UK-Cherub Forum
Cherub Chat => Sailing Stories => Topic started by: Torchy on April 18, 2012, 10:57:26 AM
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Would anybody like to tell us what they are doing to tune their boat? If a one-design can see significant speed increase...
I've been surprised how much adjusting the tension on the battens has made upwind. There's a internet dearth of articles on the subject but some sailmakers recommend adjusting tension according to the wind strength.
I'm looking at jib sheeting angle...
'T-foils slow you down in many conditions' (discuss) NB there was a time when National 12 rudders got so small you almost had to steer with the sails...apparently hull designers would like to get rid of rudders because of the drag they cause.
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I've found jib sheet settings to be critically important for upwind speed. In spite of the obvious advantages I never used a self tacking jib on Halo because I couldn't figure out a way to get the level of on the water adjustment and control I wanted without going string crazy. Halo had a track for sideways adjustment and a barber hauler for vertical. In practice I mostly just tweaked lateral position and jib sheet tension, the latter frequently.
Many ICs, esp with self tackerrs, do the vertical adjustment by moving the jib up and down the forestay, but that's more complication than I want on my boat. My IC has almost exactly the same adjustment as Halo had, but seems to want a lot more vertical adjustment. Mind you its more difficult to fine tune jib sheet tension on the singlehander!
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this is something id like to srat to refine also jim, i have put in hardpoints for a similar system to what you describe on the international canoes, but think i need to finish getting the rig right first, anyone willing to shorten my forestay for me for some money or alcohol (born slippy ;))?
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Always happy to help. pm Me?
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Is jib sheeting angle trial and error or is there any way of analysing the slot on dry land?
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The 49'ers have a huge advantage when it comes to rig tune. They use all the same kit so they can do plenty of two boat tuning, and swap equipment to find the fast kit etc. This takes alot of time just sailing along changing one thing at a time, then coming back and doing it again and again, then changing crews to eliminate that variable. Each run could be easily ruined if there is a significant wind speed change or shift. One of the guys at work spent a bit of time in the 49 and says it's the most boring thing on earth two boat tuning, but it works
We are currently working hard on getting Ronin tuned, we had a good start with the tuning guide from Pete Barton. This gave us the basic mast rakes and rig tension. We have recently changed the rig from a prebent rig to a straight rig so are starting from scratch again.
The first thing to get sorted is the rake, this determines the power that the rig developes, generally the more upright the rig is the more power it produces (so upright in light conditions), as you rake the mast back it depowers the rig (stronger winds). Rake impacts on the balance of the boat significantly and produces more weather helm as you rake it back. Getting the right rake is a feel thing, if you are fighting the boat and have tried the usual depowering methods, cunningham and kicker etc. try more rake. Rig tension is the next item. We use a reasonably high rig tension 400lbs plus on the shrouds (30-31 loos gauge). If you don't have enough rig tension two things happen, the forestay sags off to leeward which impacts the boats pointing ability, secondly the windward shroud goes stack which allows the leeward spreader to push the mast to windward which is bad, as it opens the slot and effects the mainsail set effecting both power and pointing ability. Lowers tension is next, tight lowers powers up the lower 1/3 of the mainsail, so ease them a bit if it's windy, this is nearly automatic though if you rake the rig back a hole. We actually tighten our lowers when we rake otherwise it flattens the sails too much. Uppers too little tension and you loose power in light and medium winds as the top of the mast isn't being supported sideways, but if they are too tight the top of the mast isn't allowed to flex enough to act as an automatic gust response. When it's windy we only use enough tension to keep mast in the boat down wind again to gain maximum gust response upwind and to allow the top of the main to blade off.
The key to rig tuning is calibration and therefore repeatability, if you don't know which rig setting was working or not working you can't reproduce it or avoid it, so get the tape measure and rig gauge out and write down where everything is now before changing a thing. Have fun :-)
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Useful Paul, ta
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T- foils...what is their main benefit?
Promoting planing?
Adding stability?
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reducing displacement upwind by taking some of the crew weight from the hull to the t foil, which is more efficient than the hull i think
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and swap equipment to find the fast kit etc.
Good post, but off to bed. Arup skiff hat leaves Blood boiling.
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One thing I miss from the setup I had on Aqua and Primal was easy to adjust cap shrouds. I currently have a lashing and it is neither repeatable, or adjustable.
My old 14 had a fully adjustable rig, and I learned a lot about setup from that as you could move the rig the wrong way and feel what that did to the boat, so you could learn to recognise the feeling and adjust it out.
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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.
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Just confirmed with an ex-Lark luminary.
It adjusts the slot (as I had surmised) and it's essentially tight upwind (tuned to maximise performance), loose downwind.
What I recalled as being the reverse logic (in Larks) was that in windy weather they (he) used to ease it off, upwind or down and (I think) they had it really tight upwind even in light stuff.
In a Cherub we'd just need to experiment...hours of fun 2 boat tuning?...which for some reason gets Born Slippy off on one :) or is it the 'gear swapping'?
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Larks use 16:1 purchase
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its the gear swapping
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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.
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Adjustable rig tension...no jib cunningham on Loco...yet
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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
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+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? ;D
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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.
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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.
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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.
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Sure, Torchy, but I am trying to catch up with the back of the fleet to start with.
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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.
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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.
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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.
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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.
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Ouch!
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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.
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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?
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Ok, If I have offended, I apologise. I in no way disrespect your experience or expertise. My only concern is that I have seen new cherubists join the the class before and tinker their way to the back of the fleet in the first few months, before taking years to work back forward.
Re the 18, I'm not sure what you mean by 'break point' but we do sail with varying amounts of twist depending on the conditions.
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On a beat, Max draft (according to my magic tuning book) should roughly be:
<F3 = 45% Jib 50% Main In chop = 40% Jib 45% Main (Unless really really light+flat in which case.. flat as possible)
F3-4 = 45% Jib 50% Main In chop = 40% Jib 45% Main
F5-6 = (chop) 45% Jib, 50% Main
Its a fairly standard value I would have thought, a lot of maths behind aerofoils is known, and this must work its way into our sails...
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Re the 18, I'm not sure what you mean by 'break point' but we do sail with varying amounts of twist depending on the conditions.
I've seen an 18 with the big rig up when the small rig would have been better, still able to sail fast by letting the top sag...I think it was a round topped sail tho'
I'm experimenting with having Loco's sail just at the edge of freeing off upwind - it wouldn't sag, just some reverse bend appear in the top 2 battens and that's what I mean by 'break point'. I may put a little tension back to stop the reverse bend if it causes problems
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..and Tom and I chatted...still friends
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Good info Andrew...is that from Sail to Win or another?
Seems a good place to stat from :)
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Its a fairly standard value I would have thought, a lot of maths behind aerofoils is known, and this must work its way into our sails...
The difference for us is the slot and from my understanding this is why we let the draft go further aft, especially low down (I think)...and flatter low down...tho' this is built into the sail design.
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This is a spade...
(http://www.adventuretoys.co.uk/products/spade.jpg)
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Oh mighty guru...who is that aimed at? :)
If at me...I am picking brains...and have gathered many nuggets...the secret is to keep talking even if people take one for a fool...in fact if taken for a fool all the better ;)
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Good info Andrew...is that from Sail to Win or another?
Seems a good place to stat from :)
It's a Fernhurst book called "Sail and RIg Tuning" Its mostly yacht related, but cetain things in it are translatable. I have an even better book that was published by Sobstad, Covers pretty much everything about sails, although I think you only get it when you buy a sail (Mine fell out of a bag from a new kite on the first hoist so I pocketed it..)
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Nice one Andrew, thank you
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On a beat, Max draft (according to my magic tuning book) should roughly be:
Does the book give a rationale for pulling the draft forward in a chop? I guess one would be sailing deeper but why move the draft forward too?
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Not aimed at anyone particular. More a cryptic commentary on Toms post, calling a spade a spade.
I can assure you know one in the class takes anyone for a fool. You are travelling down a well trodden path.
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Experienced people have pointed out the dangers of 'fiddling' and I would totally agree...
...if people want to discuss tuning, please do.
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btw On internet forums I have posted on previously the spade usually means 'dig yourself a hole as deep as you like' - sorry if I misunderstood your meaning Stuberry
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I seem to be a "one-setting " person - Shiny Beast had everything fixed regardless of conditions.
Maybe the 97 rig was simpler ( less need to depower )
After initial tuning ( on my own ) for mast rake, rig tension etc, I just used the same settings - fixed length jib/forestay, fixed shrouds.
Boatbreaker to fit the jib/forestay in the same place.
Enough rig tension so it never went loose downwind ( or upwind ), and meaning that the support to the mast was not changed by trapezing, and no nasty mast wobbling downwind
Fixed uppers - tight enough to prebend the mast for light winds, but giving sideways support in a breeze.
Fixed jib downhaul.
Even the kicker seemed mostly to be about the same place, except for light winds to allow twist.
Adjustable things - main downhaul was important, kicker and jib and main trim had to be right - sailing with the right heel also very important.
Jib sheeting - 4:1 on the sheet gives good leech tension/twist control.
The mast /sail combo was just perfect! enough power in light stuff, auto-opening leech. The top went inverted in a breeeze upwind.
The sails were quite flat, with smooth shape, maybe 40% back at the bottom, 30% at the top, unlike many of the full front sails of others.
Flat kite, but we were able to sail deeper than everyone else.
Two - boat tuning ? no, maybe an open, then just see how it went at the Nationals - and by luck or skill = fast ;) a few times, even with a new crew.
The best thing was being able to rig the boat in 10 mins, having a calm chill feeling before racing, knowing the settings were good for the conditions, and never having the psychological block of thinking the settings were wrong!
Batten tension? Just enough to stop windward side wrinkles, and sometimes I even let the tension off in the winter when not sailing!
Maybe 30 years of Cherubbing helps - just get sailing and do more sailing, don't worry too much about the settings.
Cherub = too hard for the Olympics ;D
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Cherub = too hard for the Olympics ;D
Priceless!
...and thanks for the post...food for thought
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Cherub = too hard for the Olympics ;D
Andy,
As ever your post was liquid gold.
But that quote is absolute genius. That's got to go at the top of the website front page or something. Think I might write it on the boat somewhere, or maybe get some stickers made up.
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Haha!
Nigel, about your battens, have you tried spraying them with some Mr.Sheen? (/Mclube if your rich)
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Good point Andy...not as yet but that is definitely in as an option
On a similar topic...what do people use for lubricating kites?
Has anybody ever tried Nikwax products like TX10?
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Also Mr.Sheen, although you do get a slight odour. Test it on a small area first as it can dissolve some cloths, but otherwise should be fine.
Some sailmakers can treat your kites, so that they become waxy/slippy like a new one, but I'm not sure how this is done or if there is a bodgers alternative.
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http://www.optimistonline.co.uk/acatalog/info_fabsil5.html
Fabsil Spinnaker waterproofing might be what you are looking for?
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yeah something like that, can't remember who recommended it but I've heard its alright.
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The mast /sail combo was just perfect!
Ultimately I think if you haven't got this right or damn near then you may as well give up, no amount of string pulling will save you, and if you have got it really right then you really need to try quite hard to stuff things up.
Cherub = too hard for the Olympics
Brilliant:-)
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Nice one guys...I was in rescue boat today with a Laser 5000 skipper and he said Fabsil 'Gold' but the one posted actually says spinnaker on it. One up for Grangers for actually knowing what a spinnaker is
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As a post script to this little thread a (slightly) repentent Loco would like to say:
If climbers and mountaineers are an easy wind up when you mention health and safety, the Cherub equivalents are 'Rules' and 'Tuning', especially if tuning might get in the way of the fun.
Beware of the Mad Dog :) and sorry Tom
btw it wasn't all wind up