Sail setting and sailing techniques

Good to see you out there in the cold, Arjan.

What I see is that on the problem-direction the mainsail is opening more in the top (so pressing the bow more downwards).
It also looks that in that direction the mast rotation is more then on the other side. (But I don't know if there is a setting-difference on the Inter for both sides.)

Anyway it is a clear and visible problem you have there.

the video is good. A couple of things:

1) it does not look like you have enough tension on the forestay and the jib luff. Rigging tension looks soft but this could be because you are not sheeting hard enough on the main sail.

2) you are not sheeting hard enough on the main sail - not close...not by a kilometer. I normally control the mainsheet while driving and with a 10:1 sheet purchase in that kind of breeze, I have two wraps on my hand as I bend my legs and I put the finishing touch on the mainsheet tension by extending my legs with everything I have. crank it. The leech of the mainsail should be very tight and you control the twist with the downhaul.

What is happening with the loose mainsheet is that as the boat pumps the rig as you go over waves, different areas of the sail are picking up slight shifts in the wind as the sail

tomahawks

. With that much twist, the top of the main usually starts to get more power as the boat slows down into the next wave - this causes the driving force to climb higher up the mast which turns into more pressure on the bows and drives them deeper. The F18 has a lot of sail up high - you need to contain it in breeze and waves.

I am not the expert, but for those wind conditions, I would consider:

Overall rig tension: Seems like the forestay and jib luff are sagging a bit too much to leeward. My understanding is this tends to create more draft in the jib resulting in lots of drag and heeling moment up front.

Mast rake: try moving the balance of sail power further aft.

Outhaul: Should be pretty tight for those wind conditions. You want the mainsail flatter and more efficient (less drag).

Downhaul/Cunningham: For this wind, should be really tight as well to flatten the top of the main. Loosen if you're not able to fly a hull.

Also...since you are now using a new jib and a new self tacker, make sure there is enough of a slot between the jib leach and mast/backside of the main. If the jib is in tight but the main is out, you will choke off the flow from the jib to the backside of the main.

If the slot is closed off, or too small, this will cause the feeling that you are overpowered, but not going fast, as you described above.

If you are not sheeting the main tight enough, as Jake said, that will close off the jib/main slot as well.

The quick and easy fix is to ease the jib a little, and sheet in the main, that will open the slot. See if that helps with the speed/overpowered feeling.

Arjan I concur with Jake and Jeff's suggestions above.

A few things:

Mast rake depends on crew weight. In those conditions if you attach a line to the trap wire, take the wire forward to the bridle attachment point on the hull, mark the line, then take it aft to the rear of the hull you should be about half way down the transom. Further forward if you're two big guys, i.e the upper rudder pintail.

Tension your rig by putting one guy on the trap wire, yanking hard and moving the sidestays. Both stays should be even at the end.

Which boom system are you using? Round or square? On my Infusion the outhaul places the clew of the main about 2" from the stern end of the boom. I basically leave it tight unless in light air. The main sheet connects to a strap that runs through the sail and around the boom. Basically you are putting 10:1 sheet loads directly on the leach of the sail. Like Jake mentioned, sheet in, get both guys on the wire and start trucking.

Let the jib traveler all the way out in heavy air. It's experimental on the crossover for traveling in some.

You probably need more downhaul than you think. Hard to say with a loose mainsheet. Sheet hard, take excess power out with the downhaul then start playing main in the puffs. I let the crew have the main upwind in breeze if they are responsible.

I'll point out again you need to check your side stays are equal. That would explain the more bagged out jib on the opposite tack, i.e you've lost forestay tension because your port side stay is looser than your starboard side stay.

Also, may need more jib downhaul but it's likely forestay sag in the video.

I'm pretty sure that's an inter18

An issue may be they are using the main sheet with the fixed points on the inter18 boom. it may be too long/too short to properly apply main sheet tension to the leech of the new F18 sail. The main should be attached to the loop they are using to attach the clew to the boom.

are they beam or broad reaching? with the main that bagged out, you'd think it's about time to hoist the spin?

Rig tension does look a little slack...

Is your traveler centered? Can't tell because the jib is blocking the view. It may help to reduce the draft of the mainsail by sheeting in (a LOT more) and moving the traveler to leeward a bit more.

If you're getting overpowered, you can drop the traveler some as well (when you're beam reaching)

You need to work slowly and sort out one or two things at a time. Start with rig tension. After checking the stays are equal tighten the rig until it becomes hard to rotate (by hand) the mast to 95 degrees

Next is the outhaul on the boom.

Point your mast spanner (rotator) at the side stays and pull your downhaul, traveller and mainsheet on as hard as you can. Now pull the outhaul on as hard as you can. Tie it off there and until your on top of everything else just leave it.

Jib traveller takes a bit of playing. Most people sent it for upwind andleave i there (kite is more important down wind) and on modern courses we don't do much reaching. The basic setting is achieved by cranking main sheet, traveller and jib sheet and the adjusting the jib traveller so that when you pinch up the windward wind indicators on the jib lift just before the ones on the main.

Reaching on and F18 is quite difficult as the boats and sails have evolved away from that point of sail. You need to really drive the boat. If it is being flightly pull the centreboards up a bit. You also need to be be able to properly control the main without moving too much sheet. This is achieved by using the traveller.as a gear stick and the main as an accelerator. When viewed from behind your main sheet should rarely be more than 20 degrees of vertical.

Nothing about 'playing' the main downhaul, for the crew, as in the puffs?

Thank you all for your very useful comments! Yesterday we went sailing again, and we've checked the tension in the rig (there is enough tension we believe) we did try to pull the downhaul with tension on the sheet. Indeed this gives a little more (we didn't know to do it this way) This way we flattened the sail out while on shore.

Then we went sailing (but with 14 knts) the boat ran very nice, and no problems at all. So we believe you're right! We need to put more power on the main sheet with more wind. This kind of sail apparenently does not accept to sail it more

relax

(the old Inter sail was more capable of that)

Of course we have to try it with more wind, and when that day comes, I'll come back on it.

Worrying about basic setup at this stage, not techniques.

http://www.youtube.com/watch?v=3ZQq5ra8uec

This is what we did yesterday, but as you can see with less windy conditions

Nice vid, looking good

Sailing is my passion and I love to do it.I am not an expert but highly motivated to get trained and learn all the skills required.Thanks for good stuff specially for me.

We tried again with a strong 5 bft last week. It's not yet fantastic, but it looks a lot better thanks to all your tips!

Thanks...

Ok, after last saturday we've learned that we're not quite there yet. Still it's a lot better, but in stronger wind (gusts around 20 knots) and only on a reach course (is this good English?)we feel the boat want's to dive in the water with it's bow. When sailing closehauled we have no problem at all, the same with the spinnaker. Only sailing somewhere in the middle we feel this, and only with stronger wind. Could you please comment the following if this is right with about 17 - 20 knots?

- At this course we're standing all the way on the back. The helmsman with one foot on the other site of the beam, standing close together trying to hold the boat in a diagonal way

- The traveler was 1/3 th out

- Downhaul couldn't be any tighter

- Main --> blocks together

- boards half way down

- jib tight and all the way out

Halfway the day we decided to try to set the mast a little more backward. We changed it by 4 holes, but it seemed to help only a little. Next time we want to have a look at the spreaders (we never did after buying the boat) we do not know if there is a lot of change possible.

Or is this boat behavior normal in these conditions?

Arjan, though not being the expert on trimming, I remember me a case in which I had a sail which did't fit with the mast.

That looks a bit on your situation. Sailing with two men in 20 kts, should be no problem. Also not in half-wind (the official English is

reaching

, but here on this forum they like to speak of jib-reaching or beam-reaching).

It seems to me that your sail cannot loose all the wind in it, which results in an (inefficient) force forwarddown. In fact it's a twist-problem.

So, take your sail one time on the ground with you holding the cunningham hole and your mate holding the top of the sail and stretch out (but not so far that the sail is curling upwards).
Then you take a rope and make a straight line also from the top to the cunningham. You can now see the pre-cutted luffcurve of the sail and also measure how much it is on the deepest point.

If this curve is too deep for your mast, you have a problem.

So, in that case I would certainly give the mast much more pre-bent with the spreaders. (For your cat I don't know the appropriate figures for the pre-bent and the prescribed luff bent in the sail.

Last but not least I would fix the mast-rotator to zero.

Arjan please read this thread: http://www.catsailor.com/forums/ubbthreads.php?ubb=showflat&Number=259280&nt=3&page=1

Twin wire jib reaching is the most difficult point of sail. You need to drop traveler and the crew should be playing the main sheet.

@Northsea

Mast rotating was indeed as tight as possible. And what you describe here is a little bit where I'm afraid of. But reading your input, we might be able to fix it a little.

Just to be sure: After measuring the sail in this way: I suppose we measure the mast in the same way? (with the rope?)And the aim of the whole exercise would be to get it as close as possible?

@ Sam

Yes I'm starting to realize the subject of that topic is rather the same, but didn't understood that before because of the terms used (e.g. jib reaching) I will read it!

You can do the measurement tricks but I'd start with your spreaders 50mm aft of the mast track as noted in the Nacra Infusion setup guide (yes I know it's a Inter 18 mast that is likely carbon, I don't have numbers for those). You want your diamonds cranked close to 43 on the Loos gauge if you're in big breeze.

Finally you might want to talk to your sail maker some about the measurements of luff curve.

Arjan, yes you can measure the prebent of the mast also with a rope from the top and then charging it with your weight in order to get the mastcurve under sail-load.

But remember there will always be (and it ought to be also!) a difference between your luffcurve of the sail and the mastcurve.
Exacly this diffence creates the (so-called external) camber of the sail. In other words, this makes a (vertical) wing of your sail!!

So the sail is always rounder then the mast! But not too much ! (around 5 cm difference is common, I believe)

By the way, in windsurf sails there are even sails who don't have any internal-camber (curving the sail by the sewing of non-linear seams) and get their profile purely out of external camber.

Twist in windsurfing sails is the most important factor.

Is the crew astern of the helmsman?

From what little I know of jib-reaching in higher wind on

short

boats (under 6 meter), flat is fast...

Boards up 1/2 way or higher (depending on water conditions) and both crew as far back as possible.

Sometimes the crew can get astern of the helm...sometimes (Alex & Nigel could figure that out). All that weight in the back helps keep the bow out of the water...

Traveler out a bit and mainsheet in hard. Both should be ready to ease at a moment's notice if the bow dives into a wave.

I guess the real debate centers on any steering change during the dive... should you steer upwind to depower, or downwind to change the wind angle?

No the crew is not astern of the helmsman. We never tried this. Seems a little difficult while the crew is handeling the sheet? (don't know if this works out)

But I do understand from the reactions that far back is normal here. (even a little bit further then we did)

But a question which I still have left is: When you are in strong wind, and the boat is constantly lifting (have to give a lot of sheet getting it down) What do you do first? get the boards up, or putting the traveler more out?

If you are reaching, you don't need the boards nearly as much - raise them half way for a reach regardless of power level (unless it's really light). The traveler will probably already be down some - but keep dropping it to try and control power. You still want to try and flatten the mainsail as much as possible with sheet tension.

I believe if you have to sheet out (mainsheet) more than about a full arm-length of line during a

lift

(or puff), you should adjust the traveler down a bit.

Of course, if conditions are really harsh (like huge puffs), you just have to work it as best you can with combination of travler, sheet, and steering.

Besides the fact that most probably we have to search in our own sailing techniques and boat settings. This week we measured the old set of sails with the new ones. We did it with the line as described by Northsea, but we also put them on top of eachother and individually put some force on it. Now you can see that the main indeed differs from the old one, but to our surprise the new sail has a little less luff curve than the old one. (allthough the difference is only a few cm's (about 3-4 at the max)There is only a difference in the 2nd half of the sail Measuring with the line shows that the total curve is over 10 cm.

The difference between the old and new jib is bigger. We came from an original jib, and replaced it by a self tacking jib (much smaller) The jib is identical top down, but misses the last 20 cm's. (this is normal with self tacking?)

After that we measured the spreader, and measured 55mm, which could be right reading about the infusion settings and our relative low weight. But is this also right for the Inter? Is there anybody who can tell?

After that we wanted to adjust the tension on the diamant wire. But this wasn't used for some years, and therefor got stuck a little. Wew had to put some force on it (only little) but doing that the whole connectionplate came out of the mast. So we have some renovating to do.

Arjan, so the upper half of the top of your new mainsail is a little flatter then your old sail.
I'm puzzeling at this moment what consequences this could have. It's in the part of your mast which is not supported by shrouds anymore, so the part that bents.

Overall you measure about 10 cm luffcurve; that's not a wrong figure. But it depends ofcourse of your mast.

I used to sail to sail on a (soft) P15 mast a mainsail with 15 cm curve. But then I changed to a sawn-off P18 mast which was very stiff (curve 1,5 cm). I modified the sail to 11 cm curve, but it was still far too much.
Now I sail with a main with 7 cm luffcurve and that's perfect.

This doesn't help you much but give you perhaps a little bit of feeling for the figures.
The difference between the mastcurve and the luffcurve of the sail is considered to be one of the secrets of the sailmakers; they all use their own secret number. It is indeed about centimeters.

Maybe your top cannot open enough?. Looking at your original video of this thread, I see less twist in the upper part as compared to my sail. I know that a lot of sailors think that a flat and tight sail is the best. But without movable waterballast like on the Imoca boats, twist in the sail is our only safety valve for overpressurizing the sail.

As you can see in the little vid which I placed in the thread about jibreaching, I have (at the ingoing course) also difficulty too to keep my leebow not to be burried in the water.