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Bench length without sagging

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Forum topic by Manitario posted 01-07-2013 07:46 PM 1630 views 0 times favorited 9 replies Add to Favorites Watch
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Manitario

2337 posts in 1536 days


01-07-2013 07:46 PM

Hey all, I’m building a bench out of a slab of elm to compliment a elm slab trestle table I’ve made for the dining room. The slab is ~2 1/2” thick and about 75” long. I’m just curious if it would be strong enough to support 4 people without bowing in the middle or if I’ll have to design some sort of support for the middle of the span. In general, is there any sort of guidelines/calculator as to how long you can make a bench span before the weight of people sitting on it will bow it?
thanks!

-- Sometimes the creative process requires foul language. -- Charles Neil


9 replies so far

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Dusty56

11659 posts in 2341 days


#1 posted 01-07-2013 08:23 PM

How far in from the ends do you plan on placing the legs ?
If they’re going to be at the very ends , I would put a support in the middle just to ease the stress on the ends and for stability. JMO : )

-- I'm absolutely positive that I couldn't be more uncertain!

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Manitario

2337 posts in 1536 days


#2 posted 01-07-2013 08:29 PM

I was planning on putting the legs within about 6” of the ends…also considering making two shorter benches instead of one long bench…

-- Sometimes the creative process requires foul language. -- Charles Neil

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Dusty56

11659 posts in 2341 days


#3 posted 01-07-2013 08:39 PM

I think the two benches would be better in the long run : )

-- I'm absolutely positive that I couldn't be more uncertain!

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DKV

3136 posts in 1158 days


#4 posted 01-07-2013 08:40 PM

Rob, try the below. It’s for shelves but aren’t benches nothing more than shelves for people? Lot’s of people use the sagulator. 2 or 3 inch edges run along the length of the bench also help with load.

http://www.woodbin.com/calcs/sagulator.htm

-- My bad, 2015 is the correct year...

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Manitario

2337 posts in 1536 days


#5 posted 01-07-2013 08:41 PM

you’re probably right…just twice the amount of work!

-- Sometimes the creative process requires foul language. -- Charles Neil

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DKV

3136 posts in 1158 days


#6 posted 01-07-2013 08:44 PM

More methods…

http://www.diyadvice.com/diy/built-ins/materials-and-hardware/sagless-spans/

-- My bad, 2015 is the correct year...

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Dusty56

11659 posts in 2341 days


#7 posted 01-07-2013 09:07 PM

I’m just thinking about creature comforts…say you have a couple of children and a couple of adults seated. The kids would need to sit closer to the table than the adults which might make for some uncomfortable dining : )

-- I'm absolutely positive that I couldn't be more uncertain!

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Manitario

2337 posts in 1536 days


#8 posted 01-07-2013 09:45 PM

Thanks DKV; that is exactly what I was looking for. Interestingly, the sag is quite a bit less than I expected, even with a presumed 200lb load/foot the sag in the center is only 0.1”. Dusty, your point is well taken though, a bench with 4 people on it is inconvenient at best, although rather convenient for me to make…

-- Sometimes the creative process requires foul language. -- Charles Neil

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Dusty56

11659 posts in 2341 days


#9 posted 01-07-2013 09:54 PM

What’s four more legs in the scheme of things ? LOL
I wasn’t really concerned with the sag factor as much as I was with the future enjoyment of your projects.

I used to have as my signature ; “Do what you want to do , you’re going to anyway” : )

-- I'm absolutely positive that I couldn't be more uncertain!

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