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eric_c View Drop Down
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    Posted: 08 Jun 22 at 9:12am
The H2 has a PN of 1034?
The Phantom, with almost no roach at all, 1004.
Blaze with a big round roach, 1033.
Dzero 1029

It's not looking like sailing's answer to nitrous oxide is it?
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CT249 View Drop Down
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[/QUOTE]

Square tops are in a sense just a modern interpretation of the traditional gaff rig.

But is it only carbon masts that they work with, that can flex and produce the desired 'gust-response'.... or can they work with aluminium/much stiffer spars?
Or could batten technology ensure that they do? (spring loaded battens!)......

[/QUOTE]

With respect;

I"ve spent a lot of time researching design history, and there seems to be little evidence that squaretops and gaffs have much to do with each other at all.

The traditional gaff rigs almost never used gust response in anything like the way we do, and that comes from a LOT of reading of books and articles from the 1800s and early 1900s. 

The gaff's advantages were due to low centre of effort, fewer problems in keeping the stick aloft and things like that. After reading many hundreds of pages (my mag collection dates back to 1894) I can find no information that indicates that gust response was seen to be better with gaffs than with contemporary bermudans.

The gaff rigs were almost always low aspect, whereas squaretops tend to be fairly high in aspect ratio. The gaffs normally had too much twist, way more depth than we use, and were sailed at wider angles of attack upwind and downwind.

In cats like the Taipan 4.9, which has a very big and stiff wingmast even for a cat, the former large roach gave way to a squaretop over a decade ago, and the class opinion was that the gust response was very much better. To give an idea of the stiffness of the 4.9 mast, Glenn Ashby (who was a champ in them before he was famous) told me that the mainsheet load on the 96kg 16' Taipan 4.9 was higher than that of the vastly larger Tornado - and yet the very flat squaretop on the 4.9 gives good gust response. You don't need much movement when the head is already very, very flat.

Incidentally the Taipan's co-designer Greg Goodall is credited by many (like sailmaker Ben Hall in an old article in US mag Sailing World) with introducing the true squaretop in an A Class that his brother used to win the worlds in back in the '80s. Greg followed on by also winning two world titles in the class, but if I recall correctly he reckons the increase in squaretop area is (like so many things) largely down to improved materials that allow sailmakers to make sails that don't distort and therefore suffer from leaches that either blow open or slam shut. I haven't seen him in years so this is just from memory.



Edited by CT249 - 08 Jun 22 at 9:51am
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Posts: 399 		Post Options Post Options   Quote CT249 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jun 22 at 9:22am
Originally posted by ChrisI

Originally posted by Mozzy


I actually think square tops are easier to get to work with a solid mast, like those used by cats rather than a whippy carbon mast seen in some other classes (skiffs). So I think they can be made to work with a pretty solid mast which is designed with very little compliance. Cats go for rotating masts which are very stiff and need less in the way of stays to keep them upright. Then use sheet tension, Cunningham and battens to control the stability of sail (response to gusts). 


But doesn't the 'gust response' you get in a cat with a stiff aluminium mast come from the fact there is no kicker tensioning the leach i.e. the gust hits and the mainsail clew rises slightly (and comes inboard slightly) opening the top of the sail...?

Nope, or not from my experience owning and sailing a couple of them. The cat don't need as much gust response as their higher upwind speed means that a gust is a lower percentage of apparent windspeed. They also (as far as I can recall) use flatter sails than skiff types, so it needs actual less twist and mast bend to create a similar depowering effect.

I've never seen my F16 or F18 clew rise or come in to windward, personally. The mainsheet loads are way too high. We took the mainsheet off our old 20' cat and stuck it on the 36' 5 ton offshore mono we have, and it's easier to work on that than it was on the cat!

The proof may come in A Class cats. They have had extremely light carbon wingmasts, rather than stiff alloy rigs, for eons. Despite the fact that they could probably design in as much bend as they want (ie by shifting from carbon to 'glass etc) they have extremely straight masts - so straight that they don't use halyards at all but just push the sail straight up the mast from the bottom because there is basically no luff curve to create resistance.  But (AFAIK) the mainsail chord is so flat that the minimal amount of mast bend created by downhaul pressure is enough to completely flatten the sail when needed. Mono sails are still deeper (AFAIK) so have more draft to be taken out so need more mast bend.

This is just my belief and there are many people who know much more; I'll grab one of them when our season starts again.


Edited by CT249 - 08 Jun 22 at 9:42am
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Posts: 399 		Post Options Post Options   Quote CT249 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jun 22 at 9:37am
Originally posted by eric_c


For a cheapskate club sailor like me, I think some of these sails have a lot of stress in them, resulting in shorter usable life than you get from a more traditional roached sail?


I bought another Tasar the other week, just to sell it within the club in the hopes of generating more boats. Unlike our good Tasar, it only had dacron sails.

We took it out for a race to see how it went and it was very interesting to drop back into dacrons from the flatter, bigger, roachier Mylar sails the class now has. The old deep dacron main required vastly more mainsheet and traveller work in gusts to keep the correct amount of twist. The mylar's bigger roach and larger, flatter shape has far more gust response and it was a shock to go back to the old way. IMHO the fleet closed up with the Mylar sails because they required less work to optimise twist.

BUT..... the Mylars stay in top "championship podium" shape for longer and then lose structural integrity far faster. The old dacron sails, unless flapped and crunched, can't be killed with a stick. The Mylars, no matter how well cared for, will tear a decade or so before dacrons would start to lose any noticeable strength.

I'm still far from sure that moving to Mylar was the correct choice for the class overall.  It's not conservatism (I've had Mylar sails for decades, and love my amazing membrane yacht headsails to bits) but as you imply, for a SMOD the durability of less-stressed pinhead dacron sails makes a lot of sense.
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Posts: 750 		Post Options Post Options   Quote H2 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jun 22 at 9:41am
Originally posted by eric_c

The H2 has a PN of 1034?
The Phantom, with almost no roach at all, 1004.
Blaze with a big round roach, 1033.
Dzero 1029

It's not looking like sailing's answer to nitrous oxide is it?

I don't think I have ever considered the sail shape on the H2 to be about maximising speed as such, its a concept that tried to balance out all the factors that people wanted from the boat. But as you raised it the H2 sail area is 9.3 sqm and the Blaze is 10 sqm and we sail off virtually the same PY and are similar lengths and widths so I would say that in this case the H2 rig would seem more efficient than the blaze one.
H2 #115 (sold)
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ChrisI View Drop Down
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Posts: 143 		Post Options Post Options   Quote ChrisI Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jun 22 at 10:07am
Originally posted by CT249



Originally posted by ChrisI

Originally posted by Mozzy


I actually think square tops are easier to get to work with a solid mast, like those used by cats rather than a whippy carbon mast seen in some other classes (skiffs). So I think they can be made to work with a pretty solid mast which is designed with very little compliance. Cats go for rotating masts which are very stiff and need less in the way of stays to keep them upright. Then use sheet tension, Cunningham and battens to control the stability of sail (response to gusts). 


But doesn't the 'gust response' you get in a cat with a stiff aluminium mast come from the fact there is no kicker tensioning the leach i.e. the gust hits and the mainsail clew rises slightly (and comes inboard slightly) opening the top of the sail...?

Nope, or not from my experience owning and sailing a couple of them. The cat don't need as much gust response as their higher upwind speed means that a gust is a lower percentage of apparent windspeed. They also (as far as I can recall) use flatter sails than skiff types, so it needs actual less twist and mast bend to create a similar depowering effect.
I've never seen my F16 or F18 clew rise or come in to windward, personally. The mainsheet loads are way too high. We took the mainsheet off our old 20' cat and stuck it on the 36' 5 ton offshore mono we have, and it's easier to work on that than it was on the cat!
The proof may come in A Class cats. They have had extremely light carbon wingmasts, rather than stiff alloy rigs, for eons. Despite the fact that they could probably design in as much bend as they want (ie by shifting from carbon to 'glass etc) they have extremely straight masts - so straight that they don't use halyards at all but just push the sail straight up the mast from the bottom because there is basically no luff curve to create resistance.  But (AFAIK) the mainsail chord is so flat that the minimal amount of mast bend created by downhaul pressure is enough to completely flatten the sail when needed. Mono sails are still deeper (AFAIK) so have more draft to be taken out so need more mast bend.
This is just my belief and there are many people who know much more; I'll grab one of them when our season starts again.



Thanks for your real life experience (I am not a cat sailor). The point about relative speeds and angles makes complete sense - i.e. travelling at such speeds they don't need it. And re the A Class and ultra straight masts - I guess that shows they are experiencing the flip side of 'gust response' which is lost energy from the wind, which they don't want.
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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 10:25am
Originally posted by ChrisI

.....And re the A Class and ultra straight masts - I guess that shows they are experiencing the flip side of 'gust response' which is lost energy from the wind, which they don't want.
If the mast is a spring without much damping, the energy of a gust is stored rather than lost. The energy is recovered as the gust eases.                                  
                                         
I think to some extent modern materials mean the flexing is better handled in the battens and sails than the topmast.
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Posts: 143 		Post Options Post Options   Quote ChrisI Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jun 22 at 10:27am
Originally posted by H2


Originally posted by eric_c


Originally posted by H2

Never had a square top before my H2 which also has a bendy carbon mast, very easy to make work in medium and strong winds but has taken us time as a class to make the rig work really well in light winds if that helps!
What are the symptoms of it 'not working well' in light winds?

The boat feels "sticky" in light winds, essentially its easy to stall the rig in light winds. We have had to learn how to flatten the fully battened sail so that the flow remains attached. This has been achieved by reducing rig tension to straighten the mast whilst also experimenting with kicker to control the roach twist. Put another way - when the H2 first came along it seemed like we could sail to our PY in medium or heavy winds but when it went light we got a total kicking in PY racing but after several years of trial and error we have found some new "gears" that keep the boat powered up as the breeze falls. Hope that helps?


Thanks for this. This is exactly where we are - exploring how one uses a square top in light winds and where I guess those Punts with square tops are. I think we were (although very happy to stand corrected) one of the first modern monohull dinghy designs to use square top rigs in a lighter wind boat (I don't count A Raters as a dinghy .) On the Thames in tide and with regular huge shifts in wind direction kicker control is critical but as per my OP bendy 'gust response' masts are important too. We still have lots to learn.

Edited by ChrisI - 08 Jun 22 at 10:36am
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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 10:30am
Originally posted by CT249

Originally posted by eric_c


For a cheapskate club sailor like me, I think some of these sails have a lot of stress in them, resulting in shorter usable life than you get from a more traditional roached sail?


I bought another Tasar the other week, just to sell it within the club in the hopes of generating more boats. Unlike our good Tasar, it only had dacron sails.

We took it out for a race to see how it went and it was very interesting to drop back into dacrons from the flatter, bigger, roachier Mylar sails the class now has. The old deep dacron main required vastly more mainsheet and traveller work in gusts to keep the correct amount of twist. The mylar's bigger roach and larger, flatter shape has far more gust response and it was a shock to go back to the old way. IMHO the fleet closed up with the Mylar sails because they required less work to optimise twist.

BUT..... the Mylars stay in top "championship podium" shape for longer and then lose structural integrity far faster. The old dacron sails, unless flapped and crunched, can't be killed with a stick. The Mylars, no matter how well cared for, will tear a decade or so before dacrons would start to lose any noticeable strength.

I'm still far from sure that moving to Mylar was the correct choice for the class overall.  It's not conservatism (I've had Mylar sails for decades, and love my amazing membrane yacht headsails to bits) but as you imply, for a SMOD the durability of less-stressed pinhead dacron sails makes a lot of sense.
I never said anything about Dacron, I had in mind more the Solo and RS400 etc sails in old fashioned planforms but more modern cloth. Dacron is for cruising yachts and things you're happy to replace frequently like Merlin jibs and replica Laser sails.
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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 10:34am
Originally posted by H2

Originally posted by eric_c

The H2 has a PN of 1034?
The Phantom, with almost no roach at all, 1004.
Blaze with a big round roach, 1033.
Dzero 1029

It's not looking like sailing's answer to nitrous oxide is it?

I don't think I have ever considered the sail shape on the H2 to be about maximising speed as such, its a concept that tried to balance out all the factors that people wanted from the boat. But as you raised it the H2 sail area is 9.3 sqm and the Blaze is 10 sqm and we sail off virtually the same PY and are similar lengths and widths so I would say that in this case the H2 rig would seem more efficient than the blaze one.

Or maybe the hull design is significant, the Blaze having a lot of wetted surface and a generally 1990s air about it? not to mention being made out of slate.
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