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The UV fabric is not the same as the Dacron sail repair material, and probably uses a different adhesive - more like the stuff that holds sail numbers on.
 

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Lots of different stuff has been talked about with the same description. To summarize and clarify (jib socks are obvious):
1. Dacron insignia tape. Lowest of the UV inhibition, lightest of the materials, easiest to remove and reapply, doesn't last long in high sun.
2. Weathermax PSA. High UV inhibition, medium weight to heavy depending on specific type, more difficult to remove and reapply, but not as bad as Dacron sail repair tape, lasts several years in high sun.
3. Dacron sail repair tape. Medium UV inhibition, medium to heavy depending on specific type, difficult to remove and reapply, lasts a few years in high sun.
4. Sunbrella sewn on. High UV inhibition, heavy, removal and reapplication requires sewing, lasts for a long time even though its UV properties might be gone long before the fabric.

Mark
 

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I believe mine is dacron... and it would be sacrificial if it breaks down and then be replaced with same... It's holding up well!
 

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Polyester does NOT offer anything like the UV protection of darker Sunbrella covers. As much as 20% of the UV gets through even when new, like a wet tee shirt. Sunbrella is >99% blockage new, >95% when very old. The limiting factor on Sunbrella is nearly always the stitching, even with the right thread (there is always chafe).

IME, by the time an Insignia or polyester cover is gone, the sail under it also has suffered critical damage and may not be worth cover replacement or repair. The lighter covers are for people who change sails more often, which may be right for you. Other people keep sails for a decade or more.

May sailmakers refuse to repair sails that used SA covers. They are hard to remove and the sail is typically damaged by UV. Too many unhappy customers.

It is not about the cover being sacrificial, it is about whether it actually blocks the UV, and lighter covers really don't. (In addition to examining many used sails, I exposed samples on test racks for up to 5 years.)
 

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... However, I would suggest to look at an article in Practical Sailor magazine (I think it was a year ago) where they tested painting along the luff and foot, just like sunbrella, with very good results.
First, samples where placed on racks for ~ 2 years to select the best paints. They were tested for chip resistance by flogging at high speed. Then the best were put on sails. So far we are at two seasons with no chips.

The project was started for an idea for very budget conscious boaters. Surely, some sails aren't worth a new cover, so it might be smarter to try paint and save the money towards a new sail. But the results surprised us enough that we are seriously considering paint for our next new sail. But not just any paint. Housepaint will flake right off. Also not white. Like white polyester colors, UV goes through white paint. It needs to be a dark color, just like Sunbrella covers. Several major sailmakers tried paint and it failed, but I believe if failed in part because they used white (they wanted the sails to look cool--many value looks over function, go figure).
 

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First of all a rolled sailing exposes only to top layer of the roll.... so most of the sail is protected.. And none of the sail is protected when it is used.
 

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The lighter covers are for people who change sails more often, which may be right for you. Other people keep sails for a decade or more.
They are also for lighter or performance sails kept a decade or more. Unavoidable tradeoff - nobody is going to put a heavy sunbrella UV strip on a light performance laminate or 3Di. If for no other reason than to avoid punching thousands of holes through it. Same with a light air screecher or Code 0 kept on a furler.

It is not about the cover being sacrificial, it is about whether it actually blocks the UV, and lighter covers really don't. (In addition to examining many used sails, I exposed samples on test racks for up to 5 years.)
Not all PSA or polyester is so UV transparent. Weathermax PSA is an example.

I don't think it is true that Sunbrella retains its high UV resistance as it ages. I remember a major sail loft doing tests many years ago showing it loses 50% of its UV resistance within a couple of years. However, I just did a quick google search and cannot find this, nor any actual data on Sunbrella UV stability.

Mark
 

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There are lots of fabrics out there
There are lots of coatings out there
There are lots of combinations

Not so easy to compare apples
 

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They are also for lighter or performance sails kept a decade or more. Unavoidable tradeoff - nobody is going to put a heavy sunbrella UV strip on a light performance laminate or 3Di. If for no other reason than to avoid punching thousands of holes through it. Same with a light air screecher or Code 0 kept on a furler.



Not all PSA or polyester is so UV transparent. Weathermax PSA is an example.

I don't think it is true that Sunbrella retains its high UV resistance as it ages. I remember a major sail loft doing tests many years ago showing it loses 50% of its UV resistance within a couple of years. However, I just did a quick google search and cannot find this, nor any actual data on Sunbrella UV stability.

Mark
Performance sail. Absolutely. I had a laminate sail that a PO added a Sunbrella cover to (not the original loft). The needle marks made a tear-here line, and it did, repeatedly.

That said, I have polyester/mylar sail that was ruined right through the PSA polyester cover. I made some repairs and replaced the cover with paint, which seems to be doing better (it is more opaque).

Sunbrella. I did some testing with used Sunbrella from the canvass shop's bin. The dark colors did quite well, off-white not so much. And this tends to be true of ALL materials, including paint. White is never really a UV block, not even with Sunbrella. This is why the best strips are dark.

If you can find that data I would love to see it. It does not match my experience, either testing or on boats. I would say most sailors would laugh at that data, after pealing off a 10-year old Sunbrella cover and finding virgin sailcloth under it, but badly burned webbing and sail cloth anywhere it was exposed. Nope, does not stand up to observation. Sounds like marketing.

As for the UV resistance of specific product, yes, I'm sure some are better. Weathermax is good. But I'm betting not so much in white. It comes down to...
  • How long do you need it to last?
  • How much weight can you tolerate?
  • What are you applying it too?
No single answer. For heavy polyester cruising sails, I think most sailors will stick with Sunbrella or equivalent in a dark color. For performance sails,
 

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The cover is presumably there to prevent the sail from "failing"?

How do furl sails fail typically? I am not referring to loss of shape.

UV does cause damage to many materials as the UV destroys chemical bonds.

Are sails rottng away?

Here's my 2005 dacron sail w/ dacron sail cloth "protection", What are the signs of failure?

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The uv guard on my 10 year old sail was starting to shred a bit, but that was helped along when the webbing loop on the head let go in 30kts of wind and the leech flogged for a bit before I got the sail sorted out. The UV had rotted out the stitching on the webbing.

The UV guard was white sunbrella, and the cloth underneath showed no signs of UV damage. I had the sailmaker replace it with a layer of white dacron because it was the cheapest option. I am planning to replace the sail in the next couple of years so didn't want to invest too much money into it.

I have seen a number of sails that have been stored on furlers long term without uv guard, including one that came with my last boat, and the vast majority of the damage has always been confined to the strip along the edge of the leech and the foot that is directly exposed to sunlight. I don't believe that uv penetrates through a layer of white cloth with enough strength to do damage. Perhaps the situation is different in tropical sun?

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