Anonymous wrote:

So that means that you have tried the mainsail with 8 and 12 % camber in its main section, right? What was your impression about the performance?

The mainsail you had before, was that an ordinary cambered JR or was it a flat sail? The mizzen, is that the same as before?

I once got an advice from a sailmaker in West Virginia (Dabbler Sails), to use black or dark blue sail covers. They collect sunshine and the sail under it will dry out faster and thus avoid mildew.

Hi Arne,

We're prototyping a rig for our new boat, a 32ft x 8ft x 1ft sailing barge, cat-ketch rigged. The rig is very similar to that of our last boat, which was entirely flat cut. 

We make a lot of use of the flat cut mizzen as a riding sail, for forcing the bow to windward while drifting, sailing backwards and short room maneuvers. While camber would help some of those, in others it doesn't help and would flog when neither set nor backwinded. Mizzen camber is still under consideration, but we waffle.

Our limiting sheeting factor into the wind is the flat cut mizzen, whose boom must be strapped in very tight to twist and draw. The SJR main, which points much higher, could be eased, swinging its thrust vector forward. In effect, the main is on a close reach when the mizzen is close hauled. This translated to considerable gain in power.

We started the main at 8% and tried a limited look at 12%, trying one (middle) panel to see how it drew relative to the 8% and how the 'pop' felt in light wind with a bobble of water (common in our area to get snap rolled in turbulent conditions... all sails get tossed, but a cambered sail 'pops' from full to backwinded and back again and again, with a little way made between).

The 12% panel began luffing slightly before those at 8% as we pinched up or eased sheet. Presumably, it developed more power, but at a slightly wider angle of incidence.

[This doesn't surprise me, but was startled that the blunt luff of the jib(let)s don't luff first! I'm guessing there must be some mast turbulence or wind shaping going on ahead of the after sail luff? Or a 'spinnaker effect' in the jibs?] 

Pop / flogging was considerably greater than the 8%.

Between the two, we decided on 8%, which we'll hopefully sew into final sails this winter. As mentioned, still waffling re mizzen camber.

I'll be posting a full write up, this winter, which I'll make available to the JRA. We dumbed the SJR concept down in several ways which appear to have worked our for us, but compromise away from power and windward ability.

Thanks for that input on sail color! Our final sails will be a dark burgundy, so we may have lucked into the right end of that advice!

We don't use covers for the same mildew issues as pockets, as UV is low at our latitudes (about 55 to 59degN) and as we often have to get going on a moment's notice at night (no engine to buy time). We may try the pouch style covers at some point.

But I assume it applies as well to sail cloth in the absence of covers.  8)

DZ

Dave Z

Anonymous wrote:

Of course the lashed-on panels work, why shouldn’t they? Camber is camber.
However, why, why, why choose such a slow way of constructing a sail? 

As for freedom to adjust the camber, well, if you have taken the trouble of tying on a number of panels to produce, say 8% camber , then it is quite unlikely that you one day will wake up in the morning and say. “Today I will re-arrange all the ties to see how 10% camber works”.
No way.

Hi Arne,

Our final methods will draw heavily on your approach, and thank you for all the development and info you've made available!

But in our case, we were prototyping a whole rig.

We wanted to see how an SJR main would work with a flat cut mizzen, given that the SJR should (and did) point much higher. Would we need less camber to get them to agree? Could we get away with more (and how does that behave in our gusty winds)? Would we prefer to camber the mizzen to get its performance closer to the main.

Our range of test cambers was 0, 4, 8 and 12%, with tick boards set up for those in advance. I agree that a 2% difference wouldn't likely be worth the trouble. As it was, we never felt the need to try 4%. 

All this had to be and was tried far from any sheltered workspace, and most adjustments were made while lying to anchor. Constructing a series of sails was out of the question.

Lashings seemed a workable means to answer these questions, and they were. With a half hour of work, we could set up to answer questions without recutting or sewing. Or at least see if a direction of inquiry was worthwhile.

We do prefer marline hitches over robands, and either over pockets in our area. Reason is we use wooden battens and sail in a boreal rainforest. Pockets I've seen up here don't dry well enough between showers and collect all sorts of nutrients... they tend to mildew and set to work on wood. They can be kept up with, but it's a chore. So we lash at batten ends and lace between. 

So, no great leap forward for JR, but I feel that lashings worked and work for our situation.

Sooo... no objections to anyone else's approaches, nor even a recommendation to emulate. I consider Thai style lashing - with camber or without - to be one of many in the JR bag of tricks. No more, no less.

Dave Z

By the way, our preferred method would have been closer to Roger Taylor's hinges with heavy duty hook and loop for quicker adjustment. But they're essentially pockets, with the same objection for our area.

It strikes me as it it did when I first saw it, that Paul's Aerojunk solves a lot of these sorts of problems.   It allows a single flat piece of sailcloth to be a cambered sail on either tack, creates a light weight and strong batten structure, and allows you to do whatever you want with camber, tying in only a few places instead of continuous lacing.    It also eliminates any of the leakage some have expressed legitimate (IMHO) concerns about.  It also makes it at least theoretically possible to change camber easily at sea.... presumably one batten at a time as you raise the sail.

     I don't buy the windage concerns people have expressed about the batten cage, but the loss of the "rip stop" effect of batten pockets is a bit of a concern, as is chafe where the fabric contacts the battens.

                                                                              H.W.

I'm interested to see if "Gap-Cambered, Split Junk Sails" are the next step.  Purposefully creating a gap between battens could increase the airflow over each panel's 'lifting' surface . . . as well as contribute to the 'turbulent air flow' I hear referenced with mystical reverence.  Seriously, though . . . has anybody purposefully created space between panels by individuating each panel to its own batten pair and separating adjoining battens by a small space?  Thanks for any replies.  Steve

John Dunn wrote:

... if you have some overlapping material it could even stuff the small gaps you get in between the eys. Reminds me of those military sarasani tents, that are made of modules, also tied together. In order to have it waterproofed, the fabric modules are tied in a certain overlapping way. Now, the question is, can you tie the modules together first and then add the pole in the backside of it with a loop? 

The key thing here is that when you tack you want the panels to swap sides, so that they pop inside out and form an aerofoil shape on the other side. The idea here is that the lashings can swivel around the battens and allow the flat sailcloth to belly out on either side, in a limited way.

Also there are various types of tracks which are mainly used to attach fabric onto campers, even double tracks are available that would enable you to slide the fabric onto the poles fairly easy leaving no gap in between. gr John

I believe that was mentioned earlier in the thread. Yes, you can do that, but then you won't get a curve out of a flat panel, and you'd be back to having a flat sail. You could of course have a shaped panel (and many people do) but the idea here is to make panel construction very simple and provide a curve with the lashings.