Mizzen standing rigging tensions

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This topic contains 6 replies, has 4 voices, and was last updated by  Kari and Lawrence 8 months, 4 weeks ago.

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September 25, 2017 at 11:54 #26163
John Tyler
John Tyler
Participant

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

October 13, 2017 at 05:57 #26175
Van
Van
Participant

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.

December 18, 2017 at 04:20 #26187

Kari and Lawrence
Participant

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

December 18, 2017 at 05:05 #26189

Kari and Lawrence
Participant

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

Enjoy

December 18, 2017 at 05:07 #26190

Kari and Lawrence
Participant

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

Have a great day.

December 27, 2017 at 21:50 #26206

Ollie Holden
Participant

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

December 29, 2017 at 10:56 #26209

Kari and Lawrence
Participant

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

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