Wiki Sail by GRF

Fighter jet with a low aspect ratio : http://www.flygplan.info/images/YF-23_800x600.jpg

Glider with high aspect ratio : http://stepleton.com/wp-content/uploads/2012/05/Screen-Shot-2011-09-22-at-9.09.30-PM.png

I wonder why?


Edited by I luv Wight - 26 Mar 13 at 4:35pm

Originally posted by iGRF Well whatever you call it, you have to bear in mind, we consider an enclosed volume, you don't, since you are sitting within it, so yes maybe displacement is a better term, but it essentially counts as the same thing, the amount of volume that the boat uses by displacing water to support the crew weight the greater the area, the bigger the crew, the faster in low winds. How do you measure that then?

 
The same way Archimedes did?

Originally posted by iGRF And, why isn't it published? You couldn't sell a sailboard without the published volume

Because it isn't useful info. The weight component of the crew makes up a very large percentage of the weight of the craft so the displacement varies hugely depending on crew weight. But it also isn't so small a craft that the addition of a persons weight would by design sink it. Much more pertinent info is what weight of crew, independant of ability, is in the best position to get the optimum performance out of the boat while using it for its designed purpose. As it's a completly useless boat if a person climbing in sinks it. But it is not necessarily a completly useless sailboard if a person climbing on sinks it.

Originally posted by iGRF Why is it you are all happy to buy your boats just on the say so of your friend, your club or because everyone else sales them so you step up to be shawn..

Because 1. 50,000 elvis fans can't all be wrong.

              2. If you're into racing but the PY system has you booking one way flights to Switzerland                     then why wouldn't you?

              3. I find it easier to trust real world experiences of others than marketing bumph.

              4. If you are looking to sail for the same reasons and to the same purpose as the rest of                     the people at the club, it stands to reason that you want the same or similar craft to                         that which they are sailing. If you wan't something else entirely then leave them to it                       and go your own way.              

Originally posted by I luv Wight Fighter jet with a low aspect ratio : http://www.flygplan.info/images/YF-23_800x600.jpgGlider with high aspect ratio : http://stepleton.com/wp-content/uploads/2012/05/Screen-Shot-2011-09-22-at-9.09.30-PM.pngI wonder why?

One is very light and has far greater lift to drag ratio than a sailboat, the other uses enormous power and flies by wire, if the computer failed it would fall from the sky.
I guess.

Edited by iGRF - 26 Mar 13 at 5:39pm

So, neither you, nor anyone else has explained why that 'displacement' all you 'boat builders' so carefully consider, isn't published as a technical specification then?

Jib and main work together like slotted Aerofoil.. Airflow is accelerated by slot between job and main reducing pressure on leeward side of main (See Bernoulli) to increase net force on sail. Aspect ratio improves effectiveness of aero foil/sail for a given area. Airflow across Aerofoil is like a vortex which migrates to the tip. Higher aspect ratio keeps vortex attached for longer producing more lift. Sail aero has some funny things going on but should be similar.
Jib/main interaction and aspect ratio are separate subjects.

Edited by Cameron Winton - 26 Mar 13 at 11:05pm