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Just finished my go bar deck. Nothing fancy but it is light weight and comes apart easily for storage. I built it out of two scrap pieces of plywood, some ABS sprinkler risers, some nipples and caps. I maybe have 13 dollars in it.

Looks nice, but I think you'll find you need some further reinforcement. You wouldn't think those tiny little bars would have much affect, but using enough go-bars to brace a top or close a box will easily bow 3/4 in Baltic Birch ply. Before I built a go-bar deck, I used the underside of my workbench and some Oak bars. The pressure was enough to bow the top, which is made of 2X10s. Hard to say the thickness of your plywood (guessing 1/2?) but I would say either throw on one more layer on top and bottom or add some structural support like cross bracing.

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Aaron Craig

As Aron said and I think you need better support on top board it's visible thin

fric

I agree with the consensus so far, looks good but a little under weight. I find it best to put this equation in your minds eye when designing a GBD... 8lb per rod x 20 rods = 160 lb.

I have 32 rods @ 9lb pressure each and yes I 'have' found occasion to use them all at one time.. 32 x 9 = 288lb...that a lot to hold for a few hours at a time so I went 1 1/4" MDF top and bottom with 7/8" allthread supports. Over kill? Probably but better than walking out to the shed and fining your cat speared through the head with a gobar...then again it depends on the cat I suppose.

Cheers

Kim

I think if the top flexes enough to let your bars loose, your bars are too short. I put a scrap of carpet on the top to give the bars some traction. I would stiffen the base though. If it flexes, you've changed the radius of whatever you're gluing. I can tell you that 4 layers of 3/4" ply on top and 6 on the bottom doesn't move much. It also encourages me to work squatting on the floor since it's so heavy and unwieldy to get up on the bench.

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Mike Lindstrom

Just another thought. I made my deck adjustable, It can accommodate OM and Dread sizes as well as just the top or back.
I raise or lower the top board and use spacers for each height needed.

Thanks for the input guys. I'll beef up the top deck.

I took your advice and added 1/2 of Baltic ply to the bottom and 3/8 Baltic ply to the top. It works like a champ and is still easy to take apart and store.

I’m getting ready to cut the sound hole out of my top but I wasn’t really happy with my circle cutting jig. While looking at Rockler’s thin rip tablesaw jig I thought it would be a good base for one. An article on standardization by Charles Fox in the Guild of American Luthiers magazine gave me the idea. It has a ¼” pivot pin but the base will do anywhere from 1 -7 inches in diameter. The yellow part is a write erase scale in 1/16” increments. This guitar has a 4” sound hole so I carefully measured out a 2” radius and tested it on some scrap. When I was satisfied it was exact I drilled a hole through the jig for a brass pin then I made a line on the scale to make it easy to find. I took the pin out, loosened everything up and put it back together with the brass pin in three times and measured it each time. Every time it measured out to exactly a 2 inch radius. As I decide what diameters I want to use consistently, ie rosettes etc, I’ll add more pin holes.

+1

After having a top deck of 2, laminated, 3/4" pieces of Baltic distort considerably over time, I went with the torsion box, top and bottom. A little more work, but after three years of use, it's still dead flat.

-Mark

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Pullman, WA

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Seems to me that both the bottom and top will flex under load the way it is now. I could be wrong...but gluing a top to a box...I would think flexing of the botton plate is the last thing you want.

You could reinforce the plates with more layers or you could glue a 2x4 diagonally on edge on both surfaces and then some reinforcing braces perpendicular to the main brace....much the same as with the bracing on an acoustic guitar top.

That will easily withstand 350 lbs. without much flex.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

I speak from experience when I say, I agree with the previous posts.
Beef up that lower deck... Lots!
And... Glue some tough fabric (I used heavy canvas) or carpet to the underside of the upper deck. It will prevent your go-bars from slipping & flying across the shop.
Or, kick the cat out of the shop whenever you use the deck.

The bottom of the go deck is 1" thick now. Add almost 3/4" for the radius dish and the fact that the bottom sits flush on my work bench. I don't think it's going anywhere. I may add some more to the top but it seems to be working fine. I put vinyl tips on all of my go bars so they don't slip. And last but not least I don't have a cat.
Today I built a radius jig for my braces. I only plan on using two radii in the foreseeable future. 28' tops and 15' backs. The cam clamps make taking out the finished brace and putting in the next one fast. Works like a champ.

After my first experience, I probably overbuilt my second deck. I also use a lot more go-bars than I often see in forum posts.
I suggest a trial run, with all the top braces clamped at once & take a good look at the bottom board. If it's not curving up at the edges, you should be fine.

Cool radius jig!

Thanks everyone. Yesterday I finally finished my Fox Bender. I trimmed my sides to length and width and used a piece of the scrap to take it and the digital bending blankets I sell for a spin. Worked like a champ. I couldn't be more pleased.

Some time ago, someone measured the force of a 5/16" go-bar. 7 pounds. No matter how much u flex it (lots of interesting discussions about that). So if you use 20-30 to hold a top, you can see the issue. It's hard to build one of these to be strong and stiff, yet not insanely heavy... Unless u employ a torsion box top and bottom. I'm not going to go into that here, u can google it. But once u understand the concept, there turns out to exist a ready made torsion box in luan flat doors which are very cheap. Cut one in half, add some mounting strips of ply wood, cover in thin painters tarp (anti-slip) and u have a strong, cheap, stiff go-bar deck. The mounting strips are for the separating bars. I used iron pipe and flanges. Gotta have something to screw the flanges to!

Mike

Not so long ago, I decided to test the theory that the force of a go bar stays the same no matter how much you flex it. I used a scale to measure this, using my 5/16" fiberglass rods. I don't remember the actual numbers now, but the force did change significantly as I flexed the bar to different degrees. If I recall correctly, it was about 8 lbs when flexed a relatively small amount, and went up over 10 lbs when flexed more.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

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I pretty much tried the same thing and my recollection was that the force stayed about the same. Now I'm going to have to go do that again to make sure I remembered it right

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Steve Smith
"Music is what feelings sound like"

Todd, I do not doubt it. These rods are probably not "ideal" isotropic materials (same properties in all directions). They are probably close though. Then there is the "hinge" mechanism. How the rod interfaces with the surface. This articledoes a good job of describing the problem, though I am not sure you will come away believing it any more. The stiffness of the deck plays a role too. If the deck flexes at all, the max will force will elude you. Keep bending if you dare. You should reach a max value that changes little with deflection.

Mike

Todd, I do not doubt it. These rods are probably not "ideal" isotropic materials (same properties in all directions). They are probably close though. Then there is the "hinge" mechanism. How the rod interfaces with the surface. This article does a good job of describing the problem, though I am not sure you will come away believing it any more. The stiffness of the deck plays a role too. If the deck flexes at all, the max force will elude you. Keep bending if you dare. You should reach a max value that changes little with deflection. Then there is the issue of linear and non-linear material behavior. I'm pretty sure the column buckling theory is based on linear properties.

Ultimately, what really matters is what you see in your shop. The idea that you can gain loads of force by increaing the strain on the rod is not realistic, and potentially dangerous. The point being, use more rods with less deflection... you will get a better result.

Mike