Hi Paul,

From reading your latest post I get the impression that you think the DBPs are placing significant forces on the rig. In practice this is not the case.

I have never made the luff of the main panels more substantial than simple folding the panel material over a 4mm luff line which is tied round each batten. I have never pulled the DBPs tight, but simply taken up the slack with finger and thumb taking up the slack and jambing them. Even with all three downhauls ‘tight’ on Poppy there was only slight insignificant bending of the top batten.

The Bermudian rig require a really tight jib forestay to stop the sail luff sagging and spoiling its inbuilt camber shape. The mainsail luff is tensioned by the Cunningham to force the camber of the sail to the desired position. None of this is required in the SJR as the camber is built in and the luff of each panel is short between the battens so no real tension is needed to keep the short luff from sagging.

Like the main panels the jib panels are also only hemmed over the luff line tied from batten to batten, and like the main luffs allow the material to rotate from tack to tack. Just like the string and bamboo models the structure of the rig is in the battens and luff and leech lines.

The DBPs simply hold the rig in place and stop it flying away from the mast or sliding up the mast due to the pressure in the sails. The only real tensions in the rig are its weight hanging from the halyard and the loads on the main sheet. If I remember correctly the Amiina Mk2 rig was built using 2.5 oz spinnaker cloth which looked like light dinghy Terylene/Dacron. Unless you experience it it’s hard to appreciate just how lightly the rig is loaded yet how powerfully it drives the boat by pressure on the mast and the sheet.

Cheers, Slieve.

I understand what you say about only needing a short yard parrel Graeme, but let me explain my thoughts. In the Solent, where Poppy was based, there are quite strong tides and shallow water so that in wind against tide conditions we suffer from the famous Solent Chop. This is a nasty bouncy situation, particularly with a fairly blunt and buoyant bowed boat, so the rig can get rattled around a bit. I have heard of junk rigs getting jambed on the wrong side of the mast which I feel is quite dangerous, so I always liked to keep the spars close to the mast. A spanned DBP between the yard and the first batten would keep a very snug top panel, particularly if conditions were so strong the that boat was reefed right down.

It’s great to see an interesting technical thread on the website with ideas for improving rig design. Long may it last.

Paul’s mention of a yawl anchor sail opens many interesting thoughts. Would it be necessary to have a permanent mast for such a set up? When at anchor how about rigging a windsurfer mast, or even a spare batten stepped on the centreline of the transom and clamped to the centre of the taffrail/ pushpit, with a flat cut, shortish chord isosceles triangular sail. With a short sprite attached to the clew and a line attached to the inner end and run through a small block or thimble attached to the middle of the mast, and tensioned down to the taffrail, then a pair of sheets run from the clew to either side of the transom would give the boat a stabilising tail feather. Just a thought.

Regarding rig design and various controls, after writing the article ‘Some Thoughts’ I had a fair idea of what I wanted in an easily handled rig with high balance, and spent some time studying what was then considered essential controls. Rather than trying to follow convention I realised that a lot of the controls were used/needed to pull the rig into shape. Luff hauling parrels were needed to pull the luff straight against the forward thrust of the fanned battens caused by the changes in angle of the tighter leech. Think of the leech tensions like the string of a bow pushing the arrow forward. To me the obvious answer was to use an angle at the luff to balance the forces caused by the angle of the leech at each batten end.

Rather than try to calculate these forces I initially took some bamboo garden canes and used string for the luff and leech lines and make a skeleton rig, but this was too small to be of use so made a bigger model with battens some 2.5 m long with parallel lower panels and three tapered and more fanned upper panels, and hung it out of a first floor bedroom window. Initially it looked awful, but by adjusting the sling point on the yard and attaching a downhaul at a suitable point on the lowest batten I got the shape I wanted. I took some photos of the result (which unfortunately I can’t now find) and transferred the shape unto a paper diagram. This was the outline shape I used for the Poppy rig.

I made one mistake in this by not making any allowance for the downward pull of the sheets on the end of the battens when close hauled, so the final rig did have some creasing. This downward force is greatest when close hauled and decreases as the sheets are eased when bearing away, so any allowance made for the force must be a compromise.

Initially Poppy had shortish batten parrels on all battens and yard, and a yard hauling parrel, as well as spanned downhauls, but eventually the combined spanned downhaul/ batten parrels replaced all but the YHP. If building another rig I would try rigging a downhaul/ batten parrel (DBP)? to the yard instead of the YHP.

The DBPs are of minimum length so that the battens are held quite close to the mast when the downhauls are slack which results in a nice snug rig when hoisting in sloppy conditions.

On the majority of our sailing I would simply hoist the rig until stopped by the DBPs as they were jambed when the sail was last dropped, sheet in, and go sailing unless we wanted a different number of panels hoisted. Considering that we really only used full sail of 7 panels or 5 panels then we probably only used the halyard and sheet for more than half of our sailing. Call me lazy, but with that little effort and still get the respect of cruising Bermudian sailors was very satisfying.

I wonder if Blondie’s original Jester with its curved luff and leech to balance the forces was tested with a model. It is a very pretty shape. Unfortunately his later rigs from PJR with parallel lower panels and fanned top panels does not lend itself to such simplicity. The fact that the SJR looks a bit like Derek van Loan’s rigs is not an accident.

Regarding the bending loads on a batten, I vaguely remember reading that a spar supported at one end (the sheet) and one other point (the mast) was under minimum bending force when the mast was at the 1/3 length point, or 33.3% chord. All Poppy’s battens, including the bottom one, were 50 x 1.5mm though I would consider using slightly thicker wall for the top one where the luff starts to taper and puts some compression loads on the batten. There no compression loads on the lower parallel panel battens.

Enough for now,

Cheers, Slieve.

Paul S,

you are about to become a first class test pilot! Your willingness to test your rig to its limits, and then report back in detail, is much appreciated.

With 27.5% mast balance, you have encountered two challenges: lee helm in light winds and the battens bending the ‘wrong way’ in stronger winds.

The lee helm should surprise no-one  -  at some point this had to happen.
As for the battens bending the wrong way; I was curious when that might happen. I guess there is a sweet spot of mast balance where the battens have a minimum bend (25-26%?).
Since you are cruising, you have to do with what you have and find a compromise position for that balance, and then just reef well before you are about to run out of rudder.

When you come home, you may consider different options to optimise your rig.

Yawl rig.
This has been the classic method to keep a light helm on most legs without big or advanced rudders. Ensure that the mainsail produces some lee helm, and then introduce a mizzen, some 10-15% the size of the main.

Adjustable mast balance.
By having running tack parrels, one may let the sail swing forward when sailing downwind. I haven’t tried it, but others appear to have had success with this. Maybe you could even try that on your existing rig?

Rudder.
Ilvy’s rudder is already good, but with a largish sloop JR, one can always use a bigger one.
Below is a sketch showing the principle for a Bigrudder. The diagram should speak for itself...

Keep up the good work!

Arne

(..full size diagram under Arne's sketches, section 2-36...)

Edit, 14.8.2023: That shown false transom on the Bigrudder diagram above, does not have to be symmetric. It may well be somewhat offset to one side as long as the distance C-D is kept long enough. This way, there will be room for the outboard engine on the opposite side of the rudder...

Just to give another example of high mast balance: on Ilvy I now increased mast balance to 27.5%. I did it by shifting the halyard sling point on the yard backwards to 60-63% yard length, and fixing the boom at 27% to the mast by one tight sling (still easy to rotate). Consequently, this allowed me to totally omit the tack parrel and boom vang. I have on little line from the boom vertically down to the partners, to hold the boom down. However, it was never tight since I installed it, so it could possibly be omited, too.

The sail sets and sails well, no real difference to the former 25%. Except one thing: hoisting and reefing squared out when running is even easier to do now already, (it was no problem before). All the rest is as fantastic as before, thanks to Arne's clever design and amazingly written sailmaking descriptions!

However, with this high mast balance and the halyard sling that far aft, it appears to me that the HK parrels are obsolete. They are almost slack, almost. However, only the slightest pull on the THP brings back huge creases in the panels. With the actual setup at 27.5% mast balance, I only pull in THP and YHP hard enough to fix the yard in its actual position, rather than trimming the sail.

--> Which supports the idea of David D., that a fixed boom/batten/yard position as with the SJR would be sufficient, including all the advantages that comes with such an attachment system such as simplicity.

However, I guess it might not be that easy to design such an exact sail position in advance, without trying out in real. Some shifting of the sails CE might still be necessary, after building, to reach a good weather helm. At least that's my experience with Ilvy. Am I alone with that experience?

On Ilvy, the mast balance of 27.5% gives her a little bit too much lee helm in light winds, but makes her very easy to helm when heeling. Maybe I reduce it back to 26%  if I bother. However, this got nothing to do with the feasibility of the high mast balance, but rather with the sail position to the hull. The sail itself works fantastic at 27.7%!

PS: This thread is quite interesting! It is so good to see when ideas evolve and progress is visible - especially when ships/sails are concerned, as their design philosophy is one of the most conservative (it has to be this way, due to safety reasons).