The lightest wood used commercially, it's used to build model airplanes & some kinds of buoys
[DOC] [TLE] Materials and Hardware used for RC Modelling ... - Gforce-RC Planes [PAR] Balsa Wood; HD Form; Depron Foam; Coroplast Sheets; EPP form; Aircraft grade 
Ply ... Its outstanding strength-to-weight ratio enables RC hobbyists to construct 
durable .... B-grain sheet balsa has some of the qualities of both type A and type 
C. Grain ...