Wood Expansion/Shrinkage

[James C]

I was reading an article on the popular woodworking magazine website that talks about how to calculate the shift in wood due to seasons.

http://www.popularwoodworking.com/video/tricks-video/how-to-calculate-wood-shrinkage-and-expansion

It involves knowing the width of a board, the change in moisture levels over a year and the "dimensional change coefficient" of the wood species. Which is derived from the chart below.

I know that some people here love maths and was wondering if it possible to be this accurate predicting wood movement?

 

[Grahamshed]

I think it depends on the wood. Oak and sycamore I know are quite intelligent and could read the article, beech on the other hand is as thick as two short planks and wouldn't know what it was supposed to do.



yes, thats my coat, the one with strings on the very long sleeves

 

[marcus]

I know that some people here love maths and was wondering if it possible to be this accurate predicting wood movement?

Yup, give or take a little

 

[AndyT]

I'm not a timber expert, but I have noticed that the subject of seasonal dimension changes in wood gets much more attention in US publications and websites than it does here in the UK. I presume this is because they have a continental climate, with extremes of very hot and wet summers followed by very cold and dry winters. We don't - our range of humidity and temperature is much less.
So in my experience, if I allow for a bit of shrinkage as the wood comes down from 'big draughty shed dry' to 'cosy home dry' - by using trad construction such as frame and panel - then everything is ok.

 

[DomDru]

I know this is 10 years late, but just in case someone stumbles upon this looking for a solution, I found this:
https://kmtools.com/pages/wood-movement-calculator

 

[Adam W.]

Yes, well......It depends on the cut/conversion/section/whatever you want to call it, thank you.

 

[Citracal]

Traditional techniques take into account wood movement so you don't have to worry about what moves more than something else. Learn tried and tested construction methods and it doesn't matter what wood you build it from.