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3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=26790		 Page 1 of 1
Author:  Link Van Cleave [ Wed Mar 31, 2010 11:21 am ]
Post subject:  3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
So it seems that around 8lbs. is a good working range. It also seems that 3/16" @ 24" gives that. So in the interest of longer bars and the subsequent higher deck with more room and access how long does a 1/4" rod have to be to get close to the 8lb. range ?
Link
Author:  WudWerkr [ Wed Mar 31, 2010 11:38 am ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
idunno HUH idunno
Author:  Barry Daniels [ Wed Mar 31, 2010 11:47 am ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
Your overthinking this.
Author:  Colin North [ Wed Mar 31, 2010 11:50 am ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
I think you would have to apply the cube rule and allow for the young's modulus of elasticity, taking into account the cross sectional area to length ratio.
Or you could just suck it and see.
Buy a length, say 6 feet, cut it into ever shortening lengths, measuring force until you get whatever you want - ?
Kitchen scales, just in case you ask.
Author:  Barry Daniels [ Wed Mar 31, 2010 12:00 pm ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
The additional length won't make much difference. The cube rule does not apply here. 3/16" bars at 36" give plenty of clamping force for me. But then again, I have some 5/16" bars that I use when I need lots of clamping force.

"What don't you get?" No need to be insulting.
Author:  Link Van Cleave [ Wed Mar 31, 2010 12:28 pm ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
Thank you Barry.

Seems like a good idea to have a few heaver bars for those "times" when you need a little extra. Do you use your deck to clamp your tops and backs to the rims ?

Link
Author:  Barry Daniels [ Wed Mar 31, 2010 12:58 pm ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
Yes, I use the go-bar deck for bracing and clamping the top or back to the rims.
Author:  Phil Marino [ Wed Mar 31, 2010 3:10 pm ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
Good question. Back in the dark ages ( before Euler) you would have had to use trial and error. Since the 1700's it's easy to figure it out.

If they're both solid ( and, the same material) , 42.5 inch long 1/4 inch rods will give you about the same force as 24 inch long 3/16 rods. If they're hollow, with the same wall thickness, then it would be about 37 inches for the 1/4 inch tubes.

Phil
Author:  Link Van Cleave [ Wed Mar 31, 2010 5:22 pm ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
Thank you Todd and Phil. That is what I wanted to know !!
Link
Author:  Andy Birko [ Fri Apr 02, 2010 5:48 pm ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
Barry Daniels wrote:
The additional length won't make much difference.


Really? That's not been my experience.

Edit: sorry, I didn't see Todd's lengthy response.
Author:  Edward Taylor [ Fri Apr 02, 2010 6:01 pm ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
I think I get about 6 lbs at 32 inches with the 3/16 bars.
Author:  Mike Lindstrom [ Fri Apr 02, 2010 6:06 pm ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
Hey Todd -

Thanks for the math. I didn't know that. Now to see if I can retain it.

Mike
Author:  Howard Klepper [ Fri Apr 02, 2010 9:10 pm ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
I made some 1/4" bars for my 24" deck and I never use them. They are too stiff to be useful in that length.

But I have noticed that 3/16" fiberglass is not all the same. Some that I got from a kitemaking supplier is stiffer than the set I started with from LMI.
Author:  WudWerkr [ Sat Apr 03, 2010 8:47 am ]
Post subject:  Re: 3/16" fiberglass rod = 8lb.@24" ? What about 1/4" @ ? =
Barry Daniels wrote:
The additional length won't make much difference. The cube rule does not apply here. 3/16" bars at 36" give plenty of clamping force for me. But then again, I have some 5/16" bars that I use when I need lots of clamping force.

"What don't you get?" No need to be insulting.



Wasnt trying to be insulting "if that was a response to me" I didnt get at first we were discussing Go-Bars since he didnt mention it in question . So I was a bit lost at first. idunno
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