How can I get my square top to give way? In my last sail, and everytime I go out, I have noticed the square top main is not really giving way in the gusts. In other words, I notice that it is pretty tight. Also when I sheet in, I notice it will get even tighter and NOT move. What can I do to have a nice curve in the mainsail, and get the top to bare off just a little bit.

Tie it in looser?
Get a lighter/thinner batten for the top?
Leave the top batten out entirely?
Ask the sailmaker (or any sailmaker)?

Tie what in looser?

Why I should I have to change what came stock on the boat? <-- this is going off, what you answered me when I asked about the adjustable trapeze lines.

That wont do anything, just make the top flap around.

I would if only I knew one, hence why I posted it here.

Tie the top batten in looser.

Changing battens -- stiffer or more flexible -- or shaving battens or whatever you have to do is common practice to get the sail shape you want.

As far as leaving the top batten out entirely, I was kidding, but actually if it is very windy, that is not always a bad thing (sort of like reefing from the top). But that would be a radical alternative for radical conditions.

As far as asking the sailmaker, I assumed you know who the sailmaker is who built the sails for your boat and can e-mail to ask advice. Matt would know.

P.S.
Another thing you could do is put the top batten in backwards, so the soft end is toward the back.

And you already know that usually downhaul makes the top of the leech fall off to leeward. So if downhaul is not doing it, that is what my other suggestions were about.

If you lay your boat on its side and sheet the sail in tight, you can see the effect that downhaul has on the top of the sail, even though you may not be able to see it when you are actually sailing.

Mary is right. Increasing cunningham tension pulls the max draft of the sail forward and opens the leech especially at the top of the sail. A stiffer top batten will improve the gust response of a square top main and allow the top to open and twist the leech. Most importantly, your sheet tension will have the greatest effect on sail twist.

Glad to hear that 701 is back.

Yeah, John, you are right. A really stiff, untapered batten up top would probably do the job of depowering, too. Personally, I would vote for a soft batten -- more like how a bird's wings work out at the wingtips.

Sorry Mary, I prefer the control that a stiffer batten will give. A soft batten can be unpredictable in medium breezes and allow the leech at the top of the sail to hook or even allow the whole top quarter or so to bowl and cause turbulence and drag unless the sheet is eased.

I've always found that flatter is faster!

So I flatter top would be better? I always thought a top that would bare off in gust would be better. Now I am confused.

Flatter top in light = good?
Flatter top in heavy = good?

Which one is it? Obviously I really need to sail more often to see what works best, but it is always good to have these discussions.

OK - you understand that if a sail hooks that is bad

Therefore a sail that has a SLIGHTLY open leech at the top is good. If the top is slightly open the rest of the leech all the way down to the boom on a correctly cut sail will not hook to windward.

I prefer to make sure that the top will open early by having the top batten stiffer than the others. In light weather (<5mph say) you want the sail twisted slightly - achieved by little downhaul tension, and little sheet tension.

In a medium breeze you want the top working and the leech standing up to allow you to point higher. Fair amount of downhaul and loads of sheet tension.

In a really good breeze you want the top to flare in the gusts, so loads of downhaul and as much sheet tension as possible without being overpowered. BUT if you are being overpowered then let the traveller off-centre (2-3 inches should be enough) and don't point quite so high - go for speed. At this level of wind the stiff top batten should be flaring automatically in the gusts - 'gust response'.

Hope this helps.

You should also check your mast pre-bend (and spreader rake). Vectorworks or Phill can probably give you some numbers to check against if you haven't got them already.

Well,

All the things that Mary suggested I would NOT do. I'm sorry Mary but you just dispensed with alot of bad advice. Most of it will do exactly what you don't want. Robi should neither shave his battens nor put them in backwards. More flexible battens will only introduce more camber in his sail and probably have his leech hook. Putting a batten in backwards will create turbulance in the front part and have his leech hook really badly. It is all just bad advice.

Robi, I have a similar sail as you (made by redhead sails Australia), of course Matt uses the same sail as you have. Matt and I are walking different ways in order to get the behaviour we want. But there are a few basic thing you must take note off.

F16 sail quite fast and the apparent wind can lay very close to the direction you are sailing in. Don't expect a huge amount of twist nor very big gust responses. Both must be noticeable but especially upwind the difference between a correct twist profile and a wrong one can be as little as 4 to 6 inches at the top of the sail, that is 28 feet up. A top that has been completely weathervaned off while going upwind will only twist off by 10 inches.

Before you start working the trim controls and setting you must make sure that all battens have just enough tension on them to prevent creashes forming around the batten pockets in any and all winds. If you don't do this than the most normal reaction is to start pulling the downhaul till all the creases are out. However this can easily lead to a sail that is both too flat and that has a leech that falls away to far. The next reaction is to pull on the mainsheet to make the leech stand up again. End result is an additional flattening of the sail, probably too much. Currently this is the case with my Redhead sail. I hardly pull on the downhaul at all as that kills my sail. Other Redhead F16 sail users are reporting that they are using reasonable amounts of downhaul. You'll need to find out what works for you.

Also you must not overdo it on the outhaul (foot tensioning of the mainsail). Completely flat is slow and hurts pointing, too full quickly give excessive weatherhelm. About an inch of draft (at the max point) on the foot seems a good starting point. This should not give weatherhelm nor hurt pointing.

But assuming your battens are at the right tension and your foot is set right than the two major controls for your mainsail are ; mainsheet and downhaul. If your spreader rake and prebend are right, or at least close to it than you must remember the following two characteristics.

Mainsheet : When pulled will flatten the top (Most) and middle (less) of the mainsail and make the leech stand up.

Downhaul : when pulled will pull creases out, pull point of maximum draft in the sail towards the mast (forward), flatten the top and middle part of the sail and make the leech fall away

So both mainsheet tension and downhaul tension make the mainsail flatter in the upper and middle regions while having opposite reactions in the position of the leech.

It is important to note that you can get any fullness of the mainsail while keeping the leech postion (twist) constant but simultaniously pulling (slacking) on the mainsheet and downhaul. This also makes clear that there are always two ways to make the leech stand up more on a F16, being :

-1- pulling harder on mainsheet
-2- pulling less hard on the downhaul

Which one you should use dependents on the conditions and the preceding trim. Important to note here is that pulling harder on the mainsail is NOT always the best thing to do. In several circumstances keeping the mainsheet tension the same and releasing the downhaul a little bit is the better action.

Learn the sail with this complexity and availability of difference solutions. We sailing F16's, not Hobie or Prindle 16's.

By far the most effective tool to introduce more twist is the mainsheet. The effect of the downhaul is in my experience relatively small. I tend to look for the right twist first and than adjust downhaul and mainsheet proportionally to get the creases out and/or get to the right fullness of the sail for the given conditions.

Be careful not to walk into the trap of ever increasing both mainsheet tension and downhaul. The twist will remain the same when both are adjusted proportionally but you'll lack power and pointing because your sail will be trimmed to flat. When the boat is flighty and lifts rapidly in the gusts than make the main flatter by first pulling on the downhaul and when necessary also pull on the mainsheet if the leech falls away to far. Take note however that no amount of downhaul can have the top fall away when you have applied a serious amount of mainsheet. The downhaul is just too weak of an adjustment to do so; at least in my own experiences. Ergo, the mainsheet is the best and most potent control for the twist in the leech. This is also the reason why I wrote that it is easy to oversheet the mainsail. If you have done so than there is no better choice to get back at proper trim (twist) than releasing some mainsheet tension. Forget about shaving battens or putting them in the wrong way. The total effect of all of these falls well short of what can be done with the mainsheet alone.

But mainsheet has its limits as well. Because mast prebend can be wrong and than adjusting the mainsheet will not have the complete desired effect. When you have to much prebend than the middle of the sail will look flatter than the rest and its leach falls away taking the top (and squaretop with it). And the otherway around. Sadly several of us are still working out what the best prebend it. Especially with the new F16 mainsails. I'm sailing with 27 mm prebend at this time and I'm serious considering reducing this to 20 mm or even less. Some other is sailing with 50 mm of prebend which is twice as much as I have and this is ALOT. Glenn Ashby was sailing his Taipan with 15-20 mm prebend in 0-10 knots of wind, 25-35 mm in 10-15 knots and 35-40 mm in 15 knots and over. Phill Brander is at 30 mm prebend I believe. Mainsails can differ from one-another even when made by the same sailmaker; so this round of trial-and-error we all need to go through.

More later. Have to go to bed now

You lose the effective drive from the top of the sail through "tip vortex" anyway (regardless of the cut or shape) so the object of the shaping at the top of the sail is to reduce "drag" as much as possible, and the best (and only) way to do that is to have the top of the sail flat. The principle of the square head is not so much to add area but to "flick off" to leeward in the gusts thereby reducing heeling moments and increasing the ratio for forward movement, in so doing giving you more control of the directional stability of the boat. The weight of the top batten is not really important as long as it keeps the head of the sail flat. To make it "lay off", is controlled totally by the amount of luff tension that is applied to the sail. If it will not lay off regardless of how it is set up, then there is an incompatability in the cut of the sail with the mast, usually there is either to much luff round cut into the luff, or the mast section is too stiff for the luff round in the sail.

There ar three "golden rules" for the shaping of a mainsail that should always be remembered as "the basics"
! the luff tension controls principally the top third shape of the sail
2 the mainsheet controlls the bottom third of the mainsail shape and the "straightness"of the leech (not the roach that is totally dependent on the battens))
3 the middle third is a "static set" that is predetermined by the amount (or lack there of) of the diamond tension.
These are the basic "set up" controls for the mains'l.
When sailing, all of these control effects can be "tuned" and adjusted by the inter action of the mast rotation the mainsheet traveller, and the foot outhaul. The effect from the combinations of all these controls is enormous so there is a fourth, and most important rule of all - never make radical and/or multipull control changes together as you will never be able to assess accurately the results of the changes but instead only make small incremental single control changes and assess fully its effect before going on to the next "experiment"
Regarding the "flick off" of the square top sail, less rotation of the mast induces easier and sooner twist off of the head of the sail.

Definately agree Daryl, If you're not getting enough flick off of the top of the main then pulling the mast rotation in will fix that to some degree and would be the first thing I would try in combination with more downhaul.
More downhaul also allows the sail to flick more open at the top so give that a go as well.

You're really only looking for flick to start happening when you are pretty well powered up and have a fair amount of downhaul on anyway.

Sorry, Wouter. I didn't know I was giving advice. I just asked some questions about possible things that he could try, assuming the normal things like downhaul and rotation and mainsheet don't work.

And I still have the same questions -- if the normal sail trim adjustments don't work, can't you experiment with different batten shape and stiffness in the top battens?

And the thing I mentioned about putting the top batten in backward is just something that has worked for us in some heavy-air circumstances.

And I did not tell Robi to shave his battens. He was saying why shouldn't he be able to sail with whatever he got with the boat. (Does anybody actually not change anything?)

Battens are not as important as they used to be. Sail makers are better at building good shape into catamaran sails, the high-tech materials do not make it as easy to change the shape of the sail by shaping battens.

But isn't it good, and fun, to experiment with different things? If there is one thing I have learned about sailing, it is that there are always new things to learn and to try. And it is important to always question and never blindly accept the technique of the day.

What works today might be obsolete tomorrow, and come back around and be the "in" thing again in a few years.

And I have also noticed that what works great for one sailor doesn't work at all for another sailor. People can have their boats set up completely different, but with identical hulls and sails, and be always fighting it out for first place.

The debates will always rage on, and nobody is ever truly RIGHT. What works for you might not work for me, and vice versa.

That's why it is more interesting to race on the water instead of on a computer.

Sure, one can do things with different battens or shaved battens. Hell I have a set of extra stiff top battens and even had the battens put in the wrong way on my Prindle 18 in heavier air. But none of these are very good things to start fiddling with before you have totally exhausted the normal tools like prebend, downhaul and mainsheet. Simply because the combined effect of these last three is much greater than the combined effect of any shaving etc. Also I feel that people go on the assumption that something is wrong with the boat over something is wrong with their way of trimming it. Or in simple words : How big is the chance that the sailmaker used the wrong batten for the sail he made in relation to the magnitude of the likelyhood that the sailor is not trimming/tuning the right in the right way ?

I would first go sailing for a season and systematically analyse all possible trim settings and only then start thinking about doing things like shaving battens and putting them in with the rear in front.

Robi should first hunt for the right prebend, mainsheet tension, downhaul tension

Wouter

Sure, one can do things with different battens or shaved battens. Hell I have a set of extra stiff top battens and even had the battens put in the wrong way on my Prindle 18 in heavier air. But none of these are very good things to start fiddling with before you have totally exhausted the normal tools like prebend, downhaul and mainsheet. Simply because the combined effect of these last three is much greater than the combined effect of any shaving etc. Also I feel that people go on the assumption that something is wrong with the boat over something is wrong with their way of trimming it. Or in simple words : How big is the chance that the sailmaker used the wrong batten for the sail he made in relation to the magnitude of the likelyhood that the sailor is not trimming/tuning it in the right way ?

I would first go sailing for a season and systematically analyse all possible trim settings and only then start thinking about doing things like shaving battens and putting them in with the rear in front.

Robi should first hunt for the right prebend, mainsheet tension, downhaul tension

Wouter

Wouter,
I could not agree with you more. I had skipped a step and made the mistake of assuming that he had already exhausted all of the normal resources for curing the problem.

Robi, here is how you measure these things. Spreader rake and prebend

By the way, Darryl refered to prebend as luff curve. Pretty much luff curve is used in relation to the round on the luff of the sail and prebend is the name used for a similar curve in the mast in its major plane.

Spreader rake is easy to measure. Just lay the boat over and hold a stiff tube or bar of wood to the spreader wires just above (or just below) the spreader arms. Now measure the distance between the back of the mast and the bar or tube. Together with the length of your spreaders (or overall between the wires) gives a good measure of the spreader rake you have on your boat.

Prebend. The best way to measure is it to used some 1 mm line (whipping twine) and have it tight between sailhook and boom fitting and fully tensioned. Make sure that the line touches the rear of the mast at the hook fitting and boom fitting. If a mast is set up with prebend that the line with move away from the mast with the maximum distance at the spreaders. Make sure that your mast is layed perfectly on it side as even a small amount of rotation will chance the prebend you measure due to the weight of the mast itself. Measure the distance between line and back of the mast at the spreaders. This is your prebend value.

Measure these for us some time and post the values on the forum so we can give better advice. Also note done you experiences with sailing the boat with the current settings. Things like; she is flighty or rather docile, she feels underpowered of overpowered, she points well or not in relation to other boats, She accellerated noticeably or not, In gust is accellerates rather then heels or pushing her bows down (or the reverse), She feels bound up, she has weatherhelm or leehelm when mainsheet is pulled and all other describtions of how she feels. These experiences together with your current settings will allow both you and others to hone in on the correct settings for your mast and sail combo.

As Mary says there in no single winning setting. In teh end all sails are a little bit difference from one another and especially sailor related style can be very different.

Example; I like the steer in the puffs rather than sheet. So I'm hunting for alot of automatics adjustment in my rig. Also I'm 85 kg's and between 150 kg and 160 kg with crew. So I'm looking for power as well, mostly to get my luff hull out of the water without making the boat flighty (heeling alot in gusts and not falling back in the water in the lulls)

Your situation may be totally the reverse.

But here is an example from my own situation.

Currently I'm running 50 mm spreader rake with 740 mm width between the wires. My prebend with these settings and my diamond wires tension (unknown) is 27 mm. I sailed singlehanded last night and my experiences with these settings are

-1- The boat feels flighty, putting on the downhaul makes her more docile but doesn't lead to much accelleration in the gust or higher speeds. Considering the wind strength and gusts I do expect both of these.

-2- When I totally release the downhaul my sail shows some medium sizes creases and shows the middle and part of the upper leach to pop up. When I apply only a little downhaul tension to get the creases out then the leech falls away already. I don't want this to happen, Don't need the leech to fall away in the middle part so easily.

-3- Pointing angle is acceptable but not particulary good. I feel there is more there.

-4- Helm is balanced, no problems there.

-5- Mast rotation was about 45 degrees.

-6- She feels underpowered for the conditions except for the gusts.

With these experiences I feel that despite the fact that I increased my spreader rake last weekend I also need to reduce my prebend by making my diamonds less tight. I'm hoping that the last will both make the top of my mast stand up and make the leach along the middle part stand up even when some downhaul is applied. This will allow my to apply some downhaul to get the creases out and shave the effects of the gusts off without losing pointing or depowering the middle of my sail to much.

I will first sail a few times with what I have right now to fully determine the effect of me increasing the spreader rake, but after that I will reduce prebend to 20 mm I think. Than of course sail several times with that and see how she handles different conditions like that. And so on till I find the right settings.

Best advice I can give you is to have a little booklet where you write down the settings used in each sail, the conditions and your experiences in sailing the boat. This really helps dialing in your rig and answer questions of others about how she handles. In found that memory is not dependable in these things.

Wouter

Don't you mean outhaul rather than mainsheet in that comment ? The outhaul has a very large effect on the bottom third of the sail. Much more than the mainsheet. Also mainsheet mostly set overall twist along the leech and so is important in trimming the middle and upper thirds as well. Its twist effect on the bottom third is neglectable when compared to teh setting of the the maintraveller. In general my experience is that the bottom third of the mainsail is set with outhaul and mainsheet traveller and that both mainsheet itself and downhaul has neglectable effects here. Thus both act far more on the middle and upper parts than on the lower parts.

I do agree that the mainsail sets the "straightness" of the leech. Although prebend is directly impacting on the straightness of the middle leech. When you have too much prebend then no amount of mainsheet tension can have it stand up.

Wouter