myiW Current Conditions and Forecasts Community Forums Windsurfing Videos Buy and Sell Services
 
Hi guest · myAccount · Log in
 SearchSearch   ProfileProfile   Log in to check your private messagesLog in to check your private messages   RegisterRegister 
Sails: Floppy Leech Gone?
Goto page Previous  1, 2, 3, 4  Next
 
Post new topic   Reply to topic    iWindsurf Community Forum Index -> Southwest USA, Hawaii, Mexico
View previous topic :: View next topic  
Author Message
hammerton



Joined: 30 Jul 2007
Posts: 42

PostPosted: Thu May 01, 2014 2:53 pm    Post subject: Reply with quote

In fact you are correct. We have been moving away from super floppy leeches. The pro guys are rigging there sails with less downhaul than I recommend to try to get a bit more low end and drive. The KS3 is a perfect example of that. Even the race sails have less twist than they used to - the GPS has less than the twin cam GP2 and is way faster! The freestyle guys had me take pretty much all the twist out of the Freestyle Pro.

The times they are a changin'
Back to top
View user's profile Send private message
KevinDo



Joined: 02 Jul 2012
Posts: 422
Location: Cabrillo Inside

PostPosted: Thu May 01, 2014 3:10 pm    Post subject: Reply with quote

hammerton wrote:
In fact you are correct. We have been moving away from super floppy leeches. The pro guys are rigging there sails with less downhaul than I recommend to try to get a bit more low end and drive. The KS3 is a perfect example of that. Even the race sails have less twist than they used to - the GPS has less than the twin cam GP2 and is way faster! The freestyle guys had me take pretty much all the twist out of the Freestyle Pro.

The times they are a changin'


With less twist, is the GPS still able to "breathe" in the gusts? (speed run rise?)
Back to top
View user's profile Send private message
kevinkan



Joined: 07 Jun 2001
Posts: 1161
Location: San Francisco

PostPosted: Thu May 01, 2014 3:59 pm    Post subject: Reply with quote

hammerton wrote:
In fact you are correct. We have been moving away from super floppy leeches. The pro guys are rigging there sails with less downhaul than I recommend to try to get a bit more low end and drive. The KS3 is a perfect example of that. Even the race sails have less twist than they used to - the GPS has less than the twin cam GP2 and is way faster! The freestyle guys had me take pretty much all the twist out of the Freestyle Pro.

The times they are a changin'


nice to get some input from a sail designer! has the lessening of twist been due to more stability in the body of the sail due to improved shaping techniques? or were we just overdoing it before? seems like sails these days have more horizontal seam shaping than in the past. Or maybe the fat heads have enough lever to open and twist w/o needing as much looseness? curious minds want to know.

_________________
Kevin Kan
Sunset Sailboards, San Francisco CA
http://www.sunsetsailboards.com
http://www.sunsetsailboards.com/blog
http://www.facebook.com/sunsetsailboards
Live Onsite Reports via Twitter
Back to top
View user's profile Send private message Visit poster's website
fxop



Joined: 13 Jun 1998
Posts: 71

PostPosted: Thu May 01, 2014 4:55 pm    Post subject: Reply with quote

It would be nice to have the gust control that twist gives without the bagginess at the top. Some sails are smooth all the way up and some aren't.

I hope we aren't swinging back to a design that pros will like because they can hang onto anything in a gust whereas we amateurs have a smaller comfort zone.

fxop
Back to top
View user's profile Send private message
isobars



Joined: 12 Dec 1999
Posts: 14319

PostPosted: Thu May 01, 2014 5:30 pm    Post subject: Reply with quote

My sails are designed to run fairly flat leeches because, by my choice based on comparative testing and advice from experts, they use Dacron leeches (the aft half of the sail, in my case). Its slight stretch allows twist without flop, and it's light. It's simply a choice, not anything unusual.
Back to top
View user's profile Send private message
cgoudie1



Joined: 10 Apr 2006
Posts: 1278
Location: Killer Sturgeon Cove

PostPosted: Thu May 01, 2014 5:47 pm    Post subject: Reply with quote

Northwave Surflites don't rig with much flop, and they really never
have. They are the smoothest most gust bust'n sails I have ridden.
Maybe they were 15 years ahead of the design curve. ;*)
Not as rangy as my Sailworks though. ;*) ;*)

-Craig


fxop wrote:
It would be nice to have the gust control that twist gives without the bagginess at the top. Some sails are smooth all the way up and some aren't.

I hope we aren't swinging back to a design that pros will like because they can hang onto anything in a gust whereas we amateurs have a smaller comfort zone.

fxop
Back to top
View user's profile Send private message Visit poster's website
dvCali



Joined: 23 Aug 2007
Posts: 454

PostPosted: Thu May 01, 2014 5:56 pm    Post subject: Reply with quote

KevinDo wrote:
hammerton wrote:
In fact you are correct. We have been moving away from super floppy leeches. The pro guys are rigging there sails with less downhaul than I recommend to try to get a bit more low end and drive. The KS3 is a perfect example of that. Even the race sails have less twist than they used to - the GPS has less than the twin cam GP2 and is way faster! The freestyle guys had me take pretty much all the twist out of the Freestyle Pro.

The times they are a changin'


With less twist, is the GPS still able to "breathe" in the gusts? (speed run rise?)

Hei! Wait a minute! I thought the GP2 down wind was not loosing much speed in respect to the GPS Evil or Very Mad

The GP2 is an absolutely wonderful sail actually (see http://www.hotsailsmaui.com/forum/viewtopic.php?id=3817), it took the place of my GPS 6.6 because it is much easier to manage in places like Crissy or Coyote (can't wait to take it into the channel). The "breathing" acceleration you are talking about is certainly there in the GP2. Something to experience: point it downwind in a gust and the things opens up effortlessly! Very Happy I wonder how much the boom cut out actually contributes to this effect, visually seems like the whole balumina (the leech) opens up, not just the top.

By the way: where is the wind? Is this a global warming foreshadow?
Back to top
View user's profile Send private message Visit poster's website
swchandler



Joined: 08 Nov 1993
Posts: 5888

PostPosted: Thu May 01, 2014 7:35 pm    Post subject: Reply with quote

Sailworks has offered differing views of their Revolution model rigged for light wind, medium wind and high wind scenarios. Without the boom being attached, it illustrates the various leech shapes very well. To view everything, just click on the red "sail tuning" selection.

http://www.sailworks.com/the-gear/sails/revolution.html
Back to top
View user's profile Send private message
BRIMAR



Joined: 03 May 2004
Posts: 99

PostPosted: Fri May 02, 2014 12:40 pm    Post subject: Reply with quote

I'm no sail designer and I could be way off here but i'll present my theory:

Loose leech sails are here to stay!
However as Bruce has done with the Hucker there isn't much of the leech that is "Flopping"
The purpose of the loose leech is to Spill the gusts and keep the lulls but there are other forces in play.
Our sails have "Winglets" just like modern airplanes have winglets. these winglets are designed to reduce a type of drag called "Induced Drag" which is directly proportional to lift, More lift = more induced drag. The winglets allow for better takeoff performance (shorter distance to lift off) and they significantly reduce fuel burn during climb and cruise by reducing induced drag at high altitude where a greater angle of attack (more lift, think sheeting in) is required due to the thinner air up there.

Loose leeches do the same thing by progressively reducing the differential pressure between the high and low pressure sides of the sail.
Why is that important?
when the low pressure on the Leeward side of the sail sucks the high pressure air from the windward side of the sail it creates a vortex!
That vortex = DRAG and the loose leech minimizes this drag by minimizing the lift at the top of the sail.

The huckers minimal loose leech achieves this.

Here's the part that's theory

The new cutaway clews are not for the purpose of allowing you to own fewer and shorter booms (although that is a very convenient design bonus)

What the cutaway clew accomplishes is very similar to what the loose leech accomplishes.
Because the sail is producing lift AFT of the rear boom end (outhaul line) the stiffness of the battens above the boom FLATTEN the sail when sheeting in HARD effectively depowering the sail and making it faster by making the sail flatter.

This newly designed (BRILLIANT) feature has allowed the designers to minimize the loose leech and utilize more of the sail as a lifting foil as opposed to so much of the foil being a depowering drag reducing foil.

Hope this helps
(I told you I wasn't an expert)



737-Split-Winglet-hres.jpg
 Description:
 Filesize:  426.63 KB
 Viewed:  878 Time(s)

737-Split-Winglet-hres.jpg


Back to top
View user's profile Send private message
mac



Joined: 07 Mar 1999
Posts: 5356

PostPosted: Fri May 02, 2014 1:21 pm    Post subject: Reply with quote

One thing that seems to be missing in this thread is what the sail looks like under load. As part of tuning a sail, you need to understand what it looks like under wind load. This can be done on shore, in simulation, by pumping the sail. It can best be done on the water, looking up. You want the head of the sail to twist off in a big gust, but to otherwise not be floppy.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    iWindsurf Community Forum Index -> Southwest USA, Hawaii, Mexico All times are GMT - 5 Hours
Goto page Previous  1, 2, 3, 4  Next
Page 2 of 4

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You can attach files in this forum
You can download files in this forum

myiW | Weather | Community | Membership | Support | Log in
like us on facebook
© Copyright 1999-2007 WeatherFlow, Inc Contact Us Ad Marketplace

Powered by phpBB © 2001, 2005 phpBB Group