Cedar Corner bench Advice

[EdF_uk]

Hi everyone,

I'm planning to make a corner bench out of cedar like the one in the picture. I have a lot of spare cedar (18mm x 44mm section) from another project which I can use for the slats. I'm now looking into how I will assemble it. Cedar is very soft and I want a sturdy bench so I'm wondering whether it is best to use a different wood for the cross supports (indicated by the blue arrows in the second picture)?. What do you think? In the shown model I have used 18 x 68 mm section cedar but these cross supports won't be on show so I'm thinking of making them out of another material. The supports are directly attached to the legs

Ed

 

[Why Not Indeed]

If you have lots of cedar of that section to use up then you should orient the supports perpendicularly as they'll be stronger in that direction.
If you have to buy more timber to make this then you might as well buy the right section to start with.

 

[EdF_uk]

Thanks for your input. Are you talking aobut something like this?

I personally prefer the longitudinal type arrangement visually but agree this would be much stronger. I was trying to replicate a corner bench I found on contemporary fencing website. See below. I will have to buy some more cedar for it anyway

 

[Why Not Indeed]

That's not what I meant actually, but maybe it is better.
I meant the front-to-back bracing would be stronger with its widest edge vertically oriented [there will be some proper technical words to explain this that I'm missing].

 

[Mike13]

Euler, the Swiss mathematician showed that stiffness increased as the cube of the depth, so in your second picture you rotate the underneath pieces so they are deeper and not wider, the bench will be much stiffer.

 

[EdF_uk]

Yes you’re both right. I am going to find some thicker cross supports. I think what is required is a section with high moment of area if I remember back to my engineering days. A long time ago!

I think the main issue is that the length wise battens, as drawn, will have a span of around 570mm between leg supports and the battens aren’t very stiff. I could make a stiffer frame that I screw the battens to and/or I might just buy another pair of supports to reduce the span.