what to do about shrunk sailrope

anchorclanker · Feb 1, 2013

Removed thread from the sail? That's probably not a good idea. You maybe just need to haul the sail up real tight, as well as the out haul, and sail it a while, and keep re-tightening the sail. It should stretch back out.

Sailboats will go their fastest 90 degrees to the wind.

oreana123 · Feb 1, 2013

OK the bolt rope will shrink until no amount of halyard tension will straighten it out. Basically, over time, the bolt roping shrinks at a different rate than the Dacron (if the dacron shrinks at all).

I have to say right now that a sail old enough to have a shrunken bolt rope should be replaced. It sounds like you sail is no longer shaped correctly, and newer sail making techniques create much better sail designs and executions.

Having stated the obvious, I can help you with this. I cannot tell if your sail has slugs. If your sail has slugs, feel free to completely remove the bolt roping. If you can and you want to take the time, you can seam rip it off of the luff and foot. Otherwise, the bolt roping can be released at the head and tack and pulled out of its sheath. At the very least, unsew the bolt rope at either the tack or head and stretch the sail with the halyard. When I do this for other sails, it is not uncommon for the bolt rope to have shrunk 18 inches!!!

Unless you remove every stitch that anchors the bolt rope, it will not release and allow the sail to straighten.

RichH · Feb 2, 2013

Those creases behind the reinforcement patches are called 'girts' and usually indicate that the sail has not been properly RAISED, ... and probably also with insufficient outhaul tension.

In your pic, the luff section, parallel to the mast, also seems 'wavy', also indicating that you are not fully raising this sail and applying proper tension to the luff by the halyard.
With woven dacron sails with 'boltropes' (a three strand rope inside a sleeve at the luff) you cant simply raise such a sail to 'just up'; you have to 'stretch out' those bolt-ropes or the sail will be quite misshapen, baggy, etc. The following URL will explain how to properly raise a bolt-roped dacron sail.
Your sail dimensions are listed below and for YOUR boat, you will have to add ~2" extra stretch to the luff and ~1" extra stretch to the foot. Just use 90° as your 'as raised' benchmark 'tack angle' --- just use a perfectly square piece of cardboard to verify the 'properly raised' sail's tack angle after applying that extra halyard tension.

Mac/Venture Sail data:
Luff 21.83ft (6653mm)
Foot 9.75ft (2971mm)
Leech-AftHdBd 23.48*ft (7156mm)
Tack Ang 88.47* = the angle that the top side of the boom makes with mast when the sail is 'properly' raised and the sail hasn't become distorted through age and abuse. USE 90° for 'testing/verifying'
Diag (clew/head) 23.67ft (7214mm)

See: http://forums.sbo.sailboatowners.com/showthread.php?t=120970 Post#1 should get you through 99.99% of the info you need.

Warren Milberg · Feb 2, 2013

If your mainsail is still in good condition, take it to any qualified sail loft and have them reset the bolt rope -- a relatively easy and inexpensive chore for them.

finding41 · Feb 2, 2013

I was looking at the shrunken bolt rope in a used sail I got. You can tell its shrunk when the sail is lying on the ground!
I recall a thread that Sumner responded to about the bolt rope. I think he cut the threads that held it in place and stretched the sail and sewed the rope back in it's new place.
I saw on my sail it is sewn in place at every slug! I'm not sure if this is common or not. I think I would have to release each of those sewn spots to get it to go strait again. Then sew each back together. (That's my plan at this point anyway.)

oreana123 · Feb 2, 2013

RichH said:
Those creases behind the reinforcement patches are called 'girts' and usually indicate that the sail has not been properly RAISED, ... and probably also with insufficient outhaul tension.

In your pic, the luff section, parallel to the mast, also seems 'wavy', also indicating that you are not fully raising this sail and applying proper tension to the luff by the halyard.
With woven dacron sails with 'boltropes' (a three strand rope inside a sleeve at the luff) you cant simply raise such a sail to 'just up'; you have to 'stretch out' those bolt-ropes or the sail will be quite misshapen, baggy, etc. The following URL will explain how to properly raise a bolt-roped dacron sail.
Your sail dimensions are listed below and for YOUR boat, you will have to add ~2" extra stretch to the luff and ~1" extra stretch to the foot. Just use 90° as your 'as raised' benchmark 'tack angle' --- just use a perfectly square piece of cardboard to verify the 'properly raised' sail's tack angle after applying that extra halyard tension.

Mac/Venture Sail data:
Luff 21.83ft (6653mm)
Foot 9.75ft (2971mm)
Leech-AftHdBd 23.48*ft (7156mm)
Tack Ang 88.47* = the angle that the top side of the boom makes with mast when the sail is 'properly' raised and the sail hasn't become distorted through age and abuse. USE 90° for 'testing/verifying'
Diag (clew/head) 23.67ft (7214mm)

See: http://forums.sbo.sailboatowners.com/showthread.php?t=120970 Post#1 should get you through 99.99% of the info you need.

Whoa I scanned a part of this article and I found it to be mis-informative. If a sailmaker is using the boltrope to create draft in the sail, go to a different sailmaker. Reference a book like the Sailmaker's Apprentice if you want info about bolt ropes and creating draft in sails.
I have recut mainsails. I always take off the bolt rope if slugs will be on the luff or foot. There is no reason otherwise to install bolt roping. Many sails don't even have bolt roping when new. Also let's face it, if the bolt roping is important to the sail, why not use a better grade of bolt rope? 3 strand nylon rope is crap. Sails built for racing, as on a Corsair trimaran for example, have high quality bolt roping and don't usually have slugs.

RichH · Feb 2, 2013

1. 3 strand dacron, not nylon, filament boltrope is used as boltropes because of its easy and predictable amount of stretch; if you use braided rope you wont get the 'easy' and 'consistent' stretch.
2. The bolt rope, if used provides and affects the stability of the position of maximum draft occurs within a certain range between the luff and the leech; the amount of draft is determined by the 'broadseaming' of the panels.
3. Many sails use extra strong luff tapes in lieu of boltropes to hold this dimensional luff shape - usually sails made of laminates or sails that fit into foils these luffs are not 'adjustable'.
4. Many boltroped sails don't need slugs, the boltrope dimension is such that the bolt rope and its sleeve fit directly inside the mast track ... and still need to be tensioned correctly for their 'preload'.

oreana123 · Feb 2, 2013

4. Many boltroped sails don't need slugs, the boltrope dimension is such that the bolt rope and its sleeve fit directly inside the mast track ... and still need to be tensioned correctly for their 'preload'.

This is the only reason for a boltrope.

The luff tension should be adjustable for wind speed, preload is just another excuse for a poorly cut sail. Or a shrunken one. And by the way, most of the cheap, off-the-rack sails I have seen had nylon boltroping. I have a roll in my shop.

RichH · Feb 2, 2013

oerana123, I think that thousands of 'good' sailmakers would disagree with that.

RichH · Feb 3, 2013

You can 'worry' the halyard:

Prep -
Put a mark (tape, etc.) on the mast next to where the halyard will be when tightened ... somewhere near 'eye level'.
Raise the sail to 'just up' and put a mark (tape, etc.) on the halyard ~2 inches above where the mark is on the mast.

'Worrying':
• Pull the halyard so that the sail is just 'up'
• Put a half turn around your halyard cleat with the halyard.
• Pull a bit of tension on the bitter end or free end of the halyard so that there will be some 'friction' of the halyard on its cleat to prevent the half turn from slipping.
• Pull perpendicularly on the halyard - away from the mast (imagine pulling a 'bow string') ... the 'pull' will be parallel to the horizontal ... as you hold 'friction' onto the cleat with your 'other hand' so that the bitter end doesnt slip when you pull perpendicularly on the halyard.
• Hold that increased tension on the halyard as you bring it back to the mast and tighten (shorten) the bitter end thats halfway around the cleat.
• Repeat as necessary until both marks 'line up'.

Note - pulling on the line 'perpendicularly' will cause approximately TEN TIMES the force 'along' the halyard that you cause by pulling it 'perpendicularly' ... for 'small' increments (no more than 2 ft. for your ~20ft. luff) of 'sideways' pull that you put into the halyard.

Then follow the directions in that 'properly raising' posting to find the 'sweet spot' of proper halyard (when sailing in your 'normal' wind strength) strain so your boat s-l-o-w-ly heads up when you let go of the tiller/wheel, etc. .. and then change one of the marks, on mast or halyard, for the approx. tension that gives you 'the best' weather helm ... where the boat on a beat 's-l-o-w-l-y heads up when you let go of the tiller/wheel. This will give you a close return reference to the exact same hayard tension each time you go sailing in 'similar' wind and wave conditions.
Doing such 'halyard strain' will properly 'shift' the point of where maximum draft - POMD occurs (forwards or aft) in a dacron cross-cut sail ... and which is responsible for 99% of 'weather helm'.

General rule / Hints:
If the boat has noticeable weather helm, pull MORE halyard tension (moves the POMD forward).
If you have 'neutral' or 'lee helm' then release some halyard strain (moves the POMD aft).
If that doesnt work, and if halyard tension adjustment cant fully correct the adverse helm, ..... then and only then adjust the mast rake, etc.
The 'amount' of sail draft is controlled by the outhaul; where that amount of maximum draft (POMD) is located is controlled by how much the luff is tensioned by its halyard.

Here's your starting point for the other trim and shape adjustments: http://shop.sailboatowners.com/prod.php?51998/Sail Trim Users Guide
Plus, there is a 'sail trim' form here on SBO: http://forums.sbo.sailboatowners.com/forumdisplay.php?f=17

Hope this helps

oreana123 · Feb 3, 2013

Um this thread has become so much more than a shrunken boltrope. Good luck

timebandit · Feb 8, 2013

Interesting article---
http://forums.sbo.sailboatowners.com/showthread.php?t=120970

what to do about shrunk sailrope

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