[C38] head stay tension

Tue Jun 25 16:25:33 EDT 2013

Don and Mark,

Here's some interesting reading.  The guys at Selden (
http://www.riggingandsails.com/pdf/selden-tuning.pdf) recommend some
pre-bend, even for a masthead rig.  They set the capshroud tension at 15%
of breaking, and have a nifty way of measuring it.  They have similar
recommendations on the backstay.

Kemp sails has similar guidance for tuning masthead rigs, and they suggest
freeing the mast at the partners before tuning.

I sure wish I knew what my PO did and why.

Ray

On Tue, Jun 25, 2013 at 11:24 AM, Don Strong <drstrong at ucdavis.edu> wrote:

>  Ray: Dunno about pinning at the partners. The PO had new rigging done by
> a big shot.
> Maybe some one else can figure this out
>
> On 6/25/13 11:02 AM, Ray Torok wrote:
>
> Don:
>
>  Interesting.  Do you know if your mast was free at the partners when the
> rig was tuned?
>
>  I'm worried that my mast is pinned at the partners with too little mast
> rake and too little headstay tension, so the only way I can get adequate
> headstay tension is by cranking on the backstay.  With the backstay at 1000
> on the gage (I'm not sure what that means really), I have quite a bit of
> mast bend, and not that much headstay tension.  This discussion is making
> me think I need to either shorten the headstay a bit or let the mast come
> back more (increase rake) at the partners and adjust the lower shrouds
> accordingly.  The alternative is to let the forward lowers pull the middle
> of the mast forward while the backstay pulls the top back to establish both
> headstay tension and mast bend.  I have to believe someone has solved this
> problem.
>
>  Thanks,
> Ray
>
>
> On Tue, Jun 25, 2013 at 10:44 AM, Don Strong <drstrong at ucdavis.edu> wrote:
>
>>  Mark:
>>   The winds are such that we go to weather when embarking on a sail from
>> the east SFB. Before leaving the dock, I tighten the jib furler by means of
>> the jib sheet led to port winch on the mast. If you don't have a furler,
>> then you would perform this tightening when you raise the jib. Then I then
>> put 1000lbs of tension on the back stay adjuster. This places more tension
>> on the jib furler, which one can see easily in reduced sag and sway of the
>> furled jib; 1000 lbs of tension gives a taught, furled head sail even in a
>> seaway. The backstay tension greatly improves the performance going to
>> weather. I echo the advice of your rigger. Too much backstay tension will
>> bend the boat. It causes the head door to jam shut on Discreet Charm. 1000
>> pounds on the gauge of our backstay adjuster does not change the shape of
>> the gap between the head door and the frame.
>>   When we head home, I release the backstay tension. This improves
>> performance before the wind.  I release tension on the jib furler before
>> disembarking.
>>
>> Others on the list are much more accomplished sailors than me, and will
>> give more sophisticated advice.
>> Regards, Don
>>
>> On 6/25/13 10:12 AM, Ray Torok wrote:
>>
>> Adding to the discussion - If the forward lower shrouds are tight and/or
>> the mast is pinned at the partners, the backstay will impart all kinds of
>> mast bend, so I don't understand your rigger's statement.
>>
>>  Ray Torok
>> Thira #37
>> San Francisco
>>
>>
>> On Tue, Jun 25, 2013 at 10:06 AM, Mark O'Dell <
>> mixedbusinesscontact at gmail.com> wrote:
>>
>>> Sorry that this might be a bit of a tangent, but Ray's question below
>>> sparked another semi-related question that I have:
>>>
>>> Last year I had my spreaders re-angled, my rig inspected and tuned.
>>> (Ended up replacing the shroud extension cable that comes through the
>>> hanging locker, as it was microscopically cracked in a few places on the
>>> swauge).
>>>
>>> Anyway, these people told me something interesting, in that they said
>>> said we don't have a mast that will have much bend to it.. so be very
>>> gentle with the backstay adjuster.  (They went so far as to making me a
>>> limit indicator on the adjuster that "I shouldn't" exceed. )
>>>
>>> They're telling me that our masthead rig isn't really bending the mast
>>> much at all... it's just pulling the mast down on the keel step harder and
>>> harder.
>>>
>>> I will also say that even if I exceed their "limit" my head stay is
>>> still sagging more than I think it should. +6"
>>>
>>> Do you guys go above 2k lbs of pressure? 3k? What you're setting?
>>>
>>> Is my mast rake out of whack?
>>>
>>> Mark O'Dell
>>> Momentous #230
>>> Baltimore, MD
>>> http://www.c38momentous.com
>>>
>>>
>>>
>>>
>>> On Jun 25, 2013, at 12:52 PM, Ray Torok <torok13731 at gmail.com> wrote:
>>>
>>> > All:
>>> >
>>> > After repairing my lower spreaders, I have to retune the whole rig.
>>>  Are there recommended settings for mast rake, pre-bend and that stuff?
>>>  Also, is there a recommended tuning procedure (several are out there on
>>> the internet)?  Should I remove the Spartite plug at the partners to start?
>>>  I have no idea if the original setup was okay.  In fact, without lots of
>>> backstay (and mast bend), the headstay seemed awfully slack to me.  Any
>>> thoughts/advice/experience would be appreciated.
>>> >
>>> > Thanks,
>>> >
>>> > Ray
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>>
>>
>>
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>>
>>
>> --
>> Donald R. Strong
>> Professor,
>> Department of Evolution and Ecology
>> and
>> The Bodega Marine Laboratory,
>> University of California, Davis,
>> Davis CA
>> 95616530 752 7886
>>
>>
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>>
>
>
> _______________________________________________
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>
>
>
> --
> Donald R. Strong
> Professor,
> Department of Evolution and Ecology
> and
> The Bodega Marine Laboratory,
> University of California, Davis,
> Davis CA
> 95616530 752 7886
>
>
> _______________________________________________
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