I usally sail alone but had the opportunity to go with some other guys recently and noticed a big difference in our choice of sails.
I'm not having a go at anyone but am genuinly interested in what others think.
I rigged a 5 metre but others were rigging anything up to 7 metre sails.
Now when we were on the water, I will admit that they were faster but not by that much, and that could be attributed to either skill level, variances in the boards or just a weight difference.
I noticed that they were using a great deal more downhaul than I was. I was setting my sail as per what I imagine the manufacturer recommends, loose at the top but not overly floppy. Their rigs were very loose and so they would only be using half of the power available for them, the rest being exhausted in the loose leech.
There must be some advantages in running sails this way but I reckon I'm better off having a smaller, lighter sail pulling to it's maximum rather than a larger, heavier sail detuned. What do you think?
I really depends what sort of sailing you are doing. I'm either sailing in the waves or doing freestyle so I always use the smallest sail I can get away with, regularly i'll be 2m^2 or more smaller than others out there but am still planing around quite happily. Sure, if it comes to a drag race I don't have a hope but it's just not the sort of sailing I do. If you are looking to sail fast or sail extreme angles (formula) you need as much power as you can hang onto, hence the big sails. It's horses for courses, if you're happy sailing with what you have, sweet, you probably won't win a drag race but you might be able to bust out some rad freestyle 
As a generalisation, big sails rigged flat with floppy leeches have a bigger range than smaller sails rigged with more draft and tighter leeches. So if you're going in a longish race, you'll be better on the bigger sail. But a smaller sail rigged fuller is more efficient over a narrower wind band. So if you're going for max speed, rig the sail that's most efficient in the gusts.
And as CJW says a smaller lighter sail has a bigger margin for error than one you're fully/over powered on
Went sailing the other day after checking the forecast. Took down the 7m as the forecast looked grim, I wish I had something bigger. But what do you know when I got there it was blowing so I downhauled the hell out of it.
Some lucky guy I've not met before had a 5m.
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I rigged too big on Boxing Day and had a *fantastic* sail, on the Gold Coast Broadwater. As said above when powered up with both a big sail and fin you can get some crazy angles happening. I was easily running from the bridge at Labrador down past Shearwater (stradbroke side) and back. The guys on smaller gear where doing the usual 300m run at Shearwater.
PS I appreciate efficiency, but sometimes being overpowered, screaming downwind and not being able to sheet out can be exciting.
Nope. Small sails are smaller than big ones
BTW - today is a small sail day... the smallest I packed was 6.2, so perhaps I should go to Lucky Bay... but it will probably be too small for that place
Thanks decrepit, the winds down here do tend to be on the gusty side and that may be the reason some guys use the larger, flatter rigs.
I prefer to use a lighter sail and will stick to what I am comfortable with. I was just curious what advantages were had with the other rig set-up.
By the way, CJW, a few good gybes would be good enough for me.
I think this depends on the type of sail and board.
... say you compare a 7.5 sqm race sail on a FSW type board against a 5.6 wave sail on the same board you'll find both sails will probably get you going in about the same wind.
If you compare a 7.5 sqm race sail on a large volume formula board against a 5.6 wave sail on that same FSW from the previous example the formula / race sail combo will probably get going earlier.
In regards to wave sailing I have to agree with CJW. Going bigger isn't always better... for example going from 5.6 to 6.2 will mean bigger mast (= more weight), more sail weight, more drag. That alone will probably kill any advantage of using a 6.2.
On the other hand going from a 4.5 to a 4.0 is a big difference. Something to do with the force of the wind increasing exponentially... but I won't bore you with the details of that.
Iceman, not sure if this was the case where you were sailing, but a lot of us sailing the bigger race sails are on dedicated slalom boards and aiming for results on our GPS's. As a general rule, we need relatively big sails than so we can bear away off the wind for max speed and also keep our speed through the lulls when going for 1 hrs or Nautical Miles. These bigger race sails can handle it if it does get windy as they have a huge range, so it's OK to rig a 7.0m in 15-25 or a 6.2 in 25-35, even though a smaller sail on a free-ride board will feel totally powered up in the same conditions.
I think in order to get your head around loose leaches you need to remember that a sail is a wing that works due to the separation of air flow around the sail. The loose leach increases the efficiency of the over all airflow. It really all depends what you are after, as the original post says the other guys were going faster, which over a race course would make a huge difference but would not necessarily make blasting back and forth that much better. On a wave sail however you also need to take into account the back hand feel that the leach tension gives you. Then you need to get the balance that is right for you between rig tension, body weight, riding style and ability.
