Sail Shape/Balance

So today was a good day for sailing, winds 15-20 mph + gusts. The boat handled really well and I'm glad I purchased the traveler and upgraded the downhaul with a pulley system and cam cleat. Makes it real easy to adjust the sail.

There is one thing I just can't seem to get right, that is having the telltales on both sides of the sail flowing correctly. I have to compromise and either have the upper windward fluttering (and the other 3 flowing) or the bottom leeward one fluttering. If my thinking is correct, this would mean the sail has to much twist.

On other boats I've had, if the jib was doing this it meant the angle of the sheet pulling on the clew wasn't right and had to be adjusted. On the Wave, the only way I can think of to adjust the angle of the sheet pulling on the clew is to adjust the mast rake. What I was thinking is to reduce the mast rake aft, reducing sail twist. From what I've read, this would decrease the ability to point and increase the possibility of pitch polling.

Just for reference, I have a 2010 club model, stock sails, main stay in the second from the top position, side stays in the 4th from the top position.

Any advice, ideas would be appreciated.

Charlie

Really like to see a pic of that if you have one. Or at least a description of the setup. I have been using a truckers hitch between the grommet and cleat.

For me, the telltales remain something of a mystery. I sometimes to get more boat lift/speed with the telltales doing exactly what you describe...

As far as mast rake, with the 10-hole adjuster, the eight hole from the bottom is about as far as I can go without feeling like I lose the ability to point well and tack easily. (Usually seven hole from bottom on forestay, and side stays in the fourth from top.)

I don't know if raking back corrects sail twist as you suggest, but it's a good question.

I assumed that mast raked back prevented pitch poling, and was used to depower; although many recommend putting the mast back as far as possible in all conditions. Don't follow their reasoning...

Recently I talked with a 505 sailor who showed me all that boat's depowering tricks and interestingly they have mast rake adjustment, outhaul, downhaul all on pulley systems inside the boat. Made the Wave look under-controlled... still think the Wave is more fun.

Since you are sailing in 15-20 mph with gusts, I do have a question, please. How do you depower? I don't like the fact that I still can't depower the sail enough when going upwind in 20-25 mph wind when I want to slow down and get things under control.

Do you depower by sheeting down to the max and flattening the sail? (I do this and it works but I am not getting enough of the wind spilling off the top of the sail that everyone mentions. Plus the boat seems to heel more.)

And did you experiment with the battens, as you mentioned in the other thread?

JJ

I'll post some pictures of my downhaul, would be a lot clearer than describing.

Most of the posts I've seen about raking the mast aft to de-power and prevent pitch poling were from racers, who can't use a traveler. When sailing off the wind without a traveler, they say the top portion of the sail gets real full which drives the bows down. Yesterday, when the traveler was out all the way and the sheet was in hard, the bows didn't dive except on the really hard gusts. That's on a beam reach.

Going upwind, Sheet in hard and downhaul on hard, it was more controllable. I believe when the downhaul is put on hard, the mast bends back, allowing the top of the sail to twist off more.

Back in the day I used to crew on a lightning and there were so many adjustments on the sails and mast it was crazy. When I took sailing lessons the instructor used to say the more adjustments you have, the more chance you have of being out of adjustment, so just get the basic shape down and sail the $#&% boat.

I took a look at the battens I had from the H-14, but they were already shaped, so wouldn't be stiffer. If my memory serves me correctly, the battens I had on a Solcat 18 were larger (width and thickness) don't know if I have any of those around to check.

Charlie

I took a photo, however the service I used to post them at isn't working, so put it up on Flickr, hope you can get to it at http://www.flickr.com/photos/44482856@N02/4090784137/.

What I used was a small swivel block with Becket attached to the clew. I had an "s" hook, but you could use a small shackle. Attached to the Mast I used a cheek block and a swivel block with cam. I didn't want to drill holes in the mast so I connected them as the original cleat was, a stainless screw with a nut inside the sail track to bind it. Slide the swivel block on first, then the cheek block. This gives a 3:1 downhaul that can be adjusted as you sit on the tramp and underway.

If you can get to the picture, let me know

Here you go!

_________________
1992 Hobie Cat 18 #16943
Hobie Fleet 198, Rapid City, SD

Thanks Tom, that's what I was trying to do.

Charlie

A cunningham! Makes for easier adjustment than sliding across the tramp and untying and yanking a truckers hitch.

I guess it's a tired old subject for veteran sailors but I ask about changing from cupped sail shape to flat shape going upwind because there is so much confusing advice on how it should be done.

I have the traveler too, btw.

In really heavy air, it seems like you can't deal with one shape at a time, you have to keep two in mind.

(Not trying to hijack your thread and hope to get back to your original question.)

First you deal with the lift off the back of the sail when it is cupped (using "cupped" for lack of better, quicker term). The boat really scats when the Bernoulli lift kicks in.

But then when the sail is flattened, you got the windward side of the sail still catching too much air. Your downhaul is good for that adjustment...

It takes a bit of raw nerve to flatten a sail by sheeting in in a high wind. Only comfort is knowing that you can spill some wind, in effect reducing the power (and area?) of the sail. The fine points of this I am not onto yet.

I am just trying to think... in moderate wind, raking the mast back some takes the twist off as you say and make all the telltales right because the pull down is less. But won't raking the mast back further really takes that twist off -- which you don't need or want in really heavy air?! It seems like this happens for me.

So therefore, there is a Catch-22 with this boat? Rake moderately for moderate air and lose the twist and get the telltales right. Rake more for heavy air, really lose the twist? So you use tighten the downhaul to compensate? It flattens the sail and and increases flathead top twist and spillage?

I have heard of some just using the traveler to adjust spillage while keeping the mainsheet in...

Sorry, not trying to over-think this, but I don't get these conditions enough to learn by trial and error. And practically, I am trying to keep the boat sailing under control in heavy air. In other words, I look up at the sail shape and think, "I have too much power and now I am going to kill the Bernoulli and backside lift by sheeting in to flatten the sail shape; and I then I am going to travel out to spill and reduce the speed." ...and have that really work???

Of course this assumes that the mast rake has been set correctly for wind conditions. Which must be around the sixth or seventh hole from the bottom for moderate to heavy air...


This whole mast rake thing is a booger...

Where am I thinking wrong? Pick my thinking (or lack of it) apart. Please.

BTW, I had one situation in 15-20 mph wind when on a beam reach where I let the mainsheet out to slow down, then let the traveler out about 3/4ths of the way to slow down more; then instead of slowing down the boat took off like a rocket. The sail was a beautiful bowed out shape and the lift was incredible. Oddly enough, the boat was balanced and I could have sailed all day like that, but what happened was the opposite of what I anticipated...

And the telltales were all wrong!

Just for the halibut, I tied a foot of cassette tape on each batten end, for the "other type" of tell-tale. I've heard they're more accurate.

Sometimes they agree with the on-the-sail tales, sometimes they don't.

The wind on my lake is too inconsistent to make a real study of it.

_________________
What - Me Worry?


2006 Hobie Wave 7358
"Ish Kabibble"

JJ

I believe Mast Rake and Twist are 2 different subjects. Mast Rake is used to move the center of force of the sails aft. On boats like the wave, this will provide better pointing ability, and increase survivability when going down wind (not so much force driving the bown down). So the higher the wind the more aft rake is desired.

Twist is controlled by how tight the leach of the sail is, which we control with the main sheet. The only time mast rake impacts Twist is when the mast is raked so far back that the blocks touch before proper leach tension can be applied.

One thing mast rake does impact is the angle the main sheet pulls on the clew of the sail. Getting back to my original question, I was wondering if changing rake (and the angle of the main sheet) will affect the sail shape and get the luff telltales (upper and lower) flowing the same way.

IndyWave,

The leach telltales do give a better indication on how the wind is exiting the sails, from what I've read, you get them flowing properly and then use the Luff tell tales to steer the boat. I've only used leach tell tales on larger boats and not on Cats. At some point there are just to many things to look at and it becomes overwhelming on a single handed boat.

So what I plan to do is the next time I have the time is to vary the mast rake and determine it affects the tell tales as I suspect. Then see if I like how the boat handles.

Charlie

True. My rambling point was that rake, twist, traveller, and downhaul interact on the Wave in unexpected ways -- especially in bigger winds.

I probably just will rig the boat up on the lawn and try a number of sail settings and look at the sail shape changes.

Indy, your idea about the telltales is a good.

One correction: I said this in an earlier post and blamed it on mast rake. Raking back did not cause this; heavy air did. Even with the mast raked back. Raking back is for better pointing.