On 15 Jul 2005 23:48:39 -0700,
lid (Jonathan Ganz)
wrote:
Again, good links, but not particular to fractional vs. masthead with
main alone.
Mo' Links:
http://www.marinearchitecture.com/fo...8&page=1&pp=15
http://cruisersforum.com/showthread.php?threadid=830
http://www.boatersed.com/forum/topic...=63707񮘔
http://www.geocities.com/bill_dietrich/BoatRigging.html
http://www.transitionrig.com/feedback.htm
The above is a discussion and rather lenghty
http://www.jutson.com/articles/oct96.html
BALANCE - THE FINE ART OF EASY SPEED
http://www.uksailmakers.com/encyclop...yclopedia.html
" UK's Encyclopedia of Sails
-- Index
Search UK's Encyclopedia of Sails:
* Chapter 1
o Forward
o Introduction
o How to Buy a Sail
o Rig Dimensions
* Chapter 2
o Sail Cloth
o Sail Cloth Fiber Comparison
* Chapter 3
o Sail Construction Methods
* Chapter 4
o Mainsails
o Genoas and Other Jibs
o Spinnakers
o Asymetrical Spinnakers
o Cruising Spinnaker (The UK Flasher)
o Dousing Sock (The UK Stasher)
o Staysails
o Drifter
o Blast Reacher
o Storm Sails
* Chapter 5
o Main Sail Trim
o Genoa Trim
o Sailing to Telltails
* Chapter 6
o Spinnaker Trim
o Spinnaker Jibes
o Spinnaker Douses
* Chapter 7
o Cruising Spinnaker Handling
o Cruising Spinnaker Trim
o Cruising Spinnaker Jibes
* Chapter 8
o Tuning Your Rig
* Chapter 9
o Sail Care
o Applying Spreader Patches
* Chapter 10
o Glossary"
http://64.233.161.104/search?q=cache...lb oats&hl=en
For the PDF Version with good diagrams TRY
http://www.j22.co.za/pdf/howdosailswork.pdf
"Masthead Rig. On a masthead rig, where the forestay is
attached to the top of the mast and both sails taper to
basically zero chordlength at their heads in a similar
fashion, the interference effects of the sails on each other
are similar along the entire height of the mast. The mainsail
ends up being rather tightly trimmed all the way up because
of the genoa’s downwash, and the genoa gains from
favorable upwash all the way up.
Fractional Rig. A fractional rig has the more compli-cated
characteristic that the top of foresail is not as high as
the top of the mainsail. This means that the top of the
foresail is very close to the front of the mainsail at a height
where there is still an ample amount of chordlength in the
mainsail. As the foresail luff approaches the mainsail luff,
the upwash on the foresail due to the mainsail increases,
because the low pressure behind the mainsail has more
affect the closer the flow gets to it. This causes the top of
the foresail to experience even more upwash and contributes
to a fractional rig’s foresail being trimmed more twisted
than a masthead rig’s foresail.
The top of the main on a fractional rig extends well
above the foresail, leaving the upper portion of the mainsail
free to experience the apparent wind without the downwash
interference of the foresail. Apparent wind toward the top
of the mast comes from a much higher angle, so the mainsail
above the foresail experiences much higher wind angles
than the lower portion of the mainsail where the genoa is
causing substantial downwash. This change in flow angle
with height on a mainsail is quite dramatic with a fractional
rig and leads to trimming a fractional rig’s mainsail with
more twist than a masthead rig’s mainsail."