When a member found my posting #3877379 to be an invitation to “a crocodile fight in a pond”, I really had to scratch my head. How little does it take to make a technical discussion turning (looking) personal? I certainly respect David’s right to do things his way, and I always find his rigs interesting. Luckily, both David and I are fairly straight-talking engineers, and I think we can exchange ideas without being accused for being personal. Now that Asmat has brought in a few important factors for rig design, I choose to (yet again?) explain how I reason when I try to convert a given vessel to a (sloop) JR for:

• 1.      I first have a good look at the hull. There must be room for fitting the mast without having to re-do the interior.

• 2.      Next is the rudder. Junks need big, effective rudders. If it is only so and so, I would either consider rigging with two masts, or I would build a new and better rudder.

• 3.      When deciding for sail area, I generally aim for a bit more than the mainsail plus biggest genoa of the Bermuda rig (just about all boats I have converted have started with BR). I want enough sail for downwind work without needing ghosters or spinnakers. The intended sort of sailing (inshore/offshore etc. ) also plays a big role when deciding on the sail area.

• 4.      The aspect ratio of the sail depends on a number of factors; the boat’s stability, the sort of mast I can get (and afford), the possible mast position and the deck length compared to the displacement.

I have designed a few rigs now, and I don’t find it is getting that much easier for each new boat. A low AR rig certainly will need more deck space and also rudder authority to work. Some boats have plenty of that (compared to displacement and stability), so will be good with low-AR sails. Some boats, with high displacement to length ratio, will struggle with finding enough space for a low-AR rig with sufficient sail area, so then one must aim for a taller rig. So far the AR of my sails have varied between 1.87 and 2.15.

It is always a struggle between what I want and what I can do....

Cheers, Arne

OK, David,

I buy your idea to start with a mast that is tall enough to take future experimental sails  -  it’s easier to chop off a mast than to add length to it.

I can also imagine that the wide fanned sail on Tystie was more than a handful, both to hoist and to sheet, and I can imagine that the rudder would have to fight against the steering moment of the sail, downwind. Therefore, I am sure that the new hi-AR sail(s) was an improvement, handling-wise.

It is just that there are big boats and there are small boats. Sails up to 25sqm comes up and down with little effort  -  these rigs are ridiculously easy to deal with compared to sails in the 50sqm+ class: The forces I need to use on handling the 20sqm sail of Frøken Sørensen feels like nothing, compared to those needed on Johanna’s sail (48sqm).

My hunch, when seeing the new sail for Weaverbird, is that it should be a good sail for upwind work, with its long luff. However, the sail area seems quite small for downwind work. After all, the 19sqm original pointy rigs of the Hunter Sonata/Dueta were meant to take extra genoas in light winds, and most probably spinnakers as well. Being under-powered downwind is boring...

Again, I repeat; any junk sail of any shape and size up to 25 sqm will feel super light compared to what you have been struggling with on Tystie.

Anyway, good luck!
Arne

Arne Kverneland wrote:David,

This confuses me. What are your reasons for jumping from the very low-AR Fantail style rig and to these very high-AR sails?

This sail for Weaverbird needs a tall mast (9.5 or 9.2m) to set that sail (18.95sqm), compared to the 7.6m mast on Frøken Sørensen which easily carries 20sqm.

Arne

David Tyler wrote:

I've uploaded my first sketch for Weaverbird's conversion from pointy-top to junk.

 

David,

This confuses me. What are your reasons for jumping from the very low-AR Fantail style rig and to these very high-AR sails?

This sail for Weaverbird needs a tall mast (9.5 or 9.2m) to set that sail (18.95sqm), compared to the 7.6m mast on Frøken Sørensen which easily carries 20sqm.

Arne

I'd have probably gone for about 145mm diameter and 4mm wall, if it had been available, but larger and thinner is actually better for stiffness/weight and strength/weight - so long as it doesn't get too thin, and 3mm wall thickness should be fine. Lliutro's first mast was 127mm diameter x 3mm wall, on a boat that was rather heavier. OK, I bent it, but that was due to grossly overloading it by using a light headsail.