[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Science feather strength debate



> > I think it is too big of a leap to go from: obligate
> glider -> must climb trees. I also don't think it is
> correct to assume elevation was needed.
> > At many coastal areas, gliders can launch from more or
> less flat ground, from about a meter or two above sea level,
> and start soaring.
> 
> 
> I'm guessing that your "gliders" are actually powered
> fliers that
> happen to glide as a prelude to soaring.  So they
> aren't really
> gliders. 

No, I'm talking true, pure gliders, as in RC airplane where a little toss is 
all that is needed, or hang gliders. The only "power" comes when they are still 
in contact with the ground, and if archie was a good runner- I don't see the 
problem.

Sure, if we look at living pure gliders, they are basically all tree dwellers, 
and their glide duration is proportional to the elevation they launch 
themselves.

But I know from RCs and hang gliders, that you can do *much* more than that 
with pure gliders, and when considering a possible gliding phase of flight, 
preceding powered flight, it may be too restrictive to only consider arboreal 
gliders incapable of soaring.
RCs, are generally the best example in terms of scale, but many are far to 
aerodynamically advanced to serve as a good example (particularly the high 
aspect ratio, low wing loading, carbon/fiberglass models - maybe the foam 
"combat" models aren't so off).
I know from hang gliders that wing loadings of 1-2 pounds/sq foot, and aspect 
ratio's of 5-7:1 are sufficient for at least a few hours of soaring most days 
of the year at many places.

Considering modern arboreal "pure gliders" often have aspect ratio's less than 
2:1, and microraptors fore wings had an aspect ratio over 7:1, I think we 
should consider a very different form of gliding flight than what we find in 
modern "pure gilder" animals.

> >  All I've heard is that archy was from an area
> that used to be islands.
> 
> 
> True.  So it is tempting to think that _Archaeopteryx_
> could use
> flight to commute between islands.  That doesn't mean
> this is what
> 
 commuting *between* islands, as noting that today there is a correlation 
between coastal areas, and good ridge soaring conditions.