From: rdsaam@att.net   
      
   On 8/18/17 1:42 AM, Tom Roberts wrote:   
   > On 8/15/17 8/15/17   1:14 PM, Richard D. Saam wrote:   
   >> Basic momentum transfer indicates faster than wind is not possible   
   >> assuming uniform wind gradient from surface to sail or propeller height.   
   >   
   > It is quite common for iceboats and modern catamarans to sail faster than the   
   > wind, sometimes much faster (3X - 5X). They do this on a reach (i.e.   
   traveling   
   > cross-wind), not a run (downwind), because then the sails can create   
   aerodynamic   
   >   lift to propel the boat forward. For most modern sailboats a close reach is   
   > the fastest point of sailing, unless waves interfere.   
   >   
   > Tom Roberts   
   >   
   >   
   Yes, iceboats and modern catamarans do sail faster than the wind   
   as well as sail planes and the albatross that stays at sea for months   
   without flapping a wing   
   as well as the pelican  that skims the ocean surface.   
      
   The captured air heat capacity by the vehicle(or bird)   
   provides the energy   
   to move the vehicle(or bird) faster than the wind.   
   It is a heat engine with the sun as the primary source.   
      
   air heat capacity availability   
   for a 1 degree temperature change (thermal gradient)   
   across the vehicle ~ (1E7 erg/g/K * 1K) = 1E7 (g/g)cm^2/sec^2.   
      
   This air heat energy availability compares   
   to wind component energy availability at 30 mph   
   as (mass/mass)(30 mph)^2  or .18E7 (g/g)cm^2/sec^2.   
      
   It is apparent that air thermal effects can predominate.   
      
   Note that during the recent solar eclipse,   
   the observers noticed an air cooling.   
   This would lower the air heat capacity availability.   
   Did it affect the local birds?   
      
   Richard Saam   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)