Troubleshooting mainsail trim

[piratesnail]

We've got a small trailer sailor (a Starwind 19) and I'm hoping for ideas or references to help me understand what is going on with our main sail. Before I describe the problem, the main is quite old, so "just replace the sail" might be the answer here. But we are hoping to avoid spending much money on the boat, so I thought it was worth asking first.

We acquired the boat a few years ago, and we've always referred to it as our "snailboat" because it is so slow - we are excited if we get 4 knots under sail. Last winter, I attached telltales to the jib and main in a bunch of places. The jib telltales seem to be doing their job, as I can usually trim for telltales flowing aft on both faces and the leech of the jib. The main, though, is a different story. I put telltales on the leech at each batten; I also put telltales on each face about 3 feet back from the luff, at 1/3 and 2/3 height. On anything between a beam reach and close hauled (say, wind angle 45-90 degrees), no matter what I do, I can't ever seem to get the telltales on each face to stream aft. Usually the one on the leeward side of the sail will flow aft, but the one on the windward side will flutter up or, perhaps more commonly, backwards toward the mast. In addition, to my eye, the leech of the main always seems closed off, and I can rarely keep more than 1 or 2 of the 4 leech telltales flowing. This seems to happen even in a decent wind (say, ~10 knots). I have experimented with:

• Mainsheet tension
• "Traveler" location (this boat really only has about 18" of a 'traveler' on a bar above the tiller, so I'm not sure this does much).
• Luff tension (though halyard tension and then through an improvised cunningham)
• Outhaul tension (though the sail uses a foot rope that has a lot of drag in its track and it is hard to adjust the outhaul force)
• Forestay/backstay tension (I don't have an adjustable backstay; I have been adjusting the tension on the forestay before stepping the mast, which clearly tightens the backstay but has had no noticeable affect on the mainsail leech).

The boat does not have a vang, but I could add one.

I understand the basic idea that a fuller sail is more powerful and a flatter sail is less powerful.

I know a picture would be useful here, but I don't get the boat out that often these days, so I don't have anything current, and it is getting harder to motivate the family to get out when they know we won't go much of anywhere. I'll work to get photos the next time we get the boat in the water. In the meantime, any ideas or references to help me understand what is going on here?

 

[dLj]

I understand the basic idea that a fuller sail is more powerful and a flatter sail is less powerful.

Not exactly - the fuller or flatter the main sail depends upon wind speed. The more wind, the flatter you want the sail. Think of the wings on planes. The slow planes have a larger curvature and faster planes have less curvature.

I'm sure your sails are stretched out and you'll never get the best sailing with them but you should be doing better than max 4 knots. I guess unless your sails are really bad

Adding in a boom vang might help a fair bit, but not so much when pointing as your main sheet is doing most of that work.

Unfortunately unless I can see what you are doing not much I can say. I'm sure there are others better at explaining than I am.

dh

 

[Foswick]

A key detail that would be useful is to know which leech telltales you can get to fly straight and what the others are doing at that time. I would ignore the other telltales (those a few feet back from the luff) for now. They are really just a distraction when your main is near end-of-life and you have relatively limted sail shaping options are your disposal. Just focus on the leech telltales. The telltales 3 feet aft of the luff are interesting, but they’re hard to interpret, especially on older sails. If your leech telltales aren’t flowing, those mid-sail ones won’t tell you much.

To break it down:

• If only the lower leech telltales flow and the uppers stall, the sail is twisted, i.e., the top is too open.
• If only the upper ones flow and the lower ones stall the sail is hooked, i.e., the top is too closed (rare unless sheeted very hard and vangless).
• If all leech telltales stall, the sail might be blown out or draft too far aft.

Given your setup, my assumption is that it is easier to get just the lower leech telltales flying, especially if your easing the sheet to try to get the mid-sail telltales to flow - because doing so opens the top more and kills the top leech flow.

To my mind, your options are limited. You already know that sheeting your main to try to reduce that twist isn't working, regardless of traveler position. So, a vang would help. Better outhaul might.

If none of the leech telltales are flying, the sail might be just too baggy or hooked - especially common with an old main. You mentioned the leech “looks closed,” which might mean the draft is far aft and the leech is cupped, causing turbulence. That’s hard to fix without sail shape controls or a new sail—but a vang and better outhaul might still help a lot.

Don’t worry too much about perfect telltale behavior on an old main. If you can get most of the leech telltales flowing on a reach or upwind, and the helm feels balanced, you’re doing fine. Any more fine-tuning is going to have only the most marginal speed improvement - likely not enough to notice or appreciate.

As DJ pointed out, you're not going to break speed records with an old sail, but you should be able to do better than 4 kts in that boat, without a lot of effort. In 10 kts wind, I would look for more like 5 kts speed, and you should be able to reach hull speed on a broad reach - even with suboptimal sails.

I would think about what is going on below the water line for clues. Most notably, it might be that your sail-trimming challenges are forcing you to maintain quite a bit of rudder deflection in order to hold your course. This will slow you way down. So, I would suggest getting your sails trimmed to "close enough", then adjusting sheets for helm balance to minimize the need for constant rudder deflection. That will likely speed you up more than having optimal sail trim ... which you probably can't get with your current setup anyway.

Hope this helps a bit.

 

[PaulK]

A photo would really help. It sounds like, as you and others say, the sail is tired. If it is too baggy at the luff from having stretched in use, keeping laminar flow on it will be tough.
The theoretical hull speed of the Starwind is about five and a quarter knots. That would be most likely on a reach as @Foswick suggests. Upwind will be slower, but you should be able to do better than four knots in a good breeze. The picture here: STARWIND 19 - sailboatdata makes it look like the slot with the jibsheet leads on the cabin top is pretty narrow. Rigging a barber-hauler to pull the leads outboard might open up the slot and improve speed. You might not point as high, but it might be faster and heading off a touch might improve flow on the main. You could simply tie a line around the sheet and lead it to a stanchion base on one side and tighten it to see if the idea works. You could compare your speeds on that and the other tack that doesn't have the adjustment to the sheet to see which is better.
P.S.: Jim Taylor designed our boat too.

 

[jssailem]

I am assuming you are not racing this boat. Possibly sailing on Cheat lake.

We should agree on expectations. The Starwood 19 has a hull speed of 5.29knots. That would be with a clean bottom and optimal power.

Your request: “any ideas or references to help me” at least in theory could be a study of the 1970’s work done by Arvel Gentry. Gentry Sailing | Recalling the research, writing and design of Arvel Gentry

• Forestay/backstay tension (I don't have an adjustable backstay; I have been adjusting the tension on the forestay before stepping the mast, which clearly tightens the backstay but has had no noticeable affect on the mainsail leech).

This approach will have no affect on the Mainsail Leech. Tensioning the fore/back stay will change the angle of the mast. If you tension the forestay the mast will be vertical or even forward leaning. This is not improving the leach and is having a negative affect on the way the main sail is shaped.

The mainsail leach is controlled by the weight of the boom and the way you trim the mainsheet.

Drawing in the mainsheet as you would when going to windward will tighten the leach.

 

[David in Sandusky]

My only thought is that opening the slot between the jib and the main by easing the jib sheet may improve your speed upwind.

Our sails were blown out when we bought Lady Lillie in 2000. We bought a new main and jib before our second summer on Lake Erie. The results were an improvement of about one knot on a reach or close hauled. That says to me that your sails could be 60% to 75% of your problem. So the improvements discussed above could result in a few tenths of a knot improvement. Do give them a try - learning to properly trim your sails in changing conditions is one of the real joys of sailing for me.

 

[shemandr]

It sounds like OP has tried different trim option with little success.
A tired sail can only be coaxed into performance so much. I could only add that I would try to make it as flat as possible - Max outhaul, max halyard tension, ease on the leach line if it exists and backstay tension to bend the mast. And if there is a bolt rope it may need to be eased.
Don't try to increase backstay tension by shortening the forestay. Create a way to adjust the backstay. By bending the mast (Mast tip aft) on a fractional rig you can flatten the upper 2/3 of the main. An alternative is to increase cap shroud tension and ease the aft lower shrouds to allow the mast to bend forward in the mid-section. That would be pre-bend. That could pull the mid main area forward and flatten the main.
Most sailers overtrim their sails. It looks nice but is slow. Continually ease the sheet so the sail is on the edge of luffing. In fact the uppermost tell tail should stall about 50% of the time. Not that you want that stall but you use it to make sure you are not over trimmed.
Remove all the extra weight on the boat and make sure the bottom is clean.
This is not going to be a fast boat - ever. It's a little fat, there's too much surface area on the bottom with that shoal keel, and stir rail sheeting doesn't pull down on the foot of the sail enough. Enjoy it for what it is.

 

[piratesnail]

Awesome - really appreciate the feedback, here. Some reactions:

I am assuming you are not racing this boat. Possibly sailing on Cheat lake.

Definitely not racing - just day sails and some sail camping trips. And we just moved to the Portland, Maine area, so we have so many more options than we did down in WV. We've really been enjoying exploring the Casco Bay islands this spring; hoping to trailer the boat up to Penobscot Bay for a week later in the summer.

This is not going to be a fast boat - ever.

Amen to that! We have never expected it to be. But it sounds like our intuition that we were on the slow side could be accurate.

Given your setup, my assumption is that it is easier to get just the lower leech telltales flying, especially if your easing the sheet to try to get the mid-sail telltales to flow - because doing so opens the top more and kills the top leech flow.

It is a little easier to get the lower leech telltales to fly, but really it feels like they are all stalled most of the time. From everything you and others here have said, I'm guessing new sails are probably a good idea. As far as steps I can take in the meantime, here is what I have gleaned:

• Adding a barber-hauler to increase the slot is a potentially easy option to explore​
• I should be careful with thinking that adjusting the forestay tension could be helpful - it might actually be hurting. I should probably consider the tune of the whole rig with a bit more care.​
• As far as mainsail trim, I should look for ways to move the draft forward
  

  • Maybe adding a vang and/or cunningham​
  • Improving the outhaul would likely be useful, too.​

I would think about what is going on below the water line for clues. Most notably, it might be that your sail-trimming challenges are forcing you to maintain quite a bit of rudder deflection in order to hold your course. This will slow you way down. So, I would suggest getting your sails trimmed to "close enough", then adjusting sheets for helm balance to minimize the need for constant rudder deflection.

This is an interesting idea, and not one I have considered. There is some weather helm when sailing upwind, and there's a chance that could be leading to more rudder deflection than I realize. I will check it out the next time we are out.

Many thanks for all the ideas, folks.

 

[LLoyd B]

stir rail sheeting ?

 

[shemandr]

stir rail sheeting ?

“Stern rail”.

 

[shemandr]

Moving the draft forward is largely halyard tension. According to rich, a former poster, to properly raise a Dacron sail you need to stretch it by over tensioning the halyard. Then set it to desired tension, which in the case of a blown out sail remains full on. If that doesn’t give the desired result you may need todo the release of the bolt rope which doesn’t stretch as much as the luff of Dacron. Therefore over years becomes the de facto luff.
I wish RichH would return to this forum. I learned a lot from his posts.

 

[Stu Jackson]

The boat does not have a vang, but I could add one.

you're missing an important sail control.

Read this

Sail Trim Users Guide

Sail Trim Users Guide

shop.sailboatowners.com

:

 

[thinwater]

We've got a small trailer sailor (a Starwind 19) and I'm hoping for ideas or references to help me understand what is going on with our main sail. Before I describe the problem, the main is quite old, so "just replace the sail" might be the answer here. But we are hoping to avoid spending much money on the boat, so I thought it was worth asking first.

We acquired the boat a few years ago, and we've always referred to it as our "snailboat" because it is so slow - we are excited if we get 4 knots under sail. Last winter, I attached telltales to the jib and main in a bunch of places. The jib telltales seem to be doing their job, as I can usually trim for telltales flowing aft on both faces and the leech of the jib. The main, though, is a different story. I put telltales on the leech at each batten; I also put telltales on each face about 3 feet back from the luff, at 1/3 and 2/3 height. On anything between a beam reach and close hauled (say, wind angle 45-90 degrees), no matter what I do, I can't ever seem to get the telltales on each face to stream aft. Usually the one on the leeward side of the sail will flow aft, but the one on the windward side will flutter up or, perhaps more commonly, backwards toward the mast. In addition, to my eye, the leech of the main always seems closed off, and I can rarely keep more than 1 or 2 of the 4 leech telltales flowing. This seems to happen even in a decent wind (say, ~10 knots). I have experimented with:

• Mainsheet tension
• "Traveler" location (this boat really only has about 18" of a 'traveler' on a bar above the tiller, so I'm not sure this does much).
• Luff tension (though halyard tension and then through an improvised cunningham)
• Outhaul tension (though the sail uses a foot rope that has a lot of drag in its track and it is hard to adjust the outhaul force)
• Forestay/backstay tension (I don't have an adjustable backstay; I have been adjusting the tension on the forestay before stepping the mast, which clearly tightens the backstay but has had no noticeable affect on the mainsail leech).

The boat does not have a vang, but I could add one.

I understand the basic idea that a fuller sail is more powerful and a flatter sail is less powerful.

I know a picture would be useful here, but I don't get the boat out that often these days, so I don't have anything current, and it is getting harder to motivate the family to get out when they know we won't go much of anywhere. I'll work to get photos the next time we get the boat in the water. In the meantime, any ideas or references to help me understand what is going on here?

Re. sail trim, photos really help. Lie on the bilge and take them facing upwards with a wide angle. We want to see the draft and the twist.

How to Photograph Sail Shape

There are a number of reasons to regularly photograph sail shape, from tracking the condition of the sail to figuring out why you can’t point. H...

www.quantumsails.com

 

[Scott T-Bird]

You may be pinching a little too high when close-hauled. Your old mainsail comes with limitations in upwind performance. The telltales on the mainsail closest to the mast will not help you much when the slot is closed as said earlier. The leeward telltales stream because they are affected by the headsail. Often, the luff of the mainsail will flutter slightly when close-hauled (especially when the slot is very closed) so the windward telltales will be slack or pointing forward. You can foot off slightly and open the jib to increase speed and probably VMG as well. But the real villian in this whole scenerio is an old mainsail that has lost its shape and lacking sail controls that could improve the shape.

 

[FastOlson]

That bagged out main may.... I say "may" be made much much better with a re-cut. When we acquired our boat, the dacron main was pretty badly stretched.
I took it to a local loft and asked if they could assess it and maybe do some re-seaming. They said the cloth did have some more years of life (although not too many) and they could unstitch many of the seams and remove some slices and re-stitch. The sailmaker, considered really talented, got it done quickly and pronounced that she had given it a "tummy tuck" !

It set and sailed well for several more years while we budgeted for a new main.
So, while the best answer is to replace, you might get by with a re-cut for a while.... depending solely on the dacron condition.

This is, FWIW, an Important part of your boat's "main engine" i.e. always first up and last down. Reefed for heavy air, and strong enough to get you home when a summer squall hits your lake or bay.

Good luck on finding a solution and fair winds to you! Your Starwind 19 would be rather rare in my sailing waters but I have heard of them. Decades ago, we started out sailing (day sailing, overnighting, and OD racing) in a (fractional rig) Ranger 20. Wonderful size of boat for young couples. Enjoy!

 

[jssailem]

Even Better!
The coast of Maine is a wonderful place to sail. Your boat will give you plenty of new life experiences.

If getting a 0.5 greater knot out of the sail can be achieved by a reasonable cost of a “tummy tuck” why not go for it. It will make you feel all the better to budget and acquire the new sail in a couple of years. Then you’ll also have a couple years experience under sail, and know how you want to spend your monies.

 

[shemandr]

... Often, the luff of the mainsail will flutter slightly when close-hauled (especially when the slot is very closed)...

Rangers sailers I know call that the "Ranger Bubble." It's more than a flutter - the main luff is actually backwinded by the 150 Genoa and was considered good upwind trim for a Ranger and probably other masthead boats.
One reason for main tell tails placed about 1/3 the way aft from the mast is to help set out haul length. If you are not getting flow there, the air maybe detaching from the sail because the sail has too much depth - especially in light wind. In light wind it's hard to know when to go from a deeper shape for power to a flat shape to maintain laminar flow. Those tell tails can help.
I've already posted I think that with a blown out sail you should max out the outhaul (But we have yet to determine the Starwind main is question is blown out.)

 

[piratesnail]

(But we have yet to determine the Starwind main is question is blown out.)

I think it is a fair assumption that it is. ¯\_(ツ)_/¯ If I can get work and family stuff settled this week I hope to get the boat on the water over the holiday weekend. If that happens I will snap what photos I can and post them here.

Yesterday I found a local “marine salvage yard” - think auto junk yard for boats - and had a very enjoyable hour poking around. For the grand total of $40 I found supplies to improve the outhaul, add a boom vang, and make an actual cunningham (vs my improvised one). Will be fun to get these set up and see if I can do more with sail shape.

 

[piratesnail]

Just an update here:

I did get out last weekend, and in the process added a fairly sizable tear to the main. I was able to patch it with sail tape to salvage the day, but the ease with which the sail tore suggests the Dacron is much more brittle than I had realized. We have a week-long sail camping trip planned for next week, and I didn't want to risk another tear during the trip - especially since a tear seems most likely to happen when you least want it, i.e., when conditions get spicy. Local sailmakers couldn't make us a sail in such a short timeframe, but I was lucky enough to find a used sail that pretty well matches the dimensions of our old one. We'll see how this goes, but I'm hopeful we will have better luck in the short term. And we'll start saving for new sails in a few years.

In addition to the new sail, I took some time this week to add the vang, cunningham, and improved outhaul that I found at the salvage yard. I also have some light line I hope to set up as barber-haulers. I'm looking forward to experimenting with all the new controls.

Thanks again for all the opinions, folks!

 

[kappykaplan]

We have a week-long sail camping trip planned for next week

I'm looking forward to experimenting with all the new controls.

Good luck with the trip and the experimentation!