UV protection, best colour?

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Quandary

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The UV protection on the furling headsails on our Finngulf supplied by North Finland was white and seemed to perform well over the 8 years I had her. The Moody I have now had a youngish Crusader genny with dark blue strips which seemed to have deteriorated very rapidly, so last winter I got them replaced with white, I was charged a fair bit because of the need to remove all traces of the navy blue but the sail will look much better.
It seems logical that the more reflective white cloth should be more effective in resisting sunlight and durable, the blue I just replaced certainly was not, but then why is dark cloth favoured? Anyone know if my experience is an aberration and if I should really have stuck with blue?
 
Slight thread drift, but is there any objection (I ask as you have recently thought it through) to one of those hoisting socks with a series of drawstrings?

I used one before and was impressed. The advantage is - you only need one to cover all your headsails; it means the headsail itself can be much lighter; and you don't have to tolerate the differential stretch of different cloths which leaves you either with a tight or a baggy leech.

I am tempted to remove the UV strip from my sails, but it probably isn't cost effective to do so. One for the future. Interested in others' views.
 
Quandary said:
The UV protection on the furling headsails on our Finngulf supplied by North Finland was white and seemed to perform well over the 8 years I had her. The Moody I have now had a youngish Crusader genny with dark blue strips which seemed to have deteriorated very rapidly, so last winter I got them replaced with white, I was charged a fair bit because of the need to remove all traces of the navy blue but the sail will look much better.
It seems logical that the more reflective white cloth should be more effective in resisting sunlight and durable, the blue I just replaced certainly was not, but then why is dark cloth favoured? Anyone know if my experience is an aberration and if I should really have stuck with blue?
Click to expand...

Darker colours absorb more UV than lighter colours: in particular,emerald green, dark blue and purple . This means that, given the same cloth quality, the darker coloured cloth will decay faster than a lighter coloured cloth. But this is exactly what the sacrificial strip is for: any UV which is absorbed by the dark coloured cloth will not affect the main part of the sail. Lighter coloured strips allow more UV to pentrate; so, although a white UV strip may last longer, it will not provide as much protection to the sail.
 
When I was doing my PhD, another student in the same lab was doing a project with ICI on wear of ceramic fibre guides. The guides are little aluminium oxide widgets over which the nylon or terylene threads ran, went round corners, etc,., on their long journey through the manufacturing process. The reason they wore out, despite the fibres being very soft and alumina being pretty hard, was because, at a fairly early stage in the process, the fibres went through a vat containing a suspension of very fine titanium oxide particles, which got Incorporated into the fibres. It was these hard particles that were wearing away at the fibre guides.

The reason titanium oxide particles were added to the fibres was to make them look white and opaque - without them, cloth woven from the fibres would be translucent or near-transparent, especially when wet. Charmingly, the titanium oxide was known as the "modesty agent"; the story is that when these fibres (without the additive) were first used to make swimsuits, their wearers got an embarrassing surprise when they emerged from the water.

Does this have any bearing on the OP's question? Possibly not... (but it's a nice story anyway). It may be that in plain white sailcloth, if the "modesty agent" method is still the one used to add whitening, only some light is reflected by the TiO2 particles,and the rest hits unprotected bits of fibre - most of the light goes straight through of course, but the occasional high-energy photon will clobber a polymer bond, and over time the fibre will degrade. In coloured sailcloth, the dye will absorb a lot of the light before it gets a chance to hit the fibres themselves.

[Caveat - before I retired, I was the sort of materials scientist who bent and broke metals; I know maybe a bit more than the Man on the Clapham Omnibus about polymers, but not much!]
 
sgr143 said:
The reason titanium oxide particles were added to the fibres was to make them look white and opaque - without them, cloth woven from the fibres would be translucent or near-transparent, especially when wet.
Click to expand...

Thanks for that. When reading up about UV protection properties of cloth, there was some mention that "whitening agents" could improve protection, but no mention of what the agent actually was.
 
As mentioned, I think it's more dependent on the type of material you specify for your uv strip. We replaced the uv strip on our furling staysail with Sunbrella fabric which should more than double the life of the uv strip for not a lot more cash. Personally I am not fond of white uv strip as it makes it more difficult to see if the sail is furled up properly. A contrasting colour allows for seeing if you have avoided the 'stripey headsail' furl.
 
dombuckley said:
Darker colours absorb more UV than lighter colours: in particular,emerald green, dark blue and purple . This means that, given the same cloth quality, the darker coloured cloth will decay faster than a lighter coloured cloth. But this is exactly what the sacrificial strip is for: any UV which is absorbed by the dark coloured cloth will not affect the main part of the sail. Lighter coloured strips allow more UV to pentrate; so, although a white UV strip may last longer, it will not provide as much protection to the sail.
Click to expand...

Thanks that makes sense, if I had thought it through more thoroughly I might have come to that conclusion. The white on the North sails did seem to protect them for much longer than the blue which fell to bits in about 5 years and I did not notice any consequent deterioration of the sails themselves but my boats are in Scotland and only in the water for 6 cloudy summer months, colour choice would be more important in the sunny south?
 
If you look at the bunting on used car lots, the white gets destroyed first, then the red, then the blue.
FWIW.
 
RJJ said:
Slight thread drift, but is there any objection (I ask as you have recently thought it through) to one of those hoisting socks with a series of drawstrings?

I used one before and was impressed. The advantage is - you only need one to cover all your headsails; it means the headsail itself can be much lighter; and you don't have to tolerate the differential stretch of different cloths which leaves you either with a tight or a baggy leech.

I am tempted to remove the UV strip from my sails, but it probably isn't cost effective to do so. One for the future. Interested in others' views.
Click to expand...

I have a headsail sock to cover my various headsails if I get back and it's too breezy to get them down easily and packed away.

Don't think I'd recommend this for anything other than occasional use, loads of extra windage, they are made to the widest part of sail at the clew or you can't pull them up, subsequently very baggy at top even with the draw strings. 14m luff was about £500 too.

I'd say a 5/10 solution.
 
Quandary said:
That is the opposite to shockcords where the dark ones always seem to go first as explained by Dom. in post 4.
Click to expand...
I remember going on a boat in Antigua which had a sun awning made out of an old dacron Jib - I got soooo badly burnt. UVA which is the more damaging and penetrating of the UV rays...
 
sgr143 said:
Charmingly, the titanium oxide was known as the "modesty agent"; the story is that when these fibres (without the additive) were first used to make swimsuits, their wearers got an embarrassing surprise when they emerged from the water.
Click to expand...
I was thirteen when I bought one of those, I only wore it once at home. I took it back for a refund.:mad:
 
Sunbrella publishes UV transmission tables. Only near-white colors transmit measurable UV. The same is true of paint.

a. No, white reflection does not help, any more than it helps with a white tee shirt. Dark is better.
b. This sounds like a quality issue.
 
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