Back in the Late 60's and early 70's when I was scratch building, I bought Midwest balsa from my local hobby shop.  Anything that had a "contest grade" sticker on it I grabbed because there really wasn't that much available, at least in the shop I bought from.

In the last couple of years, I have bought high end kits that are advertised to contain contest balsa.  So far, I haven't been disappointed.

My question is, should I elect to start scratch building again, I would like to be armed with better knowledge about balsa.  Is there some sort of chart that advises what density of balsa and what grain is desirable for different areas in the model?

Chart?

I've never seen a chart about balsa choice.

I've always used, feel, weight and color. Pinch the edge, put a sheet in each hand for weight, and the darker wood was generally heavier.

Is there more to it than that?

Charles

I believe there is.  Some grains are better suited to one part of the plane than others.  A harder slab would be preferred for a profile.

Being there in person to pinch and weigh is fine, but if you buy mail order, you are leaving the selection up to the vendor.  That may or may not be a bad thing, I don't know.  I would think the vendor would need to know what the application of each size ordered was for.

Huh.  I can't find the useful links section, either.

Most of the balsa suppliers out there will hand-select wood for you, which lets you ask for A grain or C grain (C grain is Way Good for anything that just uses a slab of sheet, like a fin or stab).  Most also list contest grade (less than 6lb/cubic foot) wood separately from 'regular old' wood.

If your wood comes in 36 x 3 x whatever sheets, it's pretty easy to get the density, because a 36 x 3 x 1 sheet that weighs 6oz is 6lb/ft^3 wood.  So if you can stand doing just a bit of math, you just take your 36 x 3 wood, weigh it in ounces, then divide it by the thickness.  Remember that to divide by 1/something means to multiply by the bottom number, so if it's 1/4 sheet you multiply the weight by four, if it's 1/8 sheet you multiply by 8, if it's 3/32 you remember that that's pretty darn close to 1/10 and multiply by 10, etc.

http://www.auszac.com/Balsa%20wood%20Properties%20Guide.pdf

This was about the best I could find.  Basically strength of balsa goes up with density.  This suggests things to think about.  There are a few things, like spars, for example, which need to be particularly strong.  So maybe one could judiciously use denser balsa for strength, with little total weight penalty.  Or maybe one could use a smaller denser piece of balsa and have more strength for the weight.

I don't buy balsa from my local hobby shop very often.  When I do, I bring my scale with me and check it.  Use this: http://www.nclra.org/Programs/BalsaDensity.php  If it doesn't meet my requirements I don't buy it.  Even when I buy wood on line I weigh and mark each piece.

"Useful Links" is 3rd "forum" from the bottom of the list. The subtitle is "Download Area".   Steve

here's the one I use for weight

It's Bill Calkins Balsa weight calculator and it works great and is downloadable
http://clflyer.tripod.com/Downloads/downloads.htm