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Main Sail Shape

Jan 4, 2013
252
Catalina 270 Rochester, NY
This is the original 1996 Mainsail. Is the shape still good or is it time to shop for a new mainsail?
IMG_20190831_115641537.jpg
 
Oct 19, 2017
6,938
O'Day 19 Littleton, NH
What type of sailing do you do? That sail looks stretched out, but the full battens help give it good shape. For casual cruising, I'd stick with it. For long distance cruising or heavy weather sailing or racing, you should change it. How is the stitching? How does she handle, lee helm, weather helm, lots of heeling?

-Will (Dragonfly)
 

BarryL

.
May 21, 2004
833
Jeanneau Sun Odyssey 409 Mt. Sinai, NY
Here’s what I see:

That sail looks good if the wind is 5-10 kts. I can see that the main halyard is loose, which is fine for light air. You can see wrinkles along the luff of the sail. The outhaul looks to be moderately tensioned -the foot of the sail is fairly flat. However there is a lot of draft in the middle and upper part of the sail. More halyard might flatten that out.

I’d like to see the sail in 12-15 kts of wind. Then we can see if the sail can be flattened or if it’s really blown out.

Barry
 

capta

.
Jun 4, 2009
4,306
Pearson 530 Admiralty Bay, Bequia SVG
I agree with BarryL that the hoist and foot are too loose. The first reefing line looks a tad tight also. Other than that, unless you are looking to do some serious racing, that doesn't look like a sail that you need to replace too soon. I suspect you'll probably have some problems with the seam thread and have to get a few seams restitched before you actually need to go shopping for a new main.
 
May 12, 2004
1,337
Hunter Cherubini 30 New Port Richey
The reefing line looks a bit tight which may not be giving us a true picture of the shape while underway. The only way to really know is if you can tear it by hand, in which case you would already have your answer, or take it to a reputable sail loft and have it evaluated.
 
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Jun 25, 2004
1,108
Corsair F24 Mk1 003 San Francisco Bay, CA
Is that sail actually loaded with wind in the picture? There's no twist in it. None. That suggests to me that the boat isn't being sailed. The sail is just luffing. There's not much we can conclude when the sail is sitting still at the dock, luffing.

Please go back out and sail close hauled upwind with at least enough wind to heel the boat 15 degrees. Then take a picture from directly under the boom at 50% of the foot, including as much of the leech and luff as possible, as well as the masthead. If you can't get the whole foot in the picture, that's okay, but please include the head of the sail.

The draft at the second and third battens is pretty deep, around 15% at the #2 batten and 13% at the #3 batten. That will get deeper when there's power in the sail. And it's probably deper than that, because it's not taken from underneath the boom. The perspective makes the draft appear shallower that it really is.Draft position fore-and-aft looks good at around 40-42 percent, but that will move aft in any breeze.

There's nothing that indicates there's not enough luff tension to me. Tightening it won't flatten the draft. On a mainsail with partial battens, tightening the luff with halyard or cunninghame would pull the draft forward some, but it won't make much difference with full battens.
Stiffer battens might make the draft shallower.

There are wrinkles along the batten pockets, so you could try putting more tension on the battens, but more tension will make the draft deeper. It doesn't look to me like the aft reefing line is causing any distortion or wrinkles in the sail, so I don't think it's too loose. Those wrinkles at the batten pockets might indicate that the fabric is stretched out; I can't tell the 3D shape from the picture.

You can't use the backstay to bend the middle of the mast to flatten the sail very much in the middle section on a C270. Maybe a little, I'm not sure.

I suspect that sail will look a lot deeper when it's being sailed close hauled in 15 knots of wind. Go sailing and send us another picture.

catalina270-261-mainsail.jpg
 
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Jan 4, 2013
252
Catalina 270 Rochester, NY
I was sailing in about 12 knots of wind with the wind moving from 60 to 90 degrees. The wind swirls a lot around here, not just come from a steady direction. I will flog the crewman who raised the main and didn't get it tight (my wife).
 
Jun 25, 2004
1,108
Corsair F24 Mk1 003 San Francisco Bay, CA
I was sailing in about 12 knots of wind with the wind moving from 60 to 90 degrees. The wind swirls a lot around here, not just come from a steady direction. I will flog the crewman who raised the main and didn't get it tight (my wife).
Let’s see it when you’re close hauled, please.
Don’t flog your wife. :;) The luff isn’t too loose.
 
Jan 1, 2006
6,076
Slickcraft 26 Greenport, NY
I can't argue with the professional sailmaker but there is some positive. I think the draft is still biased forward - again the full battens distort that. Blown out sails see the draft move aft. The trailing edge is a bit rounded and I would rather that be flat which is more conducive to attached flow holding onto the sail longer. Again a symptom of the full battens. But all in all I think it's pretty good. Not a racing sail. How does the boat behave when a gust hits?
Dr. J is that table for this sail or is it for a file design parameter for a Catalina 30 Mainsail?
 
Jun 25, 2004
1,108
Corsair F24 Mk1 003 San Francisco Bay, CA
Dr. J is that table for this sail or is it for a file design parameter for a Catalina 30 Mainsail?
That analysis is for this sail. It’s a bit off because it not taken from directly underneath the middle of the foot, but the distortion makes it look better than it is. If you enlarge it, you’ll see how I fitted curves to the middle three battens. The measurements are based on those curves.

The draft looks very deep to me. It shouldn’t be more deeper than 12 -12.5 % draft anywhere for this boat and rig. A sail that’s too full won’t point and it will heel a lot in the gusts.

To my eye, the wrinkles at the seams and battens are characteristic of a stretched out full batten sail, but I can’t be sure from just one picture. all the seams looks wrinkly whxh happens when a full batten mainsail is stretched out... but may be it looks that way be cause there isn’t enough wind in the sail.

Full battens make a blown out mainsail look better at first glance than it really is. Because they hold the draft position forward.

But what really caught my eye is that there’s no twist what so ever in the sail, which means that it’s not trimmed hard on the wind. There should be around 10-15 degrees of twist in the leech. No twist I’m this cases suggests the angle of attack is very small and the mainsheet is eased too far compared to the apparent wind angle. The mainsail is depowered by easing. So the photo doesn’t tell us much about the condition of the sail when it’s loaded up. It’ll probably look deeper when it’s loaded by sheeting in.

Those are my first impressions from just one picture. I’d prefer to see a more pictures, taken from a better angle, with the sail trimmed close hauled and showing the mast head windex so i can see the apparent wind angle.

Here’s what a new mainsail looks like (when taken from the right angle and position)
See How to Photograph Sail Shape for how to take pictures for your sailmaker.

CD2AEDD1-B512-421C-94D3-455D8033B0B8.png
 
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Oct 19, 2017
6,938
O'Day 19 Littleton, NH
I see some twist, maybe about 5 degrees, in the OP's sail. The puckers along the battens are what made it looked stretched out, to me. It doesn't look like there is a lot of wind either, but the pink telltail on the leach shows good air flow.
What strikes me, as an immediate tweak to improve, is that slack foot. Tighten the outhaul and everything may improve somewhat.
It doesn't look terrible for casual sailing. What is the goal, high performance, long life and safety on the high sea, or picnic sails and gentle overnighters? If either of the former, get a new sail, if the latter, it looks good enough.

-Will (Dragonfly)
 
Jun 25, 2004
1,108
Corsair F24 Mk1 003 San Francisco Bay, CA
I see some twist, maybe about 5 degrees, in the OP's sail
Twist is measured by the chord from the leading edge to the trailing edge. The chord at the 2nd batten is twisted 0.3 degree compared to the 4th. 188.6 degrees vs 188.9 degrees (But again, this picture wasn’t taken from underneath the boom)

Telltales fly on a sail that’s luffing with airflow attached.

I agree with Will that the main sail is probably useable condition in light winds. It will probably do okay in light winds and reaching, but be less than satisfactory when pointing in high winds. it’s going to be tough to control in strong, gusty wind. The draft looks overly full, which suggests to me that the boat will heel a lot and be easily overpowered in gusts and will need to be reefed early. An overly full sail won’t point very high either.

The bottom line line is what the OP wants from his boat. Is s/he happy as long as the boat doesn’t round up uncontrollably in every gust? To me that would be the minimum I demand from my sails. Or does the OP like to shape the sails to suit conditions, and like having a balanced helm? It’s a very personal choice.

But again, I want to qualify my conclusions because it’s just one picture, take from a less that perfect angle, under vaguely described conditions . As a professessional, I’m reluctant to draw conclusions from such a limited observation
 
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Jun 8, 2004
2,562
Catalina 320 Dana Point
Sometimes apparent from close observation, if you look at the sail and think "I could make a comfortable shirt from that" or you look at the sun thru the sail and see hundreds of pin size holes.
 
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Jan 1, 2006
6,076
Slickcraft 26 Greenport, NY
Thanks Dr. J. The two photos make the comparison easy especially in regard to depth.
 
Jan 4, 2013
252
Catalina 270 Rochester, NY
I would like to thank Dr. JudyB for all of her insights. I did not know there was a specific way to photograph a mainsail and then have everything measured. This photo was something I did on a spur of the moment while I was just sailing along. At the first opportunity I will take a proper picture while pointing in a good breeze. I'm a casual sailor but I don't want to go slow. I know a new sail would be an improvement but the question is would the improvement be worth $2K dollars? I got that 2k price from my local Quantum Sails vendor last year.
 
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Jun 25, 2004
1,108
Corsair F24 Mk1 003 San Francisco Bay, CA
@LakeOntario270 ,
There’s no way anybody but you can decide if the improvement would be worth $2k of *your* money to *you*. That’s a question that each person answers differently, depending on their budget and priorities

So, are you happy with the way the boat sails now? Does she heel a lot? Round up easily? Point as high as other boats? Does the boat have good manners in strong winds and gusty conditions?

Take a picture or two that will allow me to use the analytical software as it was intended. Take an accurate measure of the apparent wind speed and angle at the masthead, if you possibly can. Sail in enough wind to heel the boat about 15*. Then we can get some reliable data to analyze.

i don’t expect the end results of the new analysis to look better, but we might be pleasantly surprised.

Judy B
 
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Jan 1, 2006
6,076
Slickcraft 26 Greenport, NY
You should factor in that it's a masthead boat and if you are going for the 2K sail maybe it should be for the jib - a smoking 135 might bring a smile.
 

SG

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Feb 11, 2017
1,670
J/Boat J/160 Annapolis
VANG (and, or get the boom down with the sheet)

The I'd be more interested in the easing the main halyard a bit ( you're sending the point of maximum cord too far forward for that much wind). Then, I'd like to see what you can do do flatten the sail first.

After the cord is pretty even, and you've flattened the sail more, you can play with the outhaul a bit.

Look at the cord of the battens as you go up the sail. Clearly not going rotating to me.

My IMPRESSION is that the sail doesn't look crazy to me for a dacron cruising sail.

As DrJudyB points out, full battens can fool you a bit because the sail doesn't reveal itself as easily (it tends to look better than it is, sometimes). GET THAT BOOM DOWN. Don't overtighten the main. Use the outhaul first, then the cunningham (if you have one). In heavier air, you should crank the pressure up on the main (A BIT) -- but not first.
 
Oct 19, 2017
6,938
O'Day 19 Littleton, NH
I think it looks better than in the first picture. Did you tighten the outhaul? That foot doesn't look nearly as loose.
I'd be happy with that sail. But, I'm strictly a casual cruiser.

-Will (Dragonfly)