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Marcus Hand

Design help for desk

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My son asked me to build him a desk. Based on what he has shown me that he likes, I created this rough design. I've already constructed the top, which is 2" thick edge-grain construction. I'm starting on the base and am now wondering if I need an apron. With the double rails, I didn't think I would need one, but now I'm doubting. Am I asking for trouble? 

 

Ben desk.jpg

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With a 2” thick top, and it’s a desk and not scaffolding, I think you’re good to go. However, I think it would look better if you moved the top rail up and made it into an apron. But I agree with Steve, what are the dimensions? What supports the front? On the front, if you added an apron that went the full length of the longest side and continued it under the top and tied it into the apron on the back side, then put an apron on the short side and tied it into that apron? I hope that makes sense? 

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I’m wondering if you’ve thought about a drawer? I made mine last year with a metal base and timber top but didn’t include a drawer. Storage sucks without it. I’ve been too lazy to pull all my stuff off and workout some sort of drawer system. 

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I wouldnt be too quick to rely on a sagulator calculation for this, since it is laminated end grain pieces. It can give a ballpark, but deflection of wood is dependent of the grain direction. No one publishes or tests deflection characteristics for end grain, as it really isn't of structural use, but from general experience, I expect the end grain to deflect significantly more than sagulator will predict.

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Dimensions would be helpful. I built this desk the top is walnut and only 1.5" thick. I attached the 2 4 foot pieces with aligh n lock from rockkler and floating tenons that aren't glued. I hesitantly stood over the connection to test it's strength and it held. Desks don't need to hold the weight they used to.

22289710_10101565793145119_103604677575429083_o.thumb.jpg.40c1debb25c94f060a353e0814a8bb6e.jpg

If your planning on your top being 1 whole glued together piece you don't need an apron unless that desk is like 8 feet long .

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Like the image above you'll need something supporting that center corner.

I highly suspect there is some support coming out from beneath,  from that angled center.

If not, ooops.

*

The thing I've been learning with my display case project is to not confuse a nice design with a proper design.

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Rather than being concerned with an apron, I'd just go with a stretcher in the center of the long run, That will still allow for drawers, and give the support you may or may not need, but over engineering is always a good thing.

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1 hour ago, collinb said:

Like the image above you'll need something supporting that center corner.

I highly suspect there is some support coming out from beneath,  from that angled center.

If not, ooops.

*

The thing I've been learning with my display case project is to not confuse a nice design with a proper design.

You'd think that but it's not necessary. If you put a weight in the corner It is trying to rotate the top around 2 axes that are following the front edge of each side. If you look where those axes terminate they are both supported by a leg with a wide base as well as the back corner leg. The only way the inside corner would need support is from deflection of the top. Because the back corner is supported the right side would have to twist and the whole left side would have to bend. It looks far more precarious then it actually is.

Marcus I'd nix the center leg in the back on the left side, that leg really isn't doing anything other than looking weird. Also maybe move the back "apron" up to support the top this is less for top support and more to give you a place to attach the top. You say you have the top constructed can you share a picture. The seam between the main and the L can cause wood movement issues.

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12 minutes ago, Chestnut said:

You'd think that but it's not necessary. If you put a weight in the corner It is trying to rotate the top around 2 axes that are following the front edge of each side. If you look where those axes terminate they are both supported by a leg with a wide base as well as the back corner leg. The only way the inside corner would need support is from deflection of the top. Because the back corner is supported the right side would have to twist and the whole left side would have to bend. It looks far more precarious then it actually is.

Marcus I'd nix the center leg in the back on the left side, that leg really isn't doing anything other than looking weird. Also maybe move the back "apron" up to support the top this is less for top support and more to give you a place to attach the top. You say you have the top constructed can you share a picture. The seam between the main and the L can cause wood movement issues.

I see. The torque is controlled.

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The main length of the desk is 74" x 28". The small top is 30" x 24".

The top is 2" thick cherry that is built edge grain (like a classic workbench top). The legs are 3" thick oak and the rails are 1" thick by 3" oak. 

Some good advice here. 

 

 

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Chestnut is correct that the joint between the 2 sections of the top needs to allow for wood movement. I think the 3 rd leg looks fine and could serve a purpose, but I just going on my gut reaction ( I'm not an engineer).

Loose tenons and some sort of mechanical fasteners that allow movement is a good approach to joining the top. I would use Tite Joint fasteners. 

http://www.rockler.com/tite-joint-fastener?sid=V9146?utm_source=google&utm_medium=cpc&utm_term=&utm_content=pla&utm_campaign=PL&gclid=Cj0KCQjwy9LVBRDOARIsAGqoVnuGGuVIIrxP8oASy507KMG9azb1CqBpCxPXFuY8PdKzLtlnSHfvEZ4aAvQsEALw_wcB

Sagulator says acceptable, less than a 1/64 sag under 180 lb load in the center of the span. Less than a 1/32 sag under 240 pounds in the center of the span. So you can stand on the desk to change light bulbs . 3/64 sag under 500 pounds so your daughter-in-law could join him !

 

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10 minutes ago, wdwerker said:

Chestnut is correct that the joint between the 2 sections of the top needs to allow for wood movement. I think the 3 rd leg looks fine and could serve a purpose, but I just going on my gut reaction ( I'm not an engineer).

Loose tenons and some sort of mechanical fasteners that allow movement is a good approach to joining the top. I would use Tite Joint fasteners. 

http://www.rockler.com/tite-joint-fastener?sid=V9146?utm_source=google&utm_medium=cpc&utm_term=&utm_content=pla&utm_campaign=PL&gclid=Cj0KCQjwy9LVBRDOARIsAGqoVnuGGuVIIrxP8oASy507KMG9azb1CqBpCxPXFuY8PdKzLtlnSHfvEZ4aAvQsEALw_wcB

Sagulator says acceptable, less than a 1/64 sag under 180 lb load in the center of the span. Less than a 1/32 sag under 240 pounds in the center of the span. So you can stand on the desk to change light bulbs . 3/64 sag under 500 pounds so your daughter-in-law could join him !

 

I'm sure they'd be, what was it, "changing lightbulbs". Also your link wasn't working for me.

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Those who say the sagulator does not apply for end grain construction are correct.  But then again you have a very thick top.   Another thought - When a long grain board develops a crack it can still carry a load.  A crack in end grain will not because wood is weak "across" the grain.  That said and since you have the top made already - go for it.

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Thanks for all the help. In a related question, what is the proper way to refer to this kind of construction? I see it advertised as "butcher block", I always thought butcher block was end grain pointing up. 

 

 

White-Oak-Edge-Grain-Butcher-Block-Count

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That's just glued together boards in a long grain configuraton - It's that same as a table top made out of more than one board it's just that our boards are thick than they are wide.  Should be very stable - just like a work bench. Should work great for a desk.

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16 hours ago, wdwerker said:

" 2 inch thick edge grain construction " doesn't lead me to think end grain. 

You are right, I misread that last night and thought it said "end grain construction!", like a butcher block. My mistake.

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3 hours ago, Isaac said:

You are right, I misread that last night and thought it said "end grain construction!", like a butcher block. My mistake.

I did the same thing.

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