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Floating Panel Movement Allowance?

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stuartpaul

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I have a number of floating panels to install in a 'sort of' blanket chest. Most are 310 high by 286 wide but I have a couple at 340 wide.

These are currently a smidge under 15 mm thick and will be going into 10 mm x 10 mm grooves (obviously with relieved rear faces to fit). The wood is well seasoned (ex stair treads from a school and in my shed for 8 years or more) but I know it will still move.

My question is how much room to allow? I'm tempted to make the panels full size as they will certainly shrink a bit when brought indoors but more than just a bit wary of leaving no expansion room.

Thoughts please.
 

woodbloke66

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Difficult to guesstimate how much to leave in the width as that's where the possible shrinkage will take place. If, as you say, the panels are really well seasoned, you may not get any shrinkage at all. On the other hand, were the job going into a cooler room, say an unheated bedroom, they might, on the other hand, expand a fraction. I'd leave a mm or 1.5mm each side just in case - Rob
 

stuartpaul

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Thanks gents, a moisture meter isn’t going to happen I’m afraid but that’s a link to bookmark.

I think I’ll try and bring one of the panels inside for a week or so and with careful measurements see what actual movement I get and work accordingly.
 

Mike Jordan

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You could consider making the side grooves deeper, say 15mm and leaving a gap of 5mm either side. The panels and rails between them will expand and contract, if you don't allow enough space the power of expanding timber is huge.
 

dzj

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Depends where you live. In most places wood expands the most in winter months, so if this is the time when you are doing your glue up, a mm on either side is fine.
If it's in the summer months, I leave ~3mm on each side.

As I said, depends where you live. There are places where EMC changes a percent or 2 over the year and expansion is negligible.
 

Sgian Dubh

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dzj":pg5okfpo said:
Depends where you live. In most places wood expands the most in winter months,
Actually, that's only the case here in the UK if the wood experiences external weather conditions, whether sheltered or fully exposed to the weather. Wood used internally in habitable buildings generally shrinks in the later autumn and winter months and expands during the late spring summer months. RH in habitable buildings in the UK is generally lower in late autumn/ winter, and rises during late spring/ summer.

… if this is the time when you are doing your glue up, a mm on either side is fine.
If it's in the summer months, I leave ~3mm on each side.
Basically correct in that anything as narrow as described in the original question will be fine if a 3 - 4 mm allowance overall is provided for at manufacturing and assembly time, but you should be aware of the point I made above, i.e., the time of year when wood either expands and contracts all dependent upon the end use location.

Conditions and RH values at different times of year and internal/ external locations may be different where you are in Serbia. Slainte.
 

dzj

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Sgian Dubh":1zr4svuf said:
dzj":1zr4svuf said:
Depends where you live. In most places wood expands the most in winter months,
Actually, that's only the case here in the UK if the wood experiences external weather conditions, whether sheltered or fully exposed to the weather. Wood used internally in habitable buildings generally shrinks in the later autumn and winter months and expands during the late spring summer months. RH in habitable buildings in the UK is generally lower in late autumn/ winter, and rises during late spring/ summer.
Yes, that is the case over here also.
You raise an interesting question though.
Should we build furniture that can cope with the natural seasonal swing of external conditions or
should we only adhere to those which a climate controlled environment dictates?
Or combine the two by allowing for a greater than natural annual variation of EMC?
(One never knows where your prized piece will end up.)

Recently a fellow on YT took this to the extreme, claiming that wood movement is a thing of the past, since most people nowadays live in 'Smithsonian' type conditions.
 

Sgian Dubh

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It's generally prudent to allow for more expansion and contraction than you might expect in the location for which the piece was designed. For instance, if you're talking about a piece of furniture, you really have no idea where it might end up in a future life, e.g., a house move from cool and damp west coastal location in the UK to a hot dry location in Arizona, plus all the conditions the piece might experience during transportation and storage.

Recently a fellow on YT took this to the extreme, claiming that wood movement is a thing of the past, since most people nowadays live in 'Smithsonian' type conditions.
I saw that. I'd say (only gently, of course) that he's probably misguided. The only circumstance I can think of where wood doesn't expand and contract is in a location where RH never fluctuates, or only fluctuates a small amount, e.g., within perhaps 4 -6 percentage points. Not everyone lives or works in such strictly climate controlled buildings. When I heard that point of view expressed, I laughed for a wee while, ignored his guidance then, and will do so for as long as I work wood. Slainte.
 
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