Backstay Tension/Fractional Rig

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jakeroyd

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I have Hunter Ranger with a fractional rig. Not properly understanding how to use backstay tension I have been reading up on it. The week before last we were out in that lovely weekend just passed. We were close hauled in about a F4 with the full rig up just off Rame.
Reading in the manual I should as the wind strength goes up apply the flattener (the little outhaul which pulls on the leech just about 6" above the boom) and also increase backstay tension. This moves the draght of the main forward and flatter which reduces heel with no decrease in speed.
This seemed to work , we were not overpowered and were making maybe 5k which for my little boat is not bad.
My question is this , looking at the main it had lost it's airfoil shape for about the top 3 feet. Did this mean I had not enough backstay tension on or too much. Being a dimwit I should have tried it at the time , but did not , I enjoyed the sail so much I did not want to play with it too much.

Any advice gratefully received.
 
I have a Ranger too and have tried all this tweaking but it gives me a terrible thirst and then I have some beer and forget all about it.
Kemp sails have some useful info you can download. I think it does make a bit of difference but I don't race. I've had 7.5kts out of her in a good breeze according to gps. Nice boats aren't they?
 
That's what tweaking the backstay is meant to do. It pulls the top of the mast back, allowing the sail in the top third to feather, and at the same time it pushes the mast forward for the centre third of the sail, flattenening and slightly depowering.

The loss of the top section of the sail by feathering means that it is giving you reduced forward force, but not much as it's not a big sail area up there anyway, but also reduces sideways force, and hence tipping force. This a much bigger effect as the portion of the sail at the top of the mast has a great contribution to tipping by being at the end of a long lever (the mast).

By reducing tipping force you can sail more upright. Most monohulls when moving through the water at an angle are trying to turn to the high side because of the asymmetric shape of the hull now in the water. To compensate for this you need to use rudder. Using the rudder just to keep going in a straight line causes drag ,which slows you down.

So losing the forward driving force from the top of the sail when heaving on the backstay is compensated by being able to sail flatter and using less rudder. Result - no loss of speed, less weather helm, more comfortable angle of dangle. Keeping angle of dangle to 20 dgrees is a good value to aim for.
 
I too had a Ranger 245 and employed the backstay a lot in fresh conditions. When you have done all the flattening you can do and the wind still increases just whack a load of backstay on and it will be like changing gear - boat sails faster and flatter with virtually no weather helm. Cracking boat, which I miss greatly, but you may want to upgrade the backstay tackle. From memory it was a bit on the cheap side and would have benefited from a better quality block and jammer.
 
Thanks very much for the responses , it seems I have it about right. Interesting comment about upgrading the blocks so I can put more backstay tension on. I was concerned I had too much on , it seems not. Matt1 is correct , the block is a bit crap and the jammer also a bit noddy.
 
I recall when racing my Enterprise dinghy with a massive mainsail relative to waterline length, the sail depowering technique was to tighten the cunningham at the base of the mast, tighten the clew outhaul to the max, then...analogous to using a backstay...to whack on as much kicking strap (vang) tension as the rig could stand. This pushes the middle section of mast forward and bent the mast above the hounds back, flattening the sail, thus depowering it.

I only wrecked one mast this way, so don't ignore the powerful leverage effect of the backstay, and read the info from the spar manufacturers as to just how much tension you can put on safely.

It really works.

Tim
 
I would suggest you have got the backstay figured out correctly. Yes you may get more mainsail flattening with a cunningham.
That is an eye in the mainsail about 6 inches up from the tack (goseneck) You can pullk this down with a tackle to get more tension in the luff and at the same time fold up some of the foot. With the flattening reef it works like full reef only small amount.

How much tension on the backstay. A good question.

If you tie the boat to a wharf and get a helper to pull on the backstay without the main sail up you can stand back to the side of the boat with a ruler to sight along the mast. You will see the top move aft by perhaps 1 ft and the middle of mast move forward perhaps 6 inches.
You can be fairly confident this amount of backstay is OK and you can mark the backstay tackle. More may be OK.

I once went out with a friend . He had got a new mainsail and it just didn't seem to set smoothly so he got the sailmaker to come on the boat. The boat was similar size and rig to yours. The sailmaker grabbed the back stay and hauled on it till I thought the mast would come down. It fixed the sail shape. But I am still not sure. It wasn't his (the sailmakers ) boat.

Be aware incidentaly that the tension of the intermediate shrouds will affect the amount of mast bend (middle forward) as these stays oppose that movement of the middle of the mast.

good luck and enjoy that bendy mast. I love mine. olewill
 
Flippancy aside, it really does work. The issued tackle is terrible and I'll certainly be replacing mine with some sort of decent jammer.
 
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