Re: Dealing with panels warping, or not
Sgian Dubh
"fork or prong test
What is this, Richard? Are you referring to a moisture meter?"
I should perhaps have included a link to some drying faults and the fork or prong test information in my previous post. I forgot, sorry.
Incidentally, rather than trying to predict tension you're really looking for stress: tension is just one form of stress, there's also compression, torsion, etc.
If the fork or prong test reveals stress you're almost certainly wasting your time trying to deep rip a wide board to get a book matched panel. You are more likely to be able to use it if you can keep whatever stress is in there balanced, e.g., by taking roughly equal amounts off each face. You could also put that piece through a stress relieving cycle in a kiln - most likely not worth it for a single board, unless you can cobble together some sort of small home made stress relieving kiln/ device.
So, given that, it might be best to move on and find another solution to your wide panel challenge, e.g, use a different stress free board for deep ripping, or find two boards with an alternative suitable grain match. I find it acceptable to take boards that are 25 - 32 mm thick and work them down to 10 - 12 mm thick to make panels and other parts, e.g., drawer box parts. It means casually shooting up the extraction system anything up to roughly 20 mm of thickness. That's my attitude to the raw material, which I imagine others might disagree with, but it's a generally reliable methodology, and reliability has always been something of a priority for me in the kind of supplier/ client relationship I work in. Wood is cheap compared to labour, so the wood gives every time if necessary.
As to your point about using native air dried wood in western Ockerland, I can't say for sure what you're likely to be dealing with. But at a guess, it wouldn't surprise me to learn it's possible to air dry wood to something like 10% MC, unlike here in the UK where about 18-20% MC is about as low as you'll ever get for air dried stuff. And 10% MC I imagine is acceptable for indoor furniture projects in Perth, where presumably AC and other climate control measures keep habitable buildings pleasant enough to live and work in, a bit like the hell-hole of Houston where I lived for a while - hot, humid and miserable as sin outside for most of the year, but pleasant enough as long as you didn't stray far from your house, office, car, shopping mall, or swimming pool adjacent to a shaded bar, ha, ha. Slainte.