runners on an aft swept fractional rig

[30boat]

´My Fulmar has a 3/4 rig wich works fine most of the time.What worries me is that I'm never satisfied with forestay tension.I can't tension the rig any more than it it now as I'm already at 25% of the breaking strength of the wire as recomended for this kind of rig.Read somewhere that runners are not good for aft swept fractional rigs because they can induce twist on the mast,but I've seen a few boats with this arrangement and the masts were still standing.I'm tempted to follow that route and would like the forum's opinion.Thanks

 

[savageseadog]

I've seen them used on a Sigma 36. I've got a fractional swept bag rig and have made provision for them on my latest ( /forums/images/graemlins/confused.gif) mast. Mast makers I've spoken too see nothing untoward about the idea. To me it seems a much better idea for tensioning the forestay than trying to get tension from the backstay. It's difficult to get good tension from the caps because of the geometry.

 

[William_H]

Yes runners are a very good way to get more forestay tension.
I hope you are not going up front with a tension gauge. Though I do sail on one boat with a load cell in the forestay for a tension readout but it don't work now anyway.
A fractioanla rig should have static tension set up with the cap shrouds providing tension to the forestay while backstay is variable but loose in static set up. The intermediate shrouds should have a little tension but basically set to keep the mast straight. No I don't believe in static tensions anything like those quoted in terms of % of max strain of the wire. A fractioanl rig particularly is a variable tension rig adjusted by the backstay according to conditions. nd always checked under sailing pressure. (ducks for cover)
So I hope the forestay tension you are not satisfied with is purely because the forestay sags under pressure from the jib.

Usually you crank on the backstay in strong winds to pull the forestay tighter. However this on a fractional rig means the mast top will also bend (usually desirable to flatten the main.

Many racers fit running backstays which pull at the meeting point of the forestay to induce tension in the forestay.

However there is a reason they are usually only seen on racers or long distance cruisers is that they have to be set up each time you tack. This requires a dedicated crew person or very long time between tack changes. If you don't release the loaded forestay then the boom hits it and may inhibit release of air pressure so causing a broach especially when running, or excessive heel when beating.

My little boat had runners on when I bought it and the first thing I did was remove them. The makers have since abandoned runners.
They are just too much trouble unless you are keen.

There is another way to get more forestay tension and that is to fit diamond stays ona jump strut. basically this is a pair of small spreaders mounted near the forestay attach point with stays running to the top of the mast and down to near main spreader attachment. The 2 spreaders are pointed foreward infact about 60 degrees apart and oined to one another. They are tensioned quite tight (by climbing the mast at least to the main spreaders where turnscrews are fitted to the bottom of the new stays.) The stays and spreader (Jump strut) support the top of the mast in the foreward direction and also sideways.
When you pull on the backstay you get less mast bend and more forestay tension. That is what I would suggest.
I had them fitted on one mast after I bent the mast and wanted to straighten it. It worked well but present mast doesn't need it. The jump strut spreaders were about 25cms long on a 28metre mast and made of about 8 or 9mm SS tubing welded to a base plate rivetted to the front of the mast just above the forestay.

Just one other thing. Make sure your main streaders are strong in the aft swept direction. I lost a mast because one spreader swung forward and lost its aft sweep. Mast lost foreward push in the middle and crumpled middle backwards. It was actually the mount of the streader which failed.
good luck olewill

 

[oldsaltoz]

G'day 30boat,

Have a look at some of the very competitive round the cans racing where boats of the same make and size but with slight variations in rigging perform.

The classic would be the Masrams, using runners and standard swept back spreader rigs.

The champion in the nationals had a very standard swept back spreader rig and out sailed the fleet in light and heavy air.

This is just an observation, but having raced extensively with and without runners I
would never consider running back stays as a part of my rig, nor anything else that can foul the boom and give any advantage that I have seen.

Avagoodweekend......

 

[Salty John]

Before you do anything drastic like adding the complication of runners check that your upper shroud tension is adequate. (You say that you have 25% tension in the rig, I'm assuming this is only the forestay). With this type of rig it is particularly important to have correct tension in your uppers. You may need up to 20% in the uppers to stop your forestay sagging off and losing tension.

 

[Salty John]

Another thought; the forestay tension at 25% is very high, the limit of what you should ever use. For the forestay to then go loose enough to effect sailing is a bit of a concern. If you are using a Loos Type B (90M) tension gauge make sure you are pulling the pointer all the way back to the black line at the end of the scale and not stopping when the pointer reaches the shroud. This is a surprisingly common mistake and leads you to believe the rig is tighter than it is.

 

[wooslehunter]

If you're a dedicated racer then runners may work. But if you're not & do use the boat for cruising, bear in mind the crew required to tack or gybe runners. You'll need 2 extra crew plus perfect coordination.

For the benefit of anyone reading who'se not used them, here's what happens to tack.

As the boom comes across the loose runner needs to be winched in. Once it's up to basic tension that will hold up the mast, the tight one can be realeased. Then the new runner can be brought up to operating tension. Both runners on together will pin the sail in. Both off and the mast can fall down. Therefore you need perfect crew/help co-ordination. That's at least 3 people. Now you need one or more on the headsail and you have a minimum of 4-5 required to sail the boat.

Gybing gets even more interesting as someone needs to be on the main sheet as well.

Gues why most cruisers and quite a few racers don't have them.

 

[flaming]

To be fair he's not looking to support the mast, the existing set up is doing that just fine, so the runners can be slack through the tack. This was the case on the Sigma 38 that I used to race, the runners weren't needed to keep the stick in the boat, just tension the forestay and we didn't bother with them at all until we'd changed down to the number 3.

Just a thought, but how old is the rigging? Could be that just replacing the standing rigging may solve the issue.

Also, don't forget that it you already have the forestay very tight, then adding runners will only increase the load. The fulmar's mast is not a racing rig, so I'd be very wary about putting high loads through it, especially if you then go out and fall off a few big waves.

 

[Bergman]

" A fractioanla rig should have static tension set up with the cap shrouds providing tension to the forestay while backstay is variable but loose in static set up. The intermediate shrouds should have a little tension but basically set to keep the mast straight."

I don't entirely agree.

When I had a fractional rigged boat I always set the caps and intermediates together to achieve the "right" degree of pre-bend in the mast and at the same time to achieve adaquate forestay tension.

My feeling in doing as you describe the caps will be putting too much pre-bend in and losing power in light winds and/or not being able to flatten the sail enough to maintainsail area in stronger winds. You may lose the range of adjustment.

 

[30boat]

thanks for all the replies.I'm basicallly after some way of tightening the forestay in higher winds so check stays would be a more apropriated designation.By the time I'd need them I would be down to the gib.All I need now is to come up with a system for attaching the stays to the mast.

 

[William_H]

Hello Bergman yes I don't really disagree with you. The mast should be straoght when static to give max camber to the mainsail. You would need tension on the inners to acheive straight mast (or whatever prebend you think best) This will need tension onn the inners. My choice of " a little" was perhaps not good. The point I wa strying to make is that backstay increases forestay tension and bends the mast for strong winds. olewill

 

[BrendanS]

as a moboer, and non sailor. How do you decide on how much bend to put into a mast? and how to tweak it?

It's always sounded a bit dodgy to me, unless very experienced

 

[savageseadog]

A black art indeed!

 

[flaming]

It is a little bit of a black art, but there is logic to it. The first place to start is the class tuning guide, often written by, or written with the input of, the people who designed the rig.
Then it's all about the effect that the rig has on the sails. After all the only reason you have a mast at all is to support the sails.
So go sailing, set the sails and look at them. If they're not doing what you want, then adjust the running rigging, that's the halyards, sheets, outhalls etc. If you still can't make them take the shape you're after then start adjusting the rig tension. Rule of thumb is higher wind = tighter rigging as this depowers (flattens) the sails.

If you still can't make them take the shape you're after buy new sails from a different sailmaker!

 

[bryeomans]

Take a good look at whether you really need higher tension in heavy conditions - a conversation with your sailmaker should allow you to sort out the cut of genoa/jibs to cope with a lower tension set up. We have sailed with runners on our Nic 345 for many years and basically only use them up-wind to help stabilise the rig in heavy conditions and not to harden up forestay . With a No3 blade or a working jib, on reasonably firm halyard tension, the cloth shoud be cut very flat anyway and a soft entry from "loose " forestay will still give a you drive in a seaway.

One further thought, with this kind of rig and very high tensions, would strongly recommend keep a very good eye on the rig and not just the wire terminations/tangs. Spreader root and tip are really vulnerable and as earlier post had it, its exit mast if you have any weakness in that area. Checking out rivets and plates of fittings is a very good idea!.