I'm after all the help I can get as I'm racing against myself out here. Can anyone give me a benchmark to start at?

I sail with mast rake on 4 and 4th hole down on shrouds with the spreaders fairly long and forward ( never measured these but just did it when the boat was new and havent changed them.
When sailing upwind in wind against tide chop in the Solent I sail lower as soon as the boat start stalling and bobbing on the waves.  In these conditions I think you risk loosing less ground by sailing too low rather than pinching.
Downwind I sail high and fast as long as the boat is planing most of the time with all kicker and cunningham off.  
The outhaul is set between tight when windy and and about3 inch gap between sail and boom in the light stuff.  I seem to sail with it tighter than most other boats.
Hope this is of some use.
Mark 134

Hi Jnr,

I don't think the shroud settings make any difference because of the lack of a forestay - FYI I use 4 holes down and the spreaders mid way out - as with Mark not for any tuning reason but simply this is how I have had them since new and can't see any reason to change. The shrouds are only ever under tension when the kite is up - upwind as soon as you pull any vang or mainsheet on the shrouds just hang loose and given this I don't think the settings make any difference.

I do, however, use more mast rake than Mark. I use a range of 5 (light wind) to 7 (nuking) and typically just leave it on 6 - to me this makes the boat feel very sweet and tracks well upwind. I used the 10.2 for a long time and to me this needed less rake (position 4), probably because the additional roach meant the CofE was further back. The equivalent position for the 8.4 I think is about 6.

I agree with Mark about the outhaul. I have it either flat (about 3" off the boom) or very flat (creases running along the boom) and the total range of adjustment is about 50mm along the boom - I think it is a mistake to ease the outhaul too much for 'power-up' in light winds, one which I still often make. The sail becomes quite draggy and although you have more to hike against I don't think its quick.

Upwind in a blow you need a lot of kicker, infact I kicker-on pretty early, but if I have the loops tight I don't pull it quite full on block-to-block - leave about 50mm between the pulleys as I find that last bit does something very odd to the bottom part of the sail. Lots of cunningham is essential once its blowing and I tend to pull on together with the kicker although sometimes in a lull you can change mode by easing the downhaul but leaving the kicker set, which can be useful.

Downwind kicker fully off (if you have short loops it actually doesn't go fully off) and cunningham off if possible but if you can't reach it and its blowing it doesn't seem to harm to leave it on. As Paul says can be useful to pull the cunningham on if you over stand and need to reach up to the mark with the main eased. Incidently when its really windy pulling the cuuningham on hard really tames the rig and makes it easier to get into the boat if launching is difficult.

I would say you need to get a feel for what is right for you - these settings work for me.

Forgot to mention - DO NOT PINCH !!!! As soon as there is enough breeze to be hiking and definitely once there is any chop, it kills the boat dead to pinch it upwind (hence why I now use the 8.4 not the 10.2, which I was always 'feathering'). There are a few 'pinchers' in our fleet (no names !!) and if your stuck behind them and can't tack off its actually better to drop down below and you will soon pop out well in front.  
Cheers

Chris
edited by Chris421 on 14/06/2012
edited by Chris421 on 14/06/2012
edited by Chris421 on 14/06/2012

Hi Chris,
I have a question....
Mast Rake - why when it's windy do you move it towards the stern? (If I�ve got the numbers the right way around!)  I know that Greg also does so it must work cos he pretty quick in a blow but to me it doesn't make sense.  Moving it backwards it would make the lower bit of the sail fuller and not what you want when it�s windy?  This doesn�t seem to be the practice in the bigger rig, not that I what any of you little ones going any quicker ;) 
Alex

Raking the mast back should depower you. If it was mega windy I would rake back.

I understand that with the shrouds (lowering them down) but with the mast rake control?  Isn't the MRC just like lowers because it�s so close to boom attaching to the mast?  i.e. when I sailed the Phantom in big breeze you let off the lowers to let the mast bend (similar to moving the MRC forward) to flatten off the sail? Or have I got this all wrong?

Great detail. Thanks Chris

I dont think they act like lowers. Lowers stop the mast bending lower down, so technically stiffen the mast meaning it os more powered up.

All the rake does is change the rake, shouldnt have any other effects really

Excuse the crapness of picture and the extreme (for illustration purpose only) movement but I thought this what was happening.. Green for windy / red for light which seems to be the other way round?

The problem is the lack of forestay isnt it? By not having one you cant invert the mast as there is nothing pulling it forward.... I think...

I think you might be right about the forestay thing but I'm sure it's going to effect the lower bit of the sail. I might do a bit of measuring when I'm bored
edited by Alex on 15/06/2012

Hi Alex,

Like the graphic - is the green David's mast at Weymouth last year !

I don't know the science but in every craft I have sailed you rake the mast back when its windy. I think that what happens is that as you pull the controls on, particularly the cunningham,  the CofE moves forward and raking the rig back counters this and prevents lee helm.

On a number of occasions I have launched in a rush and forgot to wind the ram on - the boat sails just fine with the mast in the far back position and it is only when you go to tack and can't get under the boom that you notice it.

The BIG thing here is in my view the shrouds do nothing at all to affect the sail shape. Whilst it might appear that the sail is being flattened by winding the ram forward on shore as soon as any vang or mainsheet goes on they just hang loose. The shrouds do stop the mast bending to leeward, and thus give a bit more power, and of course they are fully loaded with the kite (the pin in the shackle has bent lots of times) but I don't think they have any affect on controlling fore and aft bend, which is what impacts sail shape. I think of it as an entirely unstayed mast, the ram sets the rake and the vang is a flattening device - again I don't think the vang really has a powering up effect as it has nothing to react against. 

I also used quite a lot of rake on the 10.2 when it was windy - I think its a depowering thing but I am only going by how it feels not any obvious science.

Chris
edited by Chris421 on 15/06/2012

as has been said by various people here; the shrouds make a very minimal difference. they obviously make a small impact otherwise the windward one wouldn't be tight on the way upwind but it's not the critical control to "shore-side" set-up of the rig.

the key effect of the mast rake is to alter the position of the the Centre of Effort for the sail. While this isn't literally depowering the sail it gives the impression of depowering as it makes the boat less truculent. with the rig more upright the CoE for the sail is fwd of the CoE for the centreboard causing the boat to round up. this isn't so much of a problem in the lighter stuff but as the wind picks up the level of this imbalance increases so we knock the mast back a few inches to reduce the moment of the forces causing the boat to round up and so on. Kicker and downhaul are your "on the water" remedies to the problem. any windsurfer should recognise the principle...

the 8.4 thread probably isn't the place for my 10.2 settings but hey ho;

up to 8-9kts = mast @ 2-3
10-15kts = mast @ 4
15kts+ = mast @ 5
edited by AndrewB on 16/06/2012
edited by AndrewB on 16/06/2012

I'm happy with everyone's suggestions about letting the kicker off fully when down wind. Especially with the kite up but what about the one sail reaches that some of us have to do in club racing? Still let it all off or sail with as much on as the leach tell tails will allow?

I always keep some kicker on one-sail reaching - gives more 'feel'.

Its interesting to discover what happens when one-sail reaching and you dump off all the kicker (this happens a lot on the spreader leg when WW/LW racing) - the boat totally and dramatically depowers to the extent that it is really easy to just roll it in to windward - happened to quite a few of us at the Paignton Nationals as the spreader leg was quite tight.

I think the same applies just general reaching - a bit of kicker is good.

If its windy you can use a lot of cunningham to control the power - did this at this years Starcross Steamer, which was a brutal reaching fest !

Chris
edited by Chris421 on 16/06/2012

Interesting. Alex raises questions that seem pretty simple and innocuous initially, but are actually pretty complex.

So here's my penny worth...
Rake: I've never seen a good scientific explanation (may have to get Bethwaite out again) as to why rake depowers a rig but there is a general consensus not only that it does, but the effect is far more significant than can be explained by reducing the height, so moment, of the CoE of the main. In a bermeduan rig, all other things being equal) it opens the slot and enables the jib to twist more, but even una-rig boats respond without that subsidiary benefit. The effect is so material though that Merlins have complex cats cradles to enable a single string to simultaneously adjust shrouds, forestay and lowers. Lots of other classes adjust these to create rake, the Phantom being a great example. It's also not a new trend, the 505s were into this 20+ years ago. So, blow the science, go with empirical, more rake depowers, but as Chris says, make sure you can get under the boom!

Lowers: a trad kicker pulls the boom partly down, but also partly forward. The latter has a bending effect on the lower sections of the mast. Sometimes you want that bend (when overpowered), sometimes you don't (powering up). So lowers counteract forward kicker thrust at gooseneck level, exactly where the thrust arrives. Of course, I guess they can also support the mast sideways too, which must help in rigs without a mast gate like a Phantom or Scorpion. In the old days we had mast rams, wedges or even tennis balls, but lets not get into that!

But we have a gnav, not a kicker, and the forces are different, particularly as the angle changes as you pull the thing on. In the unlikely event my mechanics are still working 35years since I last used them, the gnav bars provide a bending thrust at the mast counteracted by their pushing the boom back, a load applied in turn to the mast at the gooseneck. Given how close the gooseneck is to the mast gate and how close the gnav bars get to GN when the oomph is applied, I suspect the bending effect is pretty small. Where mast bend will appear it will be far more via the mainsail leech, pulling the whippy top end, not the stiff bottom end.

Mast gate: the mast is fixed at the foot and again at the gate. Without a forestay, these 2 are the only things stopping the mast falling over. The gate is therefore a rake control. It's close proximity to the GN is helpful in negating bending moments from the gnav which I suspect is a design feature rather than a 'bug'. The downside (and proof) is that there is no way I can think of to induce prebend in the mast, hence the irritation of the top-batten wanting to hook in no wind.

Personally, I like KISS, when each element does its job without crossing-over and interfering with the job of others. Writing this has made me realise quite how pure the 100 is in this regard.

Finally, one sail reaching. My Doh! moment was when it occurred to me to apply the RYA 5 essentials, vis pull the board up a chunk. That made things better. Works when hove-to too
edited by Clive on 17/06/2012
edited by Clive on 17/06/2012
edited by Clive on 17/06/2012
edited by Clive on 17/06/2012