp. fluctuations ) for 5 years now, and they are still very straight.  Since it's difficult for me rip sheets of plywood (thanks to my sub-par table saw), is constructing a framework out of poplar sufficient?  How close should the bracing be, assuming that I go no more than 2 feet deep?  I'm thinking that I'll glue 2 layers of 1" foam on top of this.

[inkaneer]

I build Ntrak modules.  Due to advancing age I have gone to what I call "airplane construction".  That is something strong but light weight but all in keeping with Ntrak specs.  My modules are 6 feet long and 2 feet wide.  I use 1X 4 clear pine for the 6 feet of length and the 2 foot end  pieces.  I use 1X2 pine for the cross supports.  I place one 6 inches in from the ends then every 12 inches.  Everything is covered with 1/4 inch luan plywood.  Also everything is primed and painted.  The modules are light enough to be handled by one person but due to their bulk and because we clamp two of them together we have two people transport them.   For your situation  use of 1X@ poplar will depend on how much of a span you will have between vertical supports.  With 1X2's I wouldn't go more than 3 feet.   The 1X2's are good for your cross supports. 

[pnolan48]

Tom,

Poplar has been maligned for many years as an unstable wood prone to warping and twisting. I started using it about 15 years ago, as a substitute for increasingly expensive furniture woods. It's performed extremely well! I think the poplar available today is much better than it was 40 years ago, when I started building furniture. It can be a bit heavy. But if it's stayed straight for a number of years, it's well-seasoned, and I wouldn't hesitate using it.

[Zox]

I use poplar for all my module framing. If you start with straight pieces, it'll stay straight--I haven't had any twisting or warping with poplar, even though I generally don't seal all four sides.

The only thing to remember is that since poplar's harder than pine, it's a bit more prone to splitting. So make sure to drill pilot holes for any screws you use and take care when driving them near the end of a board. Often, when working near the end of a board, I'll squeeze the sides of the board in a clamp while driving a screw. This insures that as the screw goes in, it compresses the wood instead of splitting it.

As for lumber dimensions: Linn Westcott, in his "How to Build Model Railroad Benchwork," suggested a maximum span of 29 inches for a 1x2 used on edge, and one-third that distance as the maximum distance for a "cantilever" supported at one end. These measurements were based on placing a 200-pound point load at the center of the span, or the extreme end of the cantilever, with less than 2% deflection--that is, strong enough to stand on.

Even though modern lumber is generally smaller and of lower quality than in Westcott's time, if you don't plan to stand on your layout, I've found his numbers are still a good guide to adequate support.

For example, 1x2s are sufficient for the framing on a 4-foot-long module: 29 inches between the legs, and 9.5-inch overhang at either end.

[sparky]

Tom-

See if you can find a cabinet shop to rip you some strips of 3/4" Baltic Birch plywood.  There's a little more waste because true BB plywood comes in 5' X 5' sheets, but it typically has 12-16 plys of thin veneers and is extremely stable.  Don't be fooled by the recent influx of Chinese made "Baltic Birch" plywood, which comes in 4' X 4' and 4' X 8' sheets- it's crap.  The best BB plywood comes from Sweden and Scandanavia.  Pre-drill your frame members with a countersinking drill bit and fasten with 2" drywall screws and carpenters glue.  You'll have super-stong, stable framwork for your modules.

[Mark4]

Why would plywood be more popular than poplar?
 

[ednadolski]

it's difficult for me rip sheets of plywood (thanks to my sub-par table saw)

A carbide-tip blade can work wonders.

I used to have a big table saw but lately I just use my little $99, 10" Ryobi.  For large sheets of plywood I just have Home Depot (or whoever) rip them down to 12" wide on their in-store panel saw -- then I can easily rip them as needed on the little home saw.   That also makes 'em a lot easier to carry and to fit into the minivan.

BTW I use the 3/4"  "cabinet grade" plywood that my local HD carries,  about $35 for a 4x8.   I also like their birch plywood but it's about $45 per sheet.   I confess, I have no idea where it comes from --- is the "China plywood" a (very?) recent thing?   I'd hate to have to bother with going to the hardwood supplier for specialty plywood, esp. if it's more costly.

Ed

[sparky]

Ed- sorry to rain on your parade, but that "cabinet grade" plywood Home Depot is selling is from China, and it's absolute crap.  I've been a carpenter/cabinetmaker for over 20 years.  I used the plywood from HD on one project for a customer for a support frame where it wouldn't be seen so I thought it was fine.  Within 6 months, the stuff I had left over in my shop was unusably warped, and the material at my customer's home had started to delaminate.  I had to re-make all the parts I had used the "cabinet grade" plywood for.  It was an expensive lesson, but a mistake I won't make again.  I will not use plywood that isn't made in the USA or Canada, with the exception of the Baltic Birch plywood I refered to earlier.  Just my $.05 (ajusted for inflation).  Your milage may vary...

[SAH]

Tom,

My 6' Spencer section uses 1x3 poplar rails with 1x2 cross members.  Solid enough to be portable.  I initially used 1x2s throughout:  Too much flex when the section was moved about.  The 1x2 version worked fine as a static layout though.  It was supported by shelf brackets on 48" centers.  Blocking the corners with a triangular gussett helps stability too.  My experience with poplar stored out in the garage is the same as yours.  If you can't rip plywood, poplar is a good option.

Steve

[tom mann]

it's difficult for me rip sheets of plywood (thanks to my sub-par table saw)

A carbide-tip blade can work wonders.

I used to have a big table saw but lately I just use my little $99, 10" Ryobi.  For large sheets of plywood I just have Home Depot (or whoever) rip them down to 12" wide on their in-store panel saw -- then I can easily rip them as needed on the little home saw.   That also makes 'em a lot easier to carry and to fit into the minivan.

Ed: actually, I have that same Ryobi and it is impossible to make nice straight cuts with mine.  The guide is not parallel to the blade, so I have to increase the tolerance a little, creating enough slop that the wood goes through but at the cost of having a wavy cut. ;D

I was so furious with this Ryobi that because of it, I promised myself that I would always buy good quality tools from then on.

[sparky]

Tom- I assume by "guide" you mean the rip fence. Yes, this is a weak point on low-end saws, but you can work around it.  If the fence doesn't lock down tightly enough to stay in place, there is usually a screw that will tighten up the locking mechanism.  Don't rely on the fence to square itself on this type of saw- lightly snug the fence, then use a ruler to measure from the fence to the teeth on the blade both in front and back, tap it into place, then finish tightening the fence.  It's a little extra work, but you can get surprisingly accurate cuts from even the cheapest table saw.

[qantaqa]

tom: just so you're warned, most of craftsman's power tools, drills and the like, are ryobi.  I used to work there selling tools, and spent some time researching part numbers and manufacturers for my own amusement...

if you're considering purchasing from sears, ask the sales person...

cheers!!

john

[sd80mac]

This is an interesting discussion as I have considered Poplar for benchwork on many occasions. I was always detered by the cost of it, but when you think of building your layout in terms of quality vs. quantity or cost you can somewhat justify it. The wood is straight, smooth, clean, and usually free of knots. In fact, a friend of mine just had a 7' x 10' O-scale demonstration layout built from Poplar and it when together quite well. It sturdy, and neatly constructed. I suppose time will tell as far as warping goes though.

Basically, if you want neat, clean, module construction, and don't have the means to rip to size even the cheap Chinese "Baltic Birch" plywood, I think Poplar is a good alternative.

Donnell

[ednadolski]

The guide is not parallel to the blade, so I have to increase the tolerance a little, creating enough slop that the wood goes through but at the cost of having a wavy cut. ;D

Sometimes you can adjust the heeling for better parallelism (that was something I was always tweaking on my old craftsman).  The rip fence on those little saws is usually kinda undersized for longer/larger stock -- sometimes just clamping a longer straightedge in place will work better than using the fence.   Supporting the work properly is important too -- I have one of those roller stands that I place behind the saw, to keep the work from falling as it exits.  And with that good/sharp blade the saw will cut more easily so you can concentrate on feeding the work as accurately as possible.

But be careful about using that fence as-is if it has too much slop -- you don't want it to bind during a cut and kick back.  that happened to me once and I do not intend to let it happen again (even a small saw can pack a pretty good amount of power).

HTH,
Ed

[ednadolski]

Ed- sorry to rain on your parade, but that "cabinet grade" plywood Home Depot is selling is from China, and it's absolute crap.  I've been a carpenter/cabinetmaker for over 20 years.  I used the plywood from HD on one project for a customer for a support frame where it wouldn't be seen so I thought it was fine.  Within 6 months, the stuff I had left over in my shop was unusably warped, and the material at my customer's home had started to delaminate.  I had to re-make all the parts I had used the "cabinet grade" plywood for.  It was an expensive lesson, but a mistake I won't make again.  I will not use plywood that isn't made in the USA or Canada, with the exception of the Baltic Birch plywood I refered to earlier.  Just my $.05 (ajusted for inflation).  Your milage may vary...

The stuff I have is from about 3 years ago and seems to have held up (no warp/de-lam), so I guess I've been fortunate at least so far.   I have seen worse stuff in the 'regular' AC plywoods, where it warps just like you say.  Here in CO it's consistently dry which might help a bit.  Crummy stuff from China seems to be getting more & more common in everything (like all those toys recalled for lead paint).