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A class mainsheet system


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#101 furling

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Posted 08 July 2012 - 01:50 AM

Hi Simon, I was curious as to how much mast rake is going on, is it the light guys eg 60 to 80 kg that are raking heaps or the more the heavier you are, unless I change my sail shape I will block out my sheets if I were to put any more mast rake, I agree with your above comments, having an anchored mid sheet verses rear on the track that might not be centered offers more support

#102 SimonN

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Posted 08 July 2012 - 06:19 AM

I really only know what rake guys who are under 80kgs are using, but I get the impression that the bigger guys are using the same rake but have stiffer masts and more grunt in their sails. To out it into perspective, when I got my Flyer 1, conventional wisdom said that in lighter conditions, you raked to somewhere between the rear beam and the hatch cover and in breeze, you rake back to the transom (for those who don't know, you measure with the trap wire and find the length down to the forestay fitting and then take that to the back of the boat to see where it touches). I found that the transom settung was best but I felt I was missing something but needed to shorten my shrouds to get more rake. At the nationals, in absolute despiration, I removed the stay adjusters and bolted the shrouds to the chain plates. This gave me a rake setting that was about half way down the transom. It transformed the boat both upwind and down, although, to be fair, I have only tested it in breeze over 15 knots.

The DNA guys in Oz seem to be sailing with about that amount of rake. It is hard to compare it with some designs because the forestays are in different positions, but from what i have been told, the Nikita guys use that sort amount of rake as well but it measures differently.

The blocking out is a serious issue. My new main has the clew cut higher than the older sail (circa 2008), which indicates to me that Steve Brewin has been taking rake into account in his recent sails. I am not sure what others are doing, although if you look at photos it doesn't look as if people have their booms either stupidly low or high. Maybe you can look mat how you attach both blocks and clew and remove a bit of distance out of the system.

#103 Lost in Translation

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Posted 09 July 2012 - 05:38 PM

I tried moving the ratchet to the boom at the gooseneck this past weekend per the recommendations here and really liked it downwind. Thanks! It helped me go wild earlier by sheeting so close to the mast when sailing downwind. I would then go back to tramp sheeting upwind though I tried sheeting from the gooseneck upwind once as well.

The only challenge with the set up is making the transition back to tramp sheeting around the leeward mark. Sometimes it took a little time to clear the line around the tramp block.

Regarding rake, we noticed that depending on the way the trap lines are rigged on the masts, the rules of thumb for measuring rake can give different results. With the same transom corner measurement, we saw 2 degree ranges of rake based on these trap line attachment points.

#104 Foghorn77

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Posted 09 July 2012 - 08:26 PM

I tried moving the ratchet to the boom at the gooseneck this past weekend per the recommendations here and really liked it downwind. Thanks! It helped me go wild earlier by sheeting so close to the mast when sailing downwind. I would then go back to tramp sheeting upwind though I tried sheeting from the gooseneck upwind once as well.

The only challenge with the set up is making the transition back to tramp sheeting around the leeward mark. Sometimes it took a little time to clear the line around the tramp block.

Regarding rake, we noticed that depending on the way the trap lines are rigged on the masts, the rules of thumb for measuring rake can give different results. With the same transom corner measurement, we saw 2 degree ranges of rake based on these trap line attachment points.


If it's not the same design your forestay tangs are in different places too. But I'm sure you already knew that. The digital level zeroed on the transom has been close enough for my hack sailing. I expect that's the least of my worries.

#105 Lost in Translation

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Posted 09 July 2012 - 09:56 PM

Hoping to see you out on the water soon. We compared the same DNA platform with two different masts. Was surprised how different the readings came out with a good digital level zeroed on the transom. One was at 5 degrees and one at 7. Assuming the measurements were accurate, it meant that I had sailed previously with a pretty small amount of rake given I was raked farther back than I have been before. The boat did seem to do a little better upwind for me.

#106 Brian Scally

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Posted 11 July 2012 - 12:49 AM

Some thoughts..

I will state my preference for rear sheeting. My personal reasons are...


1) light air seating arrangements.
2) tramp bounce, causing the main to "flutter"
3) When sheeting lots of rope you throw it forward... onto the tramp ..not behind you .. which always seem to be off the boat for me.


Some of the reasons for front sheeting are :-
1) That the systems spreads the blocks out which I think reduces the possibilities of tangles.
2) And the main is not crossing your body - possibly reducing body tangles.

Last point is that US Sailing only teaches forward sheeting mains. If other national bodies are the same than sailors become more comfortable with that system.

Brian

#107 sailingkid

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Posted 11 July 2012 - 02:45 AM

They are good points, the tramp bounce drove me crazy last time and if it happens this time I don't know how long it'll last.

I'm not sure about the us sailing comment, I know I've never done a sailing course and I imagine more people are like me. However you are correct in that most dinghies have centre sheeting except the mirror.

#108 SimonN

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Posted 11 July 2012 - 03:11 AM

Maybe I am missing something or have "cured" a problem I didn't know existed. What is this "tramp bounce" issue? I haven't noticed any issue where the tramp is influencing how the main us trimmed.

#109 sailingkid

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Posted 11 July 2012 - 10:14 AM

Simon,

On my mark 4 when I tried it you would pull the main on to the centreline and as you started to close the leech, perhaps 10% of the movement was translated into downwards force at the end of the boom. The rest was pulling the trampoline up around 20cm where the centre block attached. On my boat this was compounded by the fact I had a skinny aluminium boom that bent at a similar rate.

No doubt the Landy system helps cure this because the force is in line with the tramp, rather then directly up.

#110 SimonN

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Posted 11 July 2012 - 11:32 AM

Simon,

On my mark 4 when I tried it you would pull the main on to the centreline and as you started to close the leech, perhaps 10% of the movement was translated into downwards force at the end of the boom. The rest was pulling the trampoline up around 20cm where the centre block attached. On my boat this was compounded by the fact I had a skinny aluminium boom that bent at a similar rate.

No doubt the Landy system helps cure this because the force is in line with the tramp, rather then directly up.

OK, now this makes sense. I tried the "Ashby" system of centre sheeting and agree with you 100% I was horified by the amount the tramp added to the mainsheet load. With the cascade system, you simply don't get that. The angle it comes off the boom and travels back is shallow and therefore rather than pulling up, youy are, in effect, pulling along. And if you move the block further forward, while you get a more vertical angle, because it is closer to the front beam, it doesn't stretch.For me, it was like adding another purchase.

#111 AUS

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Posted 11 July 2012 - 01:17 PM

I have always used the Ashby mid sheeting set up 9:1 off mid boom down to tramp. Now I have 12:1 cascade going forward. If you have a good tramp and tightened correctly neither should pose an issue. Even Stevie moving to tramp sheeting now allows us to make the statement that all of the top guys sheet from the tramp.

As for rake, I agree with Simon that tuning should be based around balancing the rig and platform not the sailors weight. With such high aspect sails rake is critical. The lighter guys should be looking to remove power through sail and mast combination. With a standard sail possible coming back earlier to the max spreader angle that a particular sails luff curve will allow or going to the stiffer battens sooner. The one thing i have noticed with the new flexi fore and aft rigs is that I am now sailing almost a full hole forward from the Std Med. When sheeted upwind the tip on the new rigs move allot further aft just through normal sheet tension and this needs to be compensated. Iím not sure if Brewinís new sails have shorter leaches all around but I know Jack and a couple of the others on DNAís have plenty of room and have even put short strops between the traveller and traveller block to reduce mainsheet length.

#112 Foghorn77

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Posted 11 July 2012 - 02:29 PM

I have always used the Ashby mid sheeting set up 9:1 off mid boom down to tramp. Now I have 12:1 cascade going forward. If you have a good tramp and tightened correctly neither should pose an issue. Even Stevie moving to tramp sheeting now allows us to make the statement that all of the top guys sheet from the tramp.

As for rake, I agree with Simon that tuning should be based around balancing the rig and platform not the sailors weight. With such high aspect sails rake is critical. The lighter guys should be looking to remove power through sail and mast combination. With a standard sail possible coming back earlier to the max spreader angle that a particular sails luff curve will allow or going to the stiffer battens sooner. The one thing i have noticed with the new flexi fore and aft rigs is that I am now sailing almost a full hole forward from the Std Med. When sheeted upwind the tip on the new rigs move allot further aft just through normal sheet tension and this needs to be compensated. I'm not sure if Brewin's new sails have shorter leaches all around but I know Jack and a couple of the others on DNA's have plenty of room and have even put short strops between the traveller and traveller block to reduce mainsheet length.


Can you put up a diagram or complete pic/pics of the 12:1 set-up?

#113 sailingkid

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Posted 17 July 2012 - 10:11 AM

I'd imagine he could have 4:1 instead of 3:1 on the boom end? I bought the blocks today so I should be able to sail with the system on the weekend.

Tom

#114 Foghorn77

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Posted 17 July 2012 - 08:18 PM

I'd imagine he could have 4:1 instead of 3:1 on the boom end? I bought the blocks today so I should be able to sail with the system on the weekend.

Tom


If you get it sorted some pics of the whole set-up would be much appreciated. Icouldn't sort too much out of the sectioned up pics earlier in the thread. I was hoping Ben would post some of his, but I reckon he's busy.

#115 Waynemarlow

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Posted 17 July 2012 - 08:56 PM

Posted ImagePosted Image

Ignore the Cam cleat, this is on my F16 and downwind you have to cleat off the main.

#116 Foghorn77

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Posted 18 July 2012 - 12:07 AM

Is there a 3:1 inside the boom? If so I think I've got it. Along with an explanation from Lost in translation, it makes sense to me now. Thanks.

#117 SimonN

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Posted 18 July 2012 - 03:15 AM

I would be interested to see what others are running. 9:1 is straight forward - 3:1 at the back and 3:1 along/in the boom. However, going to 12:1, which is what I assume is being shown above, gives you 2 options. In this case there is 4:1 at the back and 3:1 in the boom but I would be tempted to do it the other way around on an A, because I feel that 3:1 at the back only just gives you enough slack when let out to the max. Going 4:1 at the back reduces the amount you can ease the sheet to 3/4s of what you can with 3:1.

So, what are other A class sailors doing?

#118 cbatchelor01

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Posted 18 July 2012 - 05:19 AM

3:1 at the back 4:1 on the boom.

#119 Waynemarlow

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Posted 18 July 2012 - 09:01 AM

3:1 at the back 4:1 on the boom.

Yes it can help to run 4:1 inside the boom but you have to have a double block in the system, this then poses problems with clearance on the ID of the tube. In my case it meant I had to reduce the block to a 20mm or so block. Wanting to use a conventional 8mm or if possible 10mm sheet meant this was not possible. If you are going external then its not a problem and a better way. Anyway if you are prepared to use the travellor a bit more then the range is fine on both the F16 and A I had been using it on and I get the bonus of a really clear under boom area which I found to be a problem with the external system, for what ever reason when you let the main sheet out, the blocks would sag along the boom and the height is even more restricted. I also felt morally that the covers used on the blocks by Landy, could be construed to be sail area as it is problably a good 1 msq of flat panel directly facing the wind, maybe thats why he's so fast: rolleyes:

A good 9:1 sytem with a mid mounted block ( in reality a 9 1/2 : 1 ) should be sufficient for most people, I had a problem with a form of " tennis elbow " for a while and went the 12:1 to help that issue and found although there is a lot more rope pulling on the start lines and in rounding up to go upwind, the better / easier control over the leech tension far outwayed the disadvantages.




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