Thread: GIS sail tweaking

Originally Posted by callsign222

Also, since I got my telltales I'm much more neurotic about not sheeting in too much, but sometimes to get the telltales to fly correctly, the luff now luffs, which has always been a huge huge no-no in my book.

Should I sheet in enough to keep the luff from luffing but the telltales suck to the other side, or do I ease off to fly the telltales and accept some luff, especially around the throat?

I also think my sail is getting tired.

Luff luffing when the leech telltails are streaming but conversely the leech telltails sucking onto the lee side when the sail is sheeted in enough to stop the luff luffing?

To me this is an indication that the sail is too full for the conditions and needs to be flattened?

Or is it that the leech is getting hooked as the sail gets tired?

Be good to get Mik or Woodeneye's take on this.

Ian

Originally Posted by warm beer

If I can't get rid of my upper leech flap, then my sail is going to die an early death I think. I really stared at it closely on Saturday, trying to figure out what causes it, and ways to limit it, and the best I could come up with is that it's caused by the yard flexing both down and out at the peak, and that maybe I might have some luck if I vary the tension of the lashing along the yard to compensate for the yard curvature, using individual lashings, instead of a continuous lashing. I read about this, I believe, in Keyhavenpotter's skow tuning discussion. Either that, or go to a stiffer yard, but like you, I sail in the ocean, and have come close a couple of times to getting dumped when the wind passes 12 knots or so, and rail hiking three miles out by myself does not seem like a wise option. Having a bendy yard is a nice safety valve! If I had my choice, I would keep the bendy yard, and have a way to eliminate the flutter, as it's loud, annoying as heck, and looks bad .

Maybe worth looking at where the halyard loop on the yard is attached. Moving it a bit towards the peak might tension the upper leech more and stop it flapping. Worth a try, but the important thing is to mark where it was so you know which way and how far you moved it and can keep it there once you get it right.

Ian

Great idea Ian! I'm lashed at a little less than 50% right now from throat to peak, towards the throat that is.

Originally Posted by IanHowick

Maybe worth looking at where the halyard loop on the yard is attached. Moving it a bit towards the peak might tension the upper leech more and stop it flapping. Worth a try, but the important thing is to mark where it was so you know which way and how far you moved it and can keep it there once you get it right.

Ian

This is a great idea!


I adjust my attachment point depending upon how many reefs I have in or not. I probably moved it too far forward when I raised my sail yesterday after the Isles of Shoals trip.

Originally Posted by callsign222

This is a great idea!


I adjust my attachment point depending upon how many reefs I have in or not. I probably moved it too far forward when I raised my sail yesterday after the Isles of Shoals trip.

Hi callsign, as you reef more deeply, which way do you move your halyard attachment point - towards the throat or towards the peak?

I've gone to second reef without moving my halyard attachment on the yard, it seemed OK to me, but of course we're talking different sails and yard stiffnesses.

Thoughts on post #392 also appreciated.

Ian

I just tried to find the video again.

Flapping is usually WAY less damaging than its opposite - which is a cupped leach from it being too tight in that area and cupping badly

Is the peak eyelet snug against the mast? I am pretty sure that it wouldn't be lifting off the surface of the yard because you are careful about that. but that would add a little more looseness to that upper area.

or is there a downward kink in the yard at about the next to last eyelet. If there is it could be worth rotating the yard and relashing the sail. But I'd expect it to be a vissible kink for this to be needed.

Or maybe the second to last eyelet has rotated around the yard a bit rather than sitting on the underside - so it is too high and taking too much of the tension (this is unlikely ... but easy to check.

A little test specifically to see if it is local would be to redo the peak lashing so the sail is actually pulled up higher now by going up beside the yard - you would have to finesse the lashing to make that happen. This will make the sail a little fuller on one tack and flatter on the other ... more a diagnostic tool to see if the flap goes away with the same adjustment a relatively minor recut would give you.

Flapping is annoying, but it is not super critical. We are talking less than a percent off the performance and no bad effects on leeway and pointing angle and early stalling that a badly cupped leach would give you.

MIK

Hey Mik,
I'll try to change the lashng to diagnose.
I showed my Dad, a lifelong sailor, and aeronautical engineer, my leech flap video. He said the same thing you did - the leech flap is not detrimental to performance and it looks like the sail is "pumping", which is not a bad thing. I guess I'm being picky without reason? Of course, I had to get a second opinion. You know ... who listens to their Dad? )

I had my yard off a month ago, and it is very straight, so no kinks. The peak eye is held snug under the yard, but not pulled up beside the yard, and the peak outhaul is rigged to pull along the bottom of the yard, not up. The lashing along the yard could be looser, it's snug from the second eye in in both directions. That's what I'm going to try - individual lashing that allow the sail to sit just below the yard, with the sewn-in yard luff cord up against the yard.

Here is my leech flap video, if that is what you were looking for. I should mention that the stronger the wind, the more vigorous and continuous the leech flap gets. The video is shot in ten knots of wind. By fifteen or more, it's really going off. Sounds like a flag in a strong wind.
[ame="http://www.youtube.com/watch?v=fwTGow0V44M"]leech flap - YouTube[/ame]

I had a really bad leech flap last year. Loud and annoying.

I had completely forgotten about it because it is gone this year. Just gone.

It could be that I lashed the sail differently -- I did re-jig the yard outhaul so I could get more tension there. Or it could be that I have the halyard attached a little further back this year. Or it could be my beefier downhaul.

It certainly wasn't anything conscious. I wish I knew what fixed it.

Back to your note about the allowing the boom to lift when sheeting out in stronger winds and how this doesn't de-power the sail as you want it to. My wife and I were out in some heavier air last week and ran into that situation. I had eased the downhaul while we were on a broad reach and forgot to tighten it for the ride back. We hit a puff and I let out some sheet and we almost went over. As soon as we were stable again, I hauled away on the downhaul and got the sail nice and flat. I was then able to dump air much more easily, making for a calmer beat back to port. As far as I'm concerned, the effect is real.

Originally Posted by warm beer

bothersome. I know this is a poor description, but suffice to say, it's better to rig your boom clew end sheeting like Gruff was rigged (spaced).

To see the vangouthaul, check the vid I just posted. I wanted to be able to adjust my outhaul on the fly, so I ran it under the boom to a block aft of the mast and down to the deck, through a 3 to 1 block arrangement. It works great, and has a secondary quality of providing a bit of vang (good), and the tertiary quality of adding to my boom bend (bad). Hence the creation of "the slab" was paramount. I use the vangouthaul all the time. For pointing in fifteen knots, I had it cranked tight, and left it that way when I fell off the wind for awhile. When I did let it go, (it has a stop), I swear that the boat was a smidgen less happy, as a gust created lift in the sail (vertical lift) and heeling force , (just a smidgen though, hardly noticeable), while with the outhaul tight, and downhaul still tight, a gust only pushed the boat faster with no change in heeling force, as the sail was being held tight as a drum and could not billow.

Sorry if I am repeating this ... I can't remember if I wrote about it recently or not.

Combining outhaul and vang might have some repercussions in strong winds and rough water and downwind.

In general if you have rough water and are going upwind you want some depth in the bottom of the sail ... that's where the power needs to be. Then the top of the sail can twist off and flatten in the gusts but the bottom of the sail will give power to crunch through the waves without too much slowing.

Even in moderate winds some depth in the bottom of the sail gives you extra power but without much extra heeling. We are all a bit influenced by having a jib, which is allowed to have similar depth in the bottom as what I am talking about (correct for any front sail) but then we get visually influenced by the mainsail on a sloop needing to be relatively flat at the bottom because it is sailing in the "header" created by the jib.

But the main on the goat needs to be trimmed more like a jib because it is the front sail on the boat. So same sheeting angles (approx 10 degrees) depth in the foot most of the time and control of twist to get the tufts to fly (or leach ribbons to fly - I've found them more reliable than the tufts on a lug rig).

Also reaching .. when the sail has attached flow ... the tufts and ribbons flying ... the normal depth for the bottom of the sail is about 1 in 7 depth to chord. But with this you generally need good vang pressure as it helps move that depth up into the mid body of the sail as well and usually you don't want much twist - or at least the right amount for all the tufts to work together.

downwind with stalled sails the system will work well because the sail needs to be flat and untwisted to maximise the projected area. Sailing by the lee is also supposed to be good at keeping the main relatively untwisted by one or two articles on the net. Though I am not sure why (any ideas Bruce?)

MIK

Originally Posted by IanHowick

Hi callsign, as you reef more deeply, which way do you move your halyard attachment point - towards the throat or towards the peak?

I've gone to second reef without moving my halyard attachment on the yard, it seemed OK to me, but of course we're talking different sails and yard stiffnesses.

Thoughts on post #392 also appreciated.

Ian

I move it aft, towards the peak, it makes things easier-- keeps the yard closer to the mast with less swing, keeps the end of the boom up a little bit more. Just seems to work better in my experience with my set-up.

I'm waiting for thoughts on post 392 as well.

Hey Paulie,
Cool, there is hope! Do you have a dw sail too? Can we hypnotize you so that you can recall what you changed?

I believe the boom lift - power up - on sheet out concept totally. I just was not experiencing it on Sunday, when I had my downhaul and vangouthaul on really tight. Interesting that you noticed it quite a bit with your downhaul loose.

Mik,
Yeah, my vangouthaul is not even close to ideal as a vang, but it is a nice secondary consequence of how the outhaul is rigged. ... and I could not figure out any other way to rig it. Thanks again for the sailing info, I truly appreciate it!! I am putting leech ribbons on my sail for the next outing.

post #392?

Yes, I see your point. Because the distance between the boom and deck is variable the outhaul might have to be adjusted for every downhaul change.

However ... just thinking through ...

Option 1 - keep the cleat for the outhaul on the boom. I would probably go for this because it fits my simplicity ideas. But there is a neat way you can set up many sail controls to be faster adjustable.

You have the line coming forward from the outhaul (or any other control line) Run it through something like a CL-211mk2 cleat.



Then slightly over one hand width behind that have a small pulley on a saddle. The control line is also fed through that. Figure of 8 knot in the end.

To pull on you can grab the control line behind the pulley and pull from almost anywhere in the boat.
To release you grab the rope between the cleat and the pulley and yank dowwards which uncleats the cleat and at the same time puts the rope in line so it won't recleat.

Option 2 - which might be a better choice as I can see you want it to hand ... have all the mechanical purchase for the outhaul on the boom but drop the single line down to the deck as vertically as possible to near the downhaul fitting. This way if you adjust the boom up or down with the downhaul by an inch then the outhaul would need to be adjusted the same amount. HOWEVER if it then runs through the multiple purchase on the boom then the outhaul movement will be reduced by the factor of the mechanical advantage on the boom.

So say you pull the boom down 25mm ... the outhaul control line will ease by 25mm but because it leads to a 4:1 mechanical advantage the actual movement at the outhaul will only be 6mm. or 8mm if the mech adv is 3:1

With both systems for the outhaul I would either put a knot in the rope or limit the outhaul itself so that at maximum release it hits the 1 in 7 depth for reaching with attached flow. So there is one setting you just don't have to think about - release and you are ready for reaching.

MIK

Can I be forgiven if I call it the vangouthaul?

Checked my current yard lash point:
total length throat to peak is 128"
current lash point is 57" from the throat

I used to have it lashed at 60", and moved it down to see if pointing improved. I have the flutter at both locations (57" and 60")

edit:
pictures of my traveller - loose for trailering, tight for sailing.



picture of gunwale car door ding protector



pictures sailing on my families C&C 35, that my uncle now owns, during our trip to NY. He changed the boat's name from "Vayu" (hindu god of the wind) because a phrase that sounds like "vayu" has negative yiddish connotations. It is now named "Delicious", though in my mind I have renamed her vayu-licious. I have many happy memories on board this boat - racing in the Chesapeake, sailing up to Newport RI for the Americas Cup, and the Tall Ships, and cruising the Bahamas and Florida Keys. It was incredibly cool for me that my kids were able to sail on her.




(that's my uncle at the helm chasing down another club boat. yes, I took for a spin)

edit edit: Can we add yard lashing locations (distance from throat) to the wiki? with matching sail manufacturer name.