the science of a flat board?

[Tayler_mann]

So here's something in my years of building that I haven't seen before or possibly paid close attention too. I am building a modular frame system for a client that does sculptures and he needed a back brace to be easily mounted on a single ladder 20' off the ground. The frames consisted of 4" x 3/4" pine the i ripped one edge off of to make into 3". The 4 frames are 35 1/8" x 80". Since it wasn't something hard or much perfection I just used select pine from Menards. The 80" boards of course had some warp and crowning effect to a certain extent. On one frame I glue it had at least a .25" twist. Meaning on one side of the board it was .25" off the table and the other side of the 3" was on the table. So I glued dominos into each joint for ease of glue and alignment and clamped it all to my table with k body clamp on each with about 1/2 a turn of pressure. When I un-clamped it I figured the board would go back to its original bowed shape. To my amazement it stayed completely perfectly flat to my table . Now I know that this happens when I take boards that are already withing a few mm of flat but this was something else. The frames completely flattened out and sits plum to my table.

I am looking for the science behind this to further understand woods movements and reactions to glue and cross grain glue ups. I've always known glue something on a flat surface and it'll be flat but I have never experienced something to this magnitude. If anyone has the cellular science of this or a vastly larger understanding than your average joe I am extremely interested to hear about what happens to such a dynamic material.

 

[bdiemer]

When working with pine try to pick boards that are as close to quarter sawn as possible. Avoid boards that have large cathedral arch grains on the flat sides. They are the most likely to cup and bend. Look for end grains that are more vertical than horizontal. The more straight up and down the end grain the more stable. That's the short of the grain issue. The other issue is moisture. If you don't have the luxury of storing the wood in a similar environment long enough to stabilize, you probably have to purchase your softwood from a hardwood dealer. I have cherry picked boards from a big box store, but bring a moisture meter and a good eye. Look it up but I think most pines stabilize between 7 and 13 percent.

 

[Tayler_mann]

When working with pine try to pick boards that are as close to quarter sawn as possible. Avoid boards that have large cathedral arch grains on the flat sides. They are the most likely to cup and bend. Look for end grains that are more vertical than horizontal. The more straight up and down the end grain the more stable. That's the short of the grain issue. The other issue is moisture. If you don't have the luxury of storing the wood in a similar environment long enough to stabilize, you probably have to purchase your softwood from a hardwood dealer. I have cherry picked boards from a big box store, but bring a moisture meter and a good eye. Look it up but I think most pines stabilize between 7 and 13 percent.

See I know all of that info. That's the general issues with softwoods but I really did not care for this project. I feel I was unclear in my description. What happened was the 2 boards I glued (butt end to edge) were both fairly warped pre-glue. Now durin the glue process I clamped both boards flat to my Mft with dominos in the joint with ample glue for WAY to much squeeze out. I left them clamped to my table for roughly 12 hours before unclamping. When I took the clamps off that held it to the MFT both pieces stayed completely flat with I bow in them. It had actually taken the twist and bow out of he board. Now of course the crown on the 80" piece stayed the same but if I clamped the frame to my table during glue up they stayed perfectly flat to my table. What I sm looking for is the cellular science of this not the average explanation

 

[nickao]

Vertical verse horizontal grain and species itself are simply the most important factor in flat boards.

It sounds like you want information down to the cellular structure and why woods act the way they do. This is the best book I have read on wood, I own both in the series. This first book will tell you what you want to know.  The topic is just too in depth for anyone to answer in a single post.

Understanding Wood : A craftsman Guide To Wood Technology

http://www.amazon.com/Understanding-Wood-Craftsmans-Guide-Technology/dp/1561583588/ref=sr_1_1?ie=UTF8&qid=1440512451&sr=8-1&keywords=understanding+wood

Here is its companion book:

Identifying Wood : Accurate Results With Simple Tools

http://www.amazon.com/Identifying-Wood-Accurate-Results-Simple/dp/0942391047/ref=sr_1_sc_1?ie=UTF8&qid=1440512520&sr=8-1-spell&keywords=identifyin+wood

And here is one more that goes great with the other two:

The Wood Book

http://www.amazon.com/Woodbook-Complete-Plates-English-German/dp/383653603X/ref=sr_1_1?ie=UTF8&qid=1440512554&sr=8-1&keywords=The+wood+book

and lastly this kit:

Wood Collection and Research Kit

http://www.woodcollection.com/EducationResearch.htm

And this web site, if you search it may have your answers, this site is getting better and better and more than just identifying:

The Wood Data Base

http://www.wood-database.com/wood-articles/fluorescence-a-secret-weapon-in-wood-identification/

If you have an exact question I can look in the book for the answer.