Info Sources For Re-Cutting Sails

[rardiH36]

I thought to post this on both the Sail Trim and Ask All Sailors:

I would like to know where I can find information about how to re-cut an older sail. Not so much techniques for doing stuff like the actual stitching, reinforcing, webbing, etc. But how to determine the improved shape.

In my case it's for an older 7 or 8 ounce'ish Dacron ~95% jib . The sail's overall condition is good for several more years, but it doesn't have enough life left to support a sail loft's charge for the work. (My time is free as the comparing benchmark!)

I recently hoisted an almost new head sail that I encountered for a song. With my split backstay tensioner also cranked down to tighten the head stay, the pointing ability of my boat was very noticeably improved. The tell tails continued to point back I would say at least five degrees more into the wind than with the older 95%'er. Problem is that this newer sail equates to maybe a 75% jib. OK for the frequent 25kt+ winds in San Francisco Bay's slot. But too small for general use.

My thought on re-cutting the ~95% sail is to keep it minimal and in line with my abilities. Cut the threads and remove the #6 luff tape. Cut away some of the sail's luff in an arc. Re-attach the #6 luff tape. The forward section of the sail will be flatter with more forward draft. Boat will point better. It's the amount to cut away that I would like to have some guidance about.

Thanks for the input.

 

[RichH]

First of all 90% of the 'shape' of a boltroped dacron sail is due to the precise length of the boltrope ... and boltropes 'shrink' overtime due to constant stretching relaxing.

If you KNOW the exact 'as built' / new dimension of the luff boltrope (and foot if also boltroped) then its EASY to DIY restore the shape in a dacron sail.
To test/evaluate if a shrunken boltrope is the cause of an 'out of shape' or 'baggy' older dacron sail, go to: http://forums.sbo.sailboatowners.com/showthread.php?t=120970 and scan down until you find "shrunken boltropes". With 'standard database' sailmaker's dimensions you can 'easily' adjust or 'ease' that boltrope back to 'proper' or as-designed length or you can adjust the flattness or amount of draft - simply by adjust that boltrope.

The biggest problem with virtually ALL dacron sails is that most people do not properly raise and then 'stretch them out to their 'design' dimensions.
And if there is a shape problem, probably 99% of all 'heavy used' boltroped woven dacron sails can be 'brought back from the dead' with a DIY (or sailmaker) boltrope adjustment. All those 'hints' are in that above 'article'.

On my racing boat(s) I readjust that damn boltrope about every 150 HOURS of hard use ... and 99% of the time thats enough to restore the sails SHAPE.

 

[GorillaToast]

Hi. I read the thread on how to raise a bolt roped mainsail, but it didn't address what to do about sails that are roped with one continuous outer rope from the head to the clew. Can that type of sail have a shrunken bolt rope cut and restiched?

 

[RichH]

Yup, if the boltrope is THREE STRAND dacron rope (in the sleeve) it sure can be 'adjusted'.... if its the very thin 'continuous support tape' with TWO small braided 'lines' (one that fits into a furler foil), then no it cant be 'eased'.

Most, especially 'mail order', sail lofts cut the boltrope to 'exact' dimensions ... which makes the boltrope difficult (but not impossible) to adjust ... you sell more sails that way.

 

[GorillaToast]

Actually, the rope is 3-strand, fairly heavy duty. I believe the sail to be the factory issue Catalina 22 sail made by Ullman. Early 1980's vintage

 

[RichH]

Is this boltrope INSIDE a sleeve or is it directly sewn to the luff/foot? If in a sleeve, then its adjustable; if directly sewn then not adustable and should have the rope cut away and sleeved boltrope applied if the boltrope is indeed shrunken.

Sailmakers Databook lists that a Cat22 Main should have a 22.0 ft luff (thats a 'stretched out' luff) ... and would equate to a 22/11 X 1" = 2" shortening of the boltrope per full hoist main.
22.0 ft. MINUS 2 inches = 21'ft. 10" for the luff when 'unstretched'. The angle that the top of the boom to the mast should be 88° when the sail is fully raised and that boltrope is 'stretched'.
;-)

 

[rardiH36]

Hello RichH:

The head sail I want to do a controlled butcher job to is fitted with luff tape that has a small bead along its entire length that slides up into the roller furler slot. No bolt rope.

I picked up on the shrunken bolt rope situation a few years ago and made the fix to my main sail which actually had some extra tail for milking into the luff rope slot. Yes, big improvement to sail shape afterward.

Sailrite has a video showing a DIY process for converting a hank-on jib (with a rope luff) to a tape luff for roller furling.

http://www.sailrite.com/Luff-Tape-Conversion-Kit-6-Support-Tape-36-42

But the video is for a sail that is in good condition. It really doesn't address in any detail about re-shaping the luff cut to help restore (even just a little bit) some of lost sail shape. That's the info I'm seeking.

 

[RichH]

Preloads can be set into a luff tape ... but its not generally easy for a DIYer to accomplish as depending on which way you want to reshape, either the luff tape has to be stretched and held stretched while being sewn to the sail panels or vice versa. I have a 'jig' with teeth that can hold the tape stretched while its being sewn to the panels.

Which way do you want to reshape? as there are other 'tricks' that can 'flatten' and 'draft up a sail' etc. ... many simply by over-tensioning an 'edge' of a sail by sail shaping once its raised.

The most common error in shaping a jib, either hanked on or on a furler, is the amount of sag in the forestay/headstay ... adjusted by backstay tension. A forestay tension that isnt 'perfect' for each day's wind and wave conditions will usually force a jib into a god-awful shape.
Start with article: for proper SHAPING of a jib and getting the 'best' performance out of a jib: http://www.ftp.tognews.com/GoogleFiles/Matching Luff Hollow.pdf ..... then see if your jib needs 'recutting' or other altering.
When reading this article also remember that a gorilla on a sheet winch can utterly over tension to point of driving the draft in a jib very far 'aft' and make that forestay act as if it had NO tension in it at all ... all due to TOO much jib sheet tension !!!!!!! ... and the boat heels over aggressively, has the 'slows', and cant 'point' worth a damn.

Jib problems are usually 'forestay' (backstay) tension problems.

 

[rardiH36]

Hello RichH:

The link you provided with your last post (#8) is a starting point. Myself, searching some more yielded this http://www.sail-depot.com/shorttacks/07-oct/recut.html. Talks about the concept of changing the cut of a stretched out sail's luff curve. But no info about how to go about determining how much and the shape. My berthing port city of Sausalito's public library I know has a good collection of sail trim and sail science books. Including the Sailmakers' Apprentice. I'll peruse the collection to look for leads. Thanks all your information.

rardi

 

[GorillaToast]

Is this boltrope INSIDE a sleeve or is it directly sewn to the luff/foot? If in a sleeve, then its adjustable; if directly sewn then not adustable and should have the rope cut away and sleeved boltrope applied if the boltrope is indeed shrunken.

Sailmakers Databook lists that a Cat22 Main should have a 22.0 ft luff (thats a 'stretched out' luff) ... and would equate to a 22/11 X 1" = 2" shortening of the boltrope per full hoist main.
22.0 ft. MINUS 2 inches = 21'ft. 10" for the luff when 'unstretched'. The angle that the top of the boom to the mast should be 88° when the sail is fully raised and that boltrope is 'stretched'.
;-)

It's sewn to the outside edge. This morning I raised the main and used my jib winch to tension the luff. There were no wrinkles in the luff, so I guess it's okay. The foot shelf is a little bagged out, tho. I think I liked the way it set the other day better with the foot loose.