Balanced Tarp

[neilm]

http://neilmoomey.com/boats/skerry/IMG_1731_balanced_tarp.JPG

I'm not happy with my Sprit rig on my Skerry so I made a prototype Balanced Lug. I just eyeballed everything. I put the daggerboard in there for reference.

What should I change? Now I'm wondering about the mast. Is my mast too far forward or leaning too much to make this type of rig usable? I actually have a curved piece of Spruce which would make a nice curved mast. I might give that a try to make the mast curve back.

Neil

[Dan St Gean]

http://neilmoomey.com/boats/skerry/IMG_1731_balanced_tarp.JPG

I'm not happy with my Sprit rig on my Skerry so I made a prototype Balanced Lug. I just eyeballed everything. I put the daggerboard in there for reference.

What should I change? Now I'm wondering about the mast. Is my mast too far forward or leaning too much to make this type of rig usable? I actually have a curved piece of Spruce which would make a nice curved mast. I might give that a try to make the mast curve back.

Neil

If you follow Todd Bradshaw's advice on finding the CE of the sail vs. the CLR of your hull (daggerboard), it looks a little foreward to my eye. You would probably experience some pretty heavy lee helm with the majority of the sail that far foreward. You could extend the yard and boom further aft and shorten sail a bit. The goal is to have a bit of weather helm and that is achieved by keeping lead relatively small relative to the CLR.

Dan

[Hwyl]

Is the tarp just a mock up? The boom and gaff need to be longer. Had you thought about a dipping lug. You'll have serious lee helm with that rig.

[Canoez]

Well, I'll wait until Todd comes through here wringing his hands and shaking his head...

[Yeadon]

Dipping lugs are way cool ... but what a pain while single-handing. What about a smaller standing lug, coupled with a mizzen? (... as long as we're throwing out fun and cool rigs ...)

[wtarzia]

What should I change? Now I'm wondering about the mast. Is my mast too far forward or leaning too much to make this type of rig usable? I actually have a curved piece of Spruce which would make a nice curved mast. I might give that a try to make the mast curve back.

--- Do you need longer boom and yard to get more outhaul on the sail? The wrinkles seem to say you need that, but perhaps everything sets well when the wind is on it?

I too am trying to tune my lug rigs (standing lugs, cat-ketch), and I am discovering all the interesting variables I never had to think about before! We are probably getting an excellent education -- keep thinking about it that way as you work on the teething problems. :-) --Wade

[David G]

Neil,

I'm no rigging expert, but I do own two boats with balanced lug rigs. You're probably aware of all the things I noticed:

1. Longer yard & boom to allow for more outhaul
2. Can't see what sort of downhaul you have rigged, but it looks like it'll need more.
3. Yes, your sail is set a bit too far forward of the mast - both for the sail to set correctly, and probably for the CE/CLR balance
4. Don't forget to taper the mast a bit and the yard substantially (more at the high end) to allow the spars to flex and take the proper form when the downhaul is cinched - and to allow the rig to flex and spill wind in a gust.
5. I don't know if it's correct or not, functionally, but I like the raked mast. It raises the aft end of the boom and gives you more room... and I like the look for that boat. Might need to straighten it to aid in the balance equation.
6. I bet you'll like the balanced lug on that boat - both for its simplicity and it's low CE.

I think the two designers who do the best job of setting up well developed balanced lug rigs are Michael Storer and Ian Oughtred. I haven't read much from Mr. O on the topic, but Mr. S had a screed on the topic on his website:

http://www.storerboatplans.com/Faq/tradrigperformance.html


"Luck is the residue of design" -- Branch Rickey

[keyhavenpotterer]

Michael Storer has a lot of information on his site about lug rigs and poly tarp sails. this thread on his forum shows a nicely setting tarp lug rig

http://www.woodworkforums.com/showthread.php?t=28107&page=21

My own lug rig, and how all the controls are set up is shown here

http://www.flickr.com/photos/27848841@N05/sets/72157606911697259/

Brian

[Todd Bradshaw]

...a balanced lug for a Skerry? Been there, done that, don't wear T-shirts. I'll look up the plan I built it from in the morning. Right now it's after 3:00 AM and I just finished eight hours of recording and am too punchy to type. We raked the mast, which both moved the C.E. aft and looks nice, but it could probably work OK with a plumb mast. I'll know more when I dig the plan out of the big box-o-rigs. Don't know where he got that wrinkle (it wasn't in there when I built the sail :)) but this was the shake-down cruise and he was still messing with details.

http://webpages.charter.net/tbradshaw/Picture%20006%20copy.jpg

[Todd Bradshaw]

new sail plan:

http://webpages.charter.net/tbradshaw/Skerry%20Lug/

[neilm]

Thanks everyone. Todd, those plans are just what I need! Thanks a bunch!

Neil

[neilm]

http://neilmoomey.com/boats/skerry/IMG_1736_bent_mast.JPG

I made a new mast this weekend. I cut a 14" scarf then flipped sides and epoxied.

http://neilmoomey.com/boats/skerry/IMG_1732_balanced_tarp2.jpg

This is the result. I think it's workable.

Neil

[Daniel Noyes]

Im not too sure about that scarf neil, the base of the mast is where all the forces are located on an unstayed mast (thats why I like stays so much) the scarf looks like it's just glued to one layer of wood grain on the base. I usually dont scarf a mast unless it's not long enough, try to keep the integrity of the wood. I would test it in some wind but close to shore or help, if you are sitting on the rail and that mast goes the skerry will likely drop you right over backwards in the water...but I did sail a dory with a closet pole mast untill I got heavy enough to break it hikeing out (about 130, by age 14) closet pole reminds me... are the spars birch trees? interesting experiment, did you consider a Leg-O-Mutton rig, it is a ancient sail plan used on the dorys of Massachusets north shore for centuries, the simples most economical sail around and I would think perfect for a Skerry as it is a dory type.
Dan
http://dansdories.googlepages.com

[Todd Bradshaw]

You also need to orient the scrim in your sail "fabric" to the leech edge to prevent the leech stretching out (which has already happened and is clearly visible in the photo). This is something that the people writing polytarp sail instructions very often fail to mention or understand because most of them never bothered to learn anything about sailmaking before they started building them and publishing information. Even a cheap material like polytarp can make a sail with decent shape (at least for a while) if the builder has a decent grasp of the basic principles of sailmaking. Without them, you're screwed.

[neilm]

I am trying to learn. I'll read up, thanks. I need to get your book Todd.

As for the scarf. My first mast in the Skerry kit was scarfed up and it worked fine. This one is the same length plus there's less end grain so it should be even stronger. Well, if it breaks it breaks. I'm working on the yards now. This is just a prototype.

Neil

[wtarzia]

... did you consider a Leg-O-Mutton rig, it is a ancient sail plan used on the dorys of Massachusets north shore for centuries, the simples most economical sail around and I would think perfect for a Skerry as it is a dory type.

--- I'm glad somebody said that. I wanna add, please put a leg-o-mutton on the *stock* skerry/skerry plan. It is a beautiful hull and the stock sail is no doubt a good sail, but together somehow (can't put my finger on it) they look butt-ugly. Somehow. -- Wade

[Dan St Gean]

--- I'm glad somebody said that. I wanna add, please put a leg-o-mutton on the *stock* skerry/skerry plan. It is a beautiful hull and the stock sail is no doubt a good sail, but together somehow (can't put my finger on it) they look butt-ugly. Somehow. -- Wade

I think it's the really high boom that allows rowing beneath it.

Dan

[Todd Bradshaw]

Those flat-topped, square-ish spritsails are quite typical on Scandinavian boats and appropriate on Scandinavian-inspired designs, like the Skerry, but their profile is sort of an acquired taste. And yes, they've stuck it way too high, which just makes it look strange.

[wtarzia]

It wasn't the sail shape or the sprit-mode, but, yes, the high set of the sail. Visibility is good to have, but it made me cringe, aesthetically. (I'd rather have a nontraditional plastic window in the sail, though some people probably think this is blasphemy on a wooden boat with traditional nods). Also, got a flashback to the days when I too had a high-set sail on my dory, for visibility and to keep the boom out of faces/heads. After a while I shortened the mast, started a habit of just watching for the boom -- but lowering the mast put boom at chest level, not quite so bad as taking it in the face (back then I knew little about boomless sails, though a dory skiff with that transom might have made that workable; a sprit boom might have worked too). And....the boat sailed noticeably better with the lower CE. Perhaps that was more important for a dory than than a skerry. I wonder if the skerry would sail better with a lower sail? -- Wade

[Todd Bradshaw]

Unless it's very light air and you're reaching up for every possible bit of wind, the shorter heeling lever from lowering the sail makes a lot more sense. The spritsail should also have a brail. That way, if you're rowing you can really get it out of the way, rather than placing the sail so high that you can sit under it. I have a very low tolerance for overly high sail placement, boomed or not. It seems to me that learning to deal with the boom or foot is just part of learning to sail and what is gained by raising them way up seldom outweighs the effects and/or problems it causes. Plus, it just isn't that difficult to learn to do it properly.

To be honest, when it comes to tacking and jibing, an awful lot of small boat sailors really aren't very good at it. They have never developed a plan for it, have never spent any more time than absolutely necessary practicing it and have never taken the time to study the various aspects involved and see what combination of actions works best on that particular boat. When a tack or jibe goes smoothly they feel lucky. Hunkering down in the hull and patiently waiting for the boom to eventually wander over on its own is not good small-boat sailing. Raising the entire rig so high. just so that tacking without getting beaned requires no skill or practice doesn't strike me as particularly good boat design.

[wtarzia]

... Raising the entire rig so high. just so that tacking without getting beaned requires no skill or practice doesn't strike me as particularly good boat design.

Yup. And back then it was a way to get my then-wife into the boat -- she was quite annoyed at having to 'be aware'. After it was clear that nothing was going to make it fun for her and she was all done, I could just sail alone, lower the mast, and do it the right way ;-) Tyen I could learnmore about jibing, but that's another story (suffice to say that you *can* sail a dory downwind back to the dock, totally swamped ;-) -- Wade

[David Gilroy]

This might be pulling the thread too far off topic, but Todd, at the risk of asking a dumb question, would you expand on the notion that there's more to tacking than just hunkering down and waiting for the boom to come around?

[Todd Bradshaw]

Sure. Step #1 is to learn the angles that make your boat tack nicely - the angle to the wind, the amount of boatspeed that you need to initiate a good tack and the amount you need to turn the rudder blade (as well as how quickly you need to turn it and at what point during the tack the rudder turns the boat best with the smallest loss of speed). These things are learned by getting out there and sailing (a dirty job, but somebody's got to do it) and they will be somewhat different for different boats and differing conditions. Spend some of that time sailing short distances and tacking and jibing a lot, just to be tacking and jibing. Sailing in tight figure-8's, where you tack or jibe as soon as the boat has come back up to speed from the last one is great for this type of practice and kind of fun.

On small boats I am a firm believer in "helping" the boom across. By "helping" I don't mean trying to pull the boom in, possibly going against what the wind wants to do to it, since this simply won't work and will likely get you in trouble. What I do mean is that at some point during every tack or jibe, the boom and sail will go limp as the wind pressure on one side eases and before it picks up on the other side. This is usually that brief period where the boom is right over your head in the cockpit, maybe wiggling a bit and you're down there trying to look up and see if it's out of your way yet so that you can sit up again. In the mean time, you are often trying to sort out the mainsheet and get ready to use it on the new tack. Rather than waiting in an uncomfortable position during this short slack period, I just reach up and pass the boom over my head to the new side. It simply gets it out of my way so that I can see what's going on and attend to what needs to be done and you can do it on little boats like dinghies as well as some pretty big cruisers. It's silly-simple to just reach up and move the boom out of the way, but it makes a difference at times.

A more important thing that I want you to do on any serious sailing outing other than the occasional late evening "beer cruise" is to start following the mainsail with the mainsheet. As your heading changes during the turn (either a tack or jibe, it doesn't matter) and the wind starts to bring the boom inward, trim the excess mainsheet as it becomes available. You don't need to be putting sheet pressure on the boom or trying to pull it in, but follow it in, keeping the amount of slack sheet to a minimum. As the boom passes overhead and starts out the other side, do the reverse - ease the sheet out to follow it and control the slack. This tends to eliminate that jerk as the sail fills on the new side, especially when jibing. On some boats (like my old Star where I had to trim and ease about 60' of mainsheet on a running or broad reaching jibe) it also helps prevent the sheet fouling around cleats or other stuff in the cockpit.

The amount that you allow the boom to go out on your new heading should normally be a bit farther out than the ideal trim position would be (or eventually will be) on that heading. This is because your boatspeed is reduced since you just made the turn. As the boat picks up speed on the new tack the aparent wind will shift forward a bit and you will be able to trim the main in closer without stalling it. Start your new tack though with the boom out a bit farther to match your reduced boatspeed and less-skewed aparent wind and then trim in small increments as you pick up speed.

These are simple basic steps, but if you learn your sailing/tacking angles and learn to maintain a close relationship between the boom and the mainsheet all the way through every tack and jibe, those tacks and jibes will be crisper, faster and you'll not only lose less boat speed and feel much more confident and in control on higher-wind jibe situations, you'll look better doing it!