2x4 weight/span

I'm not sure if I should post this here or in the woodworking group...
I'm building a workbench out of 2x4 Hem-Fir studs and I want to know the maximum span I can consider for the rails. I made one 15 years ago at my mother's house and it still is a very sturdy bench. That one has 57" rails lag-screwed to notched legs. But I have a bit more room in my garage and I wanted to build an 8 foot bench.
Should I add legs in the middle of the span? Otherwise, I'd have a nice wide bottom shelf and a wide open space underneath without a leg getting in the way.
Mike
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upand_at snipped-for-privacy@yahoo.com wrote:

There will be quite a bit more flex in the bench by adding that much length to the span. It will be up to you to determine if that flex is acceptable and whether the leg/flex tradeoff makes sense for you.
If you're doing light work on the bench it will probably be okay with an 8' span and a single layer of plywood for the top. If you wish to increase the span, keep the stiffness and still get rid of that leg look into building a torsion box top. http://www.popularwoodworking.com/features/fea32sidebar.html
R
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wrote:

steel L-channels bolted to the inside of the rails evey foot or so, to stiffen them? This isn't a bridge- whatever is laying around, or cheap at the big box, will work. A third 2x4 down the center of the top would probably also do what OP wants.
In the garage addition my 75 YO father built, he put a 22' workbench down one side, hung off wall, supported by triangle stifflegs every 3rd stud space. Floor is clear, and it doesn't sag when I stand on it.
aem sends...
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On Sun, 04 Dec 2005 18:26:39 GMT, "ameijers"

We did the exact same thing in our old garage (ca. 1913) just to be able to get crap off the floor so we could pull the cars in further more safely. Those triangle stifflegs really do the job; we used leftover 2x6 PT pieces for that. Our workbench is about the same length, and about 21" deep, and we used only lumber we had laying around, so the entire project just cost us about a day's worth of work.
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Consider horizontal members of SuperStrut from the electrical dept at Home Depot or Lowes. Cheap, very stiff and strong, and a cinch to assemble since they're already drilled.
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On 3 Dec 2005 19:30:08 -0800, upand_at snipped-for-privacy@yahoo.com wrote:

Depends on what the top is going to be and what kind of load you're expecting to put on it. A thick, rigid top will add a lot of resistance to deflection but if you're going to mount an anvil in the middle you may have a problem.
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or four at a time to make up the width you desire, plane flat and your bench will be great.
Dave
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If you double up the 2x4's you'll be alright as long as you're not pounding stuff with a sledge. Using 3/4" plywood for the top helps stiffen it all up.
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I built a loft bed out of 2x4s for my teenager. It's basicly a box 2x4s form the outer edge and the top is 3/4" OSB. It's 72"x40". The uprights are 2x4s on 90 with a load plate supporting the box. The uprights on the wall are screwed to studs. Everything's held together with Torx construction screws and the uprights are also glued. It's been up a year and there is no deflection in the long span. Richard
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or better yet, skin both the top and bottom of the 2x4's with plywood. Google for "Stressed skin platform" or "torsion box"
When a piece of wood sags, the top radius gets smaller and the bottom radius gets longer. With wood on both sides, the top sheet takes the compression force and the bottom sheet takes the expansion force. This makes for a *really* stable surface.
I'd guess that 1/2 on top and 1/4 on the bottom would be stronger than a single 3/4 in piece on top. Then you can screw a 1/4 inch sheet of masonite on top for a durable/replaceable/glue resistant worktop.
good luck!
--
be safe.
flip
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"Philip Lewis"> wrote

I saw David Marks do that on his show. I'm going to build a freestanding work table 4'x8' as a torsion box, on lockable castors. Quite a bit of work to build a torsion box correctly but its necessary to do accurate work.
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