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Re: Bridge plate question: radius?

Posted: Thu Jul 13, 2017 11:18 am
by Kevin Sjostrand
Thanks John, I'm just trying to understand. It seems that the bridge being thicker, more mass would act somewhat as a brace to keep the top in the convex/dome shape, just as the braces under the top are applied with a radius to do the same from the underside.

I do get what you say, if Martin and other successful companies/builders aren't doing it, maybe it is not necessary!

Re: Bridge plate question: radius?

Posted: Thu Jul 13, 2017 12:34 pm
by tippie53
actually that is the problem.
The top will indeed move through differing RH changes. The radius will lock things up and this will cause stress to build . I understand that you may thing this radius will help but it will only hold that under the bridge. Once the wood starts to pull the stresses will magnify pretty fast.
The flat bridge will also build stresses but not to the amount of a downward radius.

Re: Bridge plate question: radius?

Posted: Thu Jul 13, 2017 1:54 pm
by MaineGeezer
Lest things get too carried away here....

I just drew a 25' radius circle in CAD and drew a 6" long bridge. To conform to the radius, the ends of the bridge drop by 0.015". There is not a whole lot of difference between straight and radiused.

Re: Bridge plate question: radius?

Posted: Thu Jul 13, 2017 3:20 pm
by Danl8
MaineGeezer wrote:Lest things get too carried away here....

I just drew a 25' radius circle in CAD and drew a 6" long bridge. To conform to the radius, the ends of the bridge drop by 0.015". There is not a whole lot of difference between straight and radiused.
Exactly my point earlier -- over-engineering and very tiny moot differences.

Re: Bridge plate question: radius?

Posted: Thu Jul 13, 2017 9:12 pm
by tippie53
think you may be right main
it isn't much so it shows you can do it any way