This afternoon I took the chance of this amazingly hot Swedish summer day and tufted.

I did as David D. suggested, and tufted right on the batten pockets, on both sides of the sail. In addition, I added some yarn to the top edge. Have a look at these positions, all percentages are in relation to chord (batten length).

It looks like this in real:

When finished, I took the chance of the day, laying at a finger berth with an F6 right on the bow. I loosened the bow line a bit, to give Ilvy some angle to the wind, set the upper three panels and sheeted hard in. Like this, I kind of simulated a port tack situation. Unfortunately, I was not able to simulate a starboard tack situation.

I took some fotos and long videos of the telltales. Played a bit with sheeting until I got it right and all leech telltales flying. This footage I still need to analyse and evaluate, in the next days. I hope to be able to condense it into an easily readable result sketch.

Hopefully, when sailing during the next days I might be able to record more footage, and on both tacks.

One drawback of my experimental setup: the wind was probably quite disturbed by the boat (a beautiful “Grinde”) right in front of Ilvy, as well as by the small harbour buildings some 50-100 m away. For sake of completion, the following fotos describe what I mean:

Cheers,

Paul

David T, I surely agree with you about the bigger challenges of sailing to windward, offshore, against a head sea.

In 1983 we sailed Malena from Stavanger to Skagen, Denmark. Outbound, it was all downwind. Malena proved to be very fast and safe on this leg, without ever starting to roll or broach. The trip back home was another story, with sailing every inch fully close-hauled. The voluminous bow section, which I praised downwind, now frequently stopped us dead, and the smallish fin keel took its time to grip the water again.
This also happened inshore in the steep, short fjord chop, with any rig I later put on her.

Ingeborg on the other hand is not so spectacular downwind. Better not push her too hard, or she may start rolling (luffing up a few degrees helps). However, Ingeborg shines to windward against head seas. It takes more to stop her, and even if that happens, she is much quicker at getting started again, without making so much leeway.

A good and tolerant rig surely is important, but going to windward, steered by a blind helmsman (..a  windvane...), I would above all look for a boat with a keel like that on Ingeborg.

PAUL S.
HK parrels, what is the problem with them? They may flatten the leeside of the sail on port tack, but the mast does that anyway.

As for the THP, I fail to see the reason for removing it. I too would have wanted them away, if I had to adjust them during ordinary sailing, but I don’t.

You mention rudders. There will of course be less need for a big rudder when the CE of a sloop JR is moved closer to the mast. The rudder on the Maxi 77 is anyway good.

Arne

(Full size diagram in Arne's sketches, section 8)

So, instead of trying to change the luff, maybe you should be re-thinking the theory – that was a “tongue in cheek” remark, but it did make me think of Bunny Smith.

- Graeme

Graeme, aerodynamic theory is fully understood and proven - at least for the field we are talking about (supercritical flow, very high Ma-numbers and the like excepted). Though this makes wing design a more boring because less adventourous task, it gives us all the tools we need to design an optimal rig - optimal with respect not only to speed and efficiency, but also handling and safety. I see no need in inventing new aerodynamic theories, even more so that the dominating aerodynamic effects on a junk rig are not at all understood yet. We are still fishing in the dark in this respect, speculating about detached air bubbles on port tack, tip vortexes and induced drag, and so on. As long as we can't determine what's happening, and put numbers to it, i.e. xx% drag comes from induced drag, yy% drag comes from distorted profile, it is all just guessing.

That's why I really like David D.'s suggestion of more tufting. Though this won't give us numbers, it will give us a qualitative explanation of what's happening. I didn't take your suggestion as an offence, David! Instead, I might just do it this afternoon :-)

Slieve, I'm with you! It is in fact very interesting to have you as an apparently most experienced aviator onboard this discussion. I envy your flight experience! If my mediocre eyesight wouldn't have cancelled any of my aviation job dreams, I would have probably taken a similar professional choice as you did. Instead, I learned how to design those devices that I would have loved so much to fly myself. As aerodynamics are pretty well understood nowadays, only the exotic issues are being further developed today. For example, in my batchelor thesis I, in cooperation with the DLR, investigated how to increase the laminar boundary layer length on the suction side of a wing using plasma actuators. Though this was highly interesting from a technical point of view, and included me conducting tests in one of the bigger german wind tunnels as well as about 30 in-flight experiments, it was that much high-tec and such an aloofed technique that I would not never consider this as something practical.

Luckily, there is no such medical restriction in sailing! Theory itself is most boring, it is testing in practice where the fun waits.

Folks, I can’t help feeling that you are burning calories on small, and woolly improvement factors.

- Arne

I agree, Arne, that any further improvement can only be in the single-digit procentage range - which will be hard to feel in practice when sailing. However, I can only speak for myself when saying that my primary interest is understanding what is going on at the junk rig. Be assured that I do not mix up understanding with improving. Only after we understand what's going on, there could be improvements developed which are simple enough to be worth it - else it is just plain try and error and may last an indefinite amount of time to get anywhere. Only after understanding, we might consider the cambered junk rig, or split junk rig, or which other design you like, as perfect as it is - or see possibilities for improvements which cost next to nothing but provide advantages otherwise lost.

To clearify the numbers of Ilvy: she has 27% mast balance with 9% camber.

Arne, I agree with all the rest of your points. The high mast balance has proven to be of huge advantage! Especially reefing downwind is amazing. I would not want to miss this point!

However, one more question: Why is a big rudder so important? Would a well balanced CE position give a similar helm characteristic?

Cheers,

Paul

edit: now the same happened to me, Slieve. You and David T. have been faster typers than me! I definitely see your point in questioning the upper fanned panels. One huge improvement on Ilvy could be to get rid of the HK panels and even more so: the THP. If the sail could hang from its halyard sling point, like the SJR, it would need way less lines. Having one less trimline (THP) and no HK parrels would certainly be one further huge improvement - especially in choppy seas!

It’s of theoretical interest to me now Arne, but the quest for high L/D ratio is no for racing but for the ability to carry as little rig area as possible to do the job, and to reduce heeling forces.

I often sailed Poppy with only 5 panels as it gave me close to max hull speed even in moderate winds, and because I was just too lazy to haul up the last two panels. I know you like the extra area as reefing is easy, but I was happy with less area than the standard fore and aft Bermudian area when I could still get 2 knots of speed in 4 knots of breeze and outperform the Bermudian rigged boats with full sail area.

Perhaps I’m just trying to encourage a new drive in rig development which seems to me to have slowed down of late. As you say, “Unless the improvement in the rig can be made very easily, it makes little sense.” I suppose the question that with interest in increased balance, whether a change in rig outline or structure could improve performance or rig handling in any way. I’m still 100% for the KISS approach.

I believe you have taken the Hasler Mcleod rig shape to its top level, but I have never been a fan of the fanned top panels as in my eyes they don’t just simply hang there under gravity. In this respect I prefer the crude simplicity of the van Loan rig, but who is to say what is best? We’ve seen many different rig shapes over the years, but it would be nice to see even more being discussed if at all possible.

More ‘cutting and trying’ would be good.

Cheers, Slieve.

Lots of calories for small gains...

Folks, I can’t help feeling that you are burning calories on small, and woolly improvement factors. Remember, cutting 5% drag in the sail, does not necessarily lead to 5% increase in upwind speed. In a very light wind and low boat speed this cut in drag could be useful, but when approaching hull speed, the resistance-speed curve has become so steep  that there may only be 1-2% gain in speed. For racing, this is fine, if you don’t get any extra handicap penalty, but otherwise, unless the improvement in the rig can be made very easily, it makes little sense.

Group Captain Smith’s experiments with the Insect Flight Theory have been mentioned. Although worth trying, it proved to be a failure. However, Mr Smith had such a high standing because of his military achievements, that nobody dared to oppose to his theory  -  except one: In JRA NL #25, Alan Boswell put things right by showing that the bendy battens in Fenix’s rig was the main contributor to the improved performance. Later, Joddy Chapman came to similar conclusions during his PhD research work.

Paul Schnabel’s experience with his Maxi 77 this summer should open a few eyes.
His sail is a quite ordinary cambered panel sail with (8%? Corrected to 9%) camber, made with the barrel cut method  -  no broadseams or shelf foot. He has also pushed the limits for mast balance  -  and he has been generous with the sail area. 
That big sail area, combined with the moderate camber, has paid off with an impressive performance, both when close-hauled and when running before (SA/disp. is 20-22).

Moreover, by increasing the sail’s mast balance to around 25-26% (corrected to 27%), the CE of the sail has been moved close enough to the centreline to give quite light steering downwind.

As if that was not enough, this setup even lets him raise the sail when going downwind, and reef downwind without needing any downhaul.
These are real improvements, and in my view much more important than theories about keep battens, vortices and the like.

So what should one do to keep a good cruising speed in all directions without making the rig too complicated (wing sail and the like)?

·         First of all, one must be critical when choosing the vessel. Shape and size of keel and rudder must be right.

·         Then, a generous sail area should be fitted (..heard about easy reefing?).

·         Any fixed 3-blade propeller should give way to some sort of folding or feathering propeller.

·         Finally, longer and trimmer vessels just about always pay back with more miles covered. Roger Taylor’s experience with moving up from Mingming 1 to Mingming 2, should be kept in mind.
Long is good.

Cheers,
Arne

PS: As for the shown racing aeroplane below  -  come on! That thing, computer-designed, polished and probably with laminar airflow over much of the wings, is on a different planet. Those thin and small wings surely make the plane terribly fast, but I bet it is also tricky to handle and land. A potential widow maker. This is as far away from the JR philosophy as one can get.