New Posts New Posts RSS Feed: Wiki Sail by GRF
  FAQ FAQ  Forum Search   Register Register  Login Login

Wiki Sail by GRF

 Post Reply Post Reply Page  <12345 34>
Author
GarethT View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 21 Apr 07
Online Status: Offline
Posts: 714
Post Options Post Options   Quote GarethT Quote  Post ReplyReply Direct Link To This Post Topic: Wiki Sail by GRF
    Posted: 26 Mar 13 at 4:00pm
Originally posted by iGRF

The sail thing, I guess is the same reason that a hercules heavy lift aircraft wing is lower aspect than a fighter jet. At lower speeds, the greater chord length of the combined jib and main which act in unison in reality are more efficient than the same area projected vertically in say a high aspect wing mast.

 
Now you've done it.
 
Brace yourself for a Bootscooter "during the war" story.
Back to Top
I luv Wight View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 28 Jan 05
Location: United Kingdom
Online Status: Offline
Posts: 628
Post Options Post Options   Quote I luv Wight Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 13 at 4:33pm
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

http://www.bloodaxeboats.co.uk
Andy P
foiling Int Moth GBR3467
Freedom 21 Codling
Back to Top
Medway Maniac View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 13 May 05
Location: United Kingdom
Online Status: Offline
Posts: 2788
Post Options Post Options   Quote Medway Maniac Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 13 at 4:39pm
Now it's more like badger-baiting...
Back to Top
Jamie View Drop Down
Posting king
Posting king
Avatar

Joined: 12 Jul 04
Location: United Kingdom
Online Status: Offline
Posts: 164
Post Options Post Options   Quote Jamie Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 13 at 5:12pm
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.              



Back to Top
Bootscooter View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 15 May 07
Location: United Kingdom
Online Status: Offline
Posts: 1094
Post Options Post Options   Quote Bootscooter Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 13 at 5:35pm
Originally posted by GarethT

Originally posted by iGRF

The sail thing, I guess is the same reason that a hercules heavy lift aircraft wing is lower aspect than a fighter jet. At lower speeds, the greater chord length of the combined jib and main which act in unison in reality are more efficient than the same area projected vertically in say a high aspect wing mast.

 

Now you've done it.

 

Brace yourself for a Bootscooter "during the war" story.



*pulls up a sandbag/swings tilley lamp*
Back to Top
iGRF View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 07 Mar 11
Location: Hythe
Online Status: Offline
Posts: 6499
Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 13 at 5:39pm
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
Back to Top
Rupert View Drop Down
Really should get out more
Really should get out more


Joined: 11 Aug 04
Location: Whitefriars sc
Online Status: Offline
Posts: 8956
Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 13 at 9:11pm
Bloody hell, go away for a few hours, and not only has someone set up a thread for GRF to put all his usual half cocked theories on, but half the rest of you appear happy to join him in spouting half cocked delusional ideas.

The displacement thing - I'm only an ex boat builder, but even I was taught at college to calculate the displacement of a design, as well as all sorts of other things. How else would the designer know it would work? Giving the design displacement along with all up weight would give us an idea of the kind of crew weight the boat was designed for, though, wouldn't it?

As for the sails V's wing thing - just nonsense, really - they act in totally different ways, moving different objects which are immersed in different mediums. Results for one might just be different from the other, maybe?

As for badger baiting, I'm surprised SB hasn't waded in yet...
Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686
Back to Top
iGRF View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 07 Mar 11
Location: Hythe
Online Status: Offline
Posts: 6499
Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 13 at 9:21pm
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?
Back to Top
JohnW View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 17 Jul 07
Location: United Kingdom
Online Status: Offline
Posts: 552
Post Options Post Options   Quote JohnW Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 13 at 10:05pm
Originally posted by iGRF

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.

But they fill glider wings with water to make them heavier.
Go figure!
Perhaps those AC72s should fill their wing rigs with water!

Back to Top
Cameron Winton View Drop Down
Groupie
Groupie


Joined: 08 Nov 11
Location: Prestwick
Online Status: Offline
Posts: 41
Post Options Post Options   Quote Cameron Winton Quote  Post ReplyReply Direct Link To This Post Posted: 26 Mar 13 at 11:03pm
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
Back to Top
 Post Reply Post Reply Page  <12345 34>

Forum Jump Forum Permissions View Drop Down

Bulletin Board Software by Web Wiz Forums® version 9.665y
Copyright ©2001-2010 Web Wiz
Change your personal settings, or read our privacy policy