Reefing a headsail??? - Page 4 - SailNet Community
LinkBack Thread Tools
post #31 of 33 Old 01-10-2013
Senior Member
RichH's Avatar
Join Date: Jul 2000
Location: Pennsylvania
Posts: 4,449
Thanks: 42
Thanked 248 Times in 234 Posts
Rep Power: 18
Re: Reefing a headsail???

Originally Posted by deltaten View Post
Thanks Rich;

I'm having some trouble digesting the text stating; " The LP defines the sail size in terms of percentage increase beyond the J measurement as in the following examples." with the chart immediately below. It shows, under the "LP" column, a direct correlation to unit "J" past the "I" line.
It appears that roller furlers need the "LP" figure to relate the amount of sail exposed, as that's the direction of reduction; but regular (geometric term) foresail calcs rely on straight "J" numbers.
Am I missing something??
Doesn't the "IJ" fore-triangle calc describe a geometric area potentially filled by a headsail at 100% (not necessarily the actual measurements)? As I was led to believe, the increase in percentage was a function of the amount of the (base/"J") jib triangle passing the mast (height/"I") of the theoretical/geometric right triangle??
Its really VERY SIMPLE once you define 100%LP dimension that equates to the "J" dimension. Once you arrive/calculate (or do this 'graphically') all further dimensions will be directly proportional (ratio'd). Eg. a 120% LP will have is 'foot dimension' at ~120% of the 'J' dimension. .... you just have to first establish the 100% LP dimension in relation to the J dimension, .... first.
RichH is online now  
Quote Quick Reply Share with Facebook
Sponsored Links
post #32 of 33 Old 01-10-2013 Thread Starter
Senior Member
deltaten's Avatar
Join Date: Oct 2012
Location: Lancaster Co. PA/ North East, MD
Posts: 830
Thanks: 10
Thanked 21 Times in 21 Posts
Rep Power: 5
Send a message via Yahoo to deltaten
Re: Reefing a headsail???

Ummmm... yessssss.. 592 ft/2 is more than entire sailplan PLUS the wetted surface of the hull !
So then, the discussion is the manner in which I calculate the jib ....OK; but the OP was about reefing. Does it matter if I wanna reef a 150% genoa or a 145% genoa?. Any way ya slice it, it's still too damm'd big ta suit me... being a novice and all

Tastes great....less filling!
For all intents and porpoises... same-o, same-o. I don't feature being knocked down; whether it's a 150 or a 140. JUst hafta wait and see what the learning curve is... *THEN* get knocked down! LOL

thanx guise
deltaten is offline  
Quote Quick Reply Share with Facebook
post #33 of 33 Old 01-11-2013
Senior Member
AdamLein's Avatar
Join Date: Nov 2007
Location: SF Bay area
Posts: 1,940
Thanks: 9
Thanked 7 Times in 6 Posts
Rep Power: 10
Re: Reefing a headsail???

Originally Posted by RichH View Post
Once you arrive/calculate (or do this 'graphically') all further dimensions will be directly proportional (ratio'd). Eg. a 120% LP will have is 'foot dimension' at ~120% of the 'J' dimension.
Hm... this is essentially saying, "If x is an altitude of a triangle, then an adjacent side is also x." That's only true if that side is perpendicular to the side that the altitude is perpendicular to. I think the angle at the tack of a jib is usually less than perpendicular.

There is a proportionality, but only in the component of the measurement perpendicular to the luff.

Okay, to anybody still confused about LP, it's just the width of the sail. Just imagine stretching the sail out with the luff along the ground and the clew held up off the ground so the sail is flat. The LP is now the height of the clew off the ground.

s/v Laelia - 1978 Pearson 365 ketch
AdamLein is offline  
Quote Quick Reply Share with Facebook

Quick Reply

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Similar Threads
Thread Thread Starter Forum Replies Last Post
"Reefing Point" for Roller Furled Headsail? rhumbunctious Gear & Maintenance 1 05-13-2012 06:44 AM
Reefing without reefing points Rup Seamanship & Navigation 29 12-03-2009 04:19 PM
converting a furling headsail to a hanked on headsail mrkeith Gear & Maintenance 6 02-15-2007 02:36 PM
Headsail Reefing Basics Brian Hancock Seamanship Articles 0 08-05-2004 08:00 PM
Headsail Reefing Basics Brian Hancock Gear and Maintenance Articles 0 08-05-2004 08:00 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome