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Re: Those supercrested nyctosaurs




Christopher Collinson wrote:

> >> in contact with the water most of the time.<<
>
> Ok, so what happens if there is no contact with the sea?

For very brief periods (brief with respect to the inertial response of the
animal), nothing much. For longer periods, it depends somewhat on where the
animal is with respect to the boundary shear layer.  More below.

> There must also have been
> occasions when the animal was not actively using its crest to sail. How does
> the sail crest affect the pterosaur's performance in these cases?

It becomes a bit of a drag producer.  Flutter can be an issue.  Configuration is
such that flight stability is enhanced, if one does NOT presume a membrane
forward of the mast and if one also keeps the sail slightly loaded, though the
lift/drag ratio is somewhat reduced as a consequence.  We intend additional work
on flight at altitude (where the sail cannot produce thrust under any
practicable scenario) and on alternative techniques for providing sideforce and
resisting heeling moment when sailing with water contact and in the shear
layer.  I find it intriguing that the scenario trades off a substantial increase
in performance while feeding for a slight detriment while traveling.  If such
crests should turn out to be real, that trade off could be a fun topic to
explore.  Keep in mind that we are not presently saying that Nyctosaurus
supported such a crest -- we are investigating what the effects would be IF
Nyctosaurus or other pterosaurs did support such a crest.
Jim