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Because they rest on a singular point at each end because we bend them to put them in place when we use them and because there is no clamping mechanism or pinning mechanism tying the column to the deck the junction is for calculation proposes a simple supported column (other wise known as hinged –hinged) to be pinned – pinned (otherwise known as clamped-clamped) you need a cup or pin in the deck restraining the column.

Color coded dimples for different tasks.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

????

My response was in regards to the question Mike asked me if the column connection to the restraining boundaries were for calculation proposes a pip-pin or hinge-hinge type joint calculation. See pic.

You had mentioned the safety factor of using go bars that are bent too much. If both ends of the go bar are perpendicular the the clamped surface, there's no side force. Side force is where the danger comes in. If one were so inclined and you had a pretty regular work flow figured out, you could drill dimples into the top of the deck that matched where you normally clamp below. One pattern for gluing braces, one for gluing tops & backs etc.

Not really that amazing an idea but a thought anyway.

I like to live on the edge so I don't see myself buying different length go bars for different uses.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Actually it is near impossible to insure dead inline contact points. and if the sping force over comes friction of the top of the deck or the contact on the clamped part watch out. If you have not seen this happen you have not placed enough go-bars in yet

I had a bunch of spool clamps I bought years ago and don't use anymore so I use the ends of them for go bar supports on the top and back. I've found 1/4" hardware store dowels with rubber screw protectors on the ends to be just fine for tops and backs as far as clamping pressure. 5/16" for most everything else. I also use the 5/16" fiberglass driveway markers that we use up here in the north country to make sure we plow up to the edges of our driveways. They are pretty cheap and work well for top and back braces and bridgeplates.
Terry

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I tried some of the 5/16 fiberglass driveway markers from Home Depot. They were 24" and had way too much pressure for me to feel comfortable using. And to reinforce the safety comments, be very careful with these. One of mine slipped off and hit me in the cheek...and trust me it hurt! Thankfully, I did have safety glasses on, but with the force it hit me, suspect that I may have still had a serious injury if it had hit the glasses. I've not used them since.

I can relate and did the very same thing Alan........

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Ann Arbor Guitars

Well, I am still focused on the normal force issue. Although the buckling load is the max normal force, there are side forces (via friction) that rise with increased deflection (pinned-pinned). Thats where the "extra" force goes. Should the go-bar overcome this frictional force, one shall experience the wrath of the said go-bar if one is close enough.

Mike

Mike,

23.4lb for each bar is why you are getting "More than a little deflection" of your gobar deck. You are lucky this is the only problem you have encountered.

If you were to use say 20 gobars all applying this kind of pressure when gluing on the back or top that would add up to a total of 465lb. Under that kind of load, even if you did manage to build your deck strong enough to handle it, I would expect the sides to suffer a catastrophic failure as they buckle under the pressure and split longitudinally with the grain.

I recon 7-8lb per bar is plenty, especially when you have a couple of dozen set up at a time, 20 x 8 = 160.

Cheers

Kim

I recommend removing all of the mystery of the bend and using spring loaded bars.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Waddy bro I have always thought that your go-bars are very cool.

But I have been wanting to ask you if the inspiration was a toilet paper holder?

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Ann Arbor Guitars

Hesh, is your dog sniffing glue?

Mike

Just for the record the 5/16" fiberglass driveway marker rods I have (Ace Hardware) register 8lbs. on the bathroom scale test. If you put rubber thread protectors on each end and have the length in the ballpark to avoid flexing too much they won't slip and work just fine for the heavier braces and bridge plate.
Terry

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I just find using go-bar deck for gluing tops and bottoms too fiddly. Get some surgical tubing (Woodcraft sells it) and wrap the top or back side to side and top to bottom. I used this on my first and last guitar and was pleasantly surprised how well it works.

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A higher purpose for wood.
Rich Smith
Issaquah, WA

Thanks for the great info and intuitive myth debunking on gobar decks.
The data sure trumps my intuition too.

I was interested to find on this page at the Stew Mac site:

http://www.stewmac.com/tradesecrets/promo/ts0044_gobars

Tod Sams shows how he uses gobars with this quote from a side bar:

"To add more pressure to all the bars at once, he slides a piece of 1/2" plywood under the bottom deck, raising it slightly."

Someone should send Tod/stewmac this thread link.

David

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www.davidbeede.com

Okay, nuther stupid question....

With the ease of building a custom vacuum press, why would this not be a better alternative?

Glue time? Deformity? Or is it just slow to catch on?

http://www.joewoodworker.com/veneering/welcome.htm

http://www.vacuumformerplans.blogspot.com/


- Phil

Has anyone came up with an idea to make a quick release "nut" where the height of the upper deck can be adjusted easily/quickly using threaded rods? Nut's are easy.....just not that quick.

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Formerly known as Adaboy.......

I think that Kathy Matsushita came up with a cool way. Click on the go-bar deck link and there is an excellent video. http://home.comcast.net/~kathymatsushita/

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Ann Arbor Guitars

You're too humble Hesh. She gives you credit for the idea.

For those of us using threaded rod, has anyone, besides me, considered using Quick-Threading Nuts?
http://www.mcmaster.com/ part number 90125A035 since I used 5/8-11 rod.
-- sorry, I couldn't get the direct link to the part to work on their website.

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Steve Smith
"Music is what feelings sound like"

I have never used a go-bar,but if you increase the friction of both contact points,i.e. sandpaper or rubber, wouldn't you minimize the chance of slippage?

Those rubber feet do a good enough job. But slip will happen from time to time. I had one slip when I was removing it. Put a nice ding in the top. Got to try out that technique with an iron and a wet cloth. Worked like a charm! No more ding.

Mike (Hesh, I only asked about your dog 'cause he had a TP roll on his nose... )