Hey, I don't mind being wrong. In fact, it's a very good way to learn.
I'll look into it more.
The reason I said this is that I read it in a woodworking book some time ago that changing the distance between anchor points will change to force.
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| Author: | Richard_N [ Wed Dec 20, 2006 8:00 am ] |
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Hi I've set up a go bar deck with 6mm fibreglass rods . Each rod exerts approx 8 lbs force. Is this ok for gluing the top and back to the sides or should I get some thinner rods ? Thanks for your help |
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| Author: | Rod True [ Wed Dec 20, 2006 8:09 am ] |
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I'm not sure about the fiberglass rods cause I use wood, but I think most folks use 3/16" rods (5mm), but I can't see there being a problem with it. The force exerted by the rods is dependent on how much you bend them (ie: the distance between the top of the deck and the piece being glued). So to say that there is 8 lbs of force is only good for the distance you measured. Say you have a space of 20" between the top of the deck and the piece being glued and you have a 21" go-bar, you will only flex/bend it enough to change its height 1", but if you have a 24" go-bar, you will have to flex/bend it more (creating more stored energy trying to get back to it's original shape) to change its height 4". So depending on the distance between "anchor" points, the force of the go-bar will change. Having said all this, I think you'll be fine as long as you don't have to bend the rods to much. |
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| Author: | burbank [ Wed Dec 20, 2006 8:14 am ] |
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[QUOTE=Rod True] <snip> The force exerted by the rods is dependent on how much you bend them (ie: the distance between the top of the deck and the piece being glued). <snip> So depending on the distance between "anchor" points, the force of the go-bar will change. Having said all this, I think you'll be fine as long as you don't have to bend the rods to much.[/QUOTE] Rod, my friend, I must respectfully disagree. I've measured the force on my fiberglass rods at different deflections and, lo and behold, found that the force doesn't change with a change in deflection. |
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| Author: | Mattia Valente [ Wed Dec 20, 2006 8:18 am ] |
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There's practically no difference between force applied if you bend a rod past about 1-1.5" shorter than its length; there was a big discussion on this, and the why of this, not all that long ago. Check it with a bathroom scale for a rough guesstimate. For the record, I use 5mm fibreglass go-bars, work just fine for tops and backs (do use an interface caul!). |
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| Author: | Michael Dale Payne [ Wed Dec 20, 2006 8:22 am ] |
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Your fine 4 rods per brace is ok force is not an issue but I like six rods so that there is a more constant clamping from one end to the other. you can get thinner rods if you wish. They will flex a bit easier base on length. But 6mm rods will do a fine job |
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| Author: | Rod True [ Wed Dec 20, 2006 8:37 am ] |
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Hey, I don't mind being wrong. In fact, it's a very good way to learn. I'll look into it more. The reason I said this is that I read it in a woodworking book some time ago that changing the distance between anchor points will change to force.
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| Author: | burbank [ Wed Dec 20, 2006 9:28 am ] |
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Rod, I thought it would too, until I tested after seeing some discussions IIRC here and/or the MIMF. Richard, What Michael said. 6mm is fine. I started with those, but went to 5mm (~3/16"). I found that with the smaller rods, I could use more rods thereby distributing the force more evenly. From the bottom up, I do this: radius dish dense foam pad, with 1" wide outline of body shape top (or back) face up, aligned on the foam pad so the pad takes the force rim in external mold various cauls to protect body wood rods pushing down on cauls, extra rods over neck block Works for me, but like everything else, there's a whole bunch of ways to do it. I'd feel more comfortable using a couple dozen cam clamps, but my collection is too puny at this point. |
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| Author: | TonyKarol [ Wed Dec 20, 2006 9:35 am ] |
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I use the fibreglass fence rods (bars) from Home Depot, bought the longer ones and cut in half - they are about 3/16 by 3/8. $-6 per brace depending on length, and I get about 40 on a top or back with small wood cauls. |
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| Author: | Richard_N [ Wed Dec 20, 2006 6:24 pm ] |
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Thanks |
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