Arne wrote: Note: When I draw sails nowadays, I often draw them with the halyard span pointing 15 degrees aft of the vertical mast. This lets one shift the sail a bit forward or aft to optimize steering balance.

As masts are frequently raked forward, I feel that the phrase “the vertical mast” carries the risk of confusion.  Unless the reason for Arne’s good advice is actually understood, that phrase might result in someone making a poorly designed halyard arrangement. Evidently one of the issues arising from halyard angle is gravitational force on the sail bundle, which is vertical, regardless of the attitude of the mast.

It is not easy to find a simple way of better expressing this advice of Arne’s.

With respect, could I suggest the following: “…the halyard span pointing 15 degrees aft of a vertical line through the halyard crane…”

Another thought, based on problems I have been able to solve on my own rig – I would have thought that 15 degrees to the vertical ought to be the about the maximum desirable halyard angle, and that if one expects to be able to shift the sail forward or aft in order to optimise steering, perhaps a starting point for the halyard angle should be less than 15 degrees, if possible?  

However, with my rig I don’t have the luxury of being able to shift the sail forward or aft so I am speculating here, and perhaps Arne will clarify.

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Here is my advice to Niko, as one amateur to another: Arne is dead right in suggesting that you do not try to over-think all of the issues, some of which are possibly unknowable anyway, unless you are willing to just give it a try.

Well designed and proven rigs are readily available and should be the starting point for your first sail. These proven rigs should be considered as a package – a package of compromises which has proven to work very well in practice. (David has hinted at something along these lines when he wrote, for example:  “It's certainly important to consider the P/B ratio, but not at the cost of losing sight of other factors…”)

As a first-time sail maker, choose a planform which suits your boat – be it one of Arne’s, or a Weaverbird style, or whatever, there is a wide range to choose from now  – then follow the advice of the designer and implement it as a complete package. After that, when you make your next sail, that will be the best time to give rein to your creative thinking.

Wow! Thanks for the replies! There are a lot of things about junk rigs that I only now start to realize. For example the connection between angle of the yard and amount of sail before the mast (via the 5% aft of center attachement to the halyard).

Special thanks to Arne for the immediate delivery of a rig plan! :)

If it was the work on the sail alone I'd be quick to just agree to Arne and not further bother about that. But more panels means more battens, too. And that means more weight and/or higher cost.

I'd like to do some rough calculations of rigg weight and cost for the different variants: 5 panels vs. 7 panels, spars in alu and carbon.

I know I've read an article here about dimensions of spars … I just can't find it any more. Could s/o point in the right direction?

Weight of spars of course has to be considered in the context of the weight of the mast.

For the masts I was thinking about conic alu flag poles in AW6063T66 (AlMg0.7Si), ø1 = 114mm, ø2 = 76mm, wall thickness 2.5mm. With a length of 6.15m those weight about 12.5kg. It's just a guess of mine that these would be stable and stiff enough. What do you think?

Of course there also is the mast head, some blocks, light, wind instrument. Probably 14kg total.

Niko

EDIT: I made a quick and dirty mockup (in red) how a 5-panel version of Arne's sailplan could look like. Just as a basis of further discussion.

EDIT2: And another one (in green) with slightly reduced yard angle and more lead. (And slightly reduced sail area; this one would have to be scaled up a bit for 10m²)

The matter of P/B ratio

I have discussed the matter of how to create camber in junkrig sail panels of different shape (P/B ratios) quite thoroughly in Chapter 4 of  The Cambered Panel Junk Rig, (TCPJR). What limits the ability to create camber, is the ratio between the vertical height P, and the batten length B, not so much the size of the sail. As shown in that chapter, I have drawn sails with the aspect ratio (AR) ranging from 1.80 to 2.25, all with seven panels.

I have successfully made seven-panel sails for my own boats with AR between 1.90 (P/B=0.21) and 2.15 (P/B=0.25).
As can be seen in the table on Fig. 4.5 of that chapter, it takes a bit more barrel round to create 8% camber/chord if the sail has a low AR, but within the AR range of the sails I have drawn, this is no problem.

When I made Broremann’s 10sqm sail with AR= 2.15, it was an experiment, and on the drawing board it looked like an overkill to use seven panels. However, when rigged and in use, it worked brilliantly well. The small reefing steps let me set the right sail area all the time and keep that tippy boat sailing in various conditions. One must only remember to use light cloth when making small sails.

My present Ingeborg with the SA= 35sqm and AR= 1.90 speaks for herself. Achieving the planned camber was no problem.

I therefore think that it is false economy to reduce the number of panels, in particular when the rig is to be used offshore and be remote-controlled from down below or from a hatch.

Arne

Broremann  in 2009 with a too thin, temporary mast...

Niko,
I’ve owned an 18’ dinghy ( Broremann) with a 10sqm JR. I made the sail with seven panels, and if I were to make a new sail for a similar vessel, I would not change anything. On a schooner the Aspect Ratio tends to be higher than on sloops, so I think it is false economy to save on number of panels. Besides, the 7-panel rig reduces the stress on sail and battens compared to a 4-panel sail of the same area.

Below is a sketch, illustrating how a 20sqm JR schooner could look like on an 8m Yrvind-style vessel. There would be plenty of room for the sheets here. The sails are based on my master sails with AR=2.15, and are almost identical to Broremann’s sail.

As always, I recommend making the sails with cambered panels.

Cheers,
Arne

PS: Here you can see Broremann's sail in action: https://goo.gl/CyRVGv

Hi e/b,

I'm new here - at least as a post author. I've been read stuff here for quiet some time.

I'm keeping myself busy atm by concepting a small ocean cruising boat. Think of an 8m/1.5t version of Yrwinds boats, 2.5m beam, small cockpit, suitable for coastal cruising for two or ocean crossing for one.

For sake of shorter masts (less prone to dismasting when capsizing) I'm mostly drawing designs with a junk schooner rig with two identical sails & masts. This way I want to get away with mast length above deck of 5m with a sail area of about 2 x 10m².

With a sail this small I was wondering whether it would be more practical to reduce the number of panels to 3 or 4. For example 2 parallel bottom panels of 2.5m x 1.5m (3.75m²) plus a top panel of 2,5m² with a yard angle of just 45°.

Advantages: less booms, less sheetlets, easier to make.

Disadvantages: Probably less efficient?

I would love to head your thoughts about that!

All the best

Niko