Changing Sails

[Dennis Marshall]

I am currently using an 86 sq ft spritsail on my Dobler 16, but have become dissatisfied with it. I am considering a different sail plan with the following characterstics: 1)easy to raise and lower; 2)unstayed; 3) short spars fit in the boat (but not absolutely necessary; 4) fair windward efficiency.

Candidates thus far:

1. sprit boom leg-o-mutton
2. boomed lateen
3. balanced lug

Opinions, comments, observations?

Thanks,

Dennis

[J. Dillon]

Dennis,

Why are you "dissatified" ?

JD

[Dennis Marshall]

JD, that is a good question and so I will try to do my best to articulate my dissatisfaction:

1. The snotter arrangement (TF Jones calls it a stanliff -- I'm not sure I know the difference) does not allow enough tension to be put on the sprit to get decent sail shape. The sail almost almost always has a bag in the lower 1/4-1/3 near the leech that is almost impossible to get out.

2. Mast jewelry makes lacing sail to mast and raising/lowering it difficult and, I think, impractical. And, the boat is so narrow and tiddly forward that if I have to make any adjustments while sailing it is a precarious situation.

3. Setting up sail in rather sheltered ramp area usually goes smoothly and quickly, but on the exposed ramps that I mostly sail from, it is a real pain in the neck!

4. Stepping mast with sail and sprit is awkward as the devil.

I am sure that there are others, but I cannot think of them. I certainly haven't found it to be as user friendly as many of its proponents claim. I'm sure a lot has to do with operator error, but I am not sure what that might be.

Dennis

[J. Dillon]

Dennis,

Maybe the cut of the sail might be the problem but I'm sure Todd can help you there.

My " snotter" ( love that word) has an eye splice around the mast ( loose) then forms a bight ( for the insertion of the open sprit heel ) then goes into a Ligumn vite bulls eye , then down to a turning block which leads the working end back right to a console aft on the CB trunk. This enables the helmsman instant access to suit changing conditions. The tack down haul leads from the tack to another turning block then aft also to the console. This also gives me the option change tension on the luff.. Both controls seem to give shape to the sail enough for me.

My sails are not laced but rather each luff grommet has it's own roband secured with a toggle. When rasing the sail it gives no problems but do hang up a bit on the snotter thumb cleat, a touch with a finger frees it. For me a roband is much kinder to a varnished mast and probably stronger then hoops.

My main sail is 100sq ft and I leave it stepped all the time. To secure the sail I lower it, bag it still attached to the mast. Same for the jib.

When ready to sail I dump the sail out of the bag, raise it , insert the sprit to the eye in the peak , slip the heel ( snug fit) into the bight on the snotter, tension the halyard fully and belay the halyard on the port belaying pin. Then go aft to raise the sprit via the snotter. Usually I tension the tack down haul at the same time but make further adjustments after things stretch a bit or wind conditions change.

Now one of the things I like about the sprit .rig , I brail up the sail. Then take the clew and roll up the rest of the sail close to the mast and secure it with a prepared velcro hook and mating loop. The sail is all up and ready for instant filling. My dock space is very tight my neighbor just a few inches away. I back the boat out of the slip by hand , face her to the channel give a good push and jump aboard . If things are clear I yank the brail line loose from a cam cleat also on the console , yank the velcro line to release the rest of the sail and I'm on the way.

I usually have to tack out a narrow channel ( river) to clear the harbor when out, the jib goes up.

When returning I de power the sail by easing the sheet and pulling fully on the brail. This slows the boat up considerably and allows me to sail her right back to the slip. If I mis judge the speed and am slowing down too much, a release of the brail allows the sail to fill again.

This system works good for me but in your situation some of the above techniques might be of use or worth considering before giving up on the sprit. If you need any illustrations I can send them by E mail or maybe post them is others are interested. Also see WB # 140 Pg 26.

http://www.imagestation.com/picture/sraid33/pd0eb5e4b5e3cf897c348403c7cf5c74b/fd3abf71.jpg

Brailed and furled just back her out , give a push, get aboard, yank the lines and away we go.

Good luck

JD

[ 06-27-2003, 07:50 PM: Message edited by: J. Dillon ]

[Todd Bradshaw]

The baggy area, low and aft is puzzling. That area (roughly the lower, aft quarter of the sail) is generally cut nearly flat. The sailplan drawing that I found shows a loose-footed spritsail, rigged to a conventional boom and also having a roached leech with battens. That's a lot of features to try to cram into what is supposed to be a very simple sail and kind of makes me wonder why they didn't go to some other sail type if they wanted all that stuff.

I assume your sail is cross-cut, as it would be unusual to build that much roach and three battens into a vertically cut sail. If so, the shape built into the tack seam (closest panel-to-panel seam to the tack corner) might be excessive as might any shaping done on any other panel seams striking the foot, but it's a tough call without seeing it. I doubt sprit tension is a major factor in that part of the sail unless it's horribly slack. The angle of the outhaul line, from the clew to the boom might be worth playing with. Sheeting angle is critical on boomless spritsails and when you add a boom that job is pretty much re-assigned to the outhaul. It would be interesting to see what kind of sailshape you can get without the boom or maybe with a sprit-boom instead of the one shown on the plan.

At 86 sq. ft. typical measurements for the other types of sails you mentioned would be something like this:

Lateen - Luff and Foot 14' (yard and boom around 14'4"-14'6") Leech 14'5". Mast in the 10'-11' range. The C.E. would typically fall about 45" aft of the mast, though there is a fair amount of mast placement wiggle room.

Leg-O-Mutton, sprit-boomed - Luff about 16', foot 11.75', leech 16.6' The mast is probably going to need to be 17.5' or better and the sprit-boom around 11'-11.5' long. You will probably need to either rake the mast back (Dovekie-style) or move it aft to get the C.E. in the right place.

Balanced Lug: Luff 8', Head 9.4', Foot 9.15', Leech 13.85', Diag peak to tack 16.5', Mast height around 13'. Again, you may need to rake the mast or move it's support structure aft to get things to balance-out. A standing lug would be another possibility and would likely require less adjustment in mast position.

[Dennis Marshall]

Todd, thanks for your post. Yes, the sail is crosscut and yes, you are probably right about the outhaul tension. Because I have been thinking that the sprit has been causing the problems, I have hesitated to experiment with a sprit boom. Although in light of your comments, it seems a worthwhile proposition. This does not remedy most of my difficulties, but it will be worth a try. I have no difficulty with shape when boomless, however, the rhythmic rolling caused while running downwind is severe and no matter how much I trim the sail to try to dial it out, it remains enough to make me queasy. The boom tames the sail much better and I like it for that reason.

According to plan drawings, the sail’s CE is 3’9” aft of the mast and 8’6” above the LWL. When Jones got permission to redraw and sell the plans on Dobler’s death, he increased the sail area of the original by 11 or 12 ftsq.(BTW, the principle dimensions of the spars: The mast is 13’4”, sprit is 14’, and the boom is 8’8”; the sail: luff=9'8, head=7', foot=8'8", and leech=13'10" with a 6" roach). I am loath to construct new mast step and partner for a new sail unless I absolutely have to. I would not be averse to using a smaller sail if that would save me the trouble of that kind of fiddling. Would it be possible to fit a slightly smaller sail that comes close to the original sail’s CE?

Also, would it be possible to increase headroom under the boom without throwing things out of balance? As is, the boom is about 24” above seat height which means that it is a little bit lower than my chin when I sit up straight in the boat. As is, I crouch down a lot and this tends to be a real pain in the back!

Thanks,

Dennis

[Todd Bradshaw]

Since the existing sail has a lot of area aft (not even including the roach) going smaller, which tends to move the C.E. forward, is likely to just make getting the boat to balance correctly more difficult unless the mast is moved.
Here is the existing sailplan:
http://www.imagestation.com/picture/sraid67/p16872fb13dd693be708786fafab18a45/fbd13130.jpg

It is possible to switch to a Lateen or Leg-O-Mutton that works. These are the sails that I mentioned above. The lateen actually lowers the C.E. and at the same time raises the boom. With a longer mast, the current C.E. position could be maintained and the boom raised even more, though at a certain point it starts to look pretty silly, so I picked a somewhat more moderate position.
http://www.imagestation.com/picture/sraid67/p21e3f216e998a50fad019e3fdc906b9e/fbd13138.jpg

The Leg-O-Mutton with a sprit-boom is probably the most interesting, though the mast is longer than the boat. It could be shortened a bit, but there isn't much reason to have sail area below the gunwale. I'd rather it had a little more mainsheet angle, but think this would still work.
http://www.imagestation.com/picture/sraid67/p9639c29e1e6091d18ca1d103db69d4f6/fbd11339.jpg

The balanced lug is hard to do without moving the mast since they have sail area in front of the mast, moving the center forward in relation to the mast placement. I tried several and the best one seemed to use the raked mast and basic proportions of Iain's Ness Yawl mainsail (measurements above). It's also a really pretty shape and one of my favorites. You could probably leave the mast step where it is, but the partners would need to be moved aft about 5".
http://www.imagestation.com/picture/sraid67/pfdbfbb2c2a67140171d36c503c9900e4/fbd13115.jpg

Anyhow, step #1 is most likely to continue experimenting with the current rig and see if you can get it tolerable. If it continues to be more trouble than it's worth it should be possible to switch to something else without a horrible amount of hassle.

[Dennis Marshall]

Todd, Wow! Now you have me drooling! Both the Lateen and leg-o-mutton look good on the boat. I know at one time Jones used a Sunfish sail before moving to a spritsail of the same dimensions as the lateen. He complained that the sail was too full in heavy air and too flat in light air. I like the leg-o-mutton too, it really looks sharp, plus, with the sprit boom, there would be some room for tweaking sail shape in different conditions.

A couple of questions -- What type of mast dimensions would one be looking at in the case of the leg-o-mutton? What about provisions for reefing both sails? I've never heard of reef points on a boomed lateen, but I guess it is not out of the ordinary. Finally, the Dobler is very lightly constructed forward where you have the halyard tied off. It would take a lot of beefing up the foredeck to handle loads generated by the sail, although I would not know how much. So, is that arrangement necessary for the sail to work?

Thanks for the great visual aids, I appreciate it very much.

Dennis

[Todd Bradshaw]

Cleating the halyard forward as a makeshift forestay is just an option. It can sometimes help control mast bend a little. It can just as easily screw things up making the mast bend in funny ways, so it's one of those "use it if it helps" things, but is not required. On lightly built boats the stem is probably the best place to anchor it if you do try it. Otherwise, the halyard can be cleated on the mast or partners.

Masts aren't really my department, but for a 19' wooden mast I wouldn't be surprised a bit if it took a maximum diameter in the 3"-3.5" range to do the job without being too much of a noodle. The sail should be cut to match measured bend in the spar as the whole sprit-boom system generates mast bend like a bow and arrow. If a reasonable amount of bend allowance isn't built into the sail, it may wind-up being too flat most of the time. The downside to this is sometimes deeper than ideal draft in really light air, but it seems to be the lesser of two evils. All three types can be reefed. I'll dig up some drawings that show how it can be done.

[Todd Bradshaw]

Lateens reef out a wedge along the foot like this one is set-up for:
http://www.imagestation.com/picture/sraid67/pb178ecf87fe1b2d4b3435c18bd86a258/fbd0cd9a.jpg

And here is a sprit-boom Leg-o-Mutton with one way of putting in a reef. The sail is raised to a lower position on the mast and the boom attached to the reef clew. The excess sail along the foot is then bundled-up with the nettles hanging from the patches. Other systems may gather luff fabric along the mast instead, though I'm not too thrilled with the idea of a "luff bundle" as my leading edge.
http://www.imagestation.com/picture/sraid67/p18c73f625347524b545905038d7d31f6/fbd0d05d.jpg

[Dennis Marshall]

Todd, thanks so much for the visual aids. It has really helped me understand things better and you have given me much to think about. Also, thanks for all the trouble you went to in creating them. It is very much appreciated.

Dennis

[Dennis Marshall]

Todd, now that you've got me thinking, I'm finding I have some more questions. Specifically, could you explain the benefits of the sheeting arrangement you have drawn for the lateen sail? I've never seen one sheeted like that before, and I am curious and interested about it.

Thanks,

Dennis

[Todd Bradshaw]

Bear with me as this will be long, but it's a really interesting concept for such a simple-looking system and deserves to be understood.

It's the same mainsheet system used on Sunfish and some of the other, similar boats and works very well. At the aft end, there is a bridle which is connected to the hull on either side, fairly far outboard (on open boats uaually at the gunwales). It allows the tiller to move side-to-side under the bridle without interference. Some boats have a loop seized or tied, mid-bridle, like a Sunfish has, and the aft end of the mainsheet is deadened to the loop. Others have a block spliced to the aft end of the mainsheet which is free to roll side-to-side on the bridle, either fully, or in a limited area between a couple of stopper knots tied in the bridle. Allowing the aft end of the sheet to travel side to side can give a more direct, downward pull on the boom when it's not center-lined and reduce sail twist for a bit more power when you sheet in hard.

Keep in mind that Lateens aren't superlative upwind performers in terms of sailing well at very high pointing angles and you seldom trim one in much closer than having the boom over the transom's corner, but it's worth experimenting with the different possibilities for the mainsheet-to-bridle connection to see what seems to work best for you, your boat and the conditions you tend to sail in.

The sheet itself attaches to the bridle, runs up to an aft boom block, along the underside of the boom to a forward boom block, near the gooseneck, and then down into the cockpit. It's not a bad idea to mount a simple fairlead or two between the boom blocks to help keep the sheet from drooping into the cockpit as you tack. Occasionally having the mainsheet hang up on your head or life jacket when you tack is about the only drawback that I can think of for using this system but it's generally not a big deal and the system has enough advantages that it's an acceptable situation. It's also pretty easy to avoid, but I'll touch on that later.

The biggest problem in building a good lateen rig is dealing with the high amount of bend in those long, skinny spars and trying to control it's effect on the sail and use it to your advantage. The maximum amount of luff and foot curve which needs to be built into the sail to generate good draft is only about 1.25" on a sail this size. This means that as soon as the yard or boom bend 1.25" (which doesn't take much mainsheet tension or wind pressure to do) the draft is gone and the sail is undesirably dead flat. For this reason, a "bend allowance" (extra luff and foot curve) of typically 3"-4" for dinghy lateens is added to the sail's cut. The idea is to allow for the spar bend in moderate conditions with the built-in extra cloth and still maintain enough luff and foot curve to create the desired draft.

In higher winds or when sailing close-hauled, when sheet loads and wind pressure are higher and when you generally want a flatter sail, sheeting-in tight enough that spar bend exceeds the built-in bend allowance starts to eat-up the draft allowance and flatten the sail.

Unfortunately, the easiest method of attaching a mainsheet to a small sail's boom - just tying it on somewhere mid-boom and letting it hang down, encourages a lot of draft-eating-boom-bend any time you pull on it. You will often be sailing around with the bottom half of your sail (the big part that supplies most of the power) flat in conditions where you would rather have some draft in the sail. When heading or wind speeds call for sheeting in hard, it will bend even more, sometimes to the point of distorting the entire sail.

By contrast, our system with the blocks near the ends of the boom aviods direct downward pull on the boom's middle. It will still bend the boom to an extent (anything will) but less, and more controllably. Having the forward block very near the gooseneck gives us another big advantage. As you sheet in hard, it tightens the tension along the luff, which is generally (for lack of a better way to say it) the best place to pull on a sail if you want to flatten it for high wind or close-hauled sailing. It tends to temporarily gobble-up excess, draft-creating fabric and store it along the luff (in a crease if you were to pull hard enough). It also temporarily defeats sewn-in, panel-seam-generated draft placement (called broadseaming) and gives you a flatter sail with what draft it has, moved forward. Essentially, it works the same way a Cunningham Ring does on a Marconi sail and that's the type of shape we're after in those conditions.

Since it's effect here is strictly generated by mainsheet tension, it is essentially automatic. When you sheet-in hard, it's there. When the sail is eased-out, off-the-wind, and you want a fuller sail, it's gone. For such a simple system, it's really clever and works very well.

After passing through the forward boom block, the sheet heads for the cockpit and the sailor. A stock Sunfish is set-up that way. The sailor hand-holds the sheet or wraps it half-a-turn around the little metal hook in the cockpit if he wants some hand-relief and belays the sheet off of the hook. The hot Sunfish sailors figured out a long time ago that this system was not ideal. When you hand-hold a mainsheet that's hanging off of the boom, every puff in high winds is trying to pull you out of the boat. I even had one iceboat that, though not a lateen, was set up this way, and a mainsheet that's constantly trying to throw you out onto the ice at forty miles per hour is not what I would call a user-friendly system! It got changed very quickly....

Belaying the sheet off of the metal hook in the Sunfish had the advantage of re-directing the sheets pull. It was now pulling up on the hook, not the sailor, and trimming the sheet pulled the sailor down into the boat, instead of up and out of it. Big improvement! The sailors then went one step further, replacing the hook with a deck-mounted swivel block, adding a couple Clamcleats behind it and they had what is essentially the current and best system.

On an open boat, like the Dobler, the same thing can happen, especially with a lateen that large. It would be wise to fix some sort of swivel block to the partners, mast base, etc. below the forward boom block and run the sheet through it before sending it aft to the sailor and/or any type of mainsheet cleat positioned where he can reach it. It's much more pleasant than sheeting directly off of a boom block.

Drawbacks: More mainsheet line to buy (pretty cheap) more line to trim and ease on a broad-reach-to-broad-reach or run-to-run jibe, and the possibility of the dangling mid-boom section of the mainsheet hanging-up on the sailor as mentioned before. Fortunately, the last two can be eliminated with technique.

At a certain point during a tack and to some extent even during a (controlled) jibe, the sail goes slack for just an instant - right before it passes over your head. When tacking, a lateen will actually sit there center-lined and shake for a second or two. The trick is simply to watch the sail and just as it starts to luff - about the time the boom gets as far in as the gunwale, you grab both boom and sheet and pass them over your head toward the oposite gunwale. Don't force it against the wind by doing it early, wait until it just goes slack and move it over where it can start catching wind on the other side. You can even lift it a bit to clear your head if needed. As silly-stupid-simple as this sounds, it can make your tacks and jibes much faster, easier and more efficient while making sure the hanging mainsheet isn't going to strangle you.

Let's see - tiller in one hand...mainsheet in the other...OK, I'll just use my third hand to move the boom across??? Since it's generally bad form to just cast-off the mainsheet before a tack or jibe, you'll generally want to either cleat it off with a bit of slack in it before reaching for the boom or temporarily transfer it to your tiller hand for a couple seconds and hold both tiller and sheet there while moving the boom. With a little practice, it will become automatic.

Any how, that's the skinny, in depth and detail, on that mainsheet system. If I can talk Scot into printing covers for it, I'll have another book, but it's a really good system that works well on lateens, lugs and many other types of small sails and it's worth knowing about.

[Dennis Marshall]

Todd, very interesting information on sheeting the lateen. Thanks for taking the time to answer the question. I have book marked this thread for future reference.

I realize that the lateen is not a great windward performer, but it is adequate for the type of sailing I do, and it is a sail that I am familiar with -- even more so now that you have provided that goodly bit of sailing knowledge.. However, the sprit boom leg-o-mutton is attractive because I think it would give the best all around performance of the alternates you posted.

BTW, fashioned up a rough sprit boom for the spritsail.It aint pretty, but it will serve well enough as an experiment. Everything is set for sea trials this evening. The dry run seemed to work OK, although there was an interesting crease along the boom. I'm hoping that is ironed out by wind and sheet tension. I'll give a report later tonight when I am back home.

Cheers,

Dennis

[Tomcat]

Anyone ever heard of a split lug rig? Possibly to tack more readily.

[Todd Bradshaw]

I don't know of anyone who has used one and can't remember ever even seeing a photo of one in use, but from what I gather tacking one would be a real bear and is probably the reason they are not used much. You essentially have a boomless lug main and a boomless lug jib, both attached up top to the same yard. Tacking would be a matter of repositioning or detaching and re-anchoring both sails' tack corners every time you tacked or jibed. When combined with your duties steering and tending sheets, you might need four or five hands to do the job. Finding a place to tie-out the tack corners when sailing off the wind with the sail outboard is also somewhat of a problem.

I have seen an experimental variant that looked interesting. It had spars like a balanced lug (with boom) but the mainsail was all behind the mast. Hanging between the empty forward ends of the yard and boom, in front of the mast, was a seperate, boomed, lug "jib". It's small yard and boom were suspended from and between those of the main. This allowed the entire rig to swivel to windward and trimming the "jibsheet" (attached to the jib's mini-boom) allowed the slot between the mainsail and jib to be adjusted. It seemed like it might be no more difficult to operate than a normal balanced lug, but had some of the advantage a sloop rig has in terms of the jib improving the performance of the main.

[ 06-29-2003, 07:27 PM: Message edited by: Todd Bradshaw ]

[Todd Bradshaw]

Don't quote me on it, but as I remember, the rig I saw looked something like this:
http://www.imagestation.com/picture/sraid67/pb89606e1e3fe2a829fecd35d9b31fe5b/fbce75fd.jpg
and I think I saw it being used on a kayak! Don't know much more, but it looks interesting.

[Dennis Marshall]

Well, the sprit boom worked. I had no trouble with sail shape except for the fact that the foot of the sail wanted to fold up. Does that mean I had the snotter too tight?

Dennis

[Tomcat]

Thanks Todd,

I hear Dick Newick designed one for a Kayak, and mentioned to me working on one for one of his tris, but gave up on it.

What you have drawn out up there sorta looks like a poor man's aerorig.

[ 06-30-2003, 12:53 AM: Message edited by: Tomcat ]

[Todd Bradshaw]

Dennis, I think what's happening to the foot of your sail is a combination of a couple things and though it may look awful, it's fairly localized awfulness and may not be a really serious problem in terms of efficiency for the entire rig. It's still probably yielding a better overall sailshape than the problem you mentioned with the old boom at the beginning of the thread.

Sails for sprit-boom rigs are usually built with a straight foot running from the tack to the clew. There is a natural line of tension formed by the configuration of the boom and running in a pretty straight line between those two sail corners. If the sail has much foot round, like a sailmaker would normally build into a conventional loose-footed, boomed sail (like your sail) and you switch to a sprit-boom, the cloth below that tack-to-clew straight line of tension is liable to become little more than a useless flap. It may even curl due to the slightly cupped shape built into the bottom of the sail. If you decide to stick with the sprit-boom you may eventually want to have the foot re-cut, removing the round along the bottom and yielding a straight-line foot from tack ring to clew ring. It's a pretty simple operation and will remove most of the cup-shape that's built into the foot and most likely much, if not all, of the distortion.

The "line of tension" thing is also what makes sprit-boomed sails self-vanging. The cloth between the tack corner and clew corner gets pulled tight by the boom set-up and acts as a diagonal brace between the lower mast and the boom, just like a boom-vang that's on all the time. This prevents the boom's aft end from being able to lift even if mainsheet tension pulling down on it is minimal. This in turn prevents the top of the sail from twisting excessively to leeward and spilling wind.

If you're trying to get maximum power from the sail, this is usually a good thing. On the other hand, if you're getting overpowered it prevents you from using induced sail twist up high to de-power the sail. You either have to hike enough to counterbalance the entire sail or put in a reef to de-power, possibly a bit earlier than you would have to on some other types of sails which allow more twist.

[Dennis Marshall]

Todd, thanks for all of the information. I will use the sprit boom throughout the rest of this season and make a decision about whether or not to change sail plans in the fall. I appreciate all of your insightful comments.

Dennis