Rig Tune Documents

[Ed S]

Hi All,

Passing along some documents that Alan Johnstone sent me  (quick and helpful response, as always) in response to questions about mast bend on my carbon rig. I think the Hall Rigging guide has been posted recently -- at least some version of it -- but I don’t recall seeing the document on mast bend. Thought it might interest some of the mad scientists around here. :-)

Cheers,

Ed

[Sweet Ruca]

Thanks Ed,

I do wish there were some published loos gauge numbers or measurements for rake and head stay. Thinking in the last 20 years someone has to have come up with some good settings. 

So far I started with the tuning guides you posted, but have tuned the rest by sight/feel. I should take better notes and write down the numbers, but it seems cocktail hour usually gets in the way. I have yet to feel I am at an optimal base setting, and there is no one but polar numbers to compare against, which we have been able to sail 100% most times in flat water. Yesterday I tightened everything up just a bit as I was getting a little vibration in strong gusts at anchor.  

Would love to know if others have some repeatable settings and loos numbers they have found to work well. Happy to help build a boat specific tuning guide. 

Curtis

www.sweetruca.com 

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[Ed S]

Curtis,

I received the following from Alan about a year ago: Rake of the mast can be somewhat influenced by the trim of the boat, but the original J/42 rig plan with boat in level trim (fore-aft) indicates a 2.75 degree rake angle.

To your point, I guess the ultimate measurement is how the boat sails. I have not yet freed up much brain power for rig tune yet, but I finally started doing some research and playing around with it this year

Regards,

Ed

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Ed Sitver

esitver@gmail.com

WhatsApp:  +1 303-570-5071

Mobile:  +1 303-570-5071

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On Nov 3, 2020, at 16:48, Sweet Ruca <rucas...@gmail.com> wrote:



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[Jay PA]

Thanks for the rake spec.  I've been concerned that I have too much rake so will measure it.  Has anyone seen or can recommend a spec on nominal prebend, e.g., with just enough backstay to "straighten the forestay", per the Hall Prebend pdf?

Jay

J/42 Cirrus

[Ed S]

Here’s another response from Alan, this one regarding pre-bend:

“ As I recall Hall Spars would recommend up to 8" of bend to their carbon masts when applying max backstay tension and anything over that was not recommended, and you would likely start to see inversion wrinkles with most mainsail designs... so it sounds like maybe your lower shrouds are not tight enough? or your mast butt is too far aft?  or maybe the headstay is let off on the turnbuckle too far?  

How much pre-bend do you typically carry with backstay totally off?  I would start with no more than 1"-1-1/2".  I have attached a dated article by Ben Hall regarding rig tune as well as an old Hall article about Pre-bend that I am including here that hopefully will help you get tuned up.”

Regards,

Ed

------------------------------------

Ed Sitver

esi...@gmail.com

WhatsApp:  +1 303-570-5071
Mobile: +1 303-570-5071

On Jun 12, 2021, at 8:00 PM, Jay PA <svh...@gmail.com> wrote:

Thanks for the rake spec.  I've been concerned that I have too much rake so will measure it.  Has anyone seen or can recommend a spec on nominal prebend, e.g., with just enough backstay to "straighten the forestay", per the Hall Prebend pdf?

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