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 Post subject: Strength of plywood
PostPosted: Sat Nov 11, 2017 5:41 am 
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So...

Future work opportunities may or may not require me to move frequently.

I thought about making up some boxes out of plywood for the more important/fragile items:
- Clothing
- office
- kitchen
- preps
- hobbies

I am looking at making simple plywood boxes with hinged lids and internal dividers, stand them up and the dividers become shelving. they will have wheels on one side to move them in the horizontal plane, and HDPE sliders for vertical plane. the boxes will be made by gluing and nailing/screwing the pieces together. I'm aiming for a relatively lightweight box, but rugged enough for moving around

My question is as follows: I've been trying to find out weight capacity of plywood, I'm looking at using 12mm (15/32 inch) thick structural plywood, but haven't found any data on weight capacity.

Would fellow forum members have experience/knowledge/data on this question?

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 Post subject: Re: Strength of plywood
PostPosted: Sat Nov 11, 2017 6:52 am 
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By "weight capacity" do you mean "load bearing capacity"?

http://www.pacificwoodlaminates.com/img ... Tables.pdf

http://www.pfsteco.com/techtips/pdf/tt_ ... capacities

It is going to vary quite a lot by the type of wood, how it is assembled.

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 Post subject: Re: Strength of plywood
PostPosted: Sat Nov 11, 2017 7:02 am 
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When you say converting them into shelving when you aren't using them for moving things, we'd be talking about relatively large dimension boxes then, right? I'm imagining something like 24" wide, 36-48" tall, and 12-18" deep.

There are lots of resources around with performance standards for plywood, though they are mostly geared toward building construction, and are probably not going to be directly relatable to your project. They could give a back-of-the-envelope estimate to the kinds of loads you can expect the panel itself to fail at though. I think the 15/32" plywood, if it meets APA standards, would fall in the 24/0 span rating.
https://engineering.purdue.edu/~jliu/courses/CE479/extras/APA_Load_Span2011.pdf
http://apawood-europe.org/wp-content/uploads/2013/07/PS-1-09-+APA-trademarks.pdf

Unfortunately, all those ratings assume that the load will be on the side of the plywood facing away from the supports, as they would be for floors and roofs, not as it would be in box construction, where you are trying to pull the panel away from the supports. In your case, you really need to understand the fastener pull-out/pull-through, glue tensile strength/adhesion, and the internal bond strength between the plywood plies. I don't think any kind of plywood will readily have that kind of rating data available. And in reality, joint failure is more likely to be the failure mode of your box, before the panel itself cracks.

Edge gluing and fastening the whole box should be pretty strong, but if you find it iffy, you could also look at adding some corner and edge brackets. Probably the only way to be for sure would be to mock it up and test it.

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 Post subject: Re: Strength of plywood
PostPosted: Sat Nov 11, 2017 12:56 pm 
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Sounds kinda cool. However I don't think you'd need to worry at all about any sort of weight/load bearing. You'd have to stack those things with lead for them to fail, especially framing them as you describe. I'd be more worried about the type of plywood used. Over time the contractor plywood (OSB) would start to flake off and get splinters everywhere. I'd get a laminate Plywood.

What are you planning on putting in these besides clothes? What would be heavy enough to possibly worry about making the plywood fail?

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 Post subject: Re: Strength of plywood
PostPosted: Sat Nov 11, 2017 1:39 pm 
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I've had some plywood boxes for over 40 years. Well built- and painted - they have lasted despite several moves.

Good luck..

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 Post subject: Re: Strength of plywood
PostPosted: Sat Nov 11, 2017 6:59 pm 
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Halfapint wrote:
Sounds kinda cool. However I don't think you'd need to worry at all about any sort of weight/load bearing. You'd have to stack those things with lead for them to fail, especially framing them as you describe. I'd be more worried about the type of plywood used. Over time the contractor plywood (OSB) would start to flake off and get splinters everywhere. I'd get a laminate Plywood.

What are you planning on putting in these besides clothes? What would be heavy enough to possibly worry about making the plywood fail?


thanks for the comment regarding plywood. I'll prototype the box out of the cheap stuff before moving to the good stuff.
As for what I'm storing in them, my mentality is that everything I own should be able to be broken down (flat packed) or packed in these plywood boxes. I haven't settled on all dimensions, but 1200mm (4 foot) is an ideal length for me. that length allows me to use the box as a bench (in case I move to a place with limited storage options)

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 Post subject: Re: Strength of plywood
PostPosted: Sat Nov 11, 2017 8:38 pm 
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taipan821 wrote:
Halfapint wrote:
Sounds kinda cool. However I don't think you'd need to worry at all about any sort of weight/load bearing. You'd have to stack those things with lead for them to fail, especially framing them as you describe. I'd be more worried about the type of plywood used. Over time the contractor plywood (OSB) would start to flake off and get splinters everywhere. I'd get a laminate Plywood.

What are you planning on putting in these besides clothes? What would be heavy enough to possibly worry about making the plywood fail?


thanks for the comment regarding plywood. I'll prototype the box out of the cheap stuff before moving to the good stuff.
As for what I'm storing in them, my mentality is that everything I own should be able to be broken down (flat packed) or packed in these plywood boxes. I haven't settled on all dimensions, but 1200mm (4 foot) is an ideal length for me. that length allows me to use the box as a bench (in case I move to a place with limited storage options)


TacAir's is probably right along with what you'd want/need. I don't know if flying will be one of the ways you will move. But I'd consider looking at the specs for airline cargo doors, 737's being the most popular midrange plane would probably be a good start.

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 Post subject: Re: Strength of plywood
PostPosted: Sun Nov 12, 2017 2:00 am 
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How good are you for woodworking? I built some shelves to go under my workbench in the garage, and ended up having to dado slots for the shelves; it was kind of a pain (since I'm by no means more than a haphazard woodworker).

In your situation, I might make some plywood footlockers like TacAir posted, with box-jointed and glued sides. Screw an internal bracket or strip of wood in the corners for a bit more support. Drill a hole in the corner of each long side, and you could use nuts and bolts to attach them together temporarily and securely in whatever configuration is currently useful. Couple bigger holes in the short sides for rope handles. Just glue and screw internal dividers wherever needed, since they wouldn't be able to carry much weight even if the boxes were vertical (my shelves were 36" wide)

Seems to me it'd be stronger, cheaper (no wheels), and more flexible. Maybe shorter than you spec'ed, like 45x45x90cm or so.

However you do it, I really like these corner clamps I found from Izzy Swan. Easily DIYable with minimal tools, I knocked 8 together from scrap in an hour or so, and they worked well for me.


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 Post subject: Re: Strength of plywood
PostPosted: Sun Nov 12, 2017 8:30 am 
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Any plywood box that you could physically move will be strong enough.

Said another way... your back will give out before your plywood box does.

Okay, now with that said, my recomnendation would be to go with a steamer style trunk, plastic tote boxes, or rubbermaid chests.

steamer trunks (yes, kinda expensive):

https://www.birchlane.com/furniture/pdp ... r4279.html

I like these Zip Lock storage totes:

https://www.walmart.com/ip/Ziploc-60-Qt ... 13&veh=sem

which I like because the fasteners/latches for the lids cam over. The underside of the lids has a gasket or weather stripping, so the box becomes virtually waterproof. The other major advantage of these totes is that once you get the totes emptied they stack together or nest together...taking up very little room.

Then there are plastic foot lockers like this:

https://www.academy.com/webapp/wcs/stor ... gJFUPD_BwE

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 Post subject: Re: Strength of plywood
PostPosted: Sun Nov 12, 2017 10:34 am 
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FWIW I use the Plano Brand storage boxes for a variety of storage purposes. They work well albeit they are not water right but rather rain resistant. If you store them outside cover then with a tarp.

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 Post subject: Re: Strength of plywood
PostPosted: Thu Nov 16, 2017 3:29 pm 
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I asked on another forum about this.

One of the replies I got back was to google search "tack trunk plans".

yes, tack as in horse's saddles and bits and reigns.

So the one poster who replied included this pic:

http://www.horseloversstore.com/images/ ... kOpenB.jpg

Image

It really is-a nice looking box.. maybe too nice and maybe too big for what you want to do.

If you do go through with building your own plywood boxes and assuming plywood comes in 48 inches by 96 inches wherever you are, then in my opinion you want to maximize or optimize the number of trunk or footlocker parts that you can get out of a sheet.

That would or could possibly mean cutting stuff to either 15 7/8ths inches or 23 7t8" wide by like 31 7/8ths inches long..

A really long footlocker or trunk type box would be 47 7/8ths inches long.

I would think you would try to minimize the waste or scraps.

EDIT: and just to throw this out there...with the shop cabinets I made, I found it easier to finish a full 4X8 (48X96 inches) sheet of plywood first on both sides. Then I cut the drawer parts from that.

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 Post subject: Re: Strength of plywood
PostPosted: Thu Nov 23, 2017 2:56 am 
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A little update.

I've been tinkering and have made a couple of sawhorses to make an improvised table so its easier to work.

Waiting to see at the moment if I can pick up a portable table saw for a good deal, It would make things a lot easier, but not required.

also, waiting for my trailer to be returned so I can pick up some plywood sheets...damn family buying tractors too big for their own trailers :P

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