Balsa wood properties 5

[Integrator62]

Low, Medium or High density, Which types of balsa wood is most cost effective and Structurally efficient and available in market?

Is it possible to have a balsa wood block of 5ft long and 3x3" cross sectional area in market?

As this wood beam will be subjected to bending, to make it highly efficient I like to make two types of wood blocks.
At tension region Wood with strong axial fiber (A grain)
And at compression region C grain.
Then glue will be used to join them together and make them act as one single beam.

Is it a good idea?

 

[Sawbux]

Quote from a web site "the press insisted on calling it the “Spruce Goose” despite the fact that the plane is made almost entirely of birch."

My guess is that engine technology was to blame on the lack of power side. The engines look pretty small compared with the size of the airplane, even though they are huge when seen separate. The B-36 had the same problem and had jet engines placed near the wing tips in later versions.

My sailboat has 1/2" balsa cored hull. The bending strength is in the fiberglass inner and outer skins, the balsa serves as the spacer between the skins and takes some shear stress. The balsa is in mats, cut across the grain like a checker board. In that way it can be laid up to conform to the curved shapes of the hull.

 

[boo1]

the cross grain cut reduces chance for water absortion

 

[Sawbux]

True! Through penetrations should be routed oversized, then filled with epoxy. Then the hole is drilled, leaving a donut of epoxy around the hole to prevent moisture intrusion.
Since the core is primarily loaded in shear, the butcher block arrangement also loads the balsa in the cross-grain direction, which has a greater capacity in shear.