Boards of over one hundred and thirty-one grams per cubic decimetre belong at the hard end of the balsa scale. You can tell this density by feel: the board is distinctly stiffer, it will not yield to a fingernail and it resists being bent.
Modellers reach for it for spars, local reinforcement around mountings, floors, and anywhere dowels or screws are seated into the timber and a softer board would simply crumble out around them. For long straight members the better answer is often to stop using sheet at all: pine strip and beech dowel, sawn to section and far stiffer along the grain, are in wooden profiles and strip. The lighter balsa grades for sheeting, infill and ribs are explained in balsa sheet for models.
