Luff length for top-down furl gennaker

[Luffe44]

I have some challenges with getting to know my new top-down furling gennaker. It is heavy to furl up, some times the sheet horn is furled in before the bottom of the sail. I wonder if the luff is too long. My sail maker says the sail i right size, but he is not able to see the boat. What is the recommended overlength vs. the torque wire length? It is a reaching gennaker (A2).

 

[Tranona]

The torque rope length is fixed by the distance between the top fitting and the lower mounting onto the furling drum. THe luff of the sail should be less than the distance between the attachment points on the furling drum and the swivel at the top.

 

[wilkinsonsails]

The top should start to roll up first ,then down to the clew .
If they work correctly, the sail will continue to roll to the tack .
Sometimes the torque rope cannot take the full twist and acts like a spring reversing the roll on the lower section .
Fun to sort out .
Newer torque ropes are a lot stiffer ,and pricey too .These usually fix the problem .
A simple demo to see the reverse twist problem ,set up sail horizontally ,tension between the tack and head ,try rolling ,if the top of sail starts furling ok then twists the opposite way below the clew ,there is insufficient torque in the rope tension.

 

[Luffe44]

The top should start to roll up first ,then down to the clew .
If they work correctly, the sail will continue to roll to the tack .
Sometimes the torque rope cannot take the full twist and acts like a spring reversing the roll on the lower section .
Fun to sort out .
Newer torque ropes are a lot stiffer ,and pricey too .These usually fix the problem .
A simple demo to see the reverse twist problem ,set up sail horizontally ,tension between the tack and head ,try rolling ,if the top of sail starts furling ok then twists the opposite way below the clew ,there is insufficient torque in the rope tension.

Thanks Wilkinson. The furler is Selden CX with a very stiff torque line, which appears to work fine as long as I put enough tension into the halyard. But getting in the first turns on the furling is hard pulling. Also I guess that the tack should be fully furled before the sheet horn. Now they come in about the same time. Hence my question: what is the max overlength of the luff versus the connectinos at the top and bottom furler? his is a running gennaker

 

[npf1]

see my comment on this thread, as it could be a similar situation: http://www.ybw.com/forums/showthread.php?511628-BAMAR-RLG-ROLLGEN-Problem

 

[Luffe44]

Thanks npf1. Releasing sheet tension is part of the solution. Still I am unsure of the luff length. My first attempt to attach a photo:

 

[pagoda]

Thanks npf1. Releasing sheet tension is part of the solution. Still I am unsure of the luff length. My first attempt to attach a photo: View attachment 74642

My experience with furling a code0 on a fixed torque line is that the luff needs a good bit of tension to furl well. If not the torque applied by the person furling tends to pull the luff line off centre- causing grief. It's generally better to furl these sails with a bit of load on them. Don't ease the sheets too much too early. The worst combination is a slack halyard/ poor hoist/ incorrectly measured luff.

On one or two other boats I've looked at, the luff is BAR TIGHT when furled.

 

[knuterikt]

On one or two other boats I've looked at, the luff is BAR TIGHT when furled.

You can’t get the luff of a asymmetric tigt.. but the torque rope should be tight.
the tack are supposed rotate freely as the top starts furling around the torque rope.
sheets should not be loaded while you furl, as this will introduce twist in the torque rope.

 

[knuterikt]

Have you seen this document http://www.seldenmast.com/files/1524032995/595-542-E.pdf

 

[Chi34]

15% extra?
If you put a strop on the clew, it can wrap round a few times and help roll up the tack.

 

[pagoda]

You can’t get the luff of a asymmetric tigt.. but the torque rope should be tight.
the tack are supposed rotate freely as the top starts furling around the torque rope.
sheets should not be loaded while you furl, as this will introduce twist in the torque rope.

OK, strictly correct - the torque rope is bar tight.....

 

[PTB]

Thanks npf1. Releasing sheet tension is part of the solution. Still I am unsure of the luff length. My first attempt to attach a photo: View attachment 74642

You have the Selden CX with the optional tack swivel for top down furling ? That luff length looks OK on the pic .. it is an asymmetric and not a tight luff code 0 so the top down system should work OK on a separate torque rope .. Just a thought, but, particularly if you are a masthead rig, check the asymm sails headboard isnt fouling on the genoa furler at the masthead and causing you the problems with the initial furl, Mine did and resulted in a lot of pent up torque before anything happened.

 

[knuterikt]

You have the Selden CX with the optional tack swivel for top down furling ? That luff length looks OK on the pic .. it is an asymmetric and not a tight luff code 0 so the top down system should work OK on a separate torque rope .. Just a thought, but, particularly if you are a masthead rig, check the asymm sails headboard isnt fouling on the genoa furler at the masthead and causing you the problems with the initial furl, Mine did and resulted in a lot of pent up torque before anything happened.

A good point, try to observe what prevents furling top down.

 

[Luffe44]

Thanks PTP, knuterikt and others. Yes it is Selden with tack swivel and the torque line is tight (should show from the picture). "Almost" masthead, I will bring binoculars to check interference at the top next time (= next year). I thought going from symmetrical to assymmetrical should be easy...

 

[Tranona]

I have the same set up and also had problems as you describe initially and twice had the upper part of the sail go back on itself - once with the sailmaker on board and operating it!. Not clear how it happens, but rewound the sail onto the rope neatly and have not had any problems since. My technique is to spill some wind so that the luff is free flying before furling. sometimes it takes a few turns to catch the head of the sail, but once it does it furls easily, if a bit slow because of the low gearing. I have the Selden fairleads on the stanchions and the double jamming block which helps keep it under control. Useful to stop partway without worrying about it flying out again. I do all this singlehanded standing at the wheel.