Plywood and wind

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Plywood and wind

Postby Drawingablank » Fri Apr 15, 2011 7:16 am

Our new camp project involves making several roughly 4 foot square signs out of plywood. This would be anchored to two upright pieces of rebar with conduit straps bolted through with large washers on both sides of the plywood.

My first question is can 1/4 inch luan plywood with an unsupported span of 36 or 42 inches withstand the wind? Or should I plan to brace the center as well?

My second question is should I design this to elevate the bottom of the sign off the ground or just let it rest on the playa surface?

We are doing the bulk of the drive in our prius then switching over to a larger vehicle in Utah, so space / weight is at a premium for the fist leg of the trip. I would hate to go to 1/2 inch plywood due to the increased weight.
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Postby ygmir » Fri Apr 15, 2011 7:39 am

how much extra, can 1/2" plywood weigh?
and, I bet it's cheaper than1/4".

be prepared for 60 mph wind gusts.
there are web pages to figure wind force on flat panels.

make sure to over build!!
a piece of plywood, flying across the playa is very dangerous!!

What size re-bar? how deep? will there be any diagonal bracing?

good luck.
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Postby Drawingablank » Fri Apr 15, 2011 8:14 am

I was thinking 6 foot rebar pounded in 2 feet and hoping to avoid diagonal bracing or guy lines if possible since the plan is to make whats on the boards interactive and I don't want folks tripping over them.

If necessary I will beef that up. At this point it's all in planning stages so I am not commited to a design yet.

I was also considering some venting to allow some wind to pass through, but have concerns that would weaken it more than it helps.

I'll look into calculating the wind force on the panels.
Savannah: I don't know what it is, but no thread here escapes alive. You'll get 1 or 2 real answers at minimum, occasionally 10 or 12, and then we flog it until it's unrecognizable and you can't get your deposit back.

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Postby ygmir » Fri Apr 15, 2011 8:20 am

what diameter re-bar?

it's gotta be strong enough, to take max wind, considering leverage, and, not bend at ground level.
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Postby Drawingablank » Fri Apr 15, 2011 8:24 am

Hmmm, I'll have to look into available rebar sizes. Since I can pick that up after the 2k mile drive once we have the truck, weight / space won't be an issue with that.
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Postby ygmir » Fri Apr 15, 2011 8:28 am

there are good discount lumber stores in Reno, for plywood and rebar.
They'll usually cut it for you, as well.
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Postby EspressoDude » Fri Apr 15, 2011 8:30 am

use fence post T stakes then slip the conduit over the posts, or U bolt 2 x 4's to the T stakes.

4 x 8 foot span of 1/4 luan/mahogany from homies despot (framed around edges) worked last year for the Kantina Apokiliptika rubble wall/sign at 2:30 and A Sign was about 24 x 8 feet an a "Z" configuration
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Postby Drawingablank » Fri Apr 15, 2011 8:41 am

I was planning to buy hardware there, but since the plywood will have art on it that will need to be transported.

I like the T stakes idea too, but without a pounder and puller those are rather a PITA to install / remove. And thats just more weight to deal with.

I do like the u bolt idea better than conduit straps though - sounds much stronger.
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Postby TomServo » Fri Apr 15, 2011 10:14 am

Drawingablank wrote:I was planning to buy hardware there, but since the plywood will have art on it that will need to be transported.

I like the T stakes idea too, but without a pounder and puller those are rather a PITA to install / remove. And thats just more weight to deal with.

I do like the u bolt idea better than conduit straps though - sounds much stronger.



Pounder and a puller should run you about $40. If you can't find em, stop by BloodBath&Beyond. When my real comps up, Ill post some links.
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Postby Elliot » Fri Apr 15, 2011 11:34 am

Perhaps you could paint the signs on canvas, and save even more weight and bulk?
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Postby Drawingablank » Fri Apr 15, 2011 1:14 pm

I considered that, and if it were just signage that would probably be the best way to go.

The general concept is to have moveable pieces that mount on the boards and I don't think I can figure out a way to do that with fabric securely or with a mimimum of moop potential.
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Postby TomServo » Fri Apr 15, 2011 2:06 pm

I use a Hi lift jack with these pullers, but an old VW jack would probably works as well.

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Postby Bob » Fri Apr 15, 2011 4:37 pm

I'd use 3/4" ply and 3/4" dia x 4' concrete form stakes. They have holes you can drive #8 screws thru into the ply, or use steel plumber's tape wrapped around the stakes and screwed into the ply. Concrete stakes can be driven with a framing hammer or small sledge. Orient sign parallel with the major wind direction.

Or use 3/4" ply, hinge two pieces together like a sandwich sign, and use two shorter stakes at the bottom on each side.

1/4" ply is tempting the failure gods, it'll probably break on the drive up.
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Postby Bob » Fri Apr 15, 2011 4:44 pm

And keep in mind drunks, bikes and art cars will be as much of a hazard as the wind. Everything looks like a bike rack or pissing post to some people.
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Postby Drawingablank » Sat Apr 16, 2011 6:11 pm

Hmm, all this stuff to think about. I may just pick up some rebar and form stakes and rig up some destructive testing with various plywood scraps in the backyard.

I doubt anything I could transport would be effective aganst a stray MV or a determined drunk, but durabity against wind and bikes should be doable.
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Postby Bob » Sat Apr 16, 2011 6:20 pm

The lantern spires are all secured with form stakes, 3' I think. But a 4' square sign is a big wind target and t-stakes might be better if you don't go with a sandwich sign arrangement.
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Re: Plywood and wind

Postby capjbadger » Mon Apr 25, 2011 2:38 pm

Drawingablank wrote:Our new camp project involves making several roughly 4 foot square signs out of plywood. This would be anchored to two upright pieces of rebar with conduit straps bolted through with large washers on both sides of the plywood.

My first question is can 1/4 inch luan plywood with an unsupported span of 36 or 42 inches withstand the wind? Or should I plan to brace the center as well?

The wind will snap that like a twig. 3/8 or 1/2 ply and reinforce it with a couple of sticks of 2x2 running between your uprights.

Overbuild for anything you bring out there and you won't be sorry. :)

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Postby ibdave » Mon Apr 25, 2011 3:56 pm

Bob wrote:I'd use 3/4" ply and 3/4" dia x 4' concrete form stakes. They have holes you can drive #8 screws thru into the ply, or use steel plumber's tape wrapped around the stakes and screwed into the ply. Concrete stakes can be driven with a framing hammer or small sledge. Orient sign parallel with the major wind direction.

Or use 3/4" ply, hinge two pieces together like a sandwich sign, and use two shorter stakes at the bottom on each side.

1/4" ply is tempting the failure gods, it'll probably break on the drive up.


+10

don't worry about bring any heavy tools-hammers-pounders... Just look around and see what others used and then ask them if they used the same shit.. I loan tools-assist so they come back. even held the hot girlfriend in camp until the ladder came back.,. Of course the girl was well lubed by that time...... :shock: :shock: 8)
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Postby ygmir » Mon Apr 25, 2011 4:12 pm

ibdave wrote:
Bob wrote:I'd use 3/4" ply and 3/4" dia x 4' concrete form stakes. They have holes you can drive #8 screws thru into the ply, or use steel plumber's tape wrapped around the stakes and screwed into the ply. Concrete stakes can be driven with a framing hammer or small sledge. Orient sign parallel with the major wind direction.

Or use 3/4" ply, hinge two pieces together like a sandwich sign, and use two shorter stakes at the bottom on each side.

1/4" ply is tempting the failure gods, it'll probably break on the drive up.


+10

don't worry about bring any heavy tools-hammers-pounders... Just look around and see what others used and then ask them if they used the same shit.. I loan tools-assist so they come back. even held the hot girlfriend in camp until the ladder came back.,. Of course the girl was well lubed by that time...... :shock: :shock: 8)


I bet she never looked at a Vienna sausage, or sweet gherkin pickle the same, after that.
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