# Will this work????



## Tom5151 (Nov 21, 2008)

Hello,

Can you tell me if you think this bench has enough horizontal strength?

What I mean is do you think I will get any sag in the table top? The only vertical supports will be the two legs in front and the entire back of the frame will be attached (lagged) into a garage wall.

My concern is that the length span may be too much to support the table top and drawer contents without some type of middle vertical support. The frame will be constructed of 2X4 lumber. The length of the frame will be 88 inches. the table top will be 96 inches which will give me a 4 inch overhang on each side for clamping, etc. I really want to keep the entire bottom open for storage with no vertical supports in the way. 

I have changed the design a few times now and I think I am going to go with this unless some of you who know better have concerns.

Thanks all,


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## Kenbo (Sep 16, 2008)

Sag is definately a possibility, however, you could alway run support beams lengthwise on the underside of the benchtop. That would help minimize sagging. 
Ken


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## firehawkmph (Apr 26, 2008)

Tom,
The back edge shouldn't be a problem at all. Like Kenbo mentioned, a support under the top should help. If you ran a piece of straight hardwood under the front (back 4") maybe a piece of 1 1/2" x 3" oak, I think that would stiffen it up. Just drop your drawers(no pun intended):laughing: down a few inches. What are you doing for the top?
Mike Hawkins


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## CivilEngineer13 (Aug 29, 2008)

What is the top going to be? I would think that two 3/4" pieces of plywood would stiffen it up. Then you only lose 1-1/2" of storage underneath. Depending on your top (say maple or something) then only one 3/4" ply would do it.


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## CivilEngineer13 (Aug 29, 2008)

Also, How deep are you making it. That makes a big deference as well.


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## rrbrown (Feb 15, 2009)

Tom5151 said:


> Hello,





Tom5151 said:


> What I mean is do you think I will get any sag in the table top? The only vertical supports will be the two legs in front and the entire back of the frame will be attached (lagged) into a garage wall.
> 
> My concern is that the length span may be too much to support the table top and drawer contents without some type of middle vertical support. The frame will be constructed of 2X4 lumber. The length of the frame will be 88 inches. the table top will be 96 inches which will give me a 4 inch overhang on each side for clamping, etc. I really want to keep the entire bottom open for storage with no vertical supports in the way.


Depending on how much weight and the type of 2x4 used you will probably have some sag. It can be corrected pretty easy with the same design. First if you use 2x4's make sure they are pine. Plenty of people go to HD and buy those nice looking 2x4's not realizing that they are spruce which is a softer weaker wood. I also would double the front part of the frame and sandwhich a piece of plywood between them build a beam (Glue & Screw). 

2nd thing is you will probably have framing around the draws, build them the same way as above and now you just doubled the strength. If you did something like the picture below you won't have sag, it may be a little over kill but you can modify it a little if you want. Good luck hope this helps.


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## Tom5151 (Nov 21, 2008)

Hey guys,

The advice and skectches are very much appreciated.

I have gone back and forth with a few designs and actually started with something very similar to what rrbrown has pictured above....

I probably should have provided a little more detail in terms of dimensions and the main "problem" i am trying to solve. The depth of the frame wil be 26 inches and the top itself will be 30 inches deep to allow overhang for clamping. The current plan is to construct the top of 2 sheets of 3/4 plywood OR one sheet of plywood and one of MDF. Not so sure the MDF will be rugged enough to hold up. The table top frame would include additional front to back AND side to side framing members, creating somewhat of a honeycomb effect. Kind of like a torsion box but with only a top......my main concern is that even with that the front horizontal framing member will sag.

The "problem" I am trying to deal with is to make the bottom storage area completely open AND high enough to be able to store higher tools there. For example my compressor is about 25 inches high and ideally I'd like to store it there along with other tools. The main constraint however is I want the top surface to only be 39 inches high and I want the drawers to be 6 inches deep. 

I may be asking too much of this design.


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## rrbrown (Feb 15, 2009)

Tom no matter what with that span I wouldn't go any less the 3 1/2 inches high with the bracing under the front of the workbench. So if needed either do a double beam 3 2x4's with 1/2' plywood in between glued and screwed or laminate 5 or 6 3/4" birch or oak plywood by 3 1/2 inches to make that support. Either way glue everything and clamp it together then screw or bolt them all together. The plywood laminated is probably stronger. I would also go with double 2x4 uprights or better yet a 4x4 and use ½ laps for the joint. 

39" - 1 1/2' for top and another 3 1/2 for the front brace, 6 inches for drawers and probably 4 inches off the floor leaves 24 1/2" for storage. if you need more storage then that you may need to cut back on the drawer size or alter the bottom some. If you absolutely can't do that then try building the beam at 3" using the Plywood method and see how strong it is if you need more support add another layer until you get the strength you need. 

If you are interest my wife’s uncle had a 8' x 2.5' workbench made out of 5" x 3/4" plywood laminated together with dowels going all the way thru about every 18 inches or so. you could park a car on it and it was like 40 years old at least. Laminated plywood is very strong.

Just my opinion.


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## CivilEngineer13 (Aug 29, 2008)

As long as your 2x4 in the front and back is orientated so that the "4" is facing out (which I assume that's the plan) you will have no sag in that member. 

Once again, you'll just have to trust me on that.


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## rrbrown (Feb 15, 2009)

CivilEngineer13 said:


> As long as your 2x4 in the front and back is orientated so that the "4" is facing out (which I assume that's the plan) you will have no sag in that member.
> 
> Once again, you'll just have to trust me on that.


*Sorry but I have framed to many houses and built to many things, I would have to disagree with your statement.*

No way a 2x4 spanned 8 ft wont sag without center support, especially with drawers mounted under it and it used as a workbench above. a double 2x4 might even sag. I may be telling him to ever kill a little but when you build a workbench you want it solid. Never know what he hay put on top of it in the future.


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## CivilEngineer13 (Aug 29, 2008)

Well...........

Deflection = (PL^3)/(48EI)

P = 100 lbs (That's 100lb acting as a point load - actual load will be spread out)
L = 88 in.
E = 1,700,000
I = (1/12)*b*(h^3)
= (1/12)*1.5"*(3.5"^3) = 5.359 in^4

Deflection will equal 0.1558" (5/32")


So with a 100 lb POINT load at EXACTLY the middle of the beam will cause a deflection of 5/32". Now, with 2 layers of plywood top (added strength) and considering that 100 lbs will most likely not be applied at a point load; we can safely say it will not deflect. Obviously you can not get 0.00000" of deflection at any point, but it is so small that it gets neglected.

Hope this clears it up, and I hope I didn't offend you rr.


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## rrbrown (Feb 15, 2009)

Hey CivilEngineer13 I hope I didn't offend you either. I know you say the math works out but if I had a nickel for every time a Architect or engineer said that and it didn't work I would be rich. I have heard that argument for 25 years I use to believe it but not anymore. 

When I was younger the plans called for (2) 30ft double 2x12 beams with 1/2" steel plate bolted together when we built my dads 30x40 Garage all open. These were massive beams I would have swore they were right. Guess what it sagged pretty badly and then we had to come back and jack the ceiling up and truss it to the rafters. I will never be sure if that worked since Katrina took out the house. But I’m glad I don’t have to hear it anymore. :laughing: There have been a ton of problems just like that for the 25 years I have been working on houses and woodworking. 

I hope you can see my disbelief in the math.


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## CivilEngineer13 (Aug 29, 2008)

trust me. I know there is theoretical and then there is reality. I guess I just wanted to show the math so now everyone is on the same page and Tom can make his decision based on that info and your experenses. (plus I didn't want to be wrong- haha. guy thing I guess) but I agree with you. spend the extra $2 and put in one more 2x4 and overkill it.


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## rrbrown (Feb 15, 2009)

Your all right for an engineer. :laughing:

have a good night


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## woodnthings (Jan 24, 2009)

*Maybe I'm lazy, But...*

I use solid core 1 3/4" doors for all my work bench tops, 30" wide 6'8" long., covered with 1/4 masonite to protect the birch ply. Mine cost around $90 at my local family owned lumber yard. I use legal size file cabinets at either end for support, used $75 each, for ample roller bearing storage and open space underneath inbetween. $240 later I'm done, Strong, very heavy, simple and should you want to start a "home office" all you need are walls, a chair, a doorknob with a lock! :thumbsup: and a secretary! heh..heh!:laughing:


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## Tom5151 (Nov 21, 2008)

Thanks again guys.....

I LOVE the math of things. It gives me a comfort level I think. I really appreciate you guys thinking this through with me.....I think to be on the overkill side I am going to laminate 2 2X4's and a 3/4 inch peice of plywood inbetween for the front horizontal member.....I want the legs to be one 2X4 only if I can, and have the 3.5 inch side of the legs facing out to the sides so I can maximize the space undeneath. I may just attach some type of extra cleat at the top of the legs to let me carry the laminated 2X4 horizontal member


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## Gerry KIERNAN (Apr 20, 2007)

Hi Tom

Are you sure you want to bolt it to the wall? I know this will add a lot of strength to it, but what if you ever want to relocate it?

Gerry


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## rrbrown (Feb 15, 2009)

Gerry KIERNAN said:


> Hi Tom
> 
> Are you sure you want to bolt it to the wall? I know this will add a lot of strength to it, but what if you ever want to relocate it?
> 
> Gerry


 
Man Like Tom didn't have enough to think about. But it's a thought. 
:laughing::laughing::laughing:


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## Tom5151 (Nov 21, 2008)

Gerry KIERNAN said:


> Hi Tom
> 
> Are you sure you want to bolt it to the wall? I know this will add a lot of strength to it, but what if you ever want to relocate it?
> 
> Gerry


Yeah you bring up a great point......I have actually given that a lot of thought. It's going on one wall of a 2 car garage. One of our cars (mine) will be parked outside all the time.........I really won't have a lot of room in the garage to warrant making it moble. If we ever do move I plan to build it so that it can be dismantled fairly easily....but you bring up a great point and I appreciate the question......


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## smokey1945 (Feb 20, 2009)

Just a thought. Toenail a 2x4 from the front cross rail to the bottom o the back wall.


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## Tom5151 (Nov 21, 2008)

smokey1945 said:


> Just a thought. Toenail a 2x4 from the front cross rail to the bottom o the back wall.


Hi Smokey,

Thank you for your idea. My goal though is to keep the bottom space completely open and unobstructed. I think that type of brace may interfere there a bit.....I think I'll essentially just do what amounts to manufactured header there and hopefully not have any problems...

Thanks again....:thumbsup:


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## wonderwoman (Feb 11, 2009)

Tom5151 said:


> Can you tell me if you think this bench has enough horizontal strength?
> 
> ...and I think I am going to go with this unless some of you who know better have concerns.


I don't believe you have enough horizontal strength at all.

Since I'm pretty sure the task of your _workbench_ is simply function and isn't intended to be sold at a Sotheby's auction (it's value is only what you can sell it for:yes...why not piggyback/incorporate the wood onto a solid metal frame to support any potential of a sagging wood facade. I can picture it...I stand back and see...your wood is sagging...should have used steel...it stands the test of time.


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## Tony B (Jul 30, 2008)

*A 7' span is a long span for a workbench.*

This is the perfect place for a simple torsion box top. 
If you originally planned on using 2 pieces of 3/4" ply on top of a 2X4 that would be the same as 2 pieces of ply sandwiching a 3 1/2" torsion box core. Overall it will be relatively light and rigid.


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