Pressure of rode on bobstay?

[OzClipper]

Dave,
My Cheoy Lee on a swing mooring is set up with a bridle from the hawse pipes. Both legs of the bridle are protected with clear plastic hose which rubs against the bobstay rigging however causes no harm. Tubing deteriorates from UV quicker than chafe and I replace every 2 years.I have seen timber bowsprits with a single mooring line over the front roller and in one case a half inch chain. I would be uncomfortable with this arrangement considering the load imposed on the bowsprit end and back through the furler forestay to the mast top. I have also observed others with snubber arrangements which I believe only introduces further potential for damage. My bobstay is turned teak and the trick is to adjust the bridle length so that the bobstay is not damaged and the bridle rubs on the rigging. The Cheoy Lee is long keeled and sits fairly straight to the mooring line in a blow and not prone to yawing in these circumstances.

[GordMay]

Originally Posted by barnakiel

... Alas, there is also the other bobstay that makes use of an (word?) additional short spar that makes the stay travel to the spar and then onwards to the hull, making the stay bent at the spar...

Dolphin Striker or Martingale

[SailFastTri]

Anyone who doesn't think this is a valid concern doesn't understand the physics of angles under load.

Maybe I missed it, but I haven't seen anyone point out that pulling (or pushing) with a force of "x" perpendicular to a cable/line/chain bobstay in tension increases the load on that bobstay by a factor of at least 2x the pull and possibly 10x the pull, or higher, depending on the pre-load and angles. I'm not a physics genius, so I looked for a simple example online to explain this. Check the link below.

https://www.wired.com/2016/12/pull-c...ength-physics/

[barnakiel]

Originally Posted by Jim Cate

Doing anything that increases windage near the bow will increase hunting at anchor. Riding sails, which do help some boats, are set as far aft as feasible, usually from the backstay.

Jim

And they get even better if you can have a 'twin' (aka delta) design.

A single sail, even aft, may still ADD to sailing at anchor as a sail working so close to the wind direction tends to push the boat forward which in turn causes the bow to fall off further.

Not true for all boats, but sure true and tested on small monohulls with full length keel!

I am linking to the ideas that work for us:

http://i174.photobucket.com/albums/w...0/100_3174.jpg

https://encrypted-tbn3.gstatic.com/i...Y3UN1LE_5MObAg

https://www.bannerbaymarine.com/imag...x-P6210289.jpg

Cheers,
b.

[UNCIVILIZED]

To be able to hang a block near the end of the sprit, why not simply attach a large D-ring, with a seizing or Turk's Head knot, where ever you prefer it to be located on the sprit. With or without a bit of chafe protection for the wood underneath of the seizing.
And there's nothing that says that this ring couldn't be mounted right next to the Cranse Iron. So that most of the loads generated by it mostly get taken up by the various stays led to the Cranse Iron.

Also, it wouldn't be tough to have a metal collar specifically for hanging such a block from fabricated. Though personally, I'd go with the first option of a seizing. And if you want such an attachment to be stupid strong, use some Spectra or Spectra-blend cordage to make it from.
The reason I'd probably go with this option over a metal collar is that it's less likely to dig into the wood of the sprit than are the edges of a metal collar.

[Pauls]

Regarding Sail Fast Tri's post, I disagree that the forces applied to the sprit rigging are dangerous. I've done the calcs on this for my boat, applying chain breaking strength loads. I suggest that you look up how to do a force vector diagram which is a non-mathematical way to calculate forces. Brion Toss gives examples in his book and Skeene's Elements of Yacht Design has clear instructions. Do the analysis yourself, you will find that so long as the sprit end is used as support for a snubber, using a block for the snubber to run thru, loads are not high. As Brion and Ian note on his forum.

[SailFastTri]

Originally Posted by Pauls

Regarding Sail Fast Tri's post, I disagree that the forces applied to the sprit rigging are dangerous. I've done the calcs on this for my boat, applying chain breaking strength loads. I suggest that you look up how to do a force vector diagram which is a non-mathematical way to calculate forces. Brion Toss gives examples in his book and Skeene's Elements of Yacht Design has clear instructions. Do the analysis yourself, you will find that so long as the sprit end is used as support for a snubber, using a block for the snubber to run thru, loads are not high. As Brion and Ian note on his forum.

I was responding to the OP who was concerned about stress on the bobstay from sideways pressure of the anchor rode against the midpoint areas of the stay, as the boat sails at anchor. Is that what you were addressing?

[SailFastTri]

In general it doesn't seem like a great idea to use a long lever arm (sprit) as an anchor point for high anchoring loads. It's going to place much higher loads on the supporting rigging and rigging attachment points than an attachment direct to the main hull. It would even affect the headstay and mast, and backstays (which counter the headstay).

This is common sense.

Edit: imho, a snubber anchored to a strong well-backed fitting at the lower end of the bobstay makes more sense to me.