Unbeknown to me Edward has continued to experiment with the little jib leech battens, and with sheetlets back to the luff of the main panels. He has used very light battens which are very flexible at the front and stiffer towards the leech. I haven't seen them in action yet so shouldn't really comment, but they are an interesting experiment, perhaps if looking for extreme performance, but are not necessary on a cruising rig. I feel this is a case of pushing the boundaries to see what can be done. Look at how far the Bemudan rig has been pushed to get the best performance, and then look at the simpler basic cruising rig set up. Compare a F1 car with a family saloon. (the family saloon has a heater and a music centre, so I know which I prefer).

Cheers, Slieve.

Ouch! The print is too wide. Copy and paste the text into word to read it.

Hi Jami,

The hollow is a result of me being very lazy, but it works well in practice. Look at -

https://junkrigassociation.org/Resources/Documents/Slieve's%20Files/C%20and%20SJ%20P56-66%2012-03-17c.pdf

and go to page number 56.

Looking at the top seam as it is clearer than the bottom.

The lens panel is denoted by - C, D3, D5, D6, M6, M5, M3, and back to C.

The top edge of the centre panel is denoted by – C, L3, L5 & L6, and then down to P6, etc. Just by looking at them you will see that as the chord of each panel is the same but the distance round the curve of the lens is greater than the distance round the curve of the centre panel as it has greater curvature, so when you sew them together starting at the luff C, you will end up with the centre panel being shorter than the lens by the odd inch or so.

You get the same discrepancy at the bottom of the panel, so the leech then has two steps in it. I tidy this up by trimming the leeches of the lenses with straight line cuts from D6 to the leech of the centre panel at L6 at the top, and E6 to P6 at the bottom.

This gives a decent leech hollow made out of straight lines, and seems to work well.

Try it with a few scraps of roughly cut paper, but label the corners to help you put it together if you have trouble visualising it. (You could print off two copies of the diagram and cut out the lenses and the centre panel, and stick them together with tape

Does that help?

On the latest rigs I have been using only 5° batten rise.

Cheers, Slieve.

Hi Slieve I am so glad you have chimed into these conversations.

The sail catcher is such a good idea I think it deserves its own thread, so I created one.

If a sail is slow to 'inflate' could that be due to heavy stiff material? (Slieve) I don’t think so, the cloth was quite light (sorry don’t know the number.) It was new though and a little stiff. I tried to make the jib panels as accurately as possible, but I think I made a poor job of stitching them together and setting up on the battens, I will do a better job next time.

I was also going to use some construction methods I found to be working well in the previous sail. These include using 50mm seatbelt-webbing on the luff and leech… (Jami)

Trying to make as blunt an entry as possible I used thin dyneema in the luffs, inside a hem. It was easy to do, and by the way, the non-jacketed stuff is easy to stitch. I am not sure if webbing would be the best thing there, if you are looking for a jib aerofoil with the best possible entry. I might be wrong about that, and anyway it’s perhaps a minor point. But as for the leeches (of the jib panels) they carry no loading at all (other than wind pressure) so I just used tabling there and see no reason at all for webbing there. I wouldn’t put anything heavy on the leech of a SJR jib panel, I think that would be a definite mistake. It is not possible for the leech of a SJR jib panel to be under much tension, so why would you? I must have done something right, because there is no flutter in the leeches. SJR jib leeches can not be compared with the leech of a conventional jib, or the leech of a main panel. (See last paragraph.) 

Even heavy cloth will break down if you cover enough mileage, and it breaks down due to gentle flapping of reefed panels, mainly…(David T).

Even worse, when the SJR sail is reefed the jibs fall all over the place and won’t lie down and go to sleep inside the lazy jacks, like the mains do. Hence the sail catcher – my latest addition. I got rid of the lazy jacks entirely because they are no longer needed, and on the jibs they were next to useless anyway. The sail drops into the catcher and “presto” - no more flapping, gentle or otherwise.

(I copied and simplified the catcher used on Amiina  and written up in Slieve's technical notes – just two longitudinal tubes one each side of the mast, no hairpin bend at either end, no lazyjacks and no zips. Supported by two pairs of lifts, one pair at the mast and the other pair aft as far as possible (but not too far.) The so-called "mast lift" which lifts the boom is, of course, not needed either. Its simple and works a treat and the lifts do not interfere with the sail - the lifts at the mast coincide with the slot, and those at the aft end see very little camber. Its also a handy repository for an oar, a boathook – and spare battens if I were to carry them. It’s a wonderful accessory, and even somewhat aerodynamic – mine gives me steerage way in a moderate breeze!)

(The sail catcher also plays a special role in the requirements of a trailer boat too, but that’s another story. Main point here is: the sail catcher removes the above problem identified by David.)

So, no leech flutter and no “gentle flapping” when reefed. However, being cambered (and permanently sheeted out) the jibs do flog, quite a bit,  when luffing.

……

These jib panels are different from any other sail, because the leeches are loose, lifted up and supported by wind only, more like a parachute or a spinnaker. The leech is never tight like the leech of a genoa or a main sail, I am still trying to get my head around this. The weight of the bundle is carried by the two luffs and the mains leech, the jib leeches are not in the equation. Sheeting forces on the jibs are spread evenly, by the shelfs, to the head and the foot of each panel. When inflated properly the leeches themselves are full and rounded. Apart from the mild tension in the luff, these jib panels are exposed to the forces of the wind only, no rigging forces at all. I think they can be made, with advantage, from light material – but Dave Z has made his from heavier material and reported no problems, and I guess, as David T suggests, intended use is the decider. Flogging when luffing is the only issue I can see.

(PS I am now slightly confused about the experimental leech battens and not sure what was their intended purpose. I can't see how the unstressed leech can flutter, and I had thought they might have been an attempt to lift and support a sagging panel in light airs, which might actually help. I didn't want to go down that road though, it seems to me a step too far from KISS)

This is most interesting and might change my plans a bit.

Should I end up with  SJR, I was planning on using the same cloth I used for my Arne-type sail: 190 g/sqm Swela Outguard, which was very nice to sew and so far seems very strong. A good compromise between weight, price and strength.

I was also going to use some construction methods I found to be working well in the previous sail. These include using 50mm seatbelt-webbing on the luff and leech + 25mm webbing on the top and bottom edges of the panels in case I use hinges, not batten pockets (yes, I was going to try this with SJR also).

Now it looks like I might be planning serious overkill, if going for SJR. 

On the other hand, the seatbelt webbing worked very well against flogging in my previous sail. It's also a lot easier to work with it than a boltrope and leech battens.

I'll never race, but I appreciate good drive in all conditions. I also want to have a long-lasting sail - for environmental reasons, if nothing else.

What would be an in-between solution?

120-150 g/sqm (4-5 oz) rip stop polyester with 25mm webbing on luff and leech, some double/triple cloth but no leech battens?