On a few sails, there are 2 clew eyelets. On the Goya brand, the eyelets affect back hand response and also boom angle.
What do you feel is the advantage of having a boom angled such that the back hand is quite a bit lower than the front hand?
The boom height difference at the eyelets is somewhere around 3-4" or close to 10cm it feels like.
Besides the height difference, I seem to prefer the lower eyelet and run a bit less downhaul to have more grunt and a smoother more relaxed power delivery at the same time.
I have heard that you use the lower eyelet when massively overpowered, like 20kts+ wind for 9.0 on iqfoil, when you aren't going to downsize a sail. Just don't have that experience first hand as in those cases that I was that overpowered I usually downsize or use different gear.
Most tweaking I've done is on that race gear: up to 20kts I lower the boom a LOT. Not sure what point of sail this was as I was zigzagging a lot to avoid others and to stay off of beam reach, gusts slightly over 20kts. I'm clearly not fully sheeted in. Haven't used the lower clew eyelet as above 20kts winds on this setup intimidates me still as I am just not as skilled as the guys taking this gear out in 30kts.
But, the boom is very low here compared to light winds (8-12kts or so), where I usually keep it at the top of the sleeve. The combined effect with high downhaul (+4cm), high outhaul, low boom, makes it a lot more manageable than otherwise.
Select to expand quoteManuel7 said..
I take it you have adjustable harness lines?
For race gear yes, they are very long and adjustable.
All the other freeride booms I have, I use adjustables usually set to around 30-32". Even so on fin freeride I find there is a limit to how low I want to put the boom clamp before it starts feeling off and uncontrollable. Don't have the lower eyelet on any of my freeride gear except for maybe the 7.5 gator? Haven't tried it.
Select to expand quoteManuel7 said..
On a few sails, there are 2 clew eyelets. On the Goya brand, the eyelets affect back hand response and also boom angle.
What do you feel is the advantage of having a boom angled such that the back hand is quite a bit lower than the front hand?
The boom height difference at the eyelets is somewhere around 3-4" or close to 10cm it feels like.
Besides the height difference, I seem to prefer the lower eyelet and run a bit less downhaul to have more grunt and a smoother more relaxed power delivery at the same time.
I see it mostly on race sails; the concept is to loosen up the leech (not about changing the boom angle). So when you're really overpowered you can put it in the lower hole and get a looser leech without adding any more downhaul (ie, quick fix to do it out on the water).
I never used it in my life though; makes the sail feel very soft. That could be a good thing on a wave sail though... all depends on what mast you have it (could be a good way to make a stiff mast feel softer).
If you're trying to give your sail more power in low end, I would always use the TOP hole! It will tighten up your leech; better for low end.
Select to expand quoteSeanAUS120 said..Manuel7 said..
On a few sails, there are 2 clew eyelets. On the Goya brand, the eyelets affect back hand response and also boom angle.
What do you feel is the advantage of having a boom angled such that the back hand is quite a bit lower than the front hand?
The boom height difference at the eyelets is somewhere around 3-4" or close to 10cm it feels like.
Besides the height difference, I seem to prefer the lower eyelet and run a bit less downhaul to have more grunt and a smoother more relaxed power delivery at the same time.
I see it mostly on race sails; the concept is to loosen up the leech (not about changing the boom angle). So when you're really overpowered you can put it in the lower hole and get a looser leech without adding any more downhaul (ie, quick fix to do it out on the water).
I never used it in my life though; makes the sail feel very soft. That could be a good thing on a wave sail though... all depends on what mast you have it (could be a good way to make a stiff mast feel softer).
If you're trying to give your sail more power in low end, I would always use the TOP hole! It will tighten up your leech; better for low end.
Good to see you lending your vast experience on the forums Sean.
I also used my xover/wave sails with 2 eyelets the same way.
Select to expand quoteGestalt said..SeanAUS120 said..Manuel7 said..
On a few sails, there are 2 clew eyelets. On the Goya brand, the eyelets affect back hand response and also boom angle.
What do you feel is the advantage of having a boom angled such that the back hand is quite a bit lower than the front hand?
The boom height difference at the eyelets is somewhere around 3-4" or close to 10cm it feels like.
Besides the height difference, I seem to prefer the lower eyelet and run a bit less downhaul to have more grunt and a smoother more relaxed power delivery at the same time.
I see it mostly on race sails; the concept is to loosen up the leech (not about changing the boom angle). So when you're really overpowered you can put it in the lower hole and get a looser leech without adding any more downhaul (ie, quick fix to do it out on the water).
I never used it in my life though; makes the sail feel very soft. That could be a good thing on a wave sail though... all depends on what mast you have it (could be a good way to make a stiff mast feel softer).
If you're trying to give your sail more power in low end, I would always use the TOP hole! It will tighten up your leech; better for low end.
Good to see you lending your vast experience on the forums Sean.
I also used my xover/wave sails with 2 eyelets the same way.
On my NP V8s I went to the lower position when overpowered. Similar to having 0.5 less sail up. I'd be feathering the sail before then fully sheeted in with total control. I moved boom lower before adjusting clew height.
There have been so many discussions about clew height over the years, claiming various advantages, that you wonder why so many sails only have one clew cringle option.
The discussion is usually about 1) Boom height, or 2) Boom angle on the mast, or 3) Leech twist.
4) The fourth connected issue - which is rarely discussed - is outhaul tension. And that's probably the most important one.
If you are bored already, then you can stop reading right here. The rest of the stuff I'll write here is a bit nerdy.
1) Boom height. We all have our preferred boom height and if you are tall you probably set the boom front end in the upper half of the luff cutaway. That higher boom front end puts the boom at an acute angle on the mast and by using a higher clew cringle option you can get the boom more horizontal, also raising the harness line anchorage points to where you want them to be. So this clew cringle choice is really about sailing comfort and your sailing stance. Stance is, in turn, important because it's how we use our body weight to control rig power and how we transfer rig drive to the board.
2) and 3) Discussions about boom angle on the mast date back to the days when windsurfer sails were simple triangles of cloth with a few short battens. It was thought that the original windsurf 'wishbone' boom was like a yacht 'boom vang' or 'kicking strap', and thus changing the boom position on the mast controlled leech twist. (And never mind that those original Nylon or Dacron sails had no stability anyway.) The original theory was setting the front of the boom higher, or the rear of the boom lower, you increased leech tension - because the angle of the boom pushed the clew down, flattening the head of the sail and controlling excessive leech twist.
The modern theory is the opposite, and if you now drop the back end of the boom to a lower clew cringle, that is supposed to reduce leech tension - and thereby to increase sail twist to depower the rig. The modern theory is that the longer leach distance, from sail head to clew, means there's more 'give' in the leech.
And never mind that, under both theories, you've got the same body weight hanging off the same rig, pulling the boom downwards.
4) The bit that people tend to forget is that when you change clew height position - or indeed when you change the boom clamp height on the mast - you invariably alter outhaul tension. Changing the angle of the boom on the mast inevitably changes the distance from sail luff to leech, and ideally you should adjust boom length and re-set the outhaul tension.
In summary, changing clew cringle height may well give you a different feel to your sail, and may help or hinder your sail control problems and alter the power delivery. However what is actually happening is very open to debate - and it's very easy to mix up cause and effect.
Racing sailors using cambered sails are keen on their tuning options - and altering clew height is valued as one of those options. With wave sails, having a higher clew option may help the taller sailors - but wave sailors going down the line might also find the lower clew setting gets their back hand drive point lower when transferring rig power to the rail and fins in a cranked bottom turn.
The twin eyelets changing leech tension is most effective on sails with cutaway clews. It moves the clew further away from the crossover batten and allows the lower leech to open more. It's effective, I have done lots of testing. For lightwind and upwind the high clew position, for downwind or overpowered the lower position. I tested it on my foil a week or so again and I was surprised, you could notice the difference more on the foil..the sail felt a bit chocked on the top position when I started to get a bit overpowered, dropped it down and it was noticeably slipperier and faster. Thats on a KA race
Select to expand quotemr love said..
The twin eyelets changing leech tension is most effective on sails with cutaway clews. It moves the clew further away from the crossover batten and allows the lower leech to open more. It's effective, I have done lots of testing. For lightwind and upwind the high clew position, for downwind or overpowered the lower position. I tested it on my foil a week or so again and I was surprised, you could notice the difference more on the foil..the sail felt a bit chocked on the top position when I started to get a bit overpowered, dropped it down and it was noticeably slipperier and faster. Thats on a KA race
I've found it really easy to feel the tuning adjustments on a foil. Downhaul, outhaul, boom height. All very noticeable. It's helped me diagnose feel a lot more. On fin I can usually tell now when it's underdownhauled, like when I went out in light wind and tried to tighten the leech but it doesn't quite breathe well and needs more give.
Should have probably dropped the eyelet to the lower one last night on the 7.0 foil sail but I ended up just dropping the boom. Then I noticed my adjustable outhaul cleat had slipped and then I couldn't adjust it 
. Was wondering why it kept loosening up...
Select to expand quoteSeanAUS120 said..Manuel7 said..
On a few sails, there are 2 clew eyelets. On the Goya brand, the eyelets affect back hand response and also boom angle.
What do you feel is the advantage of having a boom angled such that the back hand is quite a bit lower than the front hand?
The boom height difference at the eyelets is somewhere around 3-4" or close to 10cm it feels like.
Besides the height difference, I seem to prefer the lower eyelet and run a bit less downhaul to have more grunt and a smoother more relaxed power delivery at the same time.
I see it mostly on race sails; the concept is to loosen up the leech (not about changing the boom angle). So when you're really overpowered you can put it in the lower hole and get a looser leech without adding any more downhaul (ie, quick fix to do it out on the water).
I never used it in my life though; makes the sail feel very soft. That could be a good thing on a wave sail though... all depends on what mast you have it (could be a good way to make a stiff mast feel softer).
If you're trying to give your sail more power in low end, I would always use the TOP hole! It will tighten up your leech; better for low end.
It is interesting that Point-7 has double rings on their wave sails but not on the flat water ones. Both Spy and Salt have two rings, but there is one ring for the whole AC line up. I guess because the ACs have such wide range as is. On the wave sails the rings are quite effective at further extending the range. I use the feature often, as you said top for low end, low when you are maxed out or in bigger swells.
higher eyelet tighter leech?
I've seen people convert slalom sails to foil by adding a higher eyelit?
The clew eyelets on the Goya sails are quite effective as they are connected to the carbon lines that come from each eyelet.
The top eyelet on the older sails is only connected to the one carbon line where the bottom eyelet is connected to both an upper and lower thread lines.
I used to use mine with both eyelets threaded to the outhaul and it seemed to really stabilise the sail in upper and lower sections.
The boom angle will change for sure. I also see Naish is using two clew rings in their sails now too.
Select to expand quoteWind Smurf said..
The clew eyelets on the Goya sails are quite effective as they are connected to the carbon lines that come from each eyelet.
The top eyelet on the older sails is only connected to the one carbon line where the bottom eyelet is connected to both an upper and lower thread lines.
I used to use mine with both eyelets threaded to the outhaul and it seemed to really stabilise the sail in upper and lower sections.
The boom angle will change for sure. I also see Naish is using two clew rings in their sails now too.
I've seen Karin & Patrik using both eyelets when rigging on their cammed sails. Patrik during some workshops really spoke highly about using lower position when over powered.
Select to expand quoteRoyalontheFoil said..
higher eyelet tighter leech?
I've seen people convert slalom sails to foil by adding a higher eyelit?
An higher ring stops the sail for opening up. Imagine if you had the eyelet at the bottom of the sail, the whole sail would twist.
BTW. To keep everything but the eyelet position the same the outhaul should be adjusted to reflect the vertical/horizontal offset of the rings.
Yes the lower one being offset increases looseness on the leech by quite a bit. 5cm (looser leech) x 3m = 0.15m?. quite significant.
I'll update long term. So far still riding lower eyelet despite the boom angle threatening to hook in at unwanted times! Although I think I've reached a safe boom height 
!
You thought your clew angle was weird......Although he does also have a spinnaker to deal with too.......
From the latest edition of windsurf magazine.
I customised all my slalom sails with an extra clew hole above the long batten for foiling.
www.seabreeze.com.au/forums/Windsurfing/Foiling/Foil-Racing-Slalom-Foil-vs-Crossover-Sails?page=1
Much better stability and upwind. A bit too rigid for reaching and speed runs.
The problem with that berowne is the extra boom length. On a slalom board you want to be back foot biased so you can load the fin and get it to flex and lift, really drive off the fin. The longer boom gives you a natural back foot biased stance. On a foil if you load the back foot like this you always risk foiling out. You can compensate by having your mast foot and straps further forward and using a smaller stab but its not ideal. Thus the foil specific sails have shorter booms to stop you loading your back foot as much.
There's also another issue. In super flat water ie LG when the boom is on the bottom hole ,the board wake catches the end of the boom making the sail unstable. Yes you could move the mast track further back but when you are already at the track limit to other option is the top hole. Interestingly I never had an issue at Sandy point or Invy in the flat water. Must be too bumpy 
I tried the lower clew hole yesterday on a foil specific cammed sail (7.0) when the wind picked up and it was overpowered. It did make a noticeable difference, and I could also feel the angle change of the boom a bit. I didn't change any other adjustments like boom clamp height or downhaul, but I did re-tweak the adjustable outhaul. It felt different than just an outhaul change.
I think it gave me another 30 mins or so with that sail as the wind kept ramping up and I started going more into survival mode and dropped sail size. If it hadn't been on the edge of a squall then it could've kept me on the water with that sail a lot longer, helping extend the range quite a bit.
It's the first thing I do when I'm overpowered . It makes a big difference , half a sail size.
Select to expand quotekato said..
There's also another issue. In super flat water ie LG when the boom is on the bottom hole ,the board wake catches the end of the boom making the sail unstable. Yes you could move the mast track further back but when you are already at the track limit to other option is the top hole. Interestingly I never had an issue at Sandy point or Invy in the flat water. Must be too bumpy
Only a problem if your going too fast!
Sail Tuning: GO FASTER WITH MORE CONTROL -
