Well said Arne.

Your experiments with the Hasler/ Mcleod rig on a boat you already knew well were very well though out, and very well reported. While there were other interesting experiments being carried out at about that time I believe your efforts were a major step forward in the western use of the junk rig.

It may be that the hinged battens could have been developed further, but they did not have the structural integrity not overall simplicity of the barrel cut panels. Having enjoyed sailing with you I will admit it was tempting to simply copy your well documented examples, but I came to the junk rig with a very different background and wanted to experiment with ideas based on my model and full size aeroplane experience which I wrote about in the ‘Some Thoughts’ article. This lead me to try the SJR and I’m please to say we are both very happy with our final results. I just wish I could be as enthusiastic as you when it comes to producing a write up.

Colin, with two identical boats with identical sails but with one sail well worn and stretched are not two identical boats. Obviously to blown out sail will give inferior performance even with the telltales flying, however it will give even worse performance if stalled, so the ‘tales do have their use. As I say, they are not a design tool, but are an aid to help get the best performance out of the rig in use.

Mauro, the Deskbreeze looks like great fun, but I doubt if it would help develop a better rig unless some type of balance was added.

Paul, you reference to David T’s wingsail is introducing a much more sophisticated aerodynamic set-up, but it is getting away from the simple structures of the single surface rig. For ultimate performance it has great merit, but I don’t believe that is what the average junk sailor is looking for. Yes, I am suggesting pushing the vortex up and aft, and not letting it curl down the leech. The profile of the SJR is so much better than the normal cruising Bermudan mainsail with roach in this respect that I feel it must be helping the L/D ratio. I feel Poppy would have been better with a longer yard.

Cheers, Slieve.

Paul wrote:

Considering a better aspect ratio (higher mast) is not a realistic way to go (though it would be the most effective), what else can be improved? There is one major issue in which the sewn-in, cambered junk rig (and the split rig, too) defers from the bm rig: the batten pockets and separate panels, which reduce the amount of "good" profile shape to about 60-70% of total sail area. Hmmm! Hinged battens with flat sail don't suffer from this, as well as David T.'s wingsail. Taking the wingsail aside, due to its other aerodynamic benefits: would a hinged batten sail work significantly better upwind than a sewn-in camber sail?

Paul,

I had my Albin Viggen  Malena’s sail, with both flat JR (tan), the same sail with hinges (NL #24), and finally a new (blue) sail of the same size and with cambered panels (NL #30). I don’t dare to draw too firm (or objective) conclusions  -  there were so many factors flying about  -  but here are my subjective impressions, as I remember them 30-35 years later.

Btw. when I rigged Malena with her first JR in 1990, I had already sailed her a lot for the last nine years, so I knew her well.

• ·         1990: Her first flat sail was a huge disappointment when it came to sailing in light winds and upwind. There were a few missed tacks  -  unheard of with the original rig.
  Malena was simply a lame duck in light winds. Had I not found a way to improve the rig, I would have scrapped the sail and refitted the Bermuda rig.
• ·         1991: When I modified the battens with hinges to produce a symmetric 10% camber in the same sail, the boat was like transformed. Suddenly she became powerful and close-winded. In light winds I even overtook another sister boat by being more close-winded.
  Now, suddenly Malena felt over-rigged  -  the 80kg mast on a 1400kg boat, simply became too much. The remedy was to chop a metre off the mast and plane off 1-2cm of its diameter.
• ·         1994: The first sail with 8% cambered panels, planned from the start, was built. The mast was still the shortened one, so one of the panels of the new sail was rolled up tightly on the boom, pending the arrival of a new mast.

So how did these two sails compare?
For brute force, the hinged batten sail may have been the strongest. However, the hinged sail had 10% camber versus 8% in the barrel-cut sail. On the other hand, the cambered panel sail had had the max-camber point positioned further forward (35% versus 50%), so the added weather helm experienced with the hinged sail, was gone. Overall, I felt that the cambered-panel sail was as fast or a little faster to windward than the hinged sail.

Many words have been produced about the possible reduced efficiency in this sail, near the battens. However, if we look at the first and last meter of these panels (near luff and leech), one will see that the groove is almost none-existing; the air entering the sail and leaving it will meet an almost homogenous sail (consistent angle of attack and departure).

I know, I know, these are armchair speculations from my side, so I leave it to you to look more closely into it. Until you find any hard evidence, I conclude that the cambered-panel sail is about as efficient as the hinged sail, and with much more freedom to vary the sail’s mast balance. This last point is important when planning a real JR for a real boat to sail on real water.

Conclusion: hinged sail  -  been there, done that; thanks but no thanks...

Cheers,
Arne

Slieve, I think I get what you mean with that sketch: By moving the tip aft, the induced drag is reduced by moving the tip vortex aft. However, I think this would have to be very fine-tuned to generate benefitial effects, and not increase i.e. profile drag. 

I'm a bit skeptical about the shark fin example: the dorsal shark fin is not a high L/D wing, but a high lift fin with late stalling characteristics (like a fighter jet). The shark needs it's dorsal fins for manouevering, which means generating high lift at high speeds and also at possibly high AoA's. Nature "developed" the adequate wing design for that purpose. If we would use that design for a sail, we would get a wider groove (oversheeting is less dramatic) but loose significant upwind performance due to the bad L/D, wouldn't we?

Considering a better aspect ratio (higher mast) is not a realistic way to go (though it would be the most effective), what else can be improved? There is one major issue in which the sewn-in, cambered junk rig (and the split rig, too) defers from the bm rig: the batten pockets and separate panels, which reduce the amount of "good" profile shape to about 60-70% of total sail area. Hmmm! Hinged battens with flat sail don't suffer from this, as well as David T.'s wingsail. Taking the wingsail aside, due to its other aerodynamic benefits: would a hinged batten sail work significantly better upwind than a sewn-in camber sail?

Mauro, that is a great gadget to demonstrate the aerodynamic effects that happen around a sail. It does, however, not give a clue on the significance of each effect. As Arne wrote: it is only one part of the story to have attached airflow, but the question is, how fast is that airflow.

Hi Paul, you ask, “would I consider a 30º yard as a fanned top?” Basically the answer is no, but it depends on the length of the yard.

Please excuse the totally unclear sketch, but the curly lines are a bad attempt to show how the air would leave the left hand rig from the very top, but could curl down the sloping leech in the right hand diagram. Both rigs have the yard at about 30º but the shape of the head is quite different.I believe it is important to push the tip votrex as high and as concentrated as possible. When it curls down the leech as in the right hand drawing it is effectively decreasing the height of the rig and the aspect ratio, and increases the drag.

Tony Marchaj made reference to the crescent shape of a shark fin and suggested that nature had evolved a low drag efficient shape.

If I were a few years younger and had infinite patience or funds to pay others I would try to build my ‘ultimate rig’. I believe it would have the bottom batten and the yard the same length, with the jiblet luff and the main leech both straight lines. The yard would be at about 30º and the bottom batten level, and the intermediate batten angles increasing up the sail. The top panel would not be split, but the rest would. The overall balance would be 33%, but might be slightly less at the top and more at the bottom.

With the Poppy and Amiina rigs I drew the yard shorter for aesthetic reasons, but believe that it is not noticed in practice.

I realise this posting may raise a few eyebrows, but perhaps that is a good thing.

Cheers, Slieve.

Anonymous wrote:

Mauro wrote:

Arne,

on my sail (20,4 sq m Johanna style with 70 deg yard angle) the top panel have less camber than the lower ones. I am really happy with my/your sail. Nevertheless the two top panels inflate but their tell tales seem to look mostly to the lee.
Is my sail wrong? Are there any tricks to control the twist at the top of the sail? If not, don’t you think that a fully cambered upper section would have a better angle of attack and thus an improved air flow and more lift? 

Cheers 

Mauro

Mauro,

yes, it could be that you have too little twist in your sail. In my Ingeborg I have the Johanna sheeting with its strong anti-twist. With this setup the two top panels stall a moment before the panels lower down.
However, with one or two reefs, they seem to stall at the same time as the lowers. To me, that is a good compromise.

Maybe the Pilmer sheeting with slightly less anti-twist in it would work better for your sail?

Arne

Thank you Arne, as usual you are plenty of good ideas!

I will search for the Pilmer sheeting in your files and see…

Cheers 

Mauro