Should we have running backstays ?

[Paul Elliott]

Petar,

Sorry I can't answer your specific questions, but I am wondering if the 1/2" polyester line isn't too stretchy for this application. My boat uses stainless wire from the mast down to a block and tackle that is used for tensioning. I use a secondary winch to tighten, and a cam-cleat on the lower block to hold the (dacron) line. The cam-cleat can be a bear to release, and I sometimes consider removing the cam-leat and just leaving the line on the winch. On the other hand, having the winch available for other uses is nice.

Other boats go with Spectra or similar. You need a low-stretch running backstay.

[swagman]

Originally Posted by phorvati

THis is a very informative thread. I was putting the inner forestay T tang into the mast last summer while the rig was down. The Inner forestay tang is few inches above second spreader. The runner tangs are attached via 1/2" thrubolt. The riggger pre-bend them and showed me how to drill a hole symeytrical on each side and bisect the mast exactly in half. The runner tangs are just below the intermediate shrowd tangs and about 6" below the forestay tang.
For runners I have spliced a double braid 1/2" polyester line onto a stainless thimble and attached it to the tangs.

Response. If you do not wish to use wire rope then suggest you go with a pre or non stretch fibre - sorry so say polyester will stretch too easily under the loads.

The line goes to a ronstan large snatch block on the toerail as far aft as the pedestal, and then to a #32 spinnaker winch in the cockpit. C&C has a built in aluminum toerail which provides very strong points of attachments.

Response - good to hear it is a real strong point - it should be.

The question I had was this: I have never flown this thing. I have a hank on storm sail on it.

Response. Guess by this you are now talking about the inner forestay and not the running backstay?

How do I know that the mast is back in column? As I load the ABI lever I notice a substantial amount of rake on the mast already.

Response. Back to basics. When you are not sailing and have easy means of adjustment, its always best to leave her parked up with the mast straight.
To see if a mast is in column (ie straight) simply get close to your mast track and view up it. Any deviation can usually be seen with a mk 1 eyeball.
If the ABI lever is on the inner forestay, equally if you tension this it can only ever pull the middle section of the mast foreward. You may wish to do this when racing to effect aminsail trim - but just be careful you do not overdo this - in fact for cruising I'm not sure I'd want the rig bent at all. Just ensure it is tight and rack up opposite pressure on the runners to hold that section of the mast in place to prevent it pumping.

Since we are not heeled or sailing should I try to tention one or both of the runners to bring the mast back? The inner forestay doesn't seem that tight, nowhere near as the -10 rod rig that I have.

Response. It only needs to be tight enough to stop the mast pumping fore and aft. Suggest you go for a sail in medium breezes and lie under the mast looking up. If its moving fore / aft then tighten it further. If its not moving, back it off. Once set, you can mark the adjuster so you can get back to the setting quickly. You don't really want any mast bend to be more than say 75% of the fore-aft section itself - or you might suffer from a compression failure.
In medium to heavy airs, the preset tension may not stop pumping as load arise, but thats exactly where the runners come in to do their job. Simply tension them up to stop the movement.

And when we start sailing with storm gib, how am I gonna know when enough load is put on the winward runner?

Response. You are going to watch the sag in the inner forestay and trim accordingly. The runner will be like a piano string and 'twang' if you strum it - just remember on a masthead rig it is not holding up the mast - its to stop movement.

Boat is a C&C 38 with a very bendy mast -10 rod rig, single lower shrowd and a babystay treminating at the 1st spreader. Babystay can already put a lot of rake and prevent pumping. The inner forestay was reccomended to prevent further pumping in the middle section of the mast and also to have means of balancing the boat while offshore shorthanded in gale force winds. The inner forestay is attached to the deck via ABI quick release and a base leading through to a chainplate bolted onto a reinforced v-birth bulkhead.

petar

Response. Bendy rigs for cruisers are not ideal - but great for racing tho'. Take care you do not overdo the babystay and invite too much forward bend lower down - just remember never more than 75% of mast section and you'll get away with it.
Please excuse me if all this is already known - but hoping it may help.
JOHN

[Joli]

Originally Posted by phorvati

THis is a very informative thread. I was putting the inner forestay T tang into the mast last summer while the rig was down. The Inner forestay tang is few inches above second spreader. The runner tangs are attached via 1/2" thrubolt. The riggger pre-bend them and showed me how to drill a hole symeytrical on each side and bisect the mast exactly in half. The runner tangs are just below the intermediate shrowd tangs and about 6" below the forestay tang.
For runners I have spliced a double braid 1/2" polyester line onto a stainless thimble and attached it to the tangs. The line goes to a ronstan large snatch block on the toerail as far aft as the pedestal, and then to a #32 spinnaker winch in the cockpit. C&C has a built in aluminum toerail which provides very strong points of attachments.
The question I had was this: I have never flown this thing. I have a hank on storm sail on it. How do I know that the mast is back in column? As I load the ABI lever I notice a substantial amount of rake on the mast already. Since we are not heeled or sailing should I try to tention one or both of the runners to bring the mast back? The inner forestay doesn't seem that tight, nowhere near as the -10 rod rig that I have.
And when we start sailing with storm gib, how am I gonna know when enough load is put on the winward runner?
Boat is a C&C 38 with a very bendy mast -10 rod rig, single lower shrowd and a babystay treminating at the 1st spreader. Babystay can already put a lot of rake and prevent pumping. The inner forestay was reccomended to prevent further pumping in the middle section of the mast and also to have means of balancing the boat while offshore shorthanded in gale force winds. The inner forestay is attached to the deck via ABI quick release and a base leading through to a chainplate bolted onto a reinforced v-birth bulkhead.

petar

Backstay tension is used to bow the rig. This is not rake. The backstay pulls against a lever arm (the masthead crane or eccentric) to torque the spar and create bow. This is a good thing.



The babystay tensioned will also create bow, not rake. Bowing the rig will help reduce pumping. Adding runners will stop the center of the spar from
bowing too much when you pile drive into waves. You may also want to add second set of runners at the first spreaders. This would all terminate to one tail going to the winch. I'll look to see if I have a photo of what I'm trying to describe.

I would not be afraid of sailing with 1 or 2 sections of bow, the spar is designed for that. I would secure the spar with tension on the baby, innner, and runners. Get them tight. Do no invert the rig, it is not designed for that!

And like others have said, get wire or a spec 12 dyneema. Your goal is to lock the rig in place, the bow does not matter.

[ribbony]

So, what is the difference between Bow and Rake ??

[Joli]

Bow is deflection. If you have a spar with an 8 inch section as measured from the front to the back and you bow it 2 sections you have 16 inches of mast bend or bow.

You bend or bow the mast to depower the main. (ie boarding out the main). If you over bend you will create diagonal lines from the clew to the mast center.



Rake is the perpendicular position of the masthead to the butt. Think of the schooner America, she had heavily raked masts.

Why rake? Often you are much quicker upwind with some rake but slower downwind. Going upwind the backstay is loaded to rake the spar back if the headstay is slack when the backstay is unloaded. Downwind it is quicker to reverse the rake, to do this the backstay is thrown off and the top of the rig is pulled forward with a halyard.



http://www.cruisingdirect.com/Animations/RAKE.JPG

Next time your walking down the dock, line up the spars and look at the different rakes and mast bend people sail with.

[phorvati]

Thnaks for the correction, bow is the bend in the mast when I attach the ABI release lever or when I tention the babystay. I had a alot of problems with pumping. I had to re-head and also repace parts of the rod rig due to fatigue induced by pumping.
My rigger was the one suggesting that I don't go crazy spending money on low stretch line, and just get the plyester double braid line and splice it into a thimble. The stretching will stop. The other reason why I did this is storage. I setup a self retracting runners with bungee cord going from the lower spreader chainplate to a block. The runner is a continuous line that goes thru that block, then through a snatch block on a toerail and to a winch. The lazy runner is retracted neetly all the way to the lower shrowd base leaving the end still in the cockpit This setup allows me to tack without leaving the cockpit to secure the lazy runner.

John, thanks for all your input. This was very good information for me. Does anyone know if those low stretch ropes can also be spliced onto a thimble? Do I need a whole new splicing tool set for this or is the one I am using for double braid plyester line gonna work?
Today I did another trip up the mast. This time to attach an external block for the storm gib halyard. I used a sheafer padeye with a block. I actually sawed off a small section of my spinnaker car to use as the base so that the padeye can by fastened to the leading edge of the mast. I had no other ideas on how to attach that padeye and the rigger said it has to be on the leading edge and not off centered.

Anyway, thanks again for a very informative input. Great!
joil awesome pic of the bow. I don't think I will ever be doing that with my rig. But I am sure some other C&C racing fanatics have done it.
Petar

[Catamount]

Earlier in the thread, I had suggested Navtec T-terminals. Here's a photo I remembered I have of the set up on my mast:



A question was also asked about splicing hi-tech line around thimbles. I believe the line in the photo above is New England Ropes T-900 which is a double braid with a hybrid spectra/technora core and a polyester outer layer. You can see that it is spliced around a thimble, so clearly it is possible. (But I didn't do the splice myself, so I can't tell you what is involved.)