Dinghy development: Mainsheet systems and leech tension

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Mainsheet systems and leech tension

Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=12780
Printed Date: 05 Jul 25 at 4:22am
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com

Topic: Mainsheet systems and leech tension

Posted By: Sam.Spoons
Subject: Mainsheet systems and leech tension
Date Posted: 30 Jun 17 at 11:38am

I'm just revising the systems on the new/old Supernova. I'm looking for advice regarding mainsheet systems. Nearly everybody in the 'nova fleet uses a centre mainsheet with a bridle and floor mounted ratchet. I changed the Blaze to a transom bridle and off the boom sheeting (as recommended by the CA) after one days sailing. The improvement is huge, much lower sheet loads and a totally unimpeded cockpit. So I have put the same system on the 'nova....... However the boom is (I think) lower than on the Blaze so getting leech tension is more difficult.

Question one :- Is it better to have leech tension controlled by the mainsheet when sailing upwind or separate it from sheeting angle and rely entirely on the kicker?

Q 2 :- How does a split tail mainsheet work? I've only ever seen them used on two handers where, with a jib, centring the boom is the aim. It seems that over sheeting would be a potential issue in a singlehander?

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"

Replies:

Posted By: jeffers
Date Posted: 30 Jun 17 at 11:53am

Is this arrangement permitted by the class? All the Novas i have seen use the centre main arrangement. Being a fully battened sail it may behave differently to leech tension as well.

The transon split tail on the Blaze has made it a different boat. Plus sheeting off the boom means you can keep your weight forward during tacks.

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Paul
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D-Zero GBR 74

Posted By: laser193713
Date Posted: 30 Jun 17 at 2:03pm

Bear in mind that using the kicker as your only source of leech tension will also bend the mast and flatten the mainsail a lot. You will find that you end up with less power rather than more height/power.

Posted By: JimC
Date Posted: 30 Jun 17 at 2:16pm

Originally posted by laser193713

Bear in mind that using the kicker as your only source of leech tension will also bend the mast and flatten the mainsail a lot.

That utterly depends on the rest of the rig. Its one of the reasons many boats have lowers these days.

Back to the OP, I'm not sure you're going to get any kind of consensus on what the optimal mainsheet system would be. All you're really going to get are personal preferences. I'd even venture as far as to say that until you get to Olympic level where top sailors do properly structured two boat tuning to establish what is faster even the consensus in a class is of little value in establishing what's fast or not. Its so difficult to establish whether Fred won because of his boat setup or in spite of it.

The point about checking class rules is well made.

Posted By: Presuming Ed
Date Posted: 30 Jun 17 at 2:18pm

Sounds to me like one of the ultimate "it depends" questions.

Doesn't a Blaze have lowers? So cranking on vang doesn't (necessarily) = lower mast bend?

Posted By: Fatboi
Date Posted: 30 Jun 17 at 3:53pm

If you use the mainsheet tension you get an even bend through the mast. Cranking on kicker pushes the mast forward more at gooseneck level. Lowers are generally to combat this and even the bend out.

If you use mainsheet tension, it gives you a finer and easily changeable leech tension. Rather than having to move in and grab the kicker and pull on a few inches, the mainsheet can control that leech accurately while keeping your body and steering more stable.

I use the rule of thumb I use is that until you are easing mainsheet to keep the boat flat, then generally the mainsheet is best for controlling the leech tension rather than kicker.

Posted By: Sam.Spoons
Date Posted: 30 Jun 17 at 4:37pm

Thanks, I'll try to answer in order.

Jeffers, Yes mainsheet arrangement is free on the 'nova and I believe at least one boat has used a transom bridle. You are right, the change to transom bridle and off the boom sheeting did indeed transform the Blaze.

Laser, Yes, That's what I thought, It is documented in the Blaze tuning advice that kicker depowers the rig.

JimC, I'm not expecting consensus..... it's a forum ;) just trying to avoid any obvious pitfalls.

Presuming Ed, yes Blaze (and Supernova) has lowers but the Blaze fast boys still advise no kicker upwind.

Fatboi, I use the mainsheet to control leech tension on the Spice, I like that I can ease the mainsheet to open the leech in the gusts to help keep the boat flat. As you say trying to do that with the kicker seems a bit unnecessary.

The Supernova advice seems to be that kicker for leech tension upwind is the way to go, I've asked much the same question on the 'nova forum but it is not a very active place. I've had a reply that it's legal and one asking for pics........

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"

Posted By: 423zero
Date Posted: 30 Jun 17 at 10:24pm

I sail Sprint using a estimated kicker setting, that I can if I want to adjust on the water, when beating Mainsheet pulls boom down and adjusts tension in the leech, kicker then takes over when mainsheet is eased.

Posted By: Sam.Spoons
Date Posted: 30 Jun 17 at 11:30pm

That's what I would prefer. Being 'old school' (I learned to sail in the '60s) the kicker was for off wind (well further off than close hauled anyway). But, TBF, we didn't talk about 'leech tension' back then, the kicker was there to prevent the boom rising high enough to allow a 'Chinese gybe" IIRC. Much later I had an early '60s Enterprise and the kicker was 3:1!!!!!

I'm sure using the mainsheet as the power control is the simplest way, I'm just wondering why the Supernova 'fast guys' seem to advocate much more kicker upwind than the Blaze guys. Is it a quirk of the FB sail? I only use enough kicker to be safe off wind on the Spice (which has a FB mainsail), the mainsheet controls leech tension upwind and the kicker takes over from a close reach.

I maybe should add I haven't raced a dinghy seriously since the mid '70s until last autumn when I bought the Blaze. Racing the Spice has been pretty low key for the nine years I have owned it so not much learning going on there.

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"

Posted By: JimC
Date Posted: 01 Jul 17 at 6:56am

My feeling is I want the mainsheet to control angle of incidence and the kicker to control twist. If I try and get the mainsheet to do two things at once that won't work unless I add a further complication - a traveller - so I can have the boom at the correct angle when the mainsheet adds leech control. Using the mainsheet for leech tension also adds load on the mainsheet I can do without.

To my mind, put very simply, with a modern gust responsive rig downhaul flattens the sail and controls the depower point, kicker controls twist and mainsheet controls sheeting angle, and its all fairly straightforward.

Posted By: Do Different
Date Posted: 01 Jul 17 at 8:19am

That makes a lot sense and simply put JC.

As a possible point of of interest, another mono sail boat the Contender typically uses a lot of kicker / leech tension hardy ever sheets inside the quarter and points well. I hear the term "driving off the leech" a lot in this respect.

Although I've been slow to embrace fully my two man class advocates kicker until your fingers hurt then a bit more until they bleed. When the breeze is in with crew on wire it certainly feels like it works, lower sheet loads, boom out to keep boat flat and still going and pointing at speed.

Posted By: Sam.Spoons
Date Posted: 01 Jul 17 at 9:00am

My take is that on a una-rigged boat, centring the boom is a no-no, the best sheeting angle is to have the boom over the quarter or thereabouts when the wind is up and a bit closer to the CL in the lighter stuff. That is why I think a twin tail system won't work on the Supernova or Blaze (having a jib makes being able to centre the boom useful).

As JC says some kind of traveller becomes essential unless you separate boom angle from leech tension and I have both the 'nova and the Blaze with a fixed laser style rope traveller across the transom. This works well on the Blaze (open transom) but less well on the 'nova with it's rear deck and low boom.

However, if you don't use the mainsheet for leech tension upwind surely you need to be able to play the kicker in the gusts (requiring a system that is easily accessibly when hiking/trapezing at full stretch)? I've also heard of classes where you cleat the mainsheet and play the traveller in the gusts (at this point, in a singlehander I'm rapidly running out of hands)? Times change, when I bought the Spice the received wisdom was the mainsheet was set up to tighten the leech with it's last couple of feet of travel allowing you to dump power by allowing the leech to twist. Is that not considered fast anymore?

On the Spice and Blaze the kicker controls twist/leech tension on all points except a beat where it affects twist only when I release the sheet to dump power in a gust. The Spice has a big fully battened main on a shortish, overweight hull and generates enough power to get me trapezing (sailing it solo) in 6 knots or so. It also has a hog stepped mast with a mast gate/swatcher rather than lowers.

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"

Posted By: 423zero
Date Posted: 01 Jul 17 at 10:26am

I have all controls fed to both sides, all work well, but still use mainsheet for final leech tension, works well on sprint.

http://i1149.photobucket.com/albums/o587/aquabatdinghy/Minisprint%20rebuild/WP_20160130_13_47_49_Pro.jpg

Posted By: Sam.Spoons
Date Posted: 04 Jul 17 at 1:58pm

I have all the controls led to the sides on the 'nova and Blaze apart from the forestay tension on the 'nova (not allowed on the Blaze). Your system on the MiniSprint looks like a 4:1 centre mainsheet (probably roughly equivalent to a 2:1 transom sheeted system) but with no traveller? How do you avoid over sheeting when you apply leech tension? Or is that not problem on the Sprint?

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"

Posted By: 423zero
Date Posted: 04 Jul 17 at 5:27pm

Not noticed any issues with over sheeting, other than stated, that it will pull leech down, which is in itself over sheeting.

Posted By: Sam.Spoons
Date Posted: 07 Jul 17 at 7:44pm

I've just reverted back to centre mainsheet on the 'nova, will race it on Wednesday and see what I think. Terrible race Wednesday gone, no boat speed so I'm removing as many variables as possible by setting the boat up by the numbers.

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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish"