plywood layout base

Well, I think the answer depends on how close together your crossmembers are under the top. I have a crossmember every 16", and only use 1/2" plywood myself. With 3/4" plywood, I would think you would be ok with crossmembers every 24", but no more than that. Sticking with 16" would be safer and support more load.

With a 10-foot by 5-foot table, I think you are referring to 48-inch and 72-inch diameter - not radius. That is O-48 and O-72 track. If I understand you correctly, the 10-by-5 table will not allow O-72 track.

My railroad has a 1/2-inch thick plywood table top that is 10-feet by 5-feet. The track is just an O-54 oval. The plywood overhangs the table frame by 5-3/4 inches on each of the (long) sides and 7-1/4 inches on each of the (short) ends. The track runs outside the frame along the 10-foot sides and is also outside the frame on the O-54 curves at the 5-foot ends. The layout has been running for five years and I have not had any problems with this table.

MELGAR

With 3/4" ply, I put my cross members every 24". I weigh over 300 pounds, and can walk on that. I wouldn't use nails, drywall screws are the way to go.

Drywall, fine thread nails are the best.  Get a bar of soap and wipe it across the threads.  Makes it go in much better, less squeaky and helps prevent the screws shearing as you screw it in.   

Select your target.

You mention economy  sheathing/decking.   Consider  Advantech at 84 lumber.  Aprox. $30.00 per 3/4" X 4' X 8' .  About half the cost of similar quality plywood.

You mention load bearing, Consider Advantech w/ crossmenbers on 24" centers.

You mention cantilever/overhang.  I run Advantech 6+" at times.

Fine thread screws are for metal studs.

Course thread screws are for wood products.

Consider prepositioning the decking.  Trace cross members underneath.  Invert decking, predrill clearance holes for your deck screws between drawn lines x 12".

Reposition decking to reference marks, clamp in place and drill 3/32" pilot holes in frame.

Drywall screws are for drywall.  #8 construction screws are for  construction screwing.

HD has them in T-25 drive.    1 1/4" or 1 5/8".  You will never snap off a proper fastener.

Check out the complete line of construction screws.

I can not think of any application for a nail in layout construction.

Actually, the coarse threads hold better.

Back when screws were primarily slotted heads, and the days before screw guns, soap was the trick. The Phillips or square drive and the torque and even available impact type screw guns, have rendered soap moot.

I like the squeak. It tells me the screw is gripping well. Depending on what the wood is like and where you are putting the screw, sometimes it is necessary to pilot drill for it. It is easy to split dimensional lumber if you don't. Plywood doesn't really matter.

BTW, I only break about 1% of the screws, usually just below the head. No big deal, just grab another. They are neither rare nor expensive.

Using 2x4s, I built a 7 x12 table with 3/4 inch plywood on 16 inch center cross members - all held together with HD construction screws. Track is 072, 054 and 042.  

If I am reading your question correctly, you are asking how much overhang would be possible with sheets of plywood on top on your existing 5'x10' table.  Assuming the table is strong enough to support the weight, I think you could secure three sheets of 3/4" plywood across your table, creating an 8'x12' tabletop.  The overhang on the ends and sides would only be 12" and 18" respectively, which should be no problem considering the stiffness of 3/4" plywood.  I do think I would attach a length of  1x3 underneath the edges of both sides as a stiffener, and also to keep all three sheets from warping.  A bit of overhang is good, it will give you some "toe room" when standing next to the table.

Standard gauge track is properly described by the diameter of the circle that would be made by by the sections.  Just like 0-72 means 72" diameter of 0 gauge (1.25" gauge) track, STD72 track refers to 72" diameter standard gauge (2.125" gauge) track.  Both diameters are nominal, i.e. not exactly the measured dimension of the circle, just like a 2x4 piece of wood is actually 1.5"x3.5".  In the case of STD72 track, the actual centerline diameter is 69.750.

I you want to have a double track, I would suggest STD57 and STD72, or STD72 and STD87 loops.  The resulting 7.25" track centers are ideal, and trains prefer curves wider than STD42.

Kirk Lindvig, USA Track LLC

Hi Ash Standard, 

Even though you’ve gotten a lot of information about spacing of support members and nails versus sheet rock screws I think you were asking what would be a safe overhang using 3/4 inch plywood on top of your existing table.  In my career I did consulting for a kitchen cabinet manufacturer and a kitchen design outfit. I would suggest whether you use 3/4 inch plywood or Advantech, only have a maximum of 12 inch overhang.

Also during my career I did plywood research and only God knows how consistent the inner plies are and how many voids are in them. I found by far the best plywood on the market is that made by Plum Creek.

Jim Lawson 

Advantech may be the flattest and stiffest panel on the market.  I mention predrilling a pilot hole in what I assume is Mianne because I have seen those crossmember frames split with screws.

I mention construction screws because at some point this project will be disassembled and a snapped  screw head is a royal pain if there is thought to save the cross member.

I am actually shooting brads over Loctite's Pro Line urethane mostly in module construction and bolting modules together.

Tom Lee- "I can not think of any application for a nail in layout construction."

I like to use a finishing nail to secure the pivot end of the wooden rule I use as a compass to lay out curves.  That's just about it, except as you mentioned, to temporarily secure pieces that are being glued.  There are so many great screws available today.  They make nails just about obsolete.  Deck screws are more resistant to breaking than drywall screws.

Tom Tee posted:

Select your target.

You mention economy  sheathing/decking.   Consider  Advantech at 84 lumber.  Aprox. $30.00 per 3/4" X 4' X 8' .  About half the cost of similar quality plywood.

You mention load bearing, Consider Advantech w/ crossmenbers on 24" centers.

You mention cantilever/overhang.  I run Advantech 6+" at times.

Fine thread screws are for metal studs.

Course thread screws are for wood products.

Consider prepositioning the decking.  Trace cross members underneath.  Invert decking, predrill clearance holes for your deck screws between drawn lines x 12".

Reposition decking to reference marks, clamp in place and drill 3/32" pilot holes in frame.

Drywall screws are for drywall.  #8 construction screws are for  construction screwing.

HD has them in T-25 drive.    1 1/4" or 1 5/8".  You will never snap off a proper fastener.

Check out the complete line of construction screws.

I can not think of any application for a nail in layout construction.

This is the correct information. I was going to reply too. Drywall screws are for drywall, not plywood. I use brass colored wood screws. They are not a lot more expensive than drywall screws.

George

I was wondering if the real question was about "unsupported deck overhang". Personally, I wouldn't have any, I would build my frame to match the deck size.

Now if you want to move the legs in from the edge, that's no big deal. I set the legs on my layout back 6", but could have gone further.

The table is 10 by 5 and you want to make the top bigger by covering with 3/4 plywood.

 At the 5' ends use  8' boards screwed across table. Off the edges attach boards 30" on center extending out 18" each side. The edge of the plywood should  be banded and the boards attached. 

This will give 10 by 8.  3 sheets of plywood. 

I am thinking we may be over thinking the OPs direction.  This may be a tinplate loosie-goosie-kinda-maybe....temporary...roll of grass mat casual layout.

If so, maybe just position 3 sheets of 4' X 8' Advantech on the table overhanging 18" on the side and1' on the ends, kick back snap some track together and have some fun\ on your new 8' X 12' train table surface.

Maybe fasten some splice cleats on the exposed bottom surface.  Those sheets can overhang and be leaned on w/o sea sawing up the opposite end.  Lots of inertia   weight.

Temporary being the operative word. 

That  Advantech is great stuff.  Very different, less expensive, non responsive to moisture and much better than any plywood for decking purposes.

Thanks. It is indeed temporary. maybe 3 years at the most in this house. Simple layout with no switches. Just two loops of standard gauge track and 1 loop of Lgb. On a 8x12. The Advantech with an overhang may be my solution although I do have the 8 and 10ft long standard gauge sets and fingers crossed they would be supported. a picture explanation of Splice cleats?  

Use any search engine for "splice plates".  I also make them out of plywood.

Stocked by Lowe's and HD with their joist hangers.  

Ash,

Why don't you do a little experiment with the overhang?  Temporarily secure a sheet of 3/4" thick Advantech or plywood to your table with the proposed 12' or 18" overhang, and see how much deflection there is with varying amounts of weight on the unsupported portion.  I'm guessing there will be very little if most of the sheet is supported by the table.

Kirk

Advise , myself being a King of temporary , I would follow most of what has been said .  Actually, three years is long to me. LOL.   If you head out and get your three sheets of whatever 3/4  material you choose I would also get two 8' and two 12'   1x4s to screw under the perimeter  ( on edge and not flat ). Also I would use deck screws to fasten the 3/4 sheet goods to your existing table top.  Personally   I would start with the middle sheet, getting it centered and screwed down, and using six or more screws to fasten it down .  Then butting the remaining two to the center board.  And again fastening them with six or more deck screws.   Next up would be to attach the 1x4s to the underside edge . You  may want to get smaller screws for the 1x4s ,   I highly recommend  pre drilling  pilot holes as to not split them .  The 1x4s are kind of an insurance that all the perimeter edges stay flat. Even the slightest bump could cause issues when you want to enjoy running your trains .  This is my advise to you, If I were in the same situation as you at this time this is how I would go  about  doing it.  Hopefully you will have a helping hand in carrying the 3/4 sheet goods you buy. If not , invest in a pannel carrier, $10.00 or so.  It will save you and your house .  Keep us posted on what you have done  and how you did it.        Good luck and happy rails .

Thanks Johniewalker. I’ll post results thanks.