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Advice on back panel and rigidity

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furnace

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Team,

This is a sideboard/cabinety thing for a family member. Main cabinetry is 20mm solid ash, will be through or half-blind dovetails on joint between the end panels and top/bottom, through tenons for the vertical dividers and plain housing or tapered dovetail for the horizontal divider.
I was thinking half lapped vertical boards (1/4" ish) for the back panel, but wonder if it requires something with more torsional rigidity (maybe a frame and panel) to avoid the structure racking. I've not started cutting joints yet, just prepping and gluing up panels

Thoughts on the rigidity issue (or anything else!!) appreciated?
emma.jpg
 

Jacob

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In general - if one part is fixed (the back) movement in the structure will show somewhere else (the front, and your doors may stick)), so your half lap boards sound OK, flexible and traditional.
That middle leg looks feeble - I'd give the end units 4 legs/feet each, or the whole thing just 4 feet.
I'd wonder about giving each end unit a top, or a framed top, to keep it rigid, with a separate top spanning over
 

furnace

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Thanks Jacob,
There are actually 2 legs in the middle to avoid sagging but the angle of the pic doesn't show it. I'm undecided on leg placement at the moment.
Cheers
Mark
 

Cabinetman

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I understand where you’re coming from Jacob and I agree about the feet completely, personally I would go for four under each unit as you said. The thing isn’t all that big really I think it would be strong enough Furnace if you were to just use an ash veneered MDF back panel in a rebate on the back of the unit. Ian
 

Jacob

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I understand where you’re coming from Jacob and I agree about the feet completely, personally I would go for four under each unit as you said. The thing isn’t all that big really I think it would be strong enough Furnace if you were to just use an ash veneered MDF back panel in a rebate on the back of the unit. Ian
Yes you could use a single piece back panel in a rebate but I'd do it as a slightly floating fit, so that any movement is taken up at the back, not just at the front and causing the doors to stick.
 

Cabinetman

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Second thoughts a flat veneered panel wouldn’t look very nice in that at all, it’s going to be well jointed in solid timber I don’t think it will rack at all, and a frame with vertical slats would be much better, probably three frames to be correct . Ian
 
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furnace

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I agree that a veneered board wouldn't be in keeping. I think a frame with T&G/half lap panels would look better. If I made it a two panel affair, the centre stile could be quite broad to provide anti racking integrity?
 

eribaMotters

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Why not veneered panels out of view in the two end units to reduce the racking and the TG or lapped boards in the central area that can be seen.

Colin
 

furnace

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Hmmm. Possibly.

But it makes me think about the inherent rigidity of vertical boards around 4" wide. If fitted tightly top and bottom and pinned in place with a single screw/nail there's plenty of triangulation to prevent racking

Any thoughts from someone who's tried it?
 

Jacob

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Hmmm. Possibly.

But it makes me think about the inherent rigidity of vertical boards around 4" wide. If fitted tightly top and bottom and pinned in place with a single screw/nail there's plenty of triangulation to prevent racking

Any thoughts from someone who's tried it?
Fixing racking at the back moves it to the front.
It's simple really - if you fix one end, (side, face etc) of anything, it's the other end (side, face etc) which will move.
Hence trad furniture almost always has loosely pinned back boards.
 

furnace

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I guess it depends on the depth of the cabinet. e.g. If it were only 100mm deep (front to back), there would be no appreciable racking at the front if the back were constrained.
 

doctor Bob

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All these traditional way views are a bit thin arguements in my opinion. I have seen hundreds of old pieces of furniture with sticking doors, non slidey drawers and splits. I like traditional but every thing evolves. A lot of stuff is just way over thought. Are you makingsomething to pass on to your grandchildrens grandchildren, or something useful for now.
 

doctor Bob

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I'd like to do the best I can
Indeed but that doesn't necessarily mean it has to be traditional or fantastically contructed. I'm with Jacob, loose sliding backs work well on modern and traditional stuff without trying to over complicate things.
 

Jacob

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All these traditional way views are a bit thin arguements in my opinion. I have seen hundreds of old pieces of furniture with sticking doors, non slidey drawers and splits. I like traditional but every thing evolves. A lot of stuff is just way over thought. Are you makingsomething to pass on to your grandchildrens grandchildren, or something useful for now.
"hundreds of old pieces"? Exactly! They may be sticking/split now but they probably weren't for most of their lives or they'd have been fixed, or scrapped and wouldn't be here to complain about.
 

Jacob

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Indeed but that doesn't necessarily mean it has to be traditional.
Agree but "traditional" tends to mean tried and tested and known to work, so it's always worth a gander at what they used to do, especially when doing hand work in the old fashioned way.
 

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Honestly wouldn't worry about rigidity in something like that. 20mm solid ash with the joinery you've spec'ed will be rock solid, even without a back in place! Your middle leg will be all the support it will need.

In regards to a back, I've done cabinets of a similar size with solid cedar of Lebanon backs before, set into a rebate as you would a ply or MDF back, and it's worked out well. Also done the T&G method which does look good, although obviously a bit more time and effort.
 

furnace

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Thanks for all the input. I'll cogitate until I get to a point that affects the rest of the build, but I'm veering towards tight fitting (top and bottom) T&G.

Mark
 
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