Twin yankees.

[ccscott49]

Serious question time. I have a furling yankee, on a twin groove roller reefing gear (furlex) I want to get another yankee, to run up both sails together, with twin poles and rig them "twistle" method. The confusion arises, when I talk to people, including my own bruv, who say they won't work efficiently, unless theres a gap between the sails luff, the old aerodynamic wing thing! Now then, whats the opinion of the panel on this scenario, I know the "twistle" part of the equation works ok, but what of the gap, no gap theories, Help please before I buy another yankee. Which I may never use. I'm also considering a cruising chute, but I will borropw one first to see if it would work with a heavy beast like Englander.

 

[HaraldS]

On our previous, previous boat we had a double forestay, set apart by not more than 3 inches in port starboard direction. I think it worked well as a tradewind rig, but I couldn't compare it to anything else. We usually also had a tripple reefed main to slow the rolling.

Today I think you end up underpowerd which results in some loss of speed, but more important the boat looses dynamic stabilization and rolls more. On the other hand you don't have to care about this rig much.

Our current boat is cutter rigged and I have two poles so I can do it with the gap you mentioned. I need to furl the genua somewhat since the spi pole is a bit short for it, and then the two sails are quite balanced. I think it works much the same as our previous on the doule forestay, a bit underpowered most of the time. Still we like to use it at night and set the spi during the day.

In my opinion the gap doesn't matter much when reaching.

 

[johnsomerhausen]

I had "Jenny Rolleer Wings" (two genoas on a common luff with a Wykeham-Martin furling gear) on a previous boat and the rig worked perfectly well in a crossing from France to Brazil. When the windvane breoke 12 hours out of Gran Canaria, we just led the sheets to the tiller and she continued to sail as if on a windvane
The whole trick is probably to have the twin sails angled forward so as to diminish the turbulence in the lee of the sails.
john

 

[brianhumber]

If you are on a dead run then the wind is just pushing against the area of your headsails so twin foils is ok.
The moment you come off a dead run and the wind angle is suitable for the sails to start acting as an wing , ie sucking, then the two sails on the twin foil will be less efficient because you have a horrible shape shape with a twin foil. As another has suggested, flying one free then allows 'slots' which is more efficent. Makes about 1/2 knots difference on mine, have a go yourself, exprimenting is always good fun and practice is better than theory from a book.

 

[ccscott49]

Trouble is, I dont have a twin forestay and on my boat is very difficult to rig, I could rig it flying, then I would need a wire luff or spectra etc. the sail would not then fit in the luff groove of the roller. I thought this would happen, I'm getting conflicting advice. I will wait for a few more ideas, thanks everyone for your input so far, I see the point about running directly downwind being ok, but just ioff the wind the sahpe would be wrong, unlees I let the sails belly forward, which might help. VBeing yankees, they have high clews, so give some lift, which I hope will reduce some rolling, I also can use the main and mizzen to reduce the roll, my boat rolls on wet grass! Shes not tender, but once she gets going!! Wow! I would use twin poles, with the inboard ends rigged to my staysail boom end, to control there movement. Thanks so far chaps!

 

[Sinbad1]

This isn't 'Twissle' style.

What exacerbates the rolling is the transfer of the sails forces through the spinny poles back to the mast. The 'twissle yard' rig removes this by flying the inboard ends of the twin poles free by simply connecting them on a spring which absorbs these forces. The inboard pole ends (now connected by a spring) are then tied forward, aft and upwards to prevent excessive movement.

You can actually buy this sprung joint from Ratsey & Lapthorne sailmakers who market the thing.

Alternatively, make your own variant by locking the two inboard pole ends together and have flexible rubber snubbers on the uphaul and vangs that hold the poles in position.

 

[ccscott49]

Not "twissle"?? The pole ends are free to move sideways, allowing the sails to move just on or off the wind, the poles can also move up and down, limited by topping lift and the staysail boom sheets, left with a bit of slack, this allows the whole rig to move about, the fixing to the end of the staysail boom, is just there to stop it really flopping about, and supply control of the pole ends if I have to reef the sails together, I've never heard of these springs, but can see your point, but do I really need it? The ends of the poles are still free to move which is the whole point, they aren't connected sloidly to anything.

 

[Sinbad1]

You are right. If the inboard ends of the poles are flying free its the twissle setup altho the more rigid the connection the more of the induced forces get transferred to the boat, hence my suggestion of using rubber snubbers on your vangs to absorb that energy. I haven't tried this myself yet tho and I have both twin headstays and twin grooves in the roller gear.

The beauty of using the twin grooves on the furler is that you can simply reduce sail on a run by easing the sheets and furling both sails at the same time....no need to go forward.

 

[ccscott49]

The furling reason is why I want to do it this way, but I get confused with all the info on slot or not!!

 

[summerwind]

I am very interested in conversation so far. I have twin grooves and two gennies. I have seriously considered rigging both in the luff grooves, but not tried it yet.

I am somewhat confused by the concept of not fixing the inner ends of the two poles to anything, except each other and a spring of some kind and using an up-haul.

What controls the beam to beam movement of the inner ends of the poles - the spring or snubbers? What is the spring fixed to.

Sorry if I appear thick, but am keen to learn about this setup.

 

[johnsomerhausen]

The Viking ships had no slot in their big square sail and they were doing pretty well.... Saw a film once in the Roskilde (Denmark) Viking Ship Museum showing one of them doing 5 knots 55 degrees from the wind.... It was a 40 footer and she reached 9 knots downwind in a Force 6.
john