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Go Back   SailNet Community > General Interest > General Discussion (sailing related) > New sail Dacron characteristics
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Topic Review (Newest First)
03-23-2012 12:32 PM
RichH
Re: New sail Dacron characteristics

You really have to be aware that the advantage of woven (even high modulus) dacron is its 'adjustability' of the all important shape of the sail ... ie. the adjustability of where the position of maximum draft (POMD) occurs and the relationship of the position in response to the 'stretchability' of the luff (boltrope, etc) which continues to make woven dacron the CHOICE material for cruising and occasional racing. Laminates whether sewn or glued or mold formed are essentially 'locked' in shape and are FAR less 'shape adjustable- - the shape you buy is the shape you get.

As in the case of POMD on a boltroped dacron sail, its the amount of halyard (and/or cunningham) tension that determines where the POMD is located. Most sailors with woven dacron hardly ever get this 'pre-load' from the boltrope correct when raising such a sail ... and then complain of 'weather helm'. Tape luffed sails are entirely 'different' and do not have the requirement of 'pre-load' when raising ... and since they dont have the 'boltrope' can stretchout all over the place in dynamically changeable windstrengths, etc.

When a sailmaker cuts/designs a woven dacron sail (all configurations - cross cut, radial, etc.) WITH a boltrope, that boltrope is purposely shortened (typically by 1" for every 10-11 ft. of luff/foot dimension) and if you 'just raise' and never stretch out that boltrope 'preload', the sail shape will be draft aft, over draft, and leech hooked to weather. With boltroped woven dacron you MUST stretch out that boltrope so that the sail can take on its 'AS DESIGNED' luff / foot dimension ... otherwise those described mal-shapes will occur AND the tack angle will be well beyond 'designed' (typically greater than ~89 degrees) and with the clew/boom in a drooped-into-the-cockpit shape.
Here's how to PROPERLY RAISE of a boltroped dacron sail, and what to do when the sail because of 'hysterisis' of the boltrope causes it to eventually become shorter than its OEM length and how to set up for PROPER 'weather helm' each and every time you raise such a sail. Probably 95% of ALL sailors using boltroped woven dacron NEVER do this, they just 'raise' and never 'tension' that luff !!!!!!!!: How to properly RAISE a woven dacron mainsail - SailboatOwners.com

RX: So, if you are getting 'variable' shape out of your new woven dacron boltroped sail, you probably arent applying CORRECT but variable luff, etc. tension on that boltrope when you are 'raising' it.

Woven dacron does become 'stretched' over time and hard usage. HOWEVER you 'can' readjust the boltrope 'preload dimension' by 'easing the preload tension on it' to restore the proper sail shape - thats why woven dacron 'lasts longer' because you 'can' easily 'reshape' such a sail back to 'as designed'! The downside of woven dacron is that there no means to compensate for a leech (length) that has become permanently stretched (other than reseaming the leech back to 'flat' - expensive), just about all other 'deformations' can be inexpensively corrected.
03-23-2012 11:14 AM
blt2ski
Re: New sail Dacron characteristics

Bubble,

As Jeff says, I do agree to a point, a GOOD dacron on your boat will work fine, the head sails get a laminate.

The Ullman Cal is maybe 10% more than a GOOD dacron sail. It does come std with 2 reefs, sail numbers, insignia, leach lines, draft stripes etc. Something like this may be better in the end than dacron. I have a 140 that I like for cruising and 15-20 knot winds.

Along with, laminates being as many times they can be built a bit lighter in wt, but still be as strong, they can be better for lighter winds. Either that, or as I have done, for the under 6 knot days here in Puget Sound, I have a 3oz nylon drifter, then go to the 155. A few options for the light days.

marty
03-23-2012 10:48 AM
BubbleheadMd
Re: New sail Dacron characteristics

You've all answered my questions nicely, thank you.
03-23-2012 09:34 AM
Jeff_H
Re: New sail Dacron characteristics

While I agree that a dacron mainsail makes sense on a Pearson 30, I would suggest that laminated high modulus headsails will have longer serviceable life and so have a lower life cost on a boat like yours, even if you are mostly cruising.

I also think that the mid-range products at lofts like Quantum have better lifespans since they employ better fabrics, stress mapping and fabric inspection and testing than the budget lofts. Even on broadseamed horizontal cut sails small rotations in the fiber orientation, can have a very big affect on stretch, and durability. The better lofts get that right. The key to a low life cost is to buy sails from the best loft you can, in the best materials during the time of year when they are on sale.
03-23-2012 08:46 AM
BubbleheadMd
Re: New sail Dacron characteristics

Quote:
Originally Posted by blt2ski View Post
For how you use your boat, Dacron would not even be on my list of sail cloth. Demension Polyant, or Ullmans CAL sail would. Stretch with these sails will not be an issue!

Marty
70% cruising, 30% or less racing? Especially casual, Chesapeake, light-air racing.

Dacron is fine. It's also the limit of my budget. I don't have money for high tech, laminate sails, especially to replace them every 2-5 years.
03-23-2012 01:14 AM
blt2ski
Re: New sail Dacron characteristics

For how you use your boat, Dacron would not even be on my list of sail cloth. Demension Polyant, or Ullmans CAL sail would. Stretch with these sails will not be an issue!

Marty
03-23-2012 12:11 AM
RichH
Re: New sail Dacron characteristics

Quote:
Originally Posted by BubbleheadMd View Post
Let me re-phrase the question:

Would a brand-new, quality Dacron sail experience any "settling in" when placed under loads for the first few uses?
Yes and no.
The fabric is heat calendered from crimped yarns, etc. it will very slightly change dimensions in accordance to the normal loads applied until you reach normal 'relaxation' of the crimp. This will not be visibly noticeable; solid or monofilament dacron only has a 5-6+% elasticity/elongation at 'ultimate tensile strength' (failure).

If a seam has slipped due to poor stitch tension, then yes.
03-22-2012 10:45 PM
zz4gta
Re: New sail Dacron characteristics

Bubble, I'm not sure I like these questions.

Shoot some photos close hauled looking up to the mast head from the mid point of the foot. Like these


03-22-2012 10:31 PM
GeorgeB
Re: New sail Dacron characteristics

If you are thinking that the Dacron will stretch a bit during the breaking in period, then not so much afterwards, I’m afraid that this is not the case. It will stretch according to the load you place on it. That it is why it is always a good idea to loosen the outhaul on the main and halyard on the furling jib so not to make the stretch permanent. Remember that woven cloth has warp and weave directions and the sailmaker in using his panel cutting techniques will try and get the two to stretch at the same rate. The biggest sin you can do is motor while the main is up and fluttering. “Motor boating” is music to a sailmaker’s ears. If you are thinking about racing the sail, sail with it the fewest amount of times as you can (use the old sails to deliver the boat). All sails start stretching the day you fist use them and stop the day you throw them into the dumpster.
03-22-2012 10:18 PM
BubbleheadMd
Re: New sail Dacron characteristics

Let me re-phrase the question:

Would a brand-new, quality Dacron sail experience any "settling in" when placed under loads for the first few uses?
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