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Reaching trim

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KazR View Drop Down
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    Posted: 10 Jan 16 at 9:51pm
i have a question I've never managed to get an compelling answer to. 
What is the best trim on a reach (beam or broad) in a una rigged boat. Almost every book suggests the old 'if in doubt, let it out' approach and recommend easing the main until the luff lifts and then pulling it in slightly. I'm sure in my copy of Bethwaite that he recommends pulling the main in till the leeward telltale lifts to get as much forward going power as possible. Whenever I try the general book approach it always seems slow and low powered compared to sheeting harder and getting what seems like more power. 
What's everybody else's opinion? To me it does seem like sheeting harder generates more power, but 9 out of 10 books recommend easing the sheet lots which feels slower (but is it?) but I'm not doing enough class racing to know which one works best.

Kaz
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Rupert View Drop Down
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 10 Jan 16 at 10:12pm
If you pull it in further, you simply create more heeling moment, so it may well feel faster, but I doubt it will be. What may well be faster is luffing in the lulls to keep the power on, then bearing off in the gusts to keep the boat flat without having to spill wind, rather than going in a straight line.
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iGRF View Drop Down
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 16 at 10:45am
This is an area I've always struggled with, with windsurfing it's intuitive you sheet in harder and harder and go faster and faster, but with boats you sheet in harder and tilt further and further up in the air, then the boom digs in..
I also find and especially with boats like the D zero with light sheeting loads, i can't tell where the optimum point is, so if it's light I inevitable end up just holding the boom to 'feel' the optimum pressure in the rig. This is easier to 'feel with boats with heavier sheet loading and centre sheeting I always think. Don't take my word for it, I'm a total muppet at all this, but I fully get where you're coming from.

So I tend to sheet it in as hard as I can to get it going as quick as ever, let the apparent wind build and bear away on it then I ease the sheet out a bit, then back in again to correct it, then out again, then in again, then out again, then in again. until they all start shouting at me, then I think it must be about right..
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Oatsandbeans View Drop Down
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Post Options Post Options   Quote Oatsandbeans Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 16 at 10:46am
Another way to do it is to use leach telltales. The sail should be sheeted until they are at the point of stall (just getting agitated). This in my experience works well and generally gives a more sheeted in sail than from working on the luff lifting. It also helps to set the vang as they should all break at the same time if the vang is correct.
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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 16 at 10:58am
I suspect the answer is very complicated, and may even vary according to the course. I'm sure that on a shy reach with the apparent wind coming from ahead you want the sails unstalled and low drag high lift. I'm not so clear about deep reaches, especially in slower boats. If we consider a slow boat on a dead run then the mainsail is stalled out all over, but its not that big an issue because drag is pushing the boat in the direction we want it to go anyway.

It seems to me possible that on deep reaches it may also be beneficial for the sail to be partially stalled if it increases lift and the drag is still in the right diraction. I may be wrong of course. Then there's running by the lee and the odd sail profile amd shape you have there. I find it hard to believe the sail isn't partially stalled in that condition too. Like a lot of sailing I reckon its damn complicated, but if you have sufficient boat feel you can probably get to the optimum without knowing what's going on aerodynamically, which would be why the hot guys are so much faster than me...
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Ardea View Drop Down
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Post Options Post Options   Quote Ardea Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 16 at 12:35pm
On a beam or broad reach where you are looking to generate maximum power from the rig you want good airflow over the sail which is just starting to stall as it comes off the leach.  This is not easy to achieve and involves sail shape as well as sheeting angles! Like oatsandbeans says leech streamers are usually how I try to achieve this.

Easing the main until the luff lifts allows airflow across the sail (in case it was over sheeted and stalled) then pulling it in slightly allows the sail to deflect the airflow and generate power (through lift &drag).  
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KazR View Drop Down
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Post Options Post Options   Quote KazR Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 16 at 12:52pm
I am quite comfortable on the runs where the key to me is keepin gthe flow going, either from mast to leach, or leach to mast or even bottom to top, but its the beam and broad reaching where I'm wondering what the best trimming would be. There will be a stage where you are overpowered enough that you can't keep the boat flat and the rudder unloaded and will have to ease the sheet a lot, but if you can take the power should you sheet harder either until just before the leeward side telltales at the luff lift (staling the leeward flow) generating a lot of lift in almost the same direction as you are going (on a broad reach) or ease until just before the windward telltales lift, generating less lift but it more in the direction you are going? I'm sure Bethwaite suggests the first, but I havent got a copy around to check
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 16 at 1:02pm
I honestly don't get all this, watch the tel tales, I think they are a total distraction. In my very early days windsurfing back in the late seventies, when any dinghy waller who was worth his salt was coming over to give it a go, they all came with their rigs with tel tales all over the place, so I fitted them on mine. This was in the early days of what became Division 2, so there were CYT sails, needlespar masts, experiments with boom vangs (to emulate the kicker) and topping lifts (something I tried to overcome the stupidly stiff rigs they came with so the top of the sail would twist off).
But the thing that came out of it and this was before we were pumping a lot, was whatever the tel tales told you was the optimum position according to popular consensus, was rubbish to produce board speed and the only really reliable means of telling was feel, and that was out of the harness feel, and so it was us guys that had sailed windsurfer class OD where harnesses were banned anyway, came to dominate in those early days. So the crux of the matter, feel does it every time and that has been the most difficult thing to achieve in the ten years or so Ive been blundering at this lark.

Without that essential connection direct to the rig you are so lost, I'm beginning to get a bit of feedback through the bum and I use all those other pointers, stern noise, feel through the rope (never cleat it off ever), even the sag in the lee shroud, plus the wind in your ears and knowing wether the puff is a lift or a header and making sure you act accordingly especially offwin where it's more difficult to tell, but it is so so much more difficult to pick up, especially if like me you don't practise other than to go out racing, I guess if you spent a bit more time in the boat it would come quicker..
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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 16 at 1:22pm
If you can feel a 1%, maybe even a 3% increase in speed through your bum or whatever then yes, you probably don't need tell tales.
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Post Options Post Options   Quote Oatsandbeans Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 16 at 2:26pm
iGRF is actually right on this (never thought I'd say that). With a board you have the great advantage that when sheeting in the sail with your back hand you have an immediate feedback of how much aerodynamic force is being generated. So as you sheet on you can feel when the sail stalls as then the load drops dramatically,then you sheet out until the load comes back on as the flow reattaches. The old Div2 rigs with long booms were perfect for this as there was so much feel from the back hand, no need for tell tales at all.
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