Where and how do you store plywood / balsa so it does not warp?

[BigMacDaddy]

I am curious if folks have any proven approaches to storing your fin stock so that it does not warp?

I have a few hundred sheets of 200mm x 300mm x 1.5-2mm plywood that I need to store w/ convenient access. I typically leave the wood in the packages they ship in but once I open a package there is a real risk of the wood warping. I think it is still a little wet when it is shipped to me.

I have been storing open packs as well as pre-cut fins for kits in large Ikea zip lock bags. I put some desiccant packs in each bag but then it is a pain to stack the wood (need to finagle the desiccant pack into the side space next to wood). I have also found that it helps to put some weight on the wood -- good place to store my Uline catalogues that I never open. However, it is a pain to dig through this and I lose track of what I have (plus sometimes forget to close a bag and have some the top couple of boards warp on me).

Anyway, looking for any solutions people have used.

 

[user 30299]

Where are you currently storing the plywood? Are you storing them in your work area?
Main part of the house, the basement, the garage, etc.

You may want to drop the use of the bags and desiccant. This can keep the plywood at a moisture
content lower than what your house (surrounding environment/region) is at. You want the plywood's
moisture content to acclimate to your working conditions - it's relative humidity. Once you open the
bag and remove the desiccant the plywood is going to start picking up moisture. Your concerns
about warping may come right back at you.

First thing the hardwood flooring people do is let the wood sit in a house for a couple to few weeks.
This is to let it gain or lose moisture (acclimate) and reach a stable dimension before they start the
whole installation process. They don't want to have large changes in dimensions due to the wood's
shrinking and swelling after the floor is already down; loose or buckled floor boards.

Keeping the pieces stacked flat with some modest weight on top will work fine. And their consistent
dimension of 200x300 should allow you too store them in a series of "cubby holes" (shelving?) that
could each neatly fit a couple dozen pieces (or more) with a weight on top.

I keep all my 1/8" and 1/4" plywood stacked flat, weight on top, and in my work area. No warping issues.

 

[user 30299]

Where are you currently storing the plywood? Are you storing them in your work area?
Main part of the house, the basement, the garage, etc.

You may want to drop the use of the bags and desiccant. This can keep the plywood at a moisture
content lower than what your house (surrounding environment/region) is at. You want the plywood's
moisture content to acclimate to your working conditions - it's relative humidity. Once you open the
bag and remove the desiccant the plywood is going to start picking up moisture. Your concerns
about warping may come right back at you.

First thing the hardwood flooring people do is let the wood sit in a house for a couple to few weeks.
This is to let it gain or lose moisture (acclimate) and reach a stable dimension before they start the
whole installation process. They don't want to have large changes in dimensions due to the wood's
shrinking and swelling after the floor is already down; loose or buckled floor boards.

Keeping the pieces stacked flat with some modest weight on top will work fine. And their consistent
dimension of 200x300 should allow you too store them in a series of "cubby holes" (shelving?) that
could each neatly fit a couple dozen pieces (or more) with a weight on top.

I keep all my 1/8" and 1/4" plywood stacked flat, weight on top, and in my work area. No warping issues.

I forgot to mention that I place a piece of regular plywood on top of the stack and set my
weights on that. I'll use 1/2" or 3/4" thick plywood. It should be the same dimension as
your 200mm x 300mm pieces.

 

[BigMacDaddy]

Where are you currently storing the plywood? Are you storing them in your work area?
Main part of the house, the basement, the garage, etc.

You may want to drop the use of the bags and desiccant. This can keep the plywood at a moisture
content lower than what your house (surrounding environment/region) is at. You want the plywood's
moisture content to acclimate to your working conditions - it's relative humidity. Once you open the
bag and remove the desiccant the plywood is going to start picking up moisture. Your concerns
about warping may come right back at you.

First thing the hardwood flooring people do is let the wood sit in a house for a couple to few weeks.
This is to let it gain or lose moisture (acclimate) and reach a stable dimension before they start the
whole installation process. They don't want to have large changes in dimensions due to the wood's
shrinking and swelling after the floor is already down; loose or buckled floor boards.

Keeping the pieces stacked flat with some modest weight on top will work fine. And their consistent
dimension of 200x300 should allow you too store them in a series of "cubby holes" (shelving?) that
could each neatly fit a couple dozen pieces (or more) with a weight on top.

I keep all my 1/8" and 1/4" plywood stacked flat, weight on top, and in my work area. No warping issues.

They are in my work area -- which is a bedroom so year round conditioning / heat & ac... -- in a cubby in some Ikea furniture / shelving unit.

I feel as if the wood (when I get it) has a higher moisture content than my house.

I don't actually think the little desiccant packs do much but I may be underappreciating their impact.

Most of this plywood will be cut into fins and shipped out to people so no idea what humidity situation it will encounter later. Ideally I would be able to cut it with my CNC and store the already cut sheets of wood without them warping. Currently I cut almost all the fins on demand since I am worried about it warping if I leave it sit around too long.

 

[user 30299]

If you are purchasing a birch plywood, typically it will come out of the presses with no more
than a 10% moisture content. But usually it's closer to 7%. Anything higher causes problems
with the adhesives and the pressing operation. The birch plywood manufacturers try and
maintain the 10% condition before the plywood leaves the plant to maintain dimensional
stability (little or no warp).

Here is a map of the average moisture content of wood throughout North America. This is
what it will typically acclimate to sitting out in a garage or your home. North Jersey would
put you in that 7% to 10% bracket. Down at the "shore" gets you to 13%.


When you receive your plywood shipment, if its wrapped in plastic, do you see any condensation?

Is the plywood starting out as larger sheets and then you're cutting them down to the 200mm x 300mm?

 

[lakeroadster]

When I was a pre-teen my folks owned a sawmill in Ohio. When we cut logs into boards we would use stickers & blocking to stack the wood so air could flow around it and such that it would remain flat.

It's a bit of a pain, but that's what I would suggest. Albeit on a smaller scale, based on the size of material you are speaking of.

Hope that helps.

 

[cautery]

[SELF-CLEANED]

 

[BigMacDaddy]

When I was a pre-teen my folks owned a sawmill in Ohio. When we cut logs into boards we would use stickers & blocking to stack the wood so air could flow around it and such that it would remain flat.

It's a bit of a pain, but that's what I would suggest. Albeit on a smaller scale, based on the size of material you are speaking of.

Hope that helps.



View attachment 556740

Thanks -- yeah, I saw some posts about drying plywood with blocks between layers. I think that might be difficult for me with 300 pieces of thin plywood. Might be interesting to 3D print a sheet w/ airflow built in that could be placed between plywood sheets for people using expensive aircraft plywood.

 

[BigMacDaddy]

Bulk balsa ply should be placed into a press in a single stack and maintained under appropriate pressure. Ideally, you would keep the press somewhere in a sealed compartment/room other and use the appropriate substance to regulate wood water content.... Like large Boveda packs for the correct percentage RH.

I used to keep mine in a press on the ceiling of my garage (sealed and climate controlled). In the attic I had 2x8s crossing the joists to provide an anchor/tie point. I replaced the sheet rock with 3/4" Baltic birch plywood (ceiling had already been beefed up to 3/4" rock) with a stiffening frame on the attic side.
Inside the garage, I used a second stiffened 3/4" BB ply for the other side of the press. There were holes every 12" nominal for all-thread/nuts/fender washers.

I could move the all-thread assemblies where I needed them, add, or remove as needed. Stored pretty much all my nice woodworking and hobby sheet goods up there. Very space efficient. And the balsa remained pristine.

Thank you -- this is what I am leaning towards. Basically getting a dry box (plastic storage with foam seal) and stacking all the plywood flat in there with desiccant packs in the bottom / on the sides. I will put at least one sealed pack on top as the press / weight. Probably need a solid base -- 3/4" plywood or something (although the sealed packs of plywood probably work ok). Just depends on if there is enough room for desiccant packs.

I need to experiment with my pre-cut sheets of fins. It would certainly be nice to have easy access to a dozen or so small stacks of plywood with pre-cut fins for different models. However, stacking flat does not give the best access. I was contemplating clipping stacks of them together with large ACCO clips. I have a metal file separator rack and I wonder if I could clip the plywood to the metal dividers

The discussion here is making me think about putting a humidity sensor in there just to keep track of what the relative humidity is.