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| Drawing an accurate radius-method http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=46611 |
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| Author: | PhilQ [ Thu Nov 05, 2015 3:29 pm ] |
| Post subject: | Drawing an accurate radius-method |
Hey fellas Another question: I have done a fair bit of reading and researching (and head scratching) trying to find a reliable method for tracing an arc for, say, a circle of 60ft radius, other than physically making a 60ft long piece of wood on a pivot with a pencil at the end. Do you use a mathematical formula to be able to find the amount of vertical deflection to use for a given length of a flexible piece of plastic or metal with a nail at each end and one in the middle, as outlined in Cumpiano's book? For instance, if my piece is 12 inches long and I want a 60ft radius arc, how much to I need to raise the middle nail so that I get the proper arc? Comments and suggestions greatly appreciated! |
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| Author: | kencierp [ Thu Nov 05, 2015 3:36 pm ] |
| Post subject: | Re: Drawing an accurate radius-method |
This may help http://www.liutaiomottola.com/formulae/sag.htm |
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| Author: | PhilQ [ Thu Nov 05, 2015 3:49 pm ] |
| Post subject: | Re: Drawing an accurate radius-method |
YES! Thank you!! |
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| Author: | johnparchem [ Thu Nov 05, 2015 4:28 pm ] |
| Post subject: | Re: Drawing an accurate radius-method |
a very accurate way is to use a shipwright compass. You can use it in combination with the formula for a sagitta. Here is a post for the down under forum describing its use. http://www.anzlf.com/viewtopic.php?p=70212#p70212 |
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| Author: | Rod True [ Thu Nov 05, 2015 4:59 pm ] |
| Post subject: | Re: Drawing an accurate radius-method |
And remember if you actually hit 58 foot or 62 foot it really is not going to make a big difference. |
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| Author: | DanSavage [ Thu Nov 05, 2015 7:33 pm ] |
| Post subject: | Re: Drawing an accurate radius-method |
I use a CAD program. I draw a 60' radius circle, then trim the part I want to use, then print it out. |
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