Perry Sliver Class Day Sailor

chester

Super Anarchist
6,642
1,606
Advocate:

I'm doing fine with my stash of Vegemite. Thanks for asking.

Busy trying to teach my fan club members, some of them anyway, that frac rigs on cruising boats won't kill you. It's a nice break from trying to teach them that spade rudders won't kill you.

View attachment 477719
we are such risk takers, sailors...spade rudder, frac rigs, offset companion ways always pushing the limits, putting our lives on yhe line.  Heroic really.

 

socalrider

Super Anarchist
1,422
786
San Diego CA
Advocate:

I'm doing fine with my stash of Vegemite. Thanks for asking.

Busy trying to teach my fan club members, some of them anyway, that frac rigs on cruising boats won't kill you. It's a nice break from trying to teach them that spade rudders won't kill you.
Does that mean you no longer need to teach them that fin keels won't kill you?  Thank you for your service Sir!   :)  

 

pschwenn

New member
Yes, what are the mast struts for?


Mr. Ed.

Yes, 68' Born of Water 1992. Aluminum.

The name of the sail? A mule.

View attachment 226006

View attachment 226007
I wonder too.  Maybe guessing would lead to an answer.

They are more than puzzling, seeming to obstruct passage along the deck.  Maybe they are removeable, or only seem in these photos to block, or have been added with respect to an even greater problem - the built DSPL or RM may have been so much over, that rig calculations prior to construction and fitting out had to be re-done with existing mast and standing rigging.  Maybe something was noticed underway.  Or gennaker pole forces needed opposing.

Perhaps over-speculating:  Buckling isn't intuitive or even always predictable with any means.   Demolitions seem to go wrong quite often.  When we watch most boats underway, their motion in a variety of seas seems quite natural, and exceptions may be startling.  But when you watch a structure buckle, the details routinely seem surprising.   An optimizing rig structural analysis calculation can produce quite unequal inter-spreader lengths that "look" wrong.  Perhaps an eye was drawn to what looked like too long a segment below the first spreader.

regards,

 

kimbottles

Super Anarchist
8,055
784
PNW
FRANKIE and her pals covered in snow…….

35BA0569-73FE-4BD0-AB60-BC0C8F5AE4D3.jpeg

 
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pschwenn

New member
Sam,

The reason I believe this it's likely to have been a remedy is that this rig had been subjected to an optimizer that, given the rig & deck dimensions, and working from the forces, for every wind speed and angle, delivered by a proven VPP, varies the spreader heights and standing rigging to find the lightest configuration that handles all of the worst cases of sails set, wind (with a sea to match), heading. reef, and speed.

A large safety factor is added

Even if such a rig could be lightened with  that sort of strut, the resulting danger and inconvenience is unlikely to be justified on even a very large yacht, and if its not a remedy, why not trust the optimzation already done?

It does look interesting (like the mule). Until you look along the passage between the shrouds and the deck paraphernalia. Just the shroud bases and the most inward angled lower shroud can range beyond irritating and anxiety.

Of course a single drawing or photo can mislead.

regards

 
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pschwenn

New member
Thank you Bob.

Second to last hand drawing, the 68' Born of Water.

From the Last Mohican.

View attachment 225996


Mr. Ed.

Yes, 68' Born of Water 1992. Aluminum.

The name of the sail? A mule.

View attachment 226006

View attachment 226007


Yes, what are the mast struts for?
The boat was fitted with a carbon B&R rig, thus the struts.
Olaf,

I made some guesses about the struts in an earlier post before seeing the response to your question, after which I looked more carefully at the hand-drawing and the mast as built.

In the hand-drawing above, the lower section of the mast is about 22+ ft long.  The three sections above are about 17+ ft long.  The mast is about 75' above the deck.

The boat as built has a much taller lower section of the mast at 27+ ft but the three sections above are seemingly unchanged, the mast now about 80' above the deck.

So the struts might be a way of supporting the taller mast without changing the spreaders or their layout.  For example if the same carbon mast tube were to be used for the taller rig, avoiding re-fastening the spreaders in a new layout supporting the first section without struts.

regards,
 




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