Mizzen standing rigging tensions

[John Tyler]

I will look in the manual, but any idea as to the mizzen standing rigging tensions?

[Van]

I don’t recall the manual giving specific values.

The rule of thumb is intermediates are tensioned to 10% or so of breaking strain, and caps to 15%. The Caps on our boat are 7/32″ or about 6mm and and the Intermediates are 5/32″, 4mm. The breaking strains vary by manufacturer, but are about 2800 lbs and 5400 lbs respectively. (I got these from Ronstans web site).

So, you want about 280 lbs and 540 lbs.

[Kari and Lawrence]

Hi Guys,

Erm, one has to keep in mind, the size and power of the mizzen sail itself. To my mind it seems much like a dinghy sail, therefore I go for a similar rig tension. Whilst we were in the process of purchasing our boat, we looked and had Sea Cale surveyed. Our man was very thorough and pointed out the distorted deck beneath her mizzen mast! Now, to my mind, the deck structure beneath the mizzen is supported by the main mast backstay tension. One can not theorise about the cause of Sea Cale’s problem but I’m guessing, too much rig tension and insufficient backstay tightness of her main mast, led to the aforesaid problem, which was also allowing moisture ingress, with all those assorted issues!

Happy bottle screw twisting.

Regards, Lawrence

[Kari and Lawrence]

PS, Lower shroud tension must always be equal to the capital shrouds, else the mast won’t stay in column, whilst under load.

Enjoy

[Kari and Lawrence]

Doh, so much for not checking predictive text! Cap shroud, it should of read.

Have a great day.

[Ollie Holden]

I’ve always gone for pretty loose on the mizzenmast, on the basis that there is no hanked sail which requires significant tension to maintain sail shape. The original mizzenmast mast is built like a tree trunk so you’d do well to pull it out of column.

The base of the mizzenmast is not the best piece of engineering, and I would encourage you to check that the main backstay is sufficiently anchored. Mine was just through bolted with four bolts but no backing plate. I am in the process of replacing the entire deck with a significant stainless structure to take the compression and tension loads.
https://photos.app.goo.gl/7yZseHGzTB87HsSD2

[Kari and Lawrence]

Dear Ollie,

I believe the designers and engineers got it right fifty years ago, as has been proven by the test of time. If you wish to modify stuff, then you are free to do so, I would be quite interested to know, what your experience level is?

Regards, Lawrence

[Author]

Posts