Where have you been trying to get wood from?  Contest wood is not cheep, but, in my personal view its worth every penny.  I think its very hard to use heavier wood-even in smaller sizes, and get away with a model thats suitably light.

Smart engineering is the key words in this case. For instance, you can use 3-4lb. balsa for wing ribs, but they are really too soft, and easily break or deform. Use 6-8lb. wood of the same thickness, and remove more in the way of lightening holes. The result is often parts weighing the same, and are more durable.

Figuring where the stress is going to occur, and engineering the parts to take the loads will allow the use of dimensionally thinner stock.

I often substitute 3/32' 6-8lb. balsa, for lighter 1/8" thick balsa for fuselage sides and bulkheads. I've also used 1/16" 8+ lb, balsa for fuselage sides along with using about 30% more bulkheads that are also from the same stock.

Many folks over build trying to make the plane survive the mishaps that occur. Usually the result is an overweight plane that won't perform well enough to avoid the mishaps in the first place.

So, to qrap this up, I was taught and still believe that a good stunter will turn to balsa dust when crashed, if it doesn't, then some parts were overbuilt, and could have been lighter.

 

I've always maintained that air is lighter than wood. So it's not a bad idea to just use less if you use harder/heavier. As Brett notes, it's seldom in halves as 8-12 pound wood is not twice as strong as 3-4 pound wood. But in general you can get away with just using less.

I agree with John! LOL!!   If a stunter bites the dust and doesn't turn into dust, it was overbuilt.   There are places where strength is needed, but I have seen models that appeared to have been built to withstand flying through a barn door when it was closed......

And 6lb 3/32nd" wood is plenty for almost any stunt plane's fuselage sides, especially with a proper engine crutch.  Many have used (and DO use) 1/16th" behind the wing for the sides.   

Big Bear

The wood strength is mostly proportional to the density.  It runs all the way from 4-6lb. balsa up to basswood, maple, and oak.  Really low density balsa is not as strong per/lb  as slightly heavier wood.  But once you get past 6lb/cu.ft. or so, the strength is pretty much proportional to density.  The other thing to keep in mind is wood selection.  Getting the grain correct can have as much effect on overall strength as density.  Aircraft grade spruce is selected mainly for the number of growth rings/inch.  For the same density, wood with more growth rings is significantly stronger.  For our use, pick C grain wood for parts that need to be stiff(ribs, bulkheads, solid stabs, trailing edge sheeting, etc).  Select A grain for parts that need to bend- leading edge sheeting and forming sheeting.  B grain can be used for fuse sides, bulkheads, thin solid tail surfaces, etc. 

Just as important, the amount and type of glue is just as important.  It is very easy to add several ounces to a 60 inch plane by using too much of the wrong type of glue in the wrong places.