#80369 - 07/17/06 10:01 AM
Some advice regarding doing races on F16
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Carpal Tunnel
Registered: 06/16/01
Posts: 9582
Loc: North-West Europe
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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
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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
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#80370 - 08/02/06 02:49 PM
Re: Some advice regarding doing races on F16
[Re: Wouter]
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addict
Registered: 12/25/05
Posts: 433
Loc: Edmonton, Alberta, Canada
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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?
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 F16 Blade 716
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#80372 - 08/02/06 03:14 PM
Re: Some advice regarding doing races on F16
[Re: Mary]
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addict
Registered: 12/25/05
Posts: 433
Loc: Edmonton, Alberta, Canada
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Yes, while on the beat.
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F16 Blade 716
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#80374 - 08/02/06 04:38 PM
Re: Some advice regarding doing races on F16
[Re: Mary]
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addict
Registered: 12/25/05
Posts: 433
Loc: Edmonton, Alberta, Canada
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You are going to drag this out of me bit by bit.  Yes, by break I meant that it is going forward on the leeward or back side of the main.
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F16 Blade 716
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#80376 - 08/03/06 01:41 PM
Re: Some advice regarding doing races on F16
[Re: Rolf_Nilsen]
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addict
Registered: 12/25/05
Posts: 433
Loc: Edmonton, Alberta, Canada
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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.
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F16 Blade 716
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#80378 - 08/03/06 02:25 PM
Re: Some advice regarding doing races on F16
[Re: Rolf_Nilsen]
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addict
Registered: 12/25/05
Posts: 433
Loc: Edmonton, Alberta, Canada
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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.
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F16 Blade 716
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#80381 - 08/04/06 02:01 PM
Re: Some advice regarding doing races on F16
[Re: bobcat]
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Carpal Tunnel
Registered: 06/16/01
Posts: 9582
Loc: North-West Europe
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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
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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
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#80384 - 08/04/06 05:33 PM
Re: Some advice regarding doing races on F16
[Re: Rolf_Nilsen]
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Hull Flying, Snow Sliding....
Carpal Tunnel
Registered: 02/06/04
Posts: 3526
Loc: Looking for a Job, I got credi...
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Quote:
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.
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F16 - GBR 553 - SOLD I also talk sport here
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#80385 - 08/04/06 06:05 PM
Re: Some advice regarding doing races on F16
[Re: scooby_simon]
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journeyman
Registered: 01/26/04
Posts: 57
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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
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#80386 - 08/04/06 06:47 PM
Re: Some advice regarding doing races on F16
[Re: KMarshack]
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Carpal Tunnel
Registered: 01/27/05
Posts: 5274
Loc: Sebring, Florida.
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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! 
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Blade F16
#777
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#80387 - 08/04/06 06:47 PM
Re: Some advice regarding doing races on F16
[Re: KMarshack]
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Hull Flying, Snow Sliding....
Carpal Tunnel
Registered: 02/06/04
Posts: 3526
Loc: Looking for a Job, I got credi...
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What shape was his sail ?
Pin head or fat head ?
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F16 - GBR 553 - SOLD I also talk sport here
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#80389 - 08/04/06 07:23 PM
Re: Some advice regarding doing races on F16
[Re: KMarshack]
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Carpal Tunnel
Registered: 11/12/02
Posts: 5558
Loc: Key Largo, FL & Put-in-Bay, OH...
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Quote:
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
Thank you, Ken. I was going to say something about Randy Smyth (and Rick White, too) not believing in leech telltales having any value.
But I will leave it to Rick to explain his (and Randy's) position about this. It might be a few days, because Rick is PRO for the Shark Nationals here at Put-in-Bay right now.
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#80390 - 08/04/06 08:26 PM
Re: Some advice regarding doing races on F16
[Re: Mary]
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Carpal Tunnel
Registered: 05/15/03
Posts: 4343
Loc: West coast of Norway
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Mary,
looking forward to hear what Rick has to say on the subject. Tried searching for any references to what Randy might have said, but did not find anything.
Timbo, I remember Bethwaite writing about peppering his sails with telltales in "High performance sailing", but dont remember exactly the context or results.
I agree with your aircraft wing analogy. A fuller main and a bit more mast rotation gives more power and drag, but gets you up on one hull earlier. But as we dont have a manual to sailshape, you need to know by feel and rough eyesight/experience where the limits are. I have read a lot of sailing and sailmaking books, and they all stop quite fast when they get into just what shapes are fast under which conditions. Bethwaite and Tom Whiddens book are the best I have found on the subject, but they are far from exhaustive (I guess you would need to write a book for every class of boat if it was to be meaningful).
I have found some advice I got from an old Tornado class olympian to be very good, and fast: "Put on more downhaul and mainsheet than you think you need, get your head out of the boat and go".
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#80391 - 08/05/06 12:13 AM
Re: Some advice regarding doing races on F16
[Re: Mary]
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Carpal Tunnel
Registered: 06/18/01
Posts: 10368
Loc: South Carolina
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Quote:
Quote:
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
Thank you, Ken. I was going to say something about Randy Smyth (and Rick White, too) not believing in leech telltales having any value.
But I will leave it to Rick to explain his (and Randy's) position about this. It might be a few days, because Rick is PRO for the Shark Nationals here at Put-in-Bay right now.
I was there when Randy said that and I didn't put leech tales on a main for years later because of that. It's hard to argue with expertise like Smyth and White. However, I did put them on at the mid-point last year because of some European comments I heard and I've found them to be very useful. I have people that comment on copying my downwind trim in light air because we're pretty quick downhill. In my opinion, the right amount of traveler and twist is pretty hard to get correct without more information than just the regular tales can provide. They also provide a reference to how much to sheet in upwind too. It's not that I try to get them to stream straight back all the time, but you want them to stream back about 75% of the time to indicate good flow.
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#80392 - 08/05/06 01:35 AM
Re: Some advice regarding doing races on F16
[Re: Rolf_Nilsen]
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Carpal Tunnel
Registered: 01/27/05
Posts: 5274
Loc: Sebring, Florida.
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Yes Rolf, Bethwaite's book is excellent, and he is (or was) also a competition glider pilot, he mentions that there are very many similarites between wings and sails. I'm still trying to figure out how to build a "soft" (collapsable) hard wing type sail. Maybe with inflateable battens or something? Like the C class cats but with kevlar and mylar instead of a hard wing.
Edited by Timbo (08/05/06 01:37 AM)
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Blade F16
#777
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#80395 - 08/05/06 09:34 AM
Re: Some advice regarding doing races on F16
[Re: Mary]
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Carpal Tunnel
Registered: 06/16/01
Posts: 9582
Loc: North-West Europe
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I don't think Darren Bundock or Glenn Ashby uses any tell tales in their sails and they are world champions. So maybe we need to tell Randy to get rid of his tell tales near the mast as well ?
Personally I think there are some sailors in this world who are so talented that they can sail any boat fast just by feel. This does not mean that lesser talented sailors like myself will do better by removing any aids we have and trying to imitate what these talented sailors can.
I'm personally very much helped by the leech tell tales. Like this I'm personally faster while I would be slower if I did it the Smyth/Bundock or Ashby way. So going the Smyth/Bundock and Ashby way would be downright foolish for me.
Wouter
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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
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#80397 - 08/07/06 05:08 PM
Re: Some advice regarding doing races on F16
[Re: Mary]
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member
Registered: 11/11/03
Posts: 130
Loc: CA
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Optimal = "just popping in and out" according to Bethwaite, but he assumes the reader knows what this means. I think he means supercritical: streaming aft, but with the sail trimmed in just enough that they occasionally pop behind the sail... much like Smyth's supercritical luff telltales.
Having just finished reading Bethwaite's book, I'm convinced I want to add two or three "leech ribbons" as the aussies call them. He points out that leach ribbons are a useful backup for when the luff telltales are not backlighted and cannot be seen. He does not advocate using them exclusively.
Bethwaite does have a diagram of a sail covered with telltales, but that's just to demonstrate which ones really matter: only the luff telltales.
He also mentions the fact that a properly trimmed sail will have a little turbulance due to air leakage around the leach. This is why they should be acting up a little when the sail is properly trimmed.
Bethwaite seems to advocate telltales or leech ribbons at different times, depending on the point of sail and sea state and wind strength. I'm going to have to reread to figure out when and why. However, using the two in combination seems like a great idea in most conditions because the luff telltales tell you about the size of the separation bubble (front-edge supercriticality) and the leech ribbons tell you about rear edge separation, and you want to be on the edge of both types of separation for maximum power, which requires getting the right camber (outhaul+downhaul+prebend) and the right angle of attack (sheet and traveller + helm). So, the leech ribbons do give some useful additional information not provided by luff telltales.
Also note that a small amount trailing edge separation is normal, but oversheeting increases the size of this separation, increasing drag and reducing power. The leech telltales indicate when this is happening, and large separation should always be avoided (except in light air for the bottom 2/3 of the sail...). In a breeze, you always want the leech ribbons streaming or "just popping in or out".
At least, that's my understanding after reading the book.
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#80399 - 08/07/06 11:43 PM
Re: Some advice regarding doing races on F16
[Re: Rolf_Nilsen]
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addict
Registered: 02/14/04
Posts: 461
Loc: Sydney Australia
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I believe that telltales are only necessary until you know your sail and settings and thereafter are un-necessary and even possibly a distraction. Guys like Asby have so many hours on the water, they know what works and what doesn't and they simply trim by experience and feel. For us duffers, until we reach that level of excellence, I'm afraid we are stuck with streamers 
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#80400 - 08/07/06 11:55 PM
Re: Some advice regarding doing races on F16
[Re: Berny]
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Carpal Tunnel
Registered: 01/27/05
Posts: 5274
Loc: Sebring, Florida.
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I once had the pleasure of haveing a National Champion crew for me. He spent very little time looking at my sails, which were older than most of the others out there. He almost NEVER took his eyes off the water and wind ahead of us and had me tacking about twice as much as I normally would on a lake in shifty wind. Thanks to me, we got 3 bad starts but he turned that into 3 first place finishes, all because he was wathcing the wind, called the shifts correctly and worried very little about sail trim. THAT is why those guys don't use telltales. If you never look at them anyway, why put all that drag on your sail? (Me? I need them!)
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Blade F16
#777
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#80403 - 08/08/06 03:27 PM
Re: Some advice regarding doing races on F16
[Re: RickWhite]
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Carpal Tunnel
Registered: 05/15/03
Posts: 4343
Loc: West coast of Norway
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Rick, thank you for explaining what you and Randy use and how you think about it (and thank you to Mary for bringing the topic to your attention). I am having trouble with this line of reasoning. A stall, the premature separation of flow, creates lots of drag. This drag is lost power generated in the high-lift section of the sail when you look at the sum of forces. When we stall our mainsail due to oversheeting, we can feel the boat wanting to heel over (due to the extra sideways force created by separation), but it dont want to go forward very fast. Sailing with the mainsail on the brink of stalling on the other hand, is fast in my experience. This is the trim we are looking for and are achieving when the leech telltales flick forward now and then (sail is then having early separation in the leech area some of the time, but reestablish quickly). This is especially so sub-trapeze conditions, in more wind we find it hard to oversheet the main as the wind has enough energy to follow the surface almost no matter what we do. Who is up for some two-boat testing 
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#80407 - 08/08/06 04:50 PM
Re: Some advice regarding doing races on F16
[Re: bobcat]
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member
Registered: 11/11/03
Posts: 130
Loc: CA
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I assume you mean upwind, since you hooked the sail:
Sorry to keep beating the Bethwaite drum here in the land of Smyth and White, especially since he's a Skiff (not Cat) sailor, but his flat water light air advice for Cats is to forget about the bottom 2/3 of the sail, as the only significant wind is aloft <5kts. Use a mast head balanced feather (or mast head streamer) to reveal the apparent wind aloft, maintain the upper sail 20 degrees to this apparent wind at all times, even if the skipper has to hand-hold the boom instead of using the sheet. Foot off to get some "reasonable" speed, and then head up as high as you can maintain this speed, footing immediately at any sign of lost power, and continually maintaining upper sail trim. Keep powered and keep moving, because if you stall the top of the sail it will take a long time at these wind speeds to recover (long enough for wind to pass 6 times across the sail front-to-pack). He says the boats that keep moving always win, even if much of that movement is cross wind.
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#80409 - 08/08/06 11:31 PM
Re: Some advice regarding doing races on F16
[Re: Glenn_Brown]
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member
Registered: 07/02/01
Posts: 107
Loc: Texas
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I was reading this thread concerning whether people use telltales or not. I remembered while watching the DVD entitled, ‘The Catamaran Sailing DVD’, that Ashby commented about looking at his sails while racing A-class catamarans. Well, I was bored so I went and wrote down what he said concerning looking at telltales. For what it is worth, here is what Ashby had to say on that DVD;
“It is very much a professional reflex but I am always looking at the sail to see what it is doing. I think it comes from me being coached at a very young age to look always at the sails and look at the telltales on the sail to see what is happening. I do it without thinking. Yesterday, when we had the camera on the side, it is amazing to see how many times I look at the sail. Particularly, downwind it is important to look at the sail and make sure you are getting the maximum performance out of the sail. It is very easy to be sheeted too hard and stalling the sail, and it is also very easy to be open and be loosing power.”
Anyway, I thought someone might find it interesting what a sailor of Ashby’s caliber concentrates on while sailing.
Cheers
Bob
boatless at present
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#80410 - 08/09/06 11:53 AM
Re: Some advice regarding doing races on F16
[Re: RickWhite]
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Carpal Tunnel
Registered: 06/16/01
Posts: 9582
Loc: North-West Europe
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Drag is not always directly related to the creation of lift. Seperation can and will also occur in area's with insignificant lift productions. Especially in light winds where the energy enclosed in the boundery layer may well be insufficient to traverse the pressure increase that is present near the leech. On this theoretical ground I reject the line of reasoning followed, that in addition to the experiences I gained so far in real life sailing. Quote:
Think about it. Why do you suppose modern sails have gone from low apect ration to tall, skinny, high-aspect ratio sails?
Because high aspect ratio sails have a lower Cd (drag) coefficient for the same Cl (lift)coefficient, however at the expenses for being more easily stalled and more sensitive to trim. And because in light winds their is significantly more wind further away from the surface, the is more kinetic energy in higher wind layers. This tops out at about 10 meters above the ground. In 5 or less knots of wind it is not unusual to experience twice the windspeed at the top of the mast then a 1/3rd the mast height.
Quote:
Because the leech of the sail is not nearly as productive as the area that creates the lift.
This is simply an wrong way of looking at things. The luff and leech parts of a sail interact directly with eachother and combined result in a given lift and drag situation. Removing either one will completely alter this setup. Example; you can seperate both regions as if they are completely independent of eachother. Remove the leech part and the luff segment will not at all act the same as before and the lift produced will collaps.
Therefor a properly working leech region is key, just as the luff part; its role is however different from the other segment. Pretty much the luff segment is most concerned with creating high lift by creating large suction zones, while the rear part is actually the part that reduces drag to such a level that the Cl/Cd ratio is efficient.
Quote:
Jet wings are much more high-aspect say than a DC 3.
And this example can be totally put around to combat your comments. Sailboats are much more like a DC3 then a modern high velocity (0.9 Mach) jet airliner. Ergo we should look more to the DC3 then the modern Jetliner. And as a matter of fact we do. Our mainsail aspect ratios are much more comparable to the DC3 than of the modern airliners.
But more so the operating conditions of the sailboat mainsail are still well removed from the DC3 Operating conditions which is still MUCH close then those of a modern airliners. Looking at these aviation examples is therefor of very limited use.
Anybody interested in more will do well to read bethwaites book for starters.
Wouter
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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
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#80411 - 08/09/06 11:58 AM
Re: Some advice regarding doing races on F16
[Re: Glenn_Brown]
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Carpal Tunnel
Registered: 06/16/01
Posts: 9582
Loc: North-West Europe
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Yep that is what I'm finding and the leech tell tales are always the first indicators that I'm loosing speed and power and that is why I value them so much in these conditions.
Wouter
_________________________
Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
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#80413 - 08/21/06 04:22 AM
Re: Some advice regarding doing races on F16
[Re: Rolf_Nilsen]
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old hand
Registered: 07/24/06
Posts: 1147
Loc: Bay of Islands, NZ
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This understanding has always worked for me.
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