Sail bolt rope shrinking - SailNet Community
LinkBack Thread Tools
post #1 of 5 Old 02-08-2012 Thread Starter
Senior Member
davidpm's Avatar
Join Date: Oct 2007
Location: Madison
Posts: 4,101
Thanks: 274
Thanked 63 Times in 54 Posts
Rep Power: 8
Sail bolt rope shrinking

This is a question prompted by Sqidd's excellent post about ironing sails.

Apparently there is a common problem with older sails where the bolt rope can shrink causing the sail to become more baggy.

I have seen sails like this myself and figured they were shot but maybe they can be fixed.

As to why the rope would shrink rather than stretch I'm not sure.
davidpm is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
post #2 of 5 Old 02-08-2012
Senior Member
RichH's Avatar
Join Date: Jul 2000
Location: Pennsylvania
Posts: 3,640
Thanks: 25
Thanked 172 Times in 161 Posts
Rep Power: 17
That which causes 3 strand rope, dacron rope in the case of a sail's boltrope, is called mechanical hysterisis or permanent dimensional changes due to constant 'stretching'. The same thing happens with 3 strand dock lines that are put under repetitive strain .... they get 'harder', fatter and shorter.

Here's how what happens in boltropes, how to test your boltroped sail to see if the boltrope needs replacement or 'adjustment': How to properly RAISE a woven dacron mainsail -
RichH is online now  
Quote Quick Reply Share with Facebook
post #3 of 5 Old 02-09-2012
Superior Sailor
Squidd's Avatar
Join Date: Sep 2011
Location: Eagle River Wi.
Posts: 978
Thanks: 6
Thanked 9 Times in 8 Posts
Rep Power: 5
Rich H was a great help in explaining/confirming the process of splicing in additional bolt rope to the luff line and then calculating the bolt rope "preload" to obtain/regain standard luff dimension...

I did it on an older MacGregor Venture Cat 15 sail that was baggy, hard to raise (bolt rope in track) and had a droopy boom (over 90*) unfortunatly I don't have any "before" pics and it's too cold to set up "after" pics, but here is the sail luff before adjustment...

You can see the shrinkage in the "bunching up" of the luff sleeve which made it hard to slide up the mast and did'nt allow the sail to properly tension/shape itself on the rope.

Measured "as/was" the luff was 17'8" and the recommended length is 18' 5" so you can tell the rope had shrunk close to a foot in length..!!

I cut the sleeve near the tack, pulled the bolt end free and step spliced in an additional 1'6" of 3 strand bolt rope...I also "cross stiched" the strands and bound the splice ends before sliding the additional length back into the luff sleeve...

Here you can see the luff sleeve is been relieved quite a bit as it relaxed and now I just need to set the preload dimension and reattach the bolt rope to tack...

Mast track from tack pin to halyard pulley is 19' and before the sail even when pulled excessively tight was a good foot short of top of with the restored length in luff I should be able to raise the head to height effectively raising the leach/clew and boom end as well as restoring "flatter" airfoil shape to a 40 yr old sail... If this works as well as I believe it will I'll be doing this to my PY sails next...

Full thread here...Iron your Sails...? -

"Might as well take 'er out...If anything is gonna happen...It's gonna happen out there..."
"Captin Ron"
Squidd is offline  
Quote Quick Reply Share with Facebook
post #4 of 5 Old 06-20-2012
4ksb expert.
SHNOOL's Avatar
Join Date: Jun 2007
Location: East Stroudsburg, PA
Posts: 1,725
Thanks: 11
Thanked 87 Times in 83 Posts
Rep Power: 9
Re: Sail bolt rope shrinking

Bolt rope shrinkage is a definite possibly, hadn't thought of that, but probably main cause. I bet I lost a foot for sure.

"Rum Line" a 1982, S2 7.9 - Production boat limit tester, blue-water bucket owner, with wine taste on a beer budget.
SHNOOL is offline  
Quote Quick Reply Share with Facebook
post #5 of 5 Old 06-21-2012
Tartan 27' owner
CalebD's Avatar
Join Date: Jan 2008
Location: NYC
Posts: 4,808
Thanks: 5
Thanked 110 Times in 102 Posts
Rep Power: 8
Re: Sail bolt rope shrinking

Go loose footed is all I can say.
Kick up your heels and dance away.

"The cure for anything is salt water~ sweat, tears, or the sea." ~Isak Denesen

Everybody has one:

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CalebD 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
Loose Foot Main sail vs Foot Bolt Rope in boom Track chef2sail General Discussion (sailing related) 42 02-10-2011 08:37 PM
mainsail and the luff bolt rope AllThumbs General Discussion (sailing related) 5 09-11-2008 06:42 PM
Bolt rope or Sail Slugs Finallybuyingaboat Gear & Maintenance 29 06-19-2008 02:37 PM
New Sail, bolt rope or loosefoot fireman181 Gear & Maintenance 10 01-22-2007 06:00 PM
Convert sail from bolt rope to slug sliders? CrunchyBits Gear & Maintenance 6 01-20-2007 12:28 AM

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