Spline is my choice

I would only use spline roadbed, because it is the easiest way to end up with smoothly flowing track.  There really is no problem laying it out over open grid if you have a track plan.  Just draw the gridwork over a copy of your plan and make note where the track crosses the grids, measure it in scale and use the measurement to mark your full size gridwork.  Mount your risers at the places you marked, and connect the risers with spline, sort of a connect the dots sort of thing.  The Spline with take care of the space in between the grids.

One problem you will run into, though, is that if you have a 12" grid, your drill may not fit between the joists to attach the risers.  You need to also take care to make sure your curves are constant radius; spline tends to create parabolas instead of circles.

all of the above

I use all methods on the same layout.  Plywood works best for yards, wide track area and towns.  Spline is good for single and double track.  Pins to hold the track in place are not a problem for me as I use caulk for this. 

Spline does take some effort to place properly and needs to be held in place horizontally. but it is a good base for really good looking trackwork.

Jurgen's method for placing spline is pretty close to what I use. 

I do not use MDF on a layout as I have found that, without a lot of support, it will sag.  3 ply and occasionally 4 ply plywood will sag as well so I avoid these as well

Terry

I use plywood for yards, too

Actually, Terry, you're right about plywood for yards.  Once you get to over 3 tracks wide, plywood is better just to keep things simple. 

I use dimensional 1-by lumber which is actually 3/4" high for the spline and 3/4" plywood most of the time, except in helices where I use 1/2" plywood to save space and reduce grades.  Keeping most of the roadbed the same thickness makes joining different sections together easier.

Roadbed Choices

For anything larger than the classic 4x8 layout spline roadbed is a good choice. However, I find it to be just a tad too fiddlie for me. One consideration is the need to turn those 4x8 sheets of masonite (hardboard) into 1" or 1 1/2" by 8' strips. A table saw is pretty much a necessity. I don't have one!

I experimented with MDF on my last layout and am using it exclusively on my new layout. I'm using a mix of L-girder and open grid benchwork with supports on nothing larger than 16" centers and I haven't had any problem with sagging at all.

However, I do cut my roadbed much wider than most people. I allow 2" on either side of the track centerline (on single track) and 2" on either side of two or more tracks on 2" centers. I do this for 2 reasons: 1) to give myself a place to attach my scenery to web and 2) to give me a solid base to mount my catenary poles. If I need a steep slope coming down right from the track (as in a fill) I simply cut the roadbed down as needed with a saber saw once it is in place.

George

Roadbed

If you are going to handlay, hardboard spline really doesn't make that much sense, since you have to put something over it to spike into, If you are going to glue something on top of the spline, then that is really your surface and what you have underneath it doesn't matter.  Plywood is just as good.  If you are going to handlay and want spline, use Homasote spline.

A 12 inch grid is pretty tight, 16-24 inches is much easier to work with.

Easiest, just use 1/2 in ply in a cookie cutter.  You can have it done fairly quickly.  It will actually take longer to install the roadbed than that sub-roadbed.

I'm not a big fan of foam roadbed.  On a 12" grid, I don't see why you would need 1/2 ply under the foam, if any ply at all.

Regardless of roadbed I would suggest using latex caulk to apply your flex track, unless this is an extremely temporary railroad and you plan to pull it up in a short time.

don't need homasote

I handlay and spike right into pine spline; not a problem.  For plywood I use poplar ply and it spikes really well, too.

Spline Types

A lot of current articles and postings promote using Masonite (hardboard) cut into 3/4" strips for making spline. I guess because it's already in a nice 1/8" thickness. Spiking into that would be pretty difficult/impossible.

Since you pretty much need a table saw to cut consistent 3/4" strips as well, just tighten the fence down to 3/16" and feed 1x4s through it. Spiking into pine is like spiking into warm butter and 1x4s are easier to get and handle than sheets of Homasote.

Another Spline Material

I saw a blog post not long ago where the guy was using the material from drop ceiling panels for spline. It's half an inch thick, soft enough to cut with a sharp utility knife, and flexible enough for any curve you'd want a train to go around.

I'm planning to try it on my layout when I get to that step.

Ceiling tiles, spline, and plyw

I'm not so sure you gain any advantage making spline from ceiling tiles, and it may be unstable in the long term.  I am using ceiling tiles, back side up, on top of plywood, for yard, industrial, and other generally flat areas.  That way I can carve drainage ditches and other undulations to relieve the utter flatness.  But ceiling tiles, over time will sag, even the best of them (I'm using armstrong 3/4" thick tiles).

For fixed radii curves, particularly in room corners, I cut a series of cookie-cutter sections from 3/4" 7 ply plywood. 

For a nicely sweeping S curve on a grade, I used spline, and am happy with the results.  I used masonite hardboard ripped with a radial arm saw in my driveway.  Ended up with a large pile of sawdust, but since I did two 4x8 sheets, I have a lifetime supply, and don't have to make sawdust again.

Here's a discussion about spline, the sub-hobby of C clamping, and the joys of glue flicking

http://model-railroad-hobbyist.com/node/4683?page=1

Edit:  And I adhere cork roadbed to the masonite spline with adhesive caulk, then use the same adhesive caulk to either hand lay, or use flex track, or use CVT ties and rail.  It all works.

Roadbed Choices

Many thanks to all for your comments. However, I still confess to being a bit overwhelmed with the options.  Jurgen I like your idea of pine splines.  I have a good table saw so cutting timber, masonite or anything else is no real problem.  I also have access to large quantities of 1- by pine in very long lengths. Can you confirm the thickness of each spline (before laminating).  I am picking 3/16 or 1/4 but maybe even 5/16th would be OK?

I also plan to use 12mm ply for flat areas with multiple tracks such as fiddle yards.  But I am also thinking that wiring (it will be a DCC layout) should be a lot easier with splines.

I would appreciate a bit more detail on laying track with 'caulk'.  Being a Kiwi, American brand names aren't much use to me.  I presume the caulk is something that sets relatively quickly - if it doesn't how do you hold the flex track in place while it goes off?

Cheers
Peter

Caulk

I've never heard it called any other name, but then again, I've never dome housework outside of the States either.

I use whatever I can get cheap, but definitely NOT silicone.  The cheap stuff is usually latex of some color, which spreads well, cleans up with water, and takes the glue or paint used to adhere ballast well.  What I do is spread a thin layer (maybe .040" thick at most, no blobs) and lay the track into it.  It seems sticky enough to hold the track fairly well on its own, but if needed I pin it with thumb tacks, nails, or whatever else is handy and will do the job.  Different products set up at different rates - I've seen everything form an hour to a day.  My current favorite is a product which goes on white and dries clear, making it very easy to tell when it has set properly.

depends on your radius

Quarter inch gets a little on the stiff side if you want to bend it to 24 inch or less.  You may get away with 5/16", depending on how dry the wood is.  [Edit: sorry, that last does't make sense; I was thinking 5/32 when I wrote that.]  I have had good success with 3/16".  Six pieces are wide enough to support the track, though the ties may overhang a bit.  I glue strips of styrofoam onto the sides of the splines to support the ballast and to give us something to attach the scenery to.

Warning Will Robinson!

My only caution about using caulk is to make sure that you have your track arrangement exactly like you want it before you lay you track using caulk because, once it is down, it is down to stay!

It is nearly impossible to pull up track that has been laid with caulk without extensively damage the track. And, even after you get the track up, you'll have all of that hardened caulk (with tie impressions in it) left on the roadbed which will be next to impossible to clean up, smooth over or otherwise make it go away.

George

George, Are you talking about latex caulk or silicone caulk?

Silicone has a lot of issues, not the least of which is that once cured it holds on tenaciously, but unless latex caulk holds better to track than it does to my bath tub, it should not be difficult to get it up.

It may have been silicone

It may  have been silicone.

I experimented with it a few years back when I started using code 83 flex as my standard track instead of code 100 flex. Like I said, if you know what you track plan is and you never plan to change it, it's great stuff.

However, I'm not that kind of a modeler. Not often, but sometimes I like to change things - re-align a curve, take out or put in a crossover - things that even prototype railroads do, and the caulk I was using at the time just didn't tolerate that kind of stuff.

So, I went back to using track nails to hold my track in place. Actually, I over drive the nail bowing the plastic tie down slightly. Then, I go back with my soldering iron and touch the top of the track nail for just a second or two. The tie then bows back up into its normal position as the head of the nail melts itself into the tie - becoming nearly invisible!

George

Latex Caulk Works

I use all three methods ...

I use

• masonite splines for runs between towns or sidings where it's ability to form natural easements is wonderful. Yes, you'll need a table saw (or pay a few $$ to a cabinet shop) to turn a 4x8 sheet of masonite into splines. Yes, you'll need to pay attention while laminating the splines (cabinet shop splines are likely to be much more consistent width-wise than table-saw splines) keeping their TOPS even (don't worry about the bottom of the splines). Yes, spiking is nearly impossible so I use paintable latex caulk to secure the track in place (I make a miniature "v-notched mastic spreader" from a bit of scrap styrene to keep the caulk thickness manageable. You can read more about how I use caulk to secure track in place in my article on spur tracks in the July 2010 MRH http://model-railroad-hobbyist.com/magazine/mrh-2010-JulAug/lumpy_track.My tutorial on Masonite spline roadbed is at http://s145079212.onlinehome.us/rr/howto/splines/index.shtml.
• plywood sheets for large flat areas such as towns or yards. Trying to do lots of splines running exactly parallel to each other is difficult to say the least. Much easier to be able to layout track center lines on the plywood. Be careful to check the plywood thickness at joints. Not all 3/4" plywood is the same thickness. .020" or .010" styrene makes good shim material when sheets aren't the same thickness. Keep the top of the joints smooth.
• cookie cutter plywood for places where there are lots of spurs or curves at slightly different elevations. Because I handlay most of my turnouts, turnouts and masonite splines aren't a good combination. I admit though, that when I handlay track directly on plywood, I drill pilot holes for spikes (which otherwise have a hard time punching into the plywood without bending).

Hope this helps.

Charlie

Caulk and roadbed

I used latex caulk and it works GREAT! I reworked some sections and a few minutes with a putty knife and it came up with no problems. Just take your time and think about what your doing.

I used 7/16 OSB for my subroadbed, cutting it into 4 inch and 6 inch wide strips, then cutting into sections with a angle on each end creating "segments" that allowed smooth curves and easy to make. Each segment uses a splice plate to hold. Then my foam roadbed flowed nicely on top. The segments allow the curves to be expanded when needed, the small joint is not a issue. The negative to the idea is the splice plates and a few extra screws, but it worked for me, used the plywood with only the saw cuts as waste! 1 inch drywall screws and a good cordless drill and you can put in lots in a very short time.

Caulk choice

I use DAP Dynaflex 230.  It comes in clear, white, and my new favorite, gray.  It is slightly resilient when cured, but can be removed.  It is paintable, as opposed to silicone caulks, which generally are not. 

Spreading a thin layer is sufficient.        I have removed some sections of flextrack, with only a little cleanup, and cutting/scraping of caulk, to re-use the roadbed, and the track.  I pulled up some Central Valley  (CVT) ties with rail, and there I was only able to save the rail.  The CVT ties have much less material between the ties than flextrack.

Great advice

Many thanks to all for your great advice.  I should now be able to find the Kiwi equivalent of Latex Caulk thanks to Ken's picture.  Jurgen -  I have cut some 5mm (6/32') strips of pine and they seem to bend well.

I have now temporarily covered the bench work grid with 3mm MDF and overlaid that with paper. The plan is to now draw out my track plan full size and see how many oopsies I have got.  I hope it will also help me make decisions about where to use splines or either of the other methods.

I will try to keep you informed with progress.

Cheers
Peter