headstay vs. staysail stay tension balance

[Benz]

The runner line looks like Vectran, if so, it's perfectly non-stretchy, but of limited life (UV kills that uncovered portion)
The crappy white is just double-braid polyester: it's got lots of stretch for the purpose, and running the tail to a winch might blow that tiny pin on the block. Far better to splice a covered dyneema tail to that runner that will go through a strong turning block (or low-friction ring) that will lead it fair to a winch. If you need extra purchase, you can deadend the tail on a deck padeye, pass it though a LFR on the runner, then down though a turning block to the winch. This will give you 2:1.
I think you'll be surprised how much better your stay'sl will behave with proper tension on the runner.

[Bowdrie]

Originally Posted by markxengineerin

The crappy looking white span between blocks is about 5'

Nothing wrong with that, it's better.
I too use a 4:1 with fiddle blocks.
The upper block is above head level when moving around on deck, but low enough to be within easy reach, but you won't hit your head on it whilst moving around.
The falls being long enough for the lower block to reach the water.
The long span of the tackle makes the runners quite useable as lifting/hoisting devices to haul things aboard, (think a person in a sling or an outboard motor,) that you want to get high enough to clear the lifelines.

[nofacey]

What makes you believe the staysail vibration was driven by low stay tension?

[markxengineerin]

Just a guess. It could be normal, or it could be a result of something else, I am new to sailing a boat this big and wind this high. Looking for advice.

[nofacey]

Have sailed cutter rigs extensively, haven’t seen stay tension trigger vibration.
Suggest you check sail leech line = #1 source of sail flutter

[markxengineerin]

I can try the leech line, but the flutter I was seeing was the whole sail and the stay, not the leech.

Far better to splice a covered dyneema tail to that runner that will go through a strong turning block (or low-friction ring) that will lead it fair to a winch.

This makes sense, but would involve unwrapping the stowed genoa sheets from the only available winches and putting them elsewhere when the running backs are needed. Not a big deal, but also inconvenient compared to keeping a winch-less 4:1 setup. Is 4:1 considered insufficient for the running backs on most boats, for heavy weather?

[GILow]

Originally Posted by markxengineerin

…. Is 4:1 considered insufficient for the running backs on most boats, for heavy weather?

I can speak for most boats, but 4:1 is fine for my 42 footer with its 50 foot mast. Sometimes I run the free end to a winch if things are really blowing or if I’m trying to maximise my pointing angle, but usually I just give it a jolly good heave after tacking.

[Benz]

Originally Posted by markxengineerin

I can try the leech line, but the flutter I was seeing was the whole sail and the stay, not the leech.



This makes sense, but would involve unwrapping the stowed genoa sheets from the only available winches and putting them elsewhere when the running backs are needed. Not a big deal, but also inconvenient compared to keeping a winch-less 4:1 setup. Is 4:1 considered insufficient for the running backs on most boats, for heavy weather?

I consider it insufficient--it wasn't enough to properly tension a Stevens 47 last summer--we always wanted more. I installed dedicated runner winches on my boat (Cape George 31), when 4:1 didn't cut it for me.

[MJH]

Originally Posted by markxengineerin

My pacific seacraft 37 has a cutter rig with headstay and inner forestay. They are both tensioned up by the backstay turnbuckle, and the balance between them is adjusted by a turnbuckle on the staysail stay. The headstay has no turnbuckle but can be adjusted in length with toggles.



Due to the furler foils, I have no access to either headstay or staysail stay for measuring tension.

What is the proper procedure to set tensions in this system?

Currently I have the mast sticking straight up with the backstay and uppers properly tensioned, but not sure the best strategy for tensioning the lowers and the staysail stay. I understand the goal is to have a tiny amount of bend (mast top towards the stern, mast mid-point to the bow), and "appropriate" tension on all stays.

While sailing in high wind (30-40 knots), the staysail was previously vibrating quite a bit, making me think that perhaps the staysail stay was too loose. I'm not sure, but that was the result when professionally tuned. The rigger did the balance by shaking the headstay/staysail stay with the sails still wrapped up, didn't seem to have a good idea what he was looking for. The staysail stay turnbuckle was his last step, after having done the lowers, then re-checked the lowers and may have moved them a small amount.

Pacific Seacraft 37 is a nice cutter.

I also have twin furlers on my cutter and understand the issue. Use a Loos Tension Guage on the backstay to get your desired tension. Then sail upwind; if the jib looks good and not sagging but the staysail is sagging, then the staysail needs to be tightened.

[Bowdrie]

Just thinking out loud here.
Perhaps the combination of rigging pulling in all directions at various tensions has just set-up a "node", for harmonic vibration of the forestay?
Although something like that would seem to be specific to a certain range of wind strength.
A staysail on a furling device IS a lot of drag/air pressure against a "relatively" unsupported mast section.
If we drew a force diagram the tension applied to the runners is used more to compress the mast than to tension the forestay.
The ratio becoming more advantageous for forestay tension as the runner attachments move aft.

[MJH]

Originally Posted by markxengineerin

My pacific seacraft 37 has a cutter rig with headstay and inner forestay. They are both tensioned up by the backstay turnbuckle, and the balance between them is adjusted by a turnbuckle on the staysail stay. The headstay has no turnbuckle but can be adjusted in length with toggles.



Due to the furler foils, I have no access to either headstay or staysail stay for measuring tension.

What is the proper procedure to set tensions in this system?

Currently I have the mast sticking straight up with the backstay and uppers properly tensioned, but not sure the best strategy for tensioning the lowers and the staysail stay. I understand the goal is to have a tiny amount of bend (mast top towards the stern, mast mid-point to the bow), and "appropriate" tension on all stays.

While sailing in high wind (30-40 knots), the staysail was previously vibrating quite a bit, making me think that perhaps the staysail stay was too loose. I'm not sure, but that was the result when professionally tuned. The rigger did the balance by shaking the headstay/staysail stay with the sails still wrapped up, didn't seem to have a good idea what he was looking for. The staysail stay turnbuckle was his last step, after having done the lowers, then re-checked the lowers and may have moved them a small amount.

The Pacific Seacraft 37 is a nice boat.

I have dual furlers on my forward sails and understand the issue. My rigger appears to use the same procedure as yours...using years of subjective experience "feeling" tension.

After the forestay is tensioned and not sagging, note the backstay tension with a Loos Tension Guage (it will not be the same on the forestay due to the different angle but is some objective measurement of the tension for reference). If the jib looks good/performs well and not sagging but the staysail is sagging, then the staysail needs to be tightened.

In 30-40K wind I assume you are under only staysail and reefed main. I would think the vibration has more to due with the high wind and angle than being loose, like the rigging singing (vibrating) in a high wind while in a slip or anchored.