In the spirit of recycling and actual saving of natural resources, I managed to find a way to join the top two panels in a reasonable way to turn them into a new, one-part top panel. I'm aware of potential stretch issues (although the sail hasn't seen that much use), but one does what one does to save the planet, right?

I think I saved over 4 sqm of cloth AND managed to rescue the unalome insingnia. To my eye it has to go too near to the leech, though.

The next thing is to cut the new leech, new lenses and curves to match them, as well as sew two meters of new cloth to the luff end of the panel.

Also, two jibs done.

Just in case: I would prefer - but can't afford the cloth - making a new sail rather than start playing with extending the battens for longer jib chord.

So the sail is for sale at least for a short while. I bet the mains would also make a nice, very high-AR sail without the jibs.

Contact me, if interested. Price based on the price of the same cloth for a new sail.

Hi Guys,

There's little doubt in my mind that the shape of the top of the sail has a significant effect on the performance. Back in the '70s they modified the wing tip of the Trident 2's by removing the outward sweep at the tip to relieve the structural pressure. This resulted in us having to increase the fuel burn calculations for each flight. It wasn't a big amount, but it did illustrate how the tip angle and shape could effect efficiency.

Coming up to date you only have to look at the wind tips of the latest designs to realise how much effort is being put into this area to squeeze the last drop of performance out of a wing for commercial gain.

The same must apply to the shape of the top of any sailing rig. Anything that can be done easily to improve the lift/ drag ratio by reducing the tip losses is a gain in windward performance. In this area the average 'pointy head' Bermudan rig is rubbish. When I raced Merlin Rockets a rule change let us use a quite long full length top batten, which helped push the tip vortex further up the sail and quickly was adopted as it was necessary to have it if you wanted to win races. All modern high speed rigs appear to be square topped and will have the same effect.

In 'Some Thoughts' I did mention the possibility of reducing drag with the lower yard angle, but now I think it is not just the yard angle but also the shape of the leech as well which is important. Looking at the photos of Jami's boat with the full rig there is quite a reduction in overall chord in the top panels. Trying to visualise the airflow it could be that the air splits on the yard, meets at the leech with the induced up and downward motion and the resultant vortex rolling down the tapered leech, leaving the sail near the top of the parallel section at some distance from the top, and effective reducing the height of the rig. By reefing the top panel the air might be able to curl over the 'yard' and give vortex lift (as with SST Concorde) and exit higher up and not be drawn down by the lesser tapered leech. If the vortex does leave higher than with full sail then the L/D ratio could be better and hence better performance.

If I remember correctly it was in a mail to Graeme that I suggested that if looking for performance with no regard to aesthetics than I would make luff and leech parallel all the way up and make the yard longer than the battens to accommodate the yard angle of about 30 deg.

In one of Tony Marchaj's books he describes a large yacht with a fairly long keel which had the bottom edge parallel to the water line. The performance was poor, so after water tank testing it was discovered that by changing the keel so that the bottom edge sloped downwards a few degrees from bow to stern without any significant increase in draught brought the performance up to the expected level. Where the modern trend is to have the leading edge of the keel vertical we must remember just how efficient the sloping leading edge of the Folkboat keel is, and for a fairly shallow draft can compete with the vertical keels.

We have a lot to learn in this area, and with Jami's experiments we may have learned a little bit more. Excellent work.

Cheers, Slieve.

I think that if you want a high-balance sail to"drape" nicely, with just the running parrel- downhails - and without the need for all those other ruuning lines - then I think you will find high balance calls for a lower yard angle. I guess Slieve or Arne or Paul will explain it better.

Arne wrote:

Interesting, Jami.
Did you try that other method first; just reefing the sail?

Arne

Yes :)