ailerons, elevators, and rudders. Critical Re The Reynolds number range of the paper model aircraft is reasonably wide: 2,000–12,000 for Origami aircraft 4,000–16,900 for Compound Origami (involving adhesives and aerodynamic refinements) 9,000–39,000 for Profile Performance (White Wings, Paper Pilot, et al.) 19,200–56,000 for Scale Performance (White Wings, Paper Pilot, et al.) 22,000–93,000 for Scale Models (complex structures) These ranges are indicative. As noted above the mass: density ratio of paper prevents performance from reaching those of Balsa models in terms of expressions of power to weight, but for models with wingspans of between 250 mm and 1,200 mm, the Critical Re is very similar to balsa model gliders of similar dimensions. Paper models typically have a wing aspect ratio that is very high (model sailplanes) or very low (the classic paper dart), and therefore are in almost all cases flying at velocities far below their wing planform and aerofoil Critical Re, where flow would break down from laminar to turbulent. Most origami paper darts tend to be flying within turbulent air in any case, and as such, are important to research into turbulent flow as are low-Re lifting surfaces found in nature such as leaves of trees and plants as well as the wings of insects. High performance profile and scale models do approach their wing section's critical Re in flight, which is a noteworthy achievement in terms of paper model design. Performance is derived of the fact that wings of these gliders are in fact performing as well as it is possible for them to perform, given their material limitations. Experiments in different material finishes in recent years have revealed some interesting relationships in Re and paper models. Performance of origami and compound origami structures improves markedly with the introduction of smooth paper, though this is also aided by the paper's higher mass and consequently better penetration. More marginal performance and scale types generally do not benefit from heavier, shinier surfaces. Performance profile-fuselage types do experience somewhat improved performance if shiny, slippery paper is used in construction, but although there is a velocity improvement, this is offset very often by a poorer l/d ratio. Scale types have experience negative performance at the addition of heavy shiny papers in their construction. Aerofoils Wing profile sections in models vary, depending on type: Origami : Göttingen flat-plate, or Jedelsky-form for folded leading edges. Compound Origami: Identical with origami, though often with sealed