Question on SG of brace wood

[PeteD]

I am looking at some bracewood which is Engleman and is listed at .35 SG. Is that SG in the right ballpark, or is it a bit low? Its well quartered and split versus sawn. This will be for a Sitka topped Grand Auditorium build. Sorry, still a bit of a beginner here.

[Michael Lewis]

Test it. If it is too flexible cut it larger.

[Tom West]

Pete: For me SG is not as much concern as stiffness. In a braced top most of the weight is in the plate itself, so concern about weight is not a problem if you are using the right wood. Engelmann is good bracing wood. I test my wood for stiffness by cutting to the required cross section, suspending the brace across two points 18' apart and hanging a weight in the center of the brace. This is a pipe wrench and I don't even know it's weight. I then measure the deflection with a dial indicator. After doing this over the years I know what I want for braces. Suggest if you are to continue that you start and keep records so you can get a feel for the correct stiffness. As to the wood you now have I would use it even though it could be a bit less then ideal (I don't know that it is) because beginners usually overbuild at first. Hope this is of some help. I realize at first it's hard to get a toehold on things like this but the key is to keep at it and be aware. Good luck and take care.
Tom

[Clay Schaeffer]

Using a relatively light weight wood for brace material is not a bad thing. It can allow you to optimize the dimensions of the brace to get the required stiffness , keep a reasonable gluing footprint, and not add too much weight. Alan Carruth has often mentioned that with spruce stiffness often tracks with density. From that I take that less dense spruce is less stiff, but it allows you to make the brace taller (so stiffer in that direction) but no narrower for the same weight, and so allows you to have the same gluing surface to the top.