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Re: Great blue heron - Pterosaurs
On Tue, 26 Apr 2005, James R. Cunningham wrote:
> don ohmes wrote:
> > Aerodynamic advantage-- How would that work? Were crests really large
> > enough to generate useful
> > aerodynamic force at the slow speeds involved in surface effect
> > soaring (I'm thinking Great Albatross
> > here)?
> Yes, they were. Some of the larger crests had as much surface area as
> the same animal's wing semispan (50% of the total wing area). So the
> crest aerodynamic forces could be about half that of the wings if
> generating similar lift coefficients. Equal to the wings if generating
> twice the lift coefficient (possible under some sailing scenarios). The
> speeds involved in surface effect soaring aren't slow; they are normal
> flight speeds. It is the speed made good across the water that is slow,
> not the speed made good through the apparent wind. The sailglide
> skimming technique works best when sailing close to the wind (upwind)
> and in broad reaches (across the wind). It is not effective downwind.
> And Wandering albatrosses aren't slow either. They are one of the most
> heavily loaded of all birds, consequently quite fast, and fly at similar
> lift coefficients to pterosaurs with similar aspect ratios (optimal lift
> coefficient is related to aspect ratio).
Not sure I follow this. The crest is a vertical feature. Lift?