Junk rig on modern hulls

Chinese gaff mainsail

Hi Bataan,

I own a 35' Wylo II by Nick Skeates. It is gaff rigged and has no engine. I sailed 25000 miles in it.
My original gaff mainsail is getting tired and I am thinking of replacing it with a junk mainsail.
I haven't found much information about the problem of accommodating the yard under the aft shrouds.
I stumbled upon your boat Bertie.
I would like to design a mainsail that wouldn't chafe or bind under the aft shrouds. I'd like to not change the current rigging as I don't have enough time to do that and I want to keep the 3 headsails that are small and easy to manage.
I am leaving for a year's cruise to Europe next spring.
My mast overall length is 36', the lower hounds are 23½' above deck, the upper hounds at 28', the gaff jaws at 21' above deck and the tabernacle takes 30" from the bottom of the mast. So I have a clear mast length of about 18½'.
I have made a sketch of a sail which area would be about equal to the current mainsail and its topsail with a luff length of 17', a boom length of 16' and a yard peaked at 70°.
I notice your yard is even more peaked than 70°.
How exactly do you keep your yard to the mast so that it doesn't change side?
Would it be a good idea to put the yard on a saddle or gaff jaws like on the gaffer and use 2 halyards?
Why is your boom so far forward?
I am asking this because my staysail is on a boom and very close to the mast. I would like to minimise the recutting of the mainsail if possible. So I would like to have minimum balance of the sail forward of the mast.
What kind of stagger do you get when reefing?

Thanks, Thierry, Lunenburg, NS

 

We've just returned from 3 1/2 months cruising around Vancouver Island and exploring the Queen Charlottes (Haida Gwaii) and had the main up every day, even when motoring dead upwind, as it kills the roll and helps push us. This is practical as the sail never flogs or flutters as a gaff or marconi would when head to wind.
BERTIE's main is a direct copy of the Southern Chinese type from Swatow. There is no throat angle and the sail is cut on a straight line from peak, through throat to tack. This makes the yard quite near vertical and solves the aft shroud chafe/bind problem. Yard is kept to the mast by two parrels, the normal yard parrel and what I call the throat parrel (photos), which I discovered by examining an old junk photo with a magnifying glass. To modify the luff to accommodate your staysail just cut some curve into it so the boom doesn't stick out so much. Mine catches the staysail sheet often enough to be annoying but not enough to force me to change anything. This rig was developed by me to replace the gaff sail this boat would traditionally have as I wanted more sail area and less work and it has done those things quite well. Last photo is with main reefed after a very fast downwind sail on the West coast of Vancouver Is. Here's the FB page with the trip photos on it if you are interested.https://www.facebook.com/pages/Bertie/146605035522005?ref=hl

 

Good pics - I will alert Peter to these - he is close to cutting his sail cloth. He will need to hire a small hall for the process.

 

Hi all
I came across this posting with a photo of my own boat, Johanna, with that blue junk sail. I can assure you that the cambered panels are not just a result of stretching canvas. Each panel has been cut with a barrel shape before assembly along the battens. The camber/chord ratio is about 8% in the lower panels, with the top panels being flatter.

Performanwise this junk sail with cambered panels has just about closed the gap to the Bermuda-rigged sister boats, upwind. I don't claim the JR to be as fast as a BM rig with the same sail area, but since it is easier to set a bigger sail on a junk sloop (48sqm versus 36 on the Bm rig), I make up for that. I guess the 25cm thick , hollow wooden mast produces quite some drag - quite noticeable when sailing well reefed. The max camber point in each panel has been put about 35% from the luff.

Cheers, Arne Kverneland,
Stavanger, Norway

PS: The shown boat is an Alo 28, (3 tons)

 

I bet there is a very pronounced 'bad' tack side. If there isnt, then the camber is a waste of time.

Improving performance on a junk rig is bit like adding a spoiler to a tractor

 

The bad tack is not as bad as one should think. The telltales at the leech clearly indicate an attached airflow at the lee side, but the "groove" is a bit narrower at the bad (port) tack. Anyway the overall tacking angle is just outside 90degrees on the compass, so something must be right with that rig. With my first, flat junkrig I hardly tacked inside 110degrees, even with a big sail.

Arne

 

~90 degrees is satisfactory if the rig is simpler and cheaper than a marconi. I would be pleased with that.

Flow attachment to the sail isnt seen well at the Leech, you would need to watch telltales just behind the chord, of which there is a little bit on the panels higher up. The top half looks quite like a a gaff rig, rather than junk.

The big trick with junk rigs is the value for money if you can build them yourself, so improving the tacking angle is a great bonus.

 

I was sailing on a Benford 'Badger' type recently. In 25 knots of wind, reefed, we were tacking on 100 deg on the compass. Sometimes going from port to stbd tack we'd get caught in stays and had to hold onto the foresail to bring her through the eye of the wind. Definitely one tack was better than the other.

This is one reason Tom Colvin put a jib on his hybrid junk schooner rigs, which is what I'm building.

I appreciate your efforts to get better upwind performance from a junk sail but personally I think the tradeoffs in complexity are too great. The sail is harder to sew and more fragile for maybe 5 to 10 deg better upwind pointing angle. But then I have no interest in racing and if I needed to point higher for some reason I'd fire up my engine and motor-sail.

PDW

 

PDW, just a question, first:
Did the junk sails of that Benford dory have camber in them? A while ago a builder/sailor of a Badger clone ("Zebedee") constructed a new set of sails for her and reported about great improvements in performance. He made the sails in just a week, using an instruction I had written.

It is not much more work to sew up a cambered sail than a flat one. Besides, one needs less space as you only need room to loft one panel at a time.
Handling the rig, hoisting, trimming, reefing and furling the sail is identical to that of the flat sail.

If you want to have a closer look, I suggest you check this page:

http://www.junkrigassociation.org/arne

No membership needed and completely free of any charge.

Cheers, Arne

PS: Designing the sail may be a challenge, so these days I am finishing two chapters dealing with that.

 

They were flat-cut sails as per design. I don't have time to read up on that other site at the moment, sorry.

I plan on building mine as per designer instructions and drawings. If over time I think there's room for improvement, I'll look at it then. Second-guessing the designer on sails, starting from a position of ignorance, with a new hull, is an exercise in arrogance too great for me.

The fact that you are doing one panel at a time tells me that your sails are a lot weaker than Tom's way of doing it. Or are you adding vertical reinforcing after sewing each panel together? If not, your entire sail weight is hanging off of the rows of stitching on the bottom of the top panel, and there's nothing to stop a tear propagating from luff to leech in any panel. I'm not convinced that the relatively minor performance improvement you're seeing is worth the tradeoffs.

PDW

 

PDW,
first of all, I don't criticize you for following the designers plans.
However, my plans and sails are quite well proven and they have never failed along the battens. From the photos above (a 20sqm sail for a 21' boat of mine) you will see that the middle of the panels are bulging so takes next to no vertical loads. All the load is concentrated on the luff and leech where boltropes (here 2" seatbelt webbing) keeps the sail from ripping. My ambitions as a sailor is not to win races. I just want the boat to sail so well that I can do at least 2/3 or better 3/4 of the distances under sail.

Arne

 

Arne,

that looks like an excellent modern adaptation of the junk rig. What does it look like on the opposite tack? Do you think if you could place a spacer where it passes the mast on each boomlet so to allow the fabric to take the shape so it does not touch the mast would help on opposite tack? I have thought about this and think it might help to keep the sail shape undistorted by the mast.

 

Petros,
when I rigged my first boat (23’ Albin Viggen, “Malena”) with cambered panels in 1994, I was anxious to see if the boat performed differently on each tack. I found it difficult to discern any difference. Later, a friend of mine with the same sail fitted his boat with accurate wind and speed instruments. He concluded that the boat went 2-3° lower on the bad tack, which I guess will result in 2-5% lower VMG. I think that is acceptable. My hunch why there is not a bigger difference between the tacks is this:
On these sails we use little balance, so the mast is sitting close to the separation bubble. Anyway, the airstream clearly re-attaches to the sail as long as I don't over-sheet the sail. In that case the telltales and flag at the leech flick forward, behind the sail.
On the good tack, the camber of the sail is undistorted, but on the other hand, the mast is standing proud of the sail, right into the wind, and must create quite some parasitic drag. The “sail area” of Johanna’s 25cm thick mast is 1.6sqm (17.2sqft).

On the photo of Johanna she is beam-reaching at max speed, 6.8kts in wind F4, on the edge of needing a reef. Theoretical hullspeed is 6.3kts of that hull - the same as she goes on flat water with that 9.9hp hi-thrust Yamaha.
To give you a better view of our cambered panel junk rigs in Stavanger, here is a link to a photo-article from a rally we held in 2010. Our boats certainly have no reputation of being slow.

https://dl.dropboxusercontent.com/u...to review of the Stavanger JRA Rally 2010.pdf



Cheers, Arne

 

This isnt a valid computation. VMG is VELOCITY made Good. 2-3% Tacking degrees difference wont result in a 2-3% Velocity figure.

In fact 2 degrees off the wind may give you a 10% increase in speed, depending on the boat.


Also, another factor is VMC or as I have heard it expressed CMG (Course made good ) - the ability to get to an upwind point in as short a time as possible. The optimum beating angle to achieve the best time is almost never the maximum tacking angle. (We have all been guilty of 'pinching' I am sure )

"We have heard these two terms now for over 25 years that gives us a guideline when sailing a race around the buoys, Velocity Made Good (VMG) and sailing offshore, Velocity Made good to Course (VMC)."
http://www.destinationonedesign.com/prep/index.aspx?chapter=bb0da5fbaeba4d3084bf2dd05d0b27ed

 

You may be right Mr Watson.

However, the fact is that the average tacking angle of my two present junk-rigged boats is just outside 90deg. The bad tack cannot be that much worse than 45 deg, or else the boat would have to sail well inside 45deg on the good tack to make up for it, which I doubt. Also, even without wind instruments we get a quite good clue on how the boats perform on this versus the other tack. This summer I will have been sailing for about 45 years and 20 of them with cambered panel junk rigs.

Arne