Today i start constructing the benchwork with plywood 3" strips for braces but i found out that the strips are not straight.I don't think that they were not correct cuted but that it just crooked.
And i tried plywood because i thought that it would be better than lumber.Or the plywood was a bad product?
After that i am thinking to use metal for the benchwork.
Also a question,
Is yours benchwork perfect flat?
Wood, including plywood can warp when moisture enters the picture. Even on the latest Kalmbach project they had a problem with board warping and glued the board to the stringers to help secure it.
I set mine down on top of the benchwork frame and put all kinds of weights on it. I then waited 3 weeks for it to level itself out. Then I screwed it down from underneath. I have maybe 1/16" inch warping around the edges. That's a lot better than the 1.25" it was before!
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
You are going to want to build some kind of right angle arrangement (like l-girders, if not l-girders) to take advantage of the resistance to warping that plywood has on edge. With that kind of arrangement you have resistance in both directions that can overcome the tendency to bend in the other directions. The idea is similar to a box, on their own the sides can bend and flex all over, but when joined it becomes very stable.
Jeff But it's a dry heat!
Railroad wrote: Today i start constructing the benchwork with plywood 3" strips for braces but i found out that the strips are not straight.I don't think that they were not correct cuted but that it just crooked.And i tried plywood because i thought that it would be better than lumber.Or the plywood was a bad product?After that i am thinking to use metal for the benchwork.
I would lay all the strips that you will need flat, and place a LOT of weight on them for a period of at least one week. In the interim, use some sort of dessicant in the room, so you will need to keep them in a small, humidity-controlled space and rely on weight to get them flat as they dry...if it is possible for your plywood to return to a flat condition. Then, screw them into position using at least two screws in each end.
You will have to use a form of humidity control from then on, because if they get too much humidity, they will revert to their curved shapes and place enormous strain on your benchwork, probably breaking parts of it.
Railroad wrote:Today i start constructing the benchwork with plywood 3" strips for braces but i found out that the strips are not straight.I don't think that they were not correct cuted but that it just crooked.And i tried plywood because i thought that it would be better than lumber.Or the plywood was a bad product?After that i am thinking to use metal for the benchwork.
Don't rush it. It took me a month and a half to finalize my benchwork...and my layout is just a 4x8!
Railroad wrote:Well the broblem that i mention is about the small side of the strip in which i will support the top plywood.It has a difference of 1/8" to 2/8" in 8' long.So it is important to be ok for a flat top surface.How much tolerance do we have to the eveness of the top surface?
Very very little! Even small deviations in the sub road bed will cause massive headaches later on if not nipped in the bud at the construction stage, beleive me, i speak from experiance!
Ive just built all the benchwork for my new round the walls 12x9"6' out of softwood lumber, based on the L girder principle with 3/4 ply for the road bed on risers spaced a max of 15'. Ive made doubly sure that everything is perfectly flat and level this time!
Also, have a read on the 'derailments' thread on page 2 i think it is.