Hi Scott,

I end up with hollow in the leech of the jibs automatically with my lazy way of building the sails.

I draw the lenses the desired length along the batten, and then I also draw the centre panel the same length. When the centre panel is sewn onto the lens round the edge of the curve it ends up too short, as the curve is longer than the straight line. Then I trim the leech of the lenses from their full length at the batten to the end of the leech of the centre panel, so that the leech is made of three straight lines with a significant hollow.

One little advantage with this is that a handicapper for a rating would not find the chord of the sail greater than the length on batten, and that the area calculation would be accurate.

I always include a leech line inside the hem/ tabling and have yet to see any sign of a hooked leech as I don't tension the leech line, but have it available if any motor-boating problem appears.

Cheers, Slieve.

Thank you for the full response, Slieve.  You've filled in quite a few blanks in my head, and of course, as you said, created some new ones.

The drawing I've done show the leach flaring, but only in cut.  My expectation is that the little bit of hollow will actually just keep the aft 40% flat.  I'll do test pieces to figure out how much hollow makes sense.  I'm thinking that I'll hollow not only the panel (by broadseam adjustment), but also the vertical leech itself ever so slightly, hopefully keeping the leech flat as a table.  It may be that hollowing the vertical leech actually makes things worse by putting too much of the tensional forces on the trailing edge an causing a hook.

I think that I'm falling into a similar Tin Sail trap - one that you've warned about before;  when making sails, the drawing does not equal the outcome.  I think that I'm going to spend a weekend making several models of fabric, similar to what you've described with the wallpaper.  It will be worth it to take some careful measurement and compare them all to the drawn shape.

Hi Arne,

I always fit telltales to jib luff and main leech, but when sailing am only interested in the luff ones. I fit both to see if I can find any indication of a need to increase or decrease the jib sheeting angle, and it is the the result of this and other things that makes me think that we can open up the jib sheeting angle more and sheet the rig in even tighter when close-hauled.

When sailing the lee tell tale on the jib tells everything, and when it lifts you can feel the boat slow down. Once you get in the grove you can steer without watching it, but it is a great help in getting settled down. I've only really looked at the main leech 'tales on the first outing with a new rig. (I can't remember ever stalling them, which suggests a wider jib setting and tighter sheeting.)

I had always planned to clamber around the foredeck with a fishing rod with streamers on the tip to plot the airflow along the lee side of the rig, but never got round to it. I just enjoyed sailing the boat.

It is possible to sheet the split rig right in tight and still sail to windward, tacking through a ridiculously narrow angle, much narrower than the Bermudan rig on the same hull, but the speed will be low and the VMG to windward not the best. I used to simply set the sheet to tack through just less than 90° if the sea state was reasonable. It could be that there would have be benefit in having the main in more and the jib wider, and I suppose that is the way the jib designs are going. I'm sure there is a way to go before we find the optimum parameters, but even from the first rig the performance has been well worth the effort.

For Edward to have about 3° of helm when close hauled is reasonable. I believe it makes the boat easier to sail, with just a light load on the tiller whereas a neutral rudder can become twitchy.

Cheers, Slieve.

Hi again Arne

Yes. Amiina has Leech telltails on each panel, and even more important tell tails ca. 20 cms from the luff  in each jiblet. To monitor the airflow on both sides of the jibs. The leeward side being the most important. 

Edward, and Slieve

Remember, I am not restricted by racing handicap ratings. I can see your point of being area-restrictive to compete well, and it would surprise me if a 20sqm Johanna-style sail could keep up with a 20sqm Mk II Split Junk.

I notice now that the Splinter 21 has been given a quite light keel, only 400kg (32%), versus Malena’s 600kg (42%). Pity that. The Splinter, with her slim lines, looks to me to be a boat which would have thrived with a 600kg keel; boiling along at 25-30° heel.

I guess the reason why I stick to my (second best?) rig is  -  besides laziness  -  that I find it easier to understand and thus make my sails, and also to describe to others how to do it. In addition, I like to be able to remove any sail-to-hull imbalance by adjusting the sail-to-mast balance during trial sails.

I still remember the dramatic boost in upwind-performance I experienced when the flat sail of Malena was given 10% camber (hinges, 1991). The actual progress to windward may have leapt up as much as 20%, and even more in light winds. During one match-race against a Bermuda-rigged sister boat, Malena went both faster and closer to the wind. In my head, it seems unlikely that there will be another 5% to gain from a split junk. On the other hand, for racing, even 3% speed gain is the difference between winning and losing (about 1min48s pr. hour).

Slieve, your way of sailing sounds very much like mine. The trimming lines I use (THP, YHP and FUP) are generally not touched between reefing and un-reefing the sail. The sheet forces are no doubt higher on my low-balance sails than on a SJ, but as long as I can tack without touching anything, except the tiller, I think I am fine.

One thing I wonder about is that I cannot spot any telltales on Amiina’s new sail. I find the leech telltales I fit to be very useful, both to avoid over-sheeting the sail, and to check that the twist is right.

Cheers, Arne

PS: And yes, sailing back into the finger berth is something I too do frequently. On Broremann I even used to tack my way out between the rows of expensive yachts...