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Grumpycat View Drop Down
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    Posted: 09 Jun 22 at 6:35pm
Originally posted by Cirrus

The most recent Blaze sails are made by Hartley 'in-house' - and are cosmetically more of a 'square-top' than the pre-existing North one.  The informal talk within the class has suggested that they are 'better' for the lighter crews in the fleet (esp in higher breeze) as they do shed power more easily - however the results are still mostly inconclusive and very mixed.   At my own weight (80ish KG) they seem almost identical in terms of performance - but as times go on the newer sails will no doubt dominate the front as the North supplied ones age. 
   

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Mike , looks like the top batten is different? If it is , that’s a little more than ‘ cosmetic’ .  Smile
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turnturtle View Drop Down
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Posts: 2538 		Post Options Post Options   Quote turnturtle Quote  Post ReplyReply Direct Link To This Post Posted: 09 Jun 22 at 4:24pm
it's a classy looking boat still Mike... especially in when they have a bit of space to literally stretch those legs.
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eric_c View Drop Down
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Posts: 382 		Post Options Post Options   Quote eric_c Quote  Post ReplyReply Direct Link To This Post Posted: 09 Jun 22 at 4:19pm
Difference between that and the H2 is not so much the angle of the very top, but more the chord at say 80% height, which on the H2 looks to be a very big % of the foot?
Or in other words, the H2 sail is a big % area of luff x foot ?
Nearly a rectangle?

I suspect what matters is developing the whole thing to work together, mast, sail, battens, other controls, not just picking the best planform.

Sailmakers have learned a lot across dozens of classes and dozens of yearly iterations in some of those classes, so radically moving away from what we know works pretty well is a big risk.
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Cirrus View Drop Down
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Posts: 590 		Post Options Post Options   Quote Cirrus Quote  Post ReplyReply Direct Link To This Post Posted: 09 Jun 22 at 4:04pm
The most recent Blaze sails are made by Hartley 'in-house' - and are cosmetically more of a 'square-top' than the pre-existing North one.  The informal talk within the class has suggested that they are 'better' for the lighter crews in the fleet (esp in higher breeze) as they do shed power more easily - however the results are still mostly inconclusive and very mixed.   At my own weight (80ish KG) they seem almost identical in terms of performance - but as times go on the newer sails will no doubt dominate the front as the North supplied ones age. 
   

National Championships 2023


Edited by Cirrus - 09 Jun 22 at 4:05pm
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Mozzy View Drop Down
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Posts: 209 		Post Options Post Options   Quote Mozzy Quote  Post ReplyReply Direct Link To This Post Posted: 09 Jun 22 at 10:40am
The 800 square top is quite interesting, as it was fairly openly done purely for aesthetics. In that there was a specific design brief to not be slower than the pin head, but also not make the pin head uncompetitive. 

I think in theory a square top should be a good idea for dinghies for a given mast height. In light winds when you have more RM than power you can generate lift up high where there is usually more wind and cleaner winds. Then when the breeze pick up and you have all the power you RM can balance you can dramatically lose power from up high, which lowers the CoE in sails which allows your available RM to hold down more power. 

In practice, generating power up high in light winds may sound great, but is limited by tip losses. If you force the wind to do something hard where nearby there is an option to just go around, it will usually just do that. Similar to setting a really deep foot and them all the wind dropping out under the boom. Obviously the theory to elliptical sail shapes is to taper off toward the tip as it becomes increasingly inefficient to try and generate lift toward the end. 

If you could end plate the sail against the deck, and put wind lets on the head then it would be really nice... but both are impractical in many cases.  
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423zero View Drop Down
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Posts: 3420 		Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 09 Jun 22 at 8:59am
Main benefit I can see in a racing situation is it might not capsize so much, plus more likely to catch slightly clearer air at the top of the sail over someone with a standard sail.   
Would keeping a better look out for gusts remove need for flat top? I look out for gusts hoping for a lift.
Robert
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eric_c View Drop Down
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Posts: 382 		Post Options Post Options   Quote eric_c Quote  Post ReplyReply Direct Link To This Post Posted: 09 Jun 22 at 8:46am
Originally posted by turnturtle

H2 - it wasn't a criticism; no need to be quite so defensive.

FWIW, I quite like the look of a square top sail; and if someone can tell me why it's a performance benefit, I'd happily believe them.
If someone offered me one which worked as well as H2 says in a breeze, but also outperformed Phantoms in the light stuff, I'd be tempted.
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turnturtle View Drop Down
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Posts: 2538 		Post Options Post Options   Quote turnturtle Quote  Post ReplyReply Direct Link To This Post Posted: 09 Jun 22 at 8:26am
H2 - it wasn't a criticism; no need to be quite so defensive.

FWIW, I quite like the look of a square top sail; and if someone can tell me why it's a performance benefit, I'd happily believe them.
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eric_c View Drop Down
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Posts: 382 		Post Options Post Options   Quote eric_c Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jun 22 at 7:49pm
Originally posted by JimC

No, it was awful for 50 years ago too. Untapered mast, Solo sail planform with a extension above the top batten, we knew better even then too.



Fair comment, I sometimes tend to forget most of the junk I remember from the 70s was made in the 60s. Some of it before the 60s.
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JimC View Drop Down
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Posts: 6662 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jun 22 at 3:31pm
No, it was awful for 50 years ago too. Untapered mast, Solo sail planform with a extension above the top batten, we knew better even then too.
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