Some advice regarding doing races on F16 when 1-up in shifty and light winds

Put telltales on the LEECH of your sail. Mid upper panel, just below mid leech overall and one halveway between those two. When sailing uni-rigged you have to sail by these. The telltales in the sail are not much help in really getting going because the stream to easily. I found that I'm inclined to oversheet my mainsail often.

second tip. Go to www.tacticat.com register (for free) login and do alot of races practising your tactics regarding shifts, wind strength, racing rules and general covering of the your opponents. You'll learn heaps and because after a while you know them by heart when on the water you'll make alot better use of these on the water in an actual race. I really advice this online training. Apparent quite a few of us F16 sailors are doing it as I've encountered a fair share of those in the game already. (you often race against real people and can communicate with them)

Wouter

So I have followed your advice.

What I found was that the first leech ribbon to break for the backside was always the lowest. This would have been right above the spreaders. I interpret this as saying that my prebend is wrong for these wind conditions. Would I be right in saying that I have too much pre-bend?

Are you talking about when you are going to windward?

Yes, while on the beat.

Okay, so when you say a leech telltale "breaks," what do you mean? Do you mean it is starting to flow forward? And, if so, is it going forward on the back side of the sail or on the side toward you?

You are going to drag this out of me bit by bit. <img src="http://www.catsailor.com/forums/images/graemlins/ooo.gif" alt="" />

Yes, by break I meant that it is going forward on the leeward or back side of the main.

A hard one to answer certainly (just look at all the replies).

It might be your pre-bend, but it might also be battens, the way the sail is cut, your sheeting/downhaul/helming etc. Going out trapeezing will also change how the mast bends, so there are lots of variables. If you were sailing uni with a sloop mainsail, I would expect the lower telltale to stall first.
Changing pre-bend will not only adjust the leech, but draft position and amount. Only way to be certain is to change it, and then race an identical boat to see if you now are faster or slower (or have better/worse windward abilities/height).
The sailmaker who cut your sail should be able to tell you what amount of pre-bend he cut the sail for. Usually a sensible place to start off when adjusting and trimming the mast.

Certainly seems to be a bit of a poser.
More info. It was definitely light airs. No trapezing here. It was uni rigged with the sloop main. So perhaps that is all it was.
I am not going to be able to do any boat tuning here. The fastest competition I can find here is the old tornado rig and I could beat those sailors on my old N5.2.
I did ask the sailmaker and I have got the prebend set there.

So perhaps, all is good. The only question left is whether or not I should be easing the mainsheet enough to get that leech ribbon flying in the 3 knot breezes.

Making the leech telltales fly 50% of the time is always faster than stalling them. The question we ask ourself when sailing in low wind conditions is how much downhaul we should use. There is usually a best combination of downhaul and mainsheet that will get you into the groove.
In general, we have found that the fastest settings are with more downhaul and sheet than you tought you needed..

I went down that road once when in a 1 knot drifter. Kept tightening and tightening until I had it real good and slow. The small boats walked away from me. On land, where I could see the sail better, I saw how badly I had hooked the sail. Moderation in all things. So that is why I tried the leech ribbons.

Next time, I will try some more downhaul and see how it affects that lower ribbon.

The best thing to do is have someone photo or better yet video you sailing from the back. The big top sails are designed to twist off (depending on settings of course) but it will be very difficult to get the leach tell on the top pocket to break, and if you do you will find you are way way over trimmed. In light air you can sit forward and site up the mast to get the settings right, but as it picks up getting a good perspective on what the sail shape is doing is much more difficult.

I used to rely on a leach tell on my H16 on the second pocket down almost exclusively. The tear drop mast that did not rotate made the forward tells pretty hard to read. On the new boat I have found the opposite. Up wind I can tune the downhaul and rotation pretty easily with the forward tells and sheet to feel. Up wind I no longer look at the leach tells. I do use them for gross trim when heading down wind though.

Matt

Bob,

in drifters we do something as counterintuitive as almost maxing our downhaul and sheet lightly. Idea is to keep what little airflow there is attached and exiting cleanly. With leech telltales, we dont have much trouble with hooking.

I'm much helped by these leech tell tales. On my boat and sail I now almost exlcusively sail to these WHEN I'M SINGLEHANDING UNIRIGGED. I think this is the result of using a sloop mainsail for unirig use. The lower part of the sail often tends to be to tight for unirig sailing. The top halve is more or less okay as it is cut to twist off more as their is no jib at that height skewing the flow.

We (Blade with Ashby and my own Taipan with redhead sails) are finding that alot of downhaul is fast in very light conditions. We are running the least downhaul in medium conditions then some more in light stuff and even more in really heavy stuff. It seems to help pointing and the sail tends to breath more freely making the boat go faster.

Solo, unirigged in light winds I first trim my downhaul to number 7 (which I can't translate to your settings) then I trim my traveller to have the lowest leech tell tale stream about 50 % of the time; then I add mainsheet till the upper two leech tell tales stream AT LEAST 50 % of time preferable a little more if the winds are unstable. The last seems to allow good breathing of the top. Then a I steer and steer and adjust these settings in the exact same sequence when the wind changes.

I'm finding that like this I do rather well against the two Blades at my club and other boats like F18's and Inter-20's.

I'm finding that oversheeting (top too tight) is really killing boat speed when uni-rigged. It is surprising how much twist you are sometimes using in light airs. The tell tales in my mainsail (not the leech ones) are too insensitive to signal when I'm oversheeting on either the traveller or mainsheet in these conditions.

When doublehanding or singlehanding in more winds then I start using the jib and ordinary mainsail tell tales more but not in light winds. This is for the same reason of insufficient sensitivity.

I have a 4th leech tell tale right on the corner of my squaretop but this one is pretty useless for fine trim. So don't put a leech tell tale all the way on the top of the leach, Have it at least 500 mm down.

Tuning of prebend is an art form in itself. However I do believe your current problems are trim related (sheets, downhaul) and not tuning related (prebend etc)

I hope this helps

Wouter

I still don't quite understand. Are you guys saying that it is best if the leech telltales are streaming straight back? Or is it best if they are streaming forward? Which is optimal?

The optimum (in my opinion) is that leech telltales stream aft, but break forward now and again. That way your sail is generating maximum power and minimum drag.

If the leech telltales stream aft all the time, you are probably not taking max power out of your sail but still have the same amount of drag.

If the leech telltales break forward all the time, airflow separates from the leeward side too early and you are loosing power and pointing ability at the same time as you are generating lots of drag.

100% agree, and as Wouter says, trim on the mainsail is VERY critical sailing single handed. You must have enough tension in the leach to allow you to point (and be powered up) but not too much to stall.

Leach telltails are critical in telling you when this is happening.

I went to Spring Fever couple years ago, got to meet Wouter. I took the redeye and drove from Atlanta, so I was pretty tired. What I remember may be wrong because of this. Randy Smyth gave a talk about trim. After the talk, one question that came up was about leach telltails. His comment was ...why are you looking back there when going up wind? You will never keep the flow attached back that far, and if you try you will be sheeted out way too far. He uses telltails that are very close to the mast. The one close to the spreaders is the one he uses to adjust prebend.
Randy seems to go very fast

Ken

Has anyone tried putting a row of tell tales all the way from luff to leach, say every foot or so, and then one on the leach too, both sides of the main, just to see where the flow does separate? They do this with airplane wings in the wind tunnels and in flight too, to see at what angle of attack the wing will stall and how much of the wing is stalling at any given angle of attack. Some slight separation will happen at the takeoff and landing phase of flight, where you want the maximum lift from the wing. You will also be at maximum drag but the engines are at takeoff power and they can overcome the drag.

But at cruise, you want minimum drag and the engines are only at cruise power, which is much less than takeoff power, even though you are flying 300% faster. You could equate that to sailing in very light wind vs. very high wind speeds and trying to shape your main sail for maximum lift vs. minimum drag. In the maximum lift phase you will have separation. In the minimum drag profile, you should have very little separation, so you must vary it according to the conditions, which is what makes sailing (or sail shape) so much harder than flying! <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />

What shape was his sail ?

Pin head or fat head ?

Try it for yourself Ken. You can feel it when you oversheet if you are in tune with your boat, but having some telltales on the leech is much easier. If you try it while two boat tuning or racing, it is pretty obvious which mode is fastest. Especially so with a modern square top main.

With the time Smyth has on the water, he can feel when the main is over/under-sheeted and dont need to look. We have 6 years on the same boat with the same crew, we still check the leech telltales if we are uncertain. As for "why are you looking back there when going up wind?", We'll look anywhere if it makes us go faster..
If your leech telltales never flow aft when going upwind, put on more downhaul, trim mainsheet and go faster.