Lug sail problem

[Sakari Aaltonen]

I bought a professionally-made sail for my self-built 13-foot dinghy, but am having awful problems with the main. This is a lug sail with a boom and a yard; there is a gooseneck on the mast to take the boom. What happens is that when I hoist the sail, the yard always ends up pointing 90 degrees from the boom. Maybe a more adept sailor can sail a boat like this; I can't.

The reason for this odd-looking phenomenon seems to be that the luff is not tensioned properly. If I pull it down by hand, the yard sets up very nicely, aligning itself with the boom.

Well. I checked all the dimensions of my mast/yard/boom, and they are as per the plans. Then I measured the sail, and did, indeed, find some discrepancy. The luff is a bit longer than specified, whereas all the other three sides are a bit shorter.

However, all the differences are rather small, a few percent at most. Is this enough to throw the sail off kilter this far? Like, make the boat unsailable - which it is right now?

Perplexed,
Sakari Aaltonen

[Willin']

Not to be overly simplistic but, lug sail shape is extremely sensitive to the point at which the halyard attaches to the yard. On my Shellback, moving the halyard back 2 inches took a huge ripple that ran nearly from the tack to the peak out and shaped the sail up nicely. In your case it sounds like the halyard may be too far aft on the yard. I'd experiment a bit before trying anything more drastic.

Hope this helps.

Mark

[Tonyr]

Can you adjust the gooseneck up and down? If yes, then I suggest lowering it. If not, and if the halliard is tight at the top, then the only solution (given a chosen yard hoist position) seems to be to re-locate the gooseneck.

One (experimental) approach could be to let the boom lay against the mast (i.e. not attached to the gooseneck) and rig up a simple downhaul to try varying the luff tension until you find what works. Then re-fasten the gooseneck to suit.

I agree that the location of the yard hoist is the other important variable. I don't know any theoretical way to solve your problem other than play around until the sail sets nicely.

Hope this helps.

Tony.

[Thad]

My thought might not work at all, but you might try leaving the boom ashore, downhaul the tack and sail loosefooted. If you find you want to outhaul the clew, use the boom, but leave the tack downhaul free of the boom.

[mower]

I used to have problems with luff tension on my standing lug sail. I rigged a simple downhaul from the gooseneck on the boom to the mast partner. It is a very simple solution, but works like a charm.

[Todd Bradshaw]

First of all, just to be sure, we're talking about a standing lug, right? I certainly wouldn't touch the gooseneck position as it probably won't fix the problem. It's much more likely just to move the tack corner down, swivel the whole sail a bit and be just as bad as it was. Luff tension and downhaul tension (for boats without fixed goosenecks) on a standing lug only exist if there is something for them to pull against - and from what I gather, that's what you seem to be lacking. I think Willin' probably nailed it right off the bat. If the halyard is tied to the yard too far aft you will have no luff tension and the yard will be too vertical or floppy in use. Tie it on no more than 35%-40% of the length of the yard, aft of the yard's heel. When you raise the sail on a standing lug (even a small one) you should be able to notice a distinct "tail-heavy" feel to the yard. The weight of it's aft end as well as that of the sail and boom should all be pulling down on the aft end of the yard and up on the forward end of it. Adding mainsheet tension should then increase it even more. This all pulls against the fixed tack corner at the gooseneck or the downhaul on boats with non-fixed goosenecks or boom jaws and is what creates the luff tension that you need. If you raise the sail, even with no wind and no mainsheet tension, it should still have decent luff tension and the yard should hold it's (more or less) horizontal position. If not, you're yard is too close to being balanced about the halyard tie-off point and you're not getting the tail-heavy leverage that the rig needs.

[Sakari Aaltonen]

Thank you for the suggestions. I tried moving the boom down by five inches - it didn't help (the luff is two inches longer than the plans say). So I tried raising the halyard block. Unfortunately, it then hit the shroud tangs. OK - I got rid of the tangs, drilled a vetical hole at the top of the mast, put a piece of threaded rod in the hole and tied the shrouds to that. _Then_ I moved the halyard block as far up as it would go. It didn't help. OK - I moved the halyard position on the yard forward by two inches. It didn't help.

The mast is starting to look like Swiss cheese. Also, the threaded rod at the top is not what you might call a stylish touch (it is be-hatted by a locknut.)

So I had a longish phone conversation with my sailmaker, who finally agreed to come and look at the sail (on the boat.) However, he is attending a big out-of-town regatta all this week and will come next Monday at the earliest. Oh well.

Sakari Aaltonen

[Todd Bradshaw]

It's really unusual for a 13' lug-rigged dinghy to use, or even need, either shrouds or a halyard block. What kind of boat is it?

[Sakari Aaltonen]

It's the Challenger 13 designed by Dudley Dix (http://www.dixdesign.com/challeng.htm).

Sakari Aaltonen

[Todd Bradshaw]

OK, now it makes more sense. It's a sloop rig with a fairly high-aspect main, thus the need for shrouds. It looks like the clearances between the heel of the yard and the jib's head and forestay are pretty tight, so if the main luff is longer than designed things might get interesting up there. I still lean toward the halyard tie-off point being the key to getting the main to set properly but it will be interesting to see what your sailmaker comes up with when he actually gets to eyeball the boat. Let us know what you find out.

[Sakari Aaltonen]

The sailmaker came by today, Tuesday, and had a look at the sail. He agreed that shortening the luff was the solution. and took the sail with him. I shall get it on Friday.

By the way, the sailmaker was rather surprised by the luff's tension (which seems to be the main thing keeping the yard up.) I got the impression he had thought of sprit sails when making my (lug) sail. Lug sails are regarded as very oldfashioned here; it's probably rare that anyone wants one.

But even with the shortened luff, there will be awfully little room for the yard at the top of the mast.. The shrouds and shroud tangs are in the way. A few inches more length would make a big difference. On the other hand, then the mast would not stow inside the boat...

Sakari Aaltonen

[Paul Scheuer]

Any chance that you could gain an inch or two at the step and lower the sail's position on the mast ?

[Todd Bradshaw]

I wonder if one could build (turn?) some sort of cap that would pop onto one end of the mast or the other and lengthen it by a few inches?

[Sakari Aaltonen]

Well, I got the sail on Friday. The sailmaker had shortened the luff and sewn in rope from the head to the tack (to strengthen the luff.)

Today, Sunday, we (my wife and I) went for a sail and the experience was much nicer than on the previous occasions. The sail sets much better. It's still not ideal, though. But the remaining factor limiting luff tension now seems to be not the sail, but, rather, my crew/wife who could not raise the sail all the way it could go. But the wind was so strong that I did not want to let go of the tiller (to go forward and try it myself.)

The wind was strong on one tack, yes. However, the other tack was very difficult. The best I managed was a sort of broad reach. Even then, the boat at times tended to turn almost downwind by itself. I have sometimes had this same experience with another lug-rigged (balanced) boat. Am I doing something wrong? Or is this a peculiarity of the lug rig?
Do note that I'm a beginner-class sailor.

Sakari Aaltonen