Boat tuning

[Phil Alderson]

The Larks have (had?) adjustable jib tension. It made a big difference...they left me standing at Barnt Green until they let slip that you needed the opposite tension from what I had been doing...actually I asked and they were very helpful 

Will give one of them a call and see what they say. I am thinking of temporarily rigging my boat breaker across the foredeck and playing with jib tension on the move. If it works it could be rigged under the foredeck with mini-blocks to the crew's next to the spinnaker halyard and using a similar system to the kite halyard it would be quick to trip downwind and yank on upwind...maybe.

Are you talking about adjustable rig tension via the forestay, or adjustable jib luff tension indipendent of the forestay?

If the latter I have a 4:1 jib cunningham which seems more than enough.

[Torchy]

Adjustable rig tension...no jib cunningham on Loco...yet

[MK]

Torchy, your enthusiasm for your boat is admirable, however i fear you may be about to do more harm than good

My general policy has always been, if a boat is unfamiliar, and if a boat has a proven track record, learn to sail it before changing anything, the systems and setup obviously worked for the previous owner/s and rapid change before truly understanding the boat from hours of on the water time, especially at events with other cherubs, risks all this knowledge and effort being lost, and it is your own loss

Boat tuning is a very complicated thing and it is very easy to make things worse rather than better, pointing better relative to a 400 after reducing batten tension does not necessarily mean you have instantly improved the performance of a boat which has been raced by competent/experienced sailors since being built, as we all know pointing is only one part of what makes a boat fast in terms of upwind VMG

[BenR]

+1 for what matt says,
Since getting Atum in September I have not changed anything except broken ropes and tired shock cord (if you ignore the cartwheel disaster). I have however been out as often as I can, (some might say stupidly) in any wind I think i can manage. After a few outings it became clear I hadn't the first idea how to sail a cherub where sailing my laser 2 before (albeit not well) was easy. The major plus to not changing rig tensions etc every outing when you are getting to know the boat is that you can turn up to the sailing club with the boat on the back of the car, and be on the water in little over half an hour. Wouldn't you rather be sailing than tightening shrouds? 

[Torchy]

Thanks MK, of course boat handling needs to develop also and all previous settings will be recoverable. I'll be measuring positions etc, standardising stuff eg the boat breaker that came with Loco had no marks on it...it will do soon.

You and I both know that tuning boats is a balance between altering things and keeping things static and happens over time...I'm the sad sort of git who goes around with a notebook...but I know how to have fun too 

It seems to me that having easy control of rig tension is good but I'll try it out first before complicating things - it will be informative to see on land what effect on the slot it could have. It is easy to install and to use and could perform a basic function. My Lark buddy felt it was essential in that class and I've experienced the difference in speed myself...not to say it will work in a Cherub of course.

Has anyone tried it?

...jib cunningham?...maybe, if I see the shape deteriorates in some conditions.

...and Ben, 'Wouldn't you rather be sailing than tightening shrouds?' To get to the front you need to do both and you can't rush either.

[Phil Alderson]

The thing to remember with adjusting the fore-stay is you are changing rake, his is why they are letting it off when it is windy. The change in rig tension is an unfortunate byproduct of not having adjustable shrouds.

[PaulJ]

Quote

It seems to me that having easy control of rig tension is good but I'll try it out first before complicating things - it will be informative to see on land what effect on the slot it could have. It is easy to install and to use and could perform a basic function. My Lark buddy felt it was essential in that class and I've experienced the difference in speed myself...not to say it will work in a Cherub of course.

Has anyone tried it?

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We have an adjustable rig tension on Ronin, this is combined with de-rakers on the shrouds and two fast pins. The de-rakers are plates with two slotted holes in them that keep the shrouds captive in the pin rack, so that there is never any danger of lossing the rig when changing them on the water. We always maintain the same rig tension whatever the rake.

We had a practise at changing the rake on Saturday when the breeze came up a bit. The procedure is as follows, stop the boat, ease the rig tension, pull the kicker on hard to pull the rig back, move the shrouds down one hole on the leeward side, adjust the leeward lower. Ease the kicker, pull rig tension back on,  tack the boat and repeat on the other tack.

Unfortunately it didn't go as well as hoped, we got one side sorted and tacked, eased the rig tension, then got hit by a monster gust and started going backwards at an alarming rate, eventually we did a wheelie and fell in. No problem really Peter just pulled the rig tension back on whilst we where on our side, we righted the boat and would have finished the job but the fast pin that was pulled out had come off the split ring and sunk (lesson learnt, carry a spar pin) Again not a big deal we just left it and carried on sailing.

We also have jib cunningham 4:1, we snug it up in light/medium wind and pull it on more as the wind builds, I works in a similar way to the mainsail cunningham, flattening the sail more the harder you pull it. We will probably move the jib down in more wind to sheet it more along the foot, this opens the leech up which matches it with the mainsail, keeping the slot even.

[BenR]

Sure, Torchy, but I am trying to catch up with the back of the fleet to start with.

[dave_ching]

Stating the obvious I guess but Larks sail differently to cherubs.
It is great to get ideas from as many places as possible it is just as important to try and understand why they do what they do.
Larks will probably be sailing as close to the wind as they can at all times upwind. While Cherubs go for speed fairly early on in the wind range.
I guess what the larks are doing is having the optimum rig tension until it gets heavy (gradually increasing until it gets to much). Then when the breeze hits easing probably lets the rig rake a little opens the slot and possibly adds a little twist as the sheeting angle changes ( probably not). Unless they carry very high rig tension origanly I doubt they release much tension to get a big effect.
The slot on any cherub at the moment is far from optimum. As far as I can tell most design have the track as wide as the hull where the track is fitted. Suggesting a certain amount of hit and hope. Maybe a wider track with pins to adjust would be a good starting point.

[Torchy]

Interesting points...

Loco has 2 different lateral sheeting positions but I don't think they were being used. I have re-instated them but not used the narrower angle yet. I have been thinking about installing an intermediate position.

Ronin's system sounds good. I was thinking through such a system last night but thought it could be tricky to use and complex to fit. I'm hoping to test out how much control of the slot I can get (on land) using the boat breaker set to the jib tack via a block.

Larks are very different boats...agreed, however control of the slot is 'all' when going upwind. My question is how do I get (easy) control of it in a Cherub ie with as little fiddling as possible.

On Cunninghams - with very low stretch sails the effect is much less than I am used to.

On the topic of where maximum curve should be? - Approx 45% for main? - I think Cherubs moved it back in 70s/80s...has it come back nearer to the historical '33%' or one-third back from mast?...it seems not because naturally (I think it was) the Fyfe main seemed to lie at about 50%

Where for jib? Any thoughts?

...Andrew...we'll wallow around together...this year.

[Torchy]

Missing Fast Pins...Loco has lost several...haven't replaced them yet but...it looks like Loco's rig previously could be raked even with the sails on (on land) by pulling pins with the rig slacked off.

Loco was set up to adjust jib sheet angle at sea with fast pins, which were missing but I've nicked them from the shrouds. I think with this and Cunningham I should get control of the slot,...I'll chat to Dean and Simon this weekend...once they are sober...and I think Tom might be there too. Who else has sailed Loco?

OK...maybe you guys are right  Loco's rig is actually quite clever when all the bits of the jig saw are there. I'm guessing people maybe used a gauge on the rigging because there are no marks on the boat breaker.

[Tom K]

Draft too far aft in a main sail = not enough cunningham

Battens hard to pop in a tack = not enough cunningham

I suggest you wind some batten tension back on and give the cunno a yank.  Without wishing to sound harsh, if these relative basics arnt currently obvious to you, on the water rig adjustment may be running before you can walk.

[Torchy]

Ouch!

[dave_ching]

Meow Tom
There is nothing wrong with thinking about more than one problem at once.
I have herd tell of an 18' team who once borrowed a boat and found adjusting the main sheet too much of a challenge. If these boats were easy I wouldn't bother.

[Torchy]

The newer high headed sails I am not used to and have not used fully battened for many years, so thanks for the advice...I wonder why you think I am a novice...never mind.

I do understand Cunninghams...I was talking about the natural lie of the sail (how it has been cut)...it is further back than I am used to. There have been changes to the designed position of maximum curve/draft, so where do people aim for? 30%, 40%, 50%?

..and Tom - don't the 18s sometimes let the top of the sail fall off upwind a bit in windy stuff? Feeling for the 'break point' is a good thing...no?